Merge branch 'for-6.8/mcp2221' into for-linus

[linux-2.6-microblaze.git] / fs / ext4 / extents_status.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  fs/ext4/extents_status.c
 *
 * Written by Yongqiang Yang <xiaoqiangnk@gmail.com>
 * Modified by
 *      Allison Henderson <achender@linux.vnet.ibm.com>
 *      Hugh Dickins <hughd@google.com>
 *      Zheng Liu <wenqing.lz@taobao.com>
 *
 * Ext4 extents status tree core functions.
 */
#include <linux/list_sort.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include "ext4.h"

#include <trace/events/ext4.h>

/*
 * According to previous discussion in Ext4 Developer Workshop, we
 * will introduce a new structure called io tree to track all extent
 * status in order to solve some problems that we have met
 * (e.g. Reservation space warning), and provide extent-level locking.
 * Delay extent tree is the first step to achieve this goal.  It is
 * original built by Yongqiang Yang.  At that time it is called delay
 * extent tree, whose goal is only track delayed extents in memory to
 * simplify the implementation of fiemap and bigalloc, and introduce
 * lseek SEEK_DATA/SEEK_HOLE support.  That is why it is still called
 * delay extent tree at the first commit.  But for better understand
 * what it does, it has been rename to extent status tree.
 *
 * Step1:
 * Currently the first step has been done.  All delayed extents are
 * tracked in the tree.  It maintains the delayed extent when a delayed
 * allocation is issued, and the delayed extent is written out or
 * invalidated.  Therefore the implementation of fiemap and bigalloc
 * are simplified, and SEEK_DATA/SEEK_HOLE are introduced.
 *
 * The following comment describes the implemenmtation of extent
 * status tree and future works.
 *
 * Step2:
 * In this step all extent status are tracked by extent status tree.
 * Thus, we can first try to lookup a block mapping in this tree before
 * finding it in extent tree.  Hence, single extent cache can be removed
 * because extent status tree can do a better job.  Extents in status
 * tree are loaded on-demand.  Therefore, the extent status tree may not
 * contain all of the extents in a file.  Meanwhile we define a shrinker
 * to reclaim memory from extent status tree because fragmented extent
 * tree will make status tree cost too much memory.  written/unwritten/-
 * hole extents in the tree will be reclaimed by this shrinker when we
 * are under high memory pressure.  Delayed extents will not be
 * reclimed because fiemap, bigalloc, and seek_data/hole need it.
 */

/*
 * Extent status tree implementation for ext4.
 *
 *
 * ==========================================================================
 * Extent status tree tracks all extent status.
 *
 * 1. Why we need to implement extent status tree?
 *
 * Without extent status tree, ext4 identifies a delayed extent by looking
 * up page cache, this has several deficiencies - complicated, buggy,
 * and inefficient code.
 *
 * FIEMAP, SEEK_HOLE/DATA, bigalloc, and writeout all need to know if a
 * block or a range of blocks are belonged to a delayed extent.
 *
 * Let us have a look at how they do without extent status tree.
 *   -- FIEMAP
 *      FIEMAP looks up page cache to identify delayed allocations from holes.
 *
 *   -- SEEK_HOLE/DATA
 *      SEEK_HOLE/DATA has the same problem as FIEMAP.
 *
 *   -- bigalloc
 *      bigalloc looks up page cache to figure out if a block is
 *      already under delayed allocation or not to determine whether
 *      quota reserving is needed for the cluster.
 *
 *   -- writeout
 *      Writeout looks up whole page cache to see if a buffer is
 *      mapped, If there are not very many delayed buffers, then it is
 *      time consuming.
 *
 * With extent status tree implementation, FIEMAP, SEEK_HOLE/DATA,
 * bigalloc and writeout can figure out if a block or a range of
 * blocks is under delayed allocation(belonged to a delayed extent) or
 * not by searching the extent tree.
 *
 *
 * ==========================================================================
 * 2. Ext4 extent status tree impelmentation
 *
 *   -- extent
 *      A extent is a range of blocks which are contiguous logically and
 *      physically.  Unlike extent in extent tree, this extent in ext4 is
 *      a in-memory struct, there is no corresponding on-disk data.  There
 *      is no limit on length of extent, so an extent can contain as many
 *      blocks as they are contiguous logically and physically.
 *
 *   -- extent status tree
 *      Every inode has an extent status tree and all allocation blocks
 *      are added to the tree with different status.  The extent in the
 *      tree are ordered by logical block no.
 *
 *   -- operations on a extent status tree
 *      There are three important operations on a delayed extent tree: find
 *      next extent, adding a extent(a range of blocks) and removing a extent.
 *
 *   -- race on a extent status tree
 *      Extent status tree is protected by inode->i_es_lock.
 *
 *   -- memory consumption
 *      Fragmented extent tree will make extent status tree cost too much
 *      memory.  Hence, we will reclaim written/unwritten/hole extents from
 *      the tree under a heavy memory pressure.
 *
 *
 * ==========================================================================
 * 3. Performance analysis
 *
 *   -- overhead
 *      1. There is a cache extent for write access, so if writes are
 *      not very random, adding space operaions are in O(1) time.
 *
 *   -- gain
 *      2. Code is much simpler, more readable, more maintainable and
 *      more efficient.
 *
 *
 * ==========================================================================
 * 4. TODO list
 *
 *   -- Refactor delayed space reservation
 *
 *   -- Extent-level locking
 */

static struct kmem_cache *ext4_es_cachep;
static struct kmem_cache *ext4_pending_cachep;

static int __es_insert_extent(struct inode *inode, struct extent_status *newes,
                              struct extent_status *prealloc);
static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
                              ext4_lblk_t end, int *reserved,
                              struct extent_status *prealloc);
static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan);
static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
                       struct ext4_inode_info *locked_ei);
static int __revise_pending(struct inode *inode, ext4_lblk_t lblk,
                            ext4_lblk_t len,
                            struct pending_reservation **prealloc);

int __init ext4_init_es(void)
{
        ext4_es_cachep = KMEM_CACHE(extent_status, SLAB_RECLAIM_ACCOUNT);
        if (ext4_es_cachep == NULL)
                return -ENOMEM;
        return 0;
}

void ext4_exit_es(void)
{
        kmem_cache_destroy(ext4_es_cachep);
}

void ext4_es_init_tree(struct ext4_es_tree *tree)
{
        tree->root = RB_ROOT;
        tree->cache_es = NULL;
}

#ifdef ES_DEBUG__
static void ext4_es_print_tree(struct inode *inode)
{
        struct ext4_es_tree *tree;
        struct rb_node *node;

        printk(KERN_DEBUG "status extents for inode %lu:", inode->i_ino);
        tree = &EXT4_I(inode)->i_es_tree;
        node = rb_first(&tree->root);
        while (node) {
                struct extent_status *es;
                es = rb_entry(node, struct extent_status, rb_node);
                printk(KERN_DEBUG " [%u/%u) %llu %x",
                       es->es_lblk, es->es_len,
                       ext4_es_pblock(es), ext4_es_status(es));
                node = rb_next(node);
        }
        printk(KERN_DEBUG "\n");
}
#else
#define ext4_es_print_tree(inode)
#endif

static inline ext4_lblk_t ext4_es_end(struct extent_status *es)
{
        BUG_ON(es->es_lblk + es->es_len < es->es_lblk);
        return es->es_lblk + es->es_len - 1;
}

/*
 * search through the tree for an delayed extent with a given offset.  If
 * it can't be found, try to find next extent.
 */
static struct extent_status *__es_tree_search(struct rb_root *root,
                                              ext4_lblk_t lblk)
{
        struct rb_node *node = root->rb_node;
        struct extent_status *es = NULL;

        while (node) {
                es = rb_entry(node, struct extent_status, rb_node);
                if (lblk < es->es_lblk)
                        node = node->rb_left;
                else if (lblk > ext4_es_end(es))
                        node = node->rb_right;
                else
                        return es;
        }

        if (es && lblk < es->es_lblk)
                return es;

        if (es && lblk > ext4_es_end(es)) {
                node = rb_next(&es->rb_node);
                return node ? rb_entry(node, struct extent_status, rb_node) :
                              NULL;
        }

        return NULL;
}

/*
 * ext4_es_find_extent_range - find extent with specified status within block
 *                             range or next extent following block range in
 *                             extents status tree
 *
 * @inode - file containing the range
 * @matching_fn - pointer to function that matches extents with desired status
 * @lblk - logical block defining start of range
 * @end - logical block defining end of range
 * @es - extent found, if any
 *
 * Find the first extent within the block range specified by @lblk and @end
 * in the extents status tree that satisfies @matching_fn.  If a match
 * is found, it's returned in @es.  If not, and a matching extent is found
 * beyond the block range, it's returned in @es.  If no match is found, an
 * extent is returned in @es whose es_lblk, es_len, and es_pblk components
 * are 0.
 */
static void __es_find_extent_range(struct inode *inode,
                                   int (*matching_fn)(struct extent_status *es),
                                   ext4_lblk_t lblk, ext4_lblk_t end,
                                   struct extent_status *es)
{
        struct ext4_es_tree *tree = NULL;
        struct extent_status *es1 = NULL;
        struct rb_node *node;

        WARN_ON(es == NULL);
        WARN_ON(end < lblk);

        tree = &EXT4_I(inode)->i_es_tree;

        /* see if the extent has been cached */
        es->es_lblk = es->es_len = es->es_pblk = 0;
        es1 = READ_ONCE(tree->cache_es);
        if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) {
                es_debug("%u cached by [%u/%u) %llu %x\n",
                         lblk, es1->es_lblk, es1->es_len,
                         ext4_es_pblock(es1), ext4_es_status(es1));
                goto out;
        }

        es1 = __es_tree_search(&tree->root, lblk);

out:
        if (es1 && !matching_fn(es1)) {
                while ((node = rb_next(&es1->rb_node)) != NULL) {
                        es1 = rb_entry(node, struct extent_status, rb_node);
                        if (es1->es_lblk > end) {
                                es1 = NULL;
                                break;
                        }
                        if (matching_fn(es1))
                                break;
                }
        }

        if (es1 && matching_fn(es1)) {
                WRITE_ONCE(tree->cache_es, es1);
                es->es_lblk = es1->es_lblk;
                es->es_len = es1->es_len;
                es->es_pblk = es1->es_pblk;
        }

}

/*
 * Locking for __es_find_extent_range() for external use
 */
void ext4_es_find_extent_range(struct inode *inode,
                               int (*matching_fn)(struct extent_status *es),
                               ext4_lblk_t lblk, ext4_lblk_t end,
                               struct extent_status *es)
{
        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return;

        trace_ext4_es_find_extent_range_enter(inode, lblk);

        read_lock(&EXT4_I(inode)->i_es_lock);
        __es_find_extent_range(inode, matching_fn, lblk, end, es);
        read_unlock(&EXT4_I(inode)->i_es_lock);

        trace_ext4_es_find_extent_range_exit(inode, es);
}

/*
 * __es_scan_range - search block range for block with specified status
 *                   in extents status tree
 *
 * @inode - file containing the range
 * @matching_fn - pointer to function that matches extents with desired status
 * @lblk - logical block defining start of range
 * @end - logical block defining end of range
 *
 * Returns true if at least one block in the specified block range satisfies
 * the criterion specified by @matching_fn, and false if not.  If at least
 * one extent has the specified status, then there is at least one block
 * in the cluster with that status.  Should only be called by code that has
 * taken i_es_lock.
 */
static bool __es_scan_range(struct inode *inode,
                            int (*matching_fn)(struct extent_status *es),
                            ext4_lblk_t start, ext4_lblk_t end)
{
        struct extent_status es;

        __es_find_extent_range(inode, matching_fn, start, end, &es);
        if (es.es_len == 0)
                return false;   /* no matching extent in the tree */
        else if (es.es_lblk <= start &&
                 start < es.es_lblk + es.es_len)
                return true;
        else if (start <= es.es_lblk && es.es_lblk <= end)
                return true;
        else
                return false;
}
/*
 * Locking for __es_scan_range() for external use
 */
bool ext4_es_scan_range(struct inode *inode,
                        int (*matching_fn)(struct extent_status *es),
                        ext4_lblk_t lblk, ext4_lblk_t end)
{
        bool ret;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return false;

        read_lock(&EXT4_I(inode)->i_es_lock);
        ret = __es_scan_range(inode, matching_fn, lblk, end);
        read_unlock(&EXT4_I(inode)->i_es_lock);

        return ret;
}

/*
 * __es_scan_clu - search cluster for block with specified status in
 *                 extents status tree
 *
 * @inode - file containing the cluster
 * @matching_fn - pointer to function that matches extents with desired status
 * @lblk - logical block in cluster to be searched
 *
 * Returns true if at least one extent in the cluster containing @lblk
 * satisfies the criterion specified by @matching_fn, and false if not.  If at
 * least one extent has the specified status, then there is at least one block
 * in the cluster with that status.  Should only be called by code that has
 * taken i_es_lock.
 */
static bool __es_scan_clu(struct inode *inode,
                          int (*matching_fn)(struct extent_status *es),
                          ext4_lblk_t lblk)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        ext4_lblk_t lblk_start, lblk_end;

        lblk_start = EXT4_LBLK_CMASK(sbi, lblk);
        lblk_end = lblk_start + sbi->s_cluster_ratio - 1;

        return __es_scan_range(inode, matching_fn, lblk_start, lblk_end);
}

/*
 * Locking for __es_scan_clu() for external use
 */
bool ext4_es_scan_clu(struct inode *inode,
                      int (*matching_fn)(struct extent_status *es),
                      ext4_lblk_t lblk)
{
        bool ret;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return false;

        read_lock(&EXT4_I(inode)->i_es_lock);
        ret = __es_scan_clu(inode, matching_fn, lblk);
        read_unlock(&EXT4_I(inode)->i_es_lock);

        return ret;
}

static void ext4_es_list_add(struct inode *inode)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

        if (!list_empty(&ei->i_es_list))
                return;

        spin_lock(&sbi->s_es_lock);
        if (list_empty(&ei->i_es_list)) {
                list_add_tail(&ei->i_es_list, &sbi->s_es_list);
                sbi->s_es_nr_inode++;
        }
        spin_unlock(&sbi->s_es_lock);
}

static void ext4_es_list_del(struct inode *inode)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

        spin_lock(&sbi->s_es_lock);
        if (!list_empty(&ei->i_es_list)) {
                list_del_init(&ei->i_es_list);
                sbi->s_es_nr_inode--;
                WARN_ON_ONCE(sbi->s_es_nr_inode < 0);
        }
        spin_unlock(&sbi->s_es_lock);
}

static inline struct pending_reservation *__alloc_pending(bool nofail)
{
        if (!nofail)
                return kmem_cache_alloc(ext4_pending_cachep, GFP_ATOMIC);

        return kmem_cache_zalloc(ext4_pending_cachep, GFP_KERNEL | __GFP_NOFAIL);
}

static inline void __free_pending(struct pending_reservation *pr)
{
        kmem_cache_free(ext4_pending_cachep, pr);
}

/*
 * Returns true if we cannot fail to allocate memory for this extent_status
 * entry and cannot reclaim it until its status changes.
 */
static inline bool ext4_es_must_keep(struct extent_status *es)
{
        /* fiemap, bigalloc, and seek_data/hole need to use it. */
        if (ext4_es_is_delayed(es))
                return true;

        return false;
}

static inline struct extent_status *__es_alloc_extent(bool nofail)
{
        if (!nofail)
                return kmem_cache_alloc(ext4_es_cachep, GFP_ATOMIC);

        return kmem_cache_zalloc(ext4_es_cachep, GFP_KERNEL | __GFP_NOFAIL);
}

static void ext4_es_init_extent(struct inode *inode, struct extent_status *es,
                ext4_lblk_t lblk, ext4_lblk_t len, ext4_fsblk_t pblk)
{
        es->es_lblk = lblk;
        es->es_len = len;
        es->es_pblk = pblk;

        /* We never try to reclaim a must kept extent, so we don't count it. */
        if (!ext4_es_must_keep(es)) {
                if (!EXT4_I(inode)->i_es_shk_nr++)
                        ext4_es_list_add(inode);
                percpu_counter_inc(&EXT4_SB(inode->i_sb)->
                                        s_es_stats.es_stats_shk_cnt);
        }

        EXT4_I(inode)->i_es_all_nr++;
        percpu_counter_inc(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
}

static inline void __es_free_extent(struct extent_status *es)
{
        kmem_cache_free(ext4_es_cachep, es);
}

static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
{
        EXT4_I(inode)->i_es_all_nr--;
        percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);

        /* Decrease the shrink counter when we can reclaim the extent. */
        if (!ext4_es_must_keep(es)) {
                BUG_ON(EXT4_I(inode)->i_es_shk_nr == 0);
                if (!--EXT4_I(inode)->i_es_shk_nr)
                        ext4_es_list_del(inode);
                percpu_counter_dec(&EXT4_SB(inode->i_sb)->
                                        s_es_stats.es_stats_shk_cnt);
        }

        __es_free_extent(es);
}

/*
 * Check whether or not two extents can be merged
 * Condition:
 *  - logical block number is contiguous
 *  - physical block number is contiguous
 *  - status is equal
 */
static int ext4_es_can_be_merged(struct extent_status *es1,
                                 struct extent_status *es2)
{
        if (ext4_es_type(es1) != ext4_es_type(es2))
                return 0;

        if (((__u64) es1->es_len) + es2->es_len > EXT_MAX_BLOCKS) {
                pr_warn("ES assertion failed when merging extents. "
                        "The sum of lengths of es1 (%d) and es2 (%d) "
                        "is bigger than allowed file size (%d)\n",
                        es1->es_len, es2->es_len, EXT_MAX_BLOCKS);
                WARN_ON(1);
                return 0;
        }

        if (((__u64) es1->es_lblk) + es1->es_len != es2->es_lblk)
                return 0;

        if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
            (ext4_es_pblock(es1) + es1->es_len == ext4_es_pblock(es2)))
                return 1;

        if (ext4_es_is_hole(es1))
                return 1;

        /* we need to check delayed extent is without unwritten status */
        if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
                return 1;

        return 0;
}

static struct extent_status *
ext4_es_try_to_merge_left(struct inode *inode, struct extent_status *es)
{
        struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
        struct extent_status *es1;
        struct rb_node *node;

        node = rb_prev(&es->rb_node);
        if (!node)
                return es;

        es1 = rb_entry(node, struct extent_status, rb_node);
        if (ext4_es_can_be_merged(es1, es)) {
                es1->es_len += es->es_len;
                if (ext4_es_is_referenced(es))
                        ext4_es_set_referenced(es1);
                rb_erase(&es->rb_node, &tree->root);
                ext4_es_free_extent(inode, es);
                es = es1;
        }

        return es;
}

static struct extent_status *
ext4_es_try_to_merge_right(struct inode *inode, struct extent_status *es)
{
        struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
        struct extent_status *es1;
        struct rb_node *node;

        node = rb_next(&es->rb_node);
        if (!node)
                return es;

        es1 = rb_entry(node, struct extent_status, rb_node);
        if (ext4_es_can_be_merged(es, es1)) {
                es->es_len += es1->es_len;
                if (ext4_es_is_referenced(es1))
                        ext4_es_set_referenced(es);
                rb_erase(node, &tree->root);
                ext4_es_free_extent(inode, es1);
        }

        return es;
}

#ifdef ES_AGGRESSIVE_TEST
#include "ext4_extents.h"       /* Needed when ES_AGGRESSIVE_TEST is defined */

static void ext4_es_insert_extent_ext_check(struct inode *inode,
                                            struct extent_status *es)
{
        struct ext4_ext_path *path = NULL;
        struct ext4_extent *ex;
        ext4_lblk_t ee_block;
        ext4_fsblk_t ee_start;
        unsigned short ee_len;
        int depth, ee_status, es_status;

        path = ext4_find_extent(inode, es->es_lblk, NULL, EXT4_EX_NOCACHE);
        if (IS_ERR(path))
                return;

        depth = ext_depth(inode);
        ex = path[depth].p_ext;

        if (ex) {

                ee_block = le32_to_cpu(ex->ee_block);
                ee_start = ext4_ext_pblock(ex);
                ee_len = ext4_ext_get_actual_len(ex);

                ee_status = ext4_ext_is_unwritten(ex) ? 1 : 0;
                es_status = ext4_es_is_unwritten(es) ? 1 : 0;

                /*
                 * Make sure ex and es are not overlap when we try to insert
                 * a delayed/hole extent.
                 */
                if (!ext4_es_is_written(es) && !ext4_es_is_unwritten(es)) {
                        if (in_range(es->es_lblk, ee_block, ee_len)) {
                                pr_warn("ES insert assertion failed for "
                                        "inode: %lu we can find an extent "
                                        "at block [%d/%d/%llu/%c], but we "
                                        "want to add a delayed/hole extent "
                                        "[%d/%d/%llu/%x]\n",
                                        inode->i_ino, ee_block, ee_len,
                                        ee_start, ee_status ? 'u' : 'w',
                                        es->es_lblk, es->es_len,
                                        ext4_es_pblock(es), ext4_es_status(es));
                        }
                        goto out;
                }

                /*
                 * We don't check ee_block == es->es_lblk, etc. because es
                 * might be a part of whole extent, vice versa.
                 */
                if (es->es_lblk < ee_block ||
                    ext4_es_pblock(es) != ee_start + es->es_lblk - ee_block) {
                        pr_warn("ES insert assertion failed for inode: %lu "
                                "ex_status [%d/%d/%llu/%c] != "
                                "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
                                ee_block, ee_len, ee_start,
                                ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
                                ext4_es_pblock(es), es_status ? 'u' : 'w');
                        goto out;
                }

                if (ee_status ^ es_status) {
                        pr_warn("ES insert assertion failed for inode: %lu "
                                "ex_status [%d/%d/%llu/%c] != "
                                "es_status [%d/%d/%llu/%c]\n", inode->i_ino,
                                ee_block, ee_len, ee_start,
                                ee_status ? 'u' : 'w', es->es_lblk, es->es_len,
                                ext4_es_pblock(es), es_status ? 'u' : 'w');
                }
        } else {
                /*
                 * We can't find an extent on disk.  So we need to make sure
                 * that we don't want to add an written/unwritten extent.
                 */
                if (!ext4_es_is_delayed(es) && !ext4_es_is_hole(es)) {
                        pr_warn("ES insert assertion failed for inode: %lu "
                                "can't find an extent at block %d but we want "
                                "to add a written/unwritten extent "
                                "[%d/%d/%llu/%x]\n", inode->i_ino,
                                es->es_lblk, es->es_lblk, es->es_len,
                                ext4_es_pblock(es), ext4_es_status(es));
                }
        }
out:
        ext4_free_ext_path(path);
}

static void ext4_es_insert_extent_ind_check(struct inode *inode,
                                            struct extent_status *es)
{
        struct ext4_map_blocks map;
        int retval;

        /*
         * Here we call ext4_ind_map_blocks to lookup a block mapping because
         * 'Indirect' structure is defined in indirect.c.  So we couldn't
         * access direct/indirect tree from outside.  It is too dirty to define
         * this function in indirect.c file.
         */

        map.m_lblk = es->es_lblk;
        map.m_len = es->es_len;

        retval = ext4_ind_map_blocks(NULL, inode, &map, 0);
        if (retval > 0) {
                if (ext4_es_is_delayed(es) || ext4_es_is_hole(es)) {
                        /*
                         * We want to add a delayed/hole extent but this
                         * block has been allocated.
                         */
                        pr_warn("ES insert assertion failed for inode: %lu "
                                "We can find blocks but we want to add a "
                                "delayed/hole extent [%d/%d/%llu/%x]\n",
                                inode->i_ino, es->es_lblk, es->es_len,
                                ext4_es_pblock(es), ext4_es_status(es));
                        return;
                } else if (ext4_es_is_written(es)) {
                        if (retval != es->es_len) {
                                pr_warn("ES insert assertion failed for "
                                        "inode: %lu retval %d != es_len %d\n",
                                        inode->i_ino, retval, es->es_len);
                                return;
                        }
                        if (map.m_pblk != ext4_es_pblock(es)) {
                                pr_warn("ES insert assertion failed for "
                                        "inode: %lu m_pblk %llu != "
                                        "es_pblk %llu\n",
                                        inode->i_ino, map.m_pblk,
                                        ext4_es_pblock(es));
                                return;
                        }
                } else {
                        /*
                         * We don't need to check unwritten extent because
                         * indirect-based file doesn't have it.
                         */
                        BUG();
                }
        } else if (retval == 0) {
                if (ext4_es_is_written(es)) {
                        pr_warn("ES insert assertion failed for inode: %lu "
                                "We can't find the block but we want to add "
                                "a written extent [%d/%d/%llu/%x]\n",
                                inode->i_ino, es->es_lblk, es->es_len,
                                ext4_es_pblock(es), ext4_es_status(es));
                        return;
                }
        }
}

static inline void ext4_es_insert_extent_check(struct inode *inode,
                                               struct extent_status *es)
{
        /*
         * We don't need to worry about the race condition because
         * caller takes i_data_sem locking.
         */
        BUG_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));
        if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
                ext4_es_insert_extent_ext_check(inode, es);
        else
                ext4_es_insert_extent_ind_check(inode, es);
}
#else
static inline void ext4_es_insert_extent_check(struct inode *inode,
                                               struct extent_status *es)
{
}
#endif

static int __es_insert_extent(struct inode *inode, struct extent_status *newes,
                              struct extent_status *prealloc)
{
        struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
        struct rb_node **p = &tree->root.rb_node;
        struct rb_node *parent = NULL;
        struct extent_status *es;

        while (*p) {
                parent = *p;
                es = rb_entry(parent, struct extent_status, rb_node);

                if (newes->es_lblk < es->es_lblk) {
                        if (ext4_es_can_be_merged(newes, es)) {
                                /*
                                 * Here we can modify es_lblk directly
                                 * because it isn't overlapped.
                                 */
                                es->es_lblk = newes->es_lblk;
                                es->es_len += newes->es_len;
                                if (ext4_es_is_written(es) ||
                                    ext4_es_is_unwritten(es))
                                        ext4_es_store_pblock(es,
                                                             newes->es_pblk);
                                es = ext4_es_try_to_merge_left(inode, es);
                                goto out;
                        }
                        p = &(*p)->rb_left;
                } else if (newes->es_lblk > ext4_es_end(es)) {
                        if (ext4_es_can_be_merged(es, newes)) {
                                es->es_len += newes->es_len;
                                es = ext4_es_try_to_merge_right(inode, es);
                                goto out;
                        }
                        p = &(*p)->rb_right;
                } else {
                        BUG();
                        return -EINVAL;
                }
        }

        if (prealloc)
                es = prealloc;
        else
                es = __es_alloc_extent(false);
        if (!es)
                return -ENOMEM;
        ext4_es_init_extent(inode, es, newes->es_lblk, newes->es_len,
                            newes->es_pblk);

        rb_link_node(&es->rb_node, parent, p);
        rb_insert_color(&es->rb_node, &tree->root);

out:
        tree->cache_es = es;
        return 0;
}

/*
 * ext4_es_insert_extent() adds information to an inode's extent
 * status tree.
 */
void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
                           ext4_lblk_t len, ext4_fsblk_t pblk,
                           unsigned int status)
{
        struct extent_status newes;
        ext4_lblk_t end = lblk + len - 1;
        int err1 = 0, err2 = 0, err3 = 0;
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct extent_status *es1 = NULL;
        struct extent_status *es2 = NULL;
        struct pending_reservation *pr = NULL;
        bool revise_pending = false;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return;

        es_debug("add [%u/%u) %llu %x to extent status tree of inode %lu\n",
                 lblk, len, pblk, status, inode->i_ino);

        if (!len)
                return;

        BUG_ON(end < lblk);

        if ((status & EXTENT_STATUS_DELAYED) &&
            (status & EXTENT_STATUS_WRITTEN)) {
                ext4_warning(inode->i_sb, "Inserting extent [%u/%u] as "
                                " delayed and written which can potentially "
                                " cause data loss.", lblk, len);
                WARN_ON(1);
        }

        newes.es_lblk = lblk;
        newes.es_len = len;
        ext4_es_store_pblock_status(&newes, pblk, status);
        trace_ext4_es_insert_extent(inode, &newes);

        ext4_es_insert_extent_check(inode, &newes);

        revise_pending = sbi->s_cluster_ratio > 1 &&
                         test_opt(inode->i_sb, DELALLOC) &&
                         (status & (EXTENT_STATUS_WRITTEN |
                                    EXTENT_STATUS_UNWRITTEN));
retry:
        if (err1 && !es1)
                es1 = __es_alloc_extent(true);
        if ((err1 || err2) && !es2)
                es2 = __es_alloc_extent(true);
        if ((err1 || err2 || err3) && revise_pending && !pr)
                pr = __alloc_pending(true);
        write_lock(&EXT4_I(inode)->i_es_lock);

        err1 = __es_remove_extent(inode, lblk, end, NULL, es1);
        if (err1 != 0)
                goto error;
        /* Free preallocated extent if it didn't get used. */
        if (es1) {
                if (!es1->es_len)
                        __es_free_extent(es1);
                es1 = NULL;
        }

        err2 = __es_insert_extent(inode, &newes, es2);
        if (err2 == -ENOMEM && !ext4_es_must_keep(&newes))
                err2 = 0;
        if (err2 != 0)
                goto error;
        /* Free preallocated extent if it didn't get used. */
        if (es2) {
                if (!es2->es_len)
                        __es_free_extent(es2);
                es2 = NULL;
        }

        if (revise_pending) {
                err3 = __revise_pending(inode, lblk, len, &pr);
                if (err3 != 0)
                        goto error;
                if (pr) {
                        __free_pending(pr);
                        pr = NULL;
                }
        }
error:
        write_unlock(&EXT4_I(inode)->i_es_lock);
        if (err1 || err2 || err3)
                goto retry;

        ext4_es_print_tree(inode);
        return;
}

/*
 * ext4_es_cache_extent() inserts information into the extent status
 * tree if and only if there isn't information about the range in
 * question already.
 */
void ext4_es_cache_extent(struct inode *inode, ext4_lblk_t lblk,
                          ext4_lblk_t len, ext4_fsblk_t pblk,
                          unsigned int status)
{
        struct extent_status *es;
        struct extent_status newes;
        ext4_lblk_t end = lblk + len - 1;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return;

        newes.es_lblk = lblk;
        newes.es_len = len;
        ext4_es_store_pblock_status(&newes, pblk, status);
        trace_ext4_es_cache_extent(inode, &newes);

        if (!len)
                return;

        BUG_ON(end < lblk);

        write_lock(&EXT4_I(inode)->i_es_lock);

        es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
        if (!es || es->es_lblk > end)
                __es_insert_extent(inode, &newes, NULL);
        write_unlock(&EXT4_I(inode)->i_es_lock);
}

/*
 * ext4_es_lookup_extent() looks up an extent in extent status tree.
 *
 * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.
 *
 * Return: 1 on found, 0 on not
 */
int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
                          ext4_lblk_t *next_lblk,
                          struct extent_status *es)
{
        struct ext4_es_tree *tree;
        struct ext4_es_stats *stats;
        struct extent_status *es1 = NULL;
        struct rb_node *node;
        int found = 0;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return 0;

        trace_ext4_es_lookup_extent_enter(inode, lblk);
        es_debug("lookup extent in block %u\n", lblk);

        tree = &EXT4_I(inode)->i_es_tree;
        read_lock(&EXT4_I(inode)->i_es_lock);

        /* find extent in cache firstly */
        es->es_lblk = es->es_len = es->es_pblk = 0;
        es1 = READ_ONCE(tree->cache_es);
        if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) {
                es_debug("%u cached by [%u/%u)\n",
                         lblk, es1->es_lblk, es1->es_len);
                found = 1;
                goto out;
        }

        node = tree->root.rb_node;
        while (node) {
                es1 = rb_entry(node, struct extent_status, rb_node);
                if (lblk < es1->es_lblk)
                        node = node->rb_left;
                else if (lblk > ext4_es_end(es1))
                        node = node->rb_right;
                else {
                        found = 1;
                        break;
                }
        }

out:
        stats = &EXT4_SB(inode->i_sb)->s_es_stats;
        if (found) {
                BUG_ON(!es1);
                es->es_lblk = es1->es_lblk;
                es->es_len = es1->es_len;
                es->es_pblk = es1->es_pblk;
                if (!ext4_es_is_referenced(es1))
                        ext4_es_set_referenced(es1);
                percpu_counter_inc(&stats->es_stats_cache_hits);
                if (next_lblk) {
                        node = rb_next(&es1->rb_node);
                        if (node) {
                                es1 = rb_entry(node, struct extent_status,
                                               rb_node);
                                *next_lblk = es1->es_lblk;
                        } else
                                *next_lblk = 0;
                }
        } else {
                percpu_counter_inc(&stats->es_stats_cache_misses);
        }

        read_unlock(&EXT4_I(inode)->i_es_lock);

        trace_ext4_es_lookup_extent_exit(inode, es, found);
        return found;
}

struct rsvd_count {
        int ndelonly;
        bool first_do_lblk_found;
        ext4_lblk_t first_do_lblk;
        ext4_lblk_t last_do_lblk;
        struct extent_status *left_es;
        bool partial;
        ext4_lblk_t lclu;
};

/*
 * init_rsvd - initialize reserved count data before removing block range
 *             in file from extent status tree
 *
 * @inode - file containing range
 * @lblk - first block in range
 * @es - pointer to first extent in range
 * @rc - pointer to reserved count data
 *
 * Assumes es is not NULL
 */
static void init_rsvd(struct inode *inode, ext4_lblk_t lblk,
                      struct extent_status *es, struct rsvd_count *rc)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct rb_node *node;

        rc->ndelonly = 0;

        /*
         * for bigalloc, note the first delonly block in the range has not
         * been found, record the extent containing the block to the left of
         * the region to be removed, if any, and note that there's no partial
         * cluster to track
         */
        if (sbi->s_cluster_ratio > 1) {
                rc->first_do_lblk_found = false;
                if (lblk > es->es_lblk) {
                        rc->left_es = es;
                } else {
                        node = rb_prev(&es->rb_node);
                        rc->left_es = node ? rb_entry(node,
                                                      struct extent_status,
                                                      rb_node) : NULL;
                }
                rc->partial = false;
        }
}

/*
 * count_rsvd - count the clusters containing delayed and not unwritten
 *              (delonly) blocks in a range within an extent and add to
 *              the running tally in rsvd_count
 *
 * @inode - file containing extent
 * @lblk - first block in range
 * @len - length of range in blocks
 * @es - pointer to extent containing clusters to be counted
 * @rc - pointer to reserved count data
 *
 * Tracks partial clusters found at the beginning and end of extents so
 * they aren't overcounted when they span adjacent extents
 */
static void count_rsvd(struct inode *inode, ext4_lblk_t lblk, long len,
                       struct extent_status *es, struct rsvd_count *rc)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        ext4_lblk_t i, end, nclu;

        if (!ext4_es_is_delonly(es))
                return;

        WARN_ON(len <= 0);

        if (sbi->s_cluster_ratio == 1) {
                rc->ndelonly += (int) len;
                return;
        }

        /* bigalloc */

        i = (lblk < es->es_lblk) ? es->es_lblk : lblk;
        end = lblk + (ext4_lblk_t) len - 1;
        end = (end > ext4_es_end(es)) ? ext4_es_end(es) : end;

        /* record the first block of the first delonly extent seen */
        if (!rc->first_do_lblk_found) {
                rc->first_do_lblk = i;
                rc->first_do_lblk_found = true;
        }

        /* update the last lblk in the region seen so far */
        rc->last_do_lblk = end;

        /*
         * if we're tracking a partial cluster and the current extent
         * doesn't start with it, count it and stop tracking
         */
        if (rc->partial && (rc->lclu != EXT4_B2C(sbi, i))) {
                rc->ndelonly++;
                rc->partial = false;
        }

        /*
         * if the first cluster doesn't start on a cluster boundary but
         * ends on one, count it
         */
        if (EXT4_LBLK_COFF(sbi, i) != 0) {
                if (end >= EXT4_LBLK_CFILL(sbi, i)) {
                        rc->ndelonly++;
                        rc->partial = false;
                        i = EXT4_LBLK_CFILL(sbi, i) + 1;
                }
        }

        /*
         * if the current cluster starts on a cluster boundary, count the
         * number of whole delonly clusters in the extent
         */
        if ((i + sbi->s_cluster_ratio - 1) <= end) {
                nclu = (end - i + 1) >> sbi->s_cluster_bits;
                rc->ndelonly += nclu;
                i += nclu << sbi->s_cluster_bits;
        }

        /*
         * start tracking a partial cluster if there's a partial at the end
         * of the current extent and we're not already tracking one
         */
        if (!rc->partial && i <= end) {
                rc->partial = true;
                rc->lclu = EXT4_B2C(sbi, i);
        }
}

/*
 * __pr_tree_search - search for a pending cluster reservation
 *
 * @root - root of pending reservation tree
 * @lclu - logical cluster to search for
 *
 * Returns the pending reservation for the cluster identified by @lclu
 * if found.  If not, returns a reservation for the next cluster if any,
 * and if not, returns NULL.
 */
static struct pending_reservation *__pr_tree_search(struct rb_root *root,
                                                    ext4_lblk_t lclu)
{
        struct rb_node *node = root->rb_node;
        struct pending_reservation *pr = NULL;

        while (node) {
                pr = rb_entry(node, struct pending_reservation, rb_node);
                if (lclu < pr->lclu)
                        node = node->rb_left;
                else if (lclu > pr->lclu)
                        node = node->rb_right;
                else
                        return pr;
        }
        if (pr && lclu < pr->lclu)
                return pr;
        if (pr && lclu > pr->lclu) {
                node = rb_next(&pr->rb_node);
                return node ? rb_entry(node, struct pending_reservation,
                                       rb_node) : NULL;
        }
        return NULL;
}

/*
 * get_rsvd - calculates and returns the number of cluster reservations to be
 *            released when removing a block range from the extent status tree
 *            and releases any pending reservations within the range
 *
 * @inode - file containing block range
 * @end - last block in range
 * @right_es - pointer to extent containing next block beyond end or NULL
 * @rc - pointer to reserved count data
 *
 * The number of reservations to be released is equal to the number of
 * clusters containing delayed and not unwritten (delonly) blocks within
 * the range, minus the number of clusters still containing delonly blocks
 * at the ends of the range, and minus the number of pending reservations
 * within the range.
 */
static unsigned int get_rsvd(struct inode *inode, ext4_lblk_t end,
                             struct extent_status *right_es,
                             struct rsvd_count *rc)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct pending_reservation *pr;
        struct ext4_pending_tree *tree = &EXT4_I(inode)->i_pending_tree;
        struct rb_node *node;
        ext4_lblk_t first_lclu, last_lclu;
        bool left_delonly, right_delonly, count_pending;
        struct extent_status *es;

        if (sbi->s_cluster_ratio > 1) {
                /* count any remaining partial cluster */
                if (rc->partial)
                        rc->ndelonly++;

                if (rc->ndelonly == 0)
                        return 0;

                first_lclu = EXT4_B2C(sbi, rc->first_do_lblk);
                last_lclu = EXT4_B2C(sbi, rc->last_do_lblk);

                /*
                 * decrease the delonly count by the number of clusters at the
                 * ends of the range that still contain delonly blocks -
                 * these clusters still need to be reserved
                 */
                left_delonly = right_delonly = false;

                es = rc->left_es;
                while (es && ext4_es_end(es) >=
                       EXT4_LBLK_CMASK(sbi, rc->first_do_lblk)) {
                        if (ext4_es_is_delonly(es)) {
                                rc->ndelonly--;
                                left_delonly = true;
                                break;
                        }
                        node = rb_prev(&es->rb_node);
                        if (!node)
                                break;
                        es = rb_entry(node, struct extent_status, rb_node);
                }
                if (right_es && (!left_delonly || first_lclu != last_lclu)) {
                        if (end < ext4_es_end(right_es)) {
                                es = right_es;
                        } else {
                                node = rb_next(&right_es->rb_node);
                                es = node ? rb_entry(node, struct extent_status,
                                                     rb_node) : NULL;
                        }
                        while (es && es->es_lblk <=
                               EXT4_LBLK_CFILL(sbi, rc->last_do_lblk)) {
                                if (ext4_es_is_delonly(es)) {
                                        rc->ndelonly--;
                                        right_delonly = true;
                                        break;
                                }
                                node = rb_next(&es->rb_node);
                                if (!node)
                                        break;
                                es = rb_entry(node, struct extent_status,
                                              rb_node);
                        }
                }

                /*
                 * Determine the block range that should be searched for
                 * pending reservations, if any.  Clusters on the ends of the
                 * original removed range containing delonly blocks are
                 * excluded.  They've already been accounted for and it's not
                 * possible to determine if an associated pending reservation
                 * should be released with the information available in the
                 * extents status tree.
                 */
                if (first_lclu == last_lclu) {
                        if (left_delonly | right_delonly)
                                count_pending = false;
                        else
                                count_pending = true;
                } else {
                        if (left_delonly)
                                first_lclu++;
                        if (right_delonly)
                                last_lclu--;
                        if (first_lclu <= last_lclu)
                                count_pending = true;
                        else
                                count_pending = false;
                }

                /*
                 * a pending reservation found between first_lclu and last_lclu
                 * represents an allocated cluster that contained at least one
                 * delonly block, so the delonly total must be reduced by one
                 * for each pending reservation found and released
                 */
                if (count_pending) {
                        pr = __pr_tree_search(&tree->root, first_lclu);
                        while (pr && pr->lclu <= last_lclu) {
                                rc->ndelonly--;
                                node = rb_next(&pr->rb_node);
                                rb_erase(&pr->rb_node, &tree->root);
                                __free_pending(pr);
                                if (!node)
                                        break;
                                pr = rb_entry(node, struct pending_reservation,
                                              rb_node);
                        }
                }
        }
        return rc->ndelonly;
}


/*
 * __es_remove_extent - removes block range from extent status tree
 *
 * @inode - file containing range
 * @lblk - first block in range
 * @end - last block in range
 * @reserved - number of cluster reservations released
 * @prealloc - pre-allocated es to avoid memory allocation failures
 *
 * If @reserved is not NULL and delayed allocation is enabled, counts
 * block/cluster reservations freed by removing range and if bigalloc
 * enabled cancels pending reservations as needed. Returns 0 on success,
 * error code on failure.
 */
static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
                              ext4_lblk_t end, int *reserved,
                              struct extent_status *prealloc)
{
        struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
        struct rb_node *node;
        struct extent_status *es;
        struct extent_status orig_es;
        ext4_lblk_t len1, len2;
        ext4_fsblk_t block;
        int err = 0;
        bool count_reserved = true;
        struct rsvd_count rc;

        if (reserved == NULL || !test_opt(inode->i_sb, DELALLOC))
                count_reserved = false;

        es = __es_tree_search(&tree->root, lblk);
        if (!es)
                goto out;
        if (es->es_lblk > end)
                goto out;

        /* Simply invalidate cache_es. */
        tree->cache_es = NULL;
        if (count_reserved)
                init_rsvd(inode, lblk, es, &rc);

        orig_es.es_lblk = es->es_lblk;
        orig_es.es_len = es->es_len;
        orig_es.es_pblk = es->es_pblk;

        len1 = lblk > es->es_lblk ? lblk - es->es_lblk : 0;
        len2 = ext4_es_end(es) > end ? ext4_es_end(es) - end : 0;
        if (len1 > 0)
                es->es_len = len1;
        if (len2 > 0) {
                if (len1 > 0) {
                        struct extent_status newes;

                        newes.es_lblk = end + 1;
                        newes.es_len = len2;
                        block = 0x7FDEADBEEFULL;
                        if (ext4_es_is_written(&orig_es) ||
                            ext4_es_is_unwritten(&orig_es))
                                block = ext4_es_pblock(&orig_es) +
                                        orig_es.es_len - len2;
                        ext4_es_store_pblock_status(&newes, block,
                                                    ext4_es_status(&orig_es));
                        err = __es_insert_extent(inode, &newes, prealloc);
                        if (err) {
                                if (!ext4_es_must_keep(&newes))
                                        return 0;

                                es->es_lblk = orig_es.es_lblk;
                                es->es_len = orig_es.es_len;
                                goto out;
                        }
                } else {
                        es->es_lblk = end + 1;
                        es->es_len = len2;
                        if (ext4_es_is_written(es) ||
                            ext4_es_is_unwritten(es)) {
                                block = orig_es.es_pblk + orig_es.es_len - len2;
                                ext4_es_store_pblock(es, block);
                        }
                }
                if (count_reserved)
                        count_rsvd(inode, orig_es.es_lblk + len1,
                                   orig_es.es_len - len1 - len2, &orig_es, &rc);
                goto out_get_reserved;
        }

        if (len1 > 0) {
                if (count_reserved)
                        count_rsvd(inode, lblk, orig_es.es_len - len1,
                                   &orig_es, &rc);
                node = rb_next(&es->rb_node);
                if (node)
                        es = rb_entry(node, struct extent_status, rb_node);
                else
                        es = NULL;
        }

        while (es && ext4_es_end(es) <= end) {
                if (count_reserved)
                        count_rsvd(inode, es->es_lblk, es->es_len, es, &rc);
                node = rb_next(&es->rb_node);
                rb_erase(&es->rb_node, &tree->root);
                ext4_es_free_extent(inode, es);
                if (!node) {
                        es = NULL;
                        break;
                }
                es = rb_entry(node, struct extent_status, rb_node);
        }

        if (es && es->es_lblk < end + 1) {
                ext4_lblk_t orig_len = es->es_len;

                len1 = ext4_es_end(es) - end;
                if (count_reserved)
                        count_rsvd(inode, es->es_lblk, orig_len - len1,
                                   es, &rc);
                es->es_lblk = end + 1;
                es->es_len = len1;
                if (ext4_es_is_written(es) || ext4_es_is_unwritten(es)) {
                        block = es->es_pblk + orig_len - len1;
                        ext4_es_store_pblock(es, block);
                }
        }

out_get_reserved:
        if (count_reserved)
                *reserved = get_rsvd(inode, end, es, &rc);
out:
        return err;
}

/*
 * ext4_es_remove_extent - removes block range from extent status tree
 *
 * @inode - file containing range
 * @lblk - first block in range
 * @len - number of blocks to remove
 *
 * Reduces block/cluster reservation count and for bigalloc cancels pending
 * reservations as needed.
 */
void ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
                           ext4_lblk_t len)
{
        ext4_lblk_t end;
        int err = 0;
        int reserved = 0;
        struct extent_status *es = NULL;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return;

        trace_ext4_es_remove_extent(inode, lblk, len);
        es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
                 lblk, len, inode->i_ino);

        if (!len)
                return;

        end = lblk + len - 1;
        BUG_ON(end < lblk);

retry:
        if (err && !es)
                es = __es_alloc_extent(true);
        /*
         * ext4_clear_inode() depends on us taking i_es_lock unconditionally
         * so that we are sure __es_shrink() is done with the inode before it
         * is reclaimed.
         */
        write_lock(&EXT4_I(inode)->i_es_lock);
        err = __es_remove_extent(inode, lblk, end, &reserved, es);
        /* Free preallocated extent if it didn't get used. */
        if (es) {
                if (!es->es_len)
                        __es_free_extent(es);
                es = NULL;
        }
        write_unlock(&EXT4_I(inode)->i_es_lock);
        if (err)
                goto retry;

        ext4_es_print_tree(inode);
        ext4_da_release_space(inode, reserved);
        return;
}

static int __es_shrink(struct ext4_sb_info *sbi, int nr_to_scan,
                       struct ext4_inode_info *locked_ei)
{
        struct ext4_inode_info *ei;
        struct ext4_es_stats *es_stats;
        ktime_t start_time;
        u64 scan_time;
        int nr_to_walk;
        int nr_shrunk = 0;
        int retried = 0, nr_skipped = 0;

        es_stats = &sbi->s_es_stats;
        start_time = ktime_get();

retry:
        spin_lock(&sbi->s_es_lock);
        nr_to_walk = sbi->s_es_nr_inode;
        while (nr_to_walk-- > 0) {
                if (list_empty(&sbi->s_es_list)) {
                        spin_unlock(&sbi->s_es_lock);
                        goto out;
                }
                ei = list_first_entry(&sbi->s_es_list, struct ext4_inode_info,
                                      i_es_list);
                /* Move the inode to the tail */
                list_move_tail(&ei->i_es_list, &sbi->s_es_list);

                /*
                 * Normally we try hard to avoid shrinking precached inodes,
                 * but we will as a last resort.
                 */
                if (!retried && ext4_test_inode_state(&ei->vfs_inode,
                                                EXT4_STATE_EXT_PRECACHED)) {
                        nr_skipped++;
                        continue;
                }

                if (ei == locked_ei || !write_trylock(&ei->i_es_lock)) {
                        nr_skipped++;
                        continue;
                }
                /*
                 * Now we hold i_es_lock which protects us from inode reclaim
                 * freeing inode under us
                 */
                spin_unlock(&sbi->s_es_lock);

                nr_shrunk += es_reclaim_extents(ei, &nr_to_scan);
                write_unlock(&ei->i_es_lock);

                if (nr_to_scan <= 0)
                        goto out;
                spin_lock(&sbi->s_es_lock);
        }
        spin_unlock(&sbi->s_es_lock);

        /*
         * If we skipped any inodes, and we weren't able to make any
         * forward progress, try again to scan precached inodes.
         */
        if ((nr_shrunk == 0) && nr_skipped && !retried) {
                retried++;
                goto retry;
        }

        if (locked_ei && nr_shrunk == 0)
                nr_shrunk = es_reclaim_extents(locked_ei, &nr_to_scan);

out:
        scan_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
        if (likely(es_stats->es_stats_scan_time))
                es_stats->es_stats_scan_time = (scan_time +
                                es_stats->es_stats_scan_time*3) / 4;
        else
                es_stats->es_stats_scan_time = scan_time;
        if (scan_time > es_stats->es_stats_max_scan_time)
                es_stats->es_stats_max_scan_time = scan_time;
        if (likely(es_stats->es_stats_shrunk))
                es_stats->es_stats_shrunk = (nr_shrunk +
                                es_stats->es_stats_shrunk*3) / 4;
        else
                es_stats->es_stats_shrunk = nr_shrunk;

        trace_ext4_es_shrink(sbi->s_sb, nr_shrunk, scan_time,
                             nr_skipped, retried);
        return nr_shrunk;
}

static unsigned long ext4_es_count(struct shrinker *shrink,
                                   struct shrink_control *sc)
{
        unsigned long nr;
        struct ext4_sb_info *sbi;

        sbi = shrink->private_data;
        nr = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
        trace_ext4_es_shrink_count(sbi->s_sb, sc->nr_to_scan, nr);
        return nr;
}

static unsigned long ext4_es_scan(struct shrinker *shrink,
                                  struct shrink_control *sc)
{
        struct ext4_sb_info *sbi = shrink->private_data;
        int nr_to_scan = sc->nr_to_scan;
        int ret, nr_shrunk;

        ret = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
        trace_ext4_es_shrink_scan_enter(sbi->s_sb, nr_to_scan, ret);

        nr_shrunk = __es_shrink(sbi, nr_to_scan, NULL);

        ret = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
        trace_ext4_es_shrink_scan_exit(sbi->s_sb, nr_shrunk, ret);
        return nr_shrunk;
}

int ext4_seq_es_shrinker_info_show(struct seq_file *seq, void *v)
{
        struct ext4_sb_info *sbi = EXT4_SB((struct super_block *) seq->private);
        struct ext4_es_stats *es_stats = &sbi->s_es_stats;
        struct ext4_inode_info *ei, *max = NULL;
        unsigned int inode_cnt = 0;

        if (v != SEQ_START_TOKEN)
                return 0;

        /* here we just find an inode that has the max nr. of objects */
        spin_lock(&sbi->s_es_lock);
        list_for_each_entry(ei, &sbi->s_es_list, i_es_list) {
                inode_cnt++;
                if (max && max->i_es_all_nr < ei->i_es_all_nr)
                        max = ei;
                else if (!max)
                        max = ei;
        }
        spin_unlock(&sbi->s_es_lock);

        seq_printf(seq, "stats:\n  %lld objects\n  %lld reclaimable objects\n",
                   percpu_counter_sum_positive(&es_stats->es_stats_all_cnt),
                   percpu_counter_sum_positive(&es_stats->es_stats_shk_cnt));
        seq_printf(seq, "  %lld/%lld cache hits/misses\n",
                   percpu_counter_sum_positive(&es_stats->es_stats_cache_hits),
                   percpu_counter_sum_positive(&es_stats->es_stats_cache_misses));
        if (inode_cnt)
                seq_printf(seq, "  %d inodes on list\n", inode_cnt);

        seq_printf(seq, "average:\n  %llu us scan time\n",
            div_u64(es_stats->es_stats_scan_time, 1000));
        seq_printf(seq, "  %lu shrunk objects\n", es_stats->es_stats_shrunk);
        if (inode_cnt)
                seq_printf(seq,
                    "maximum:\n  %lu inode (%u objects, %u reclaimable)\n"
                    "  %llu us max scan time\n",
                    max->vfs_inode.i_ino, max->i_es_all_nr, max->i_es_shk_nr,
                    div_u64(es_stats->es_stats_max_scan_time, 1000));

        return 0;
}

int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
{
        int err;

        /* Make sure we have enough bits for physical block number */
        BUILD_BUG_ON(ES_SHIFT < 48);
        INIT_LIST_HEAD(&sbi->s_es_list);
        sbi->s_es_nr_inode = 0;
        spin_lock_init(&sbi->s_es_lock);
        sbi->s_es_stats.es_stats_shrunk = 0;
        err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_hits, 0,
                                  GFP_KERNEL);
        if (err)
                return err;
        err = percpu_counter_init(&sbi->s_es_stats.es_stats_cache_misses, 0,
                                  GFP_KERNEL);
        if (err)
                goto err1;
        sbi->s_es_stats.es_stats_scan_time = 0;
        sbi->s_es_stats.es_stats_max_scan_time = 0;
        err = percpu_counter_init(&sbi->s_es_stats.es_stats_all_cnt, 0, GFP_KERNEL);
        if (err)
                goto err2;
        err = percpu_counter_init(&sbi->s_es_stats.es_stats_shk_cnt, 0, GFP_KERNEL);
        if (err)
                goto err3;

        sbi->s_es_shrinker = shrinker_alloc(0, "ext4-es:%s", sbi->s_sb->s_id);
        if (!sbi->s_es_shrinker) {
                err = -ENOMEM;
                goto err4;
        }

        sbi->s_es_shrinker->scan_objects = ext4_es_scan;
        sbi->s_es_shrinker->count_objects = ext4_es_count;
        sbi->s_es_shrinker->private_data = sbi;

        shrinker_register(sbi->s_es_shrinker);

        return 0;
err4:
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
err3:
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
err2:
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_misses);
err1:
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_hits);
        return err;
}

void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi)
{
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_hits);
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_misses);
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
        percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
        shrinker_free(sbi->s_es_shrinker);
}

/*
 * Shrink extents in given inode from ei->i_es_shrink_lblk till end. Scan at
 * most *nr_to_scan extents, update *nr_to_scan accordingly.
 *
 * Return 0 if we hit end of tree / interval, 1 if we exhausted nr_to_scan.
 * Increment *nr_shrunk by the number of reclaimed extents. Also update
 * ei->i_es_shrink_lblk to where we should continue scanning.
 */
static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,
                                 int *nr_to_scan, int *nr_shrunk)
{
        struct inode *inode = &ei->vfs_inode;
        struct ext4_es_tree *tree = &ei->i_es_tree;
        struct extent_status *es;
        struct rb_node *node;

        es = __es_tree_search(&tree->root, ei->i_es_shrink_lblk);
        if (!es)
                goto out_wrap;

        while (*nr_to_scan > 0) {
                if (es->es_lblk > end) {
                        ei->i_es_shrink_lblk = end + 1;
                        return 0;
                }

                (*nr_to_scan)--;
                node = rb_next(&es->rb_node);

                if (ext4_es_must_keep(es))
                        goto next;
                if (ext4_es_is_referenced(es)) {
                        ext4_es_clear_referenced(es);
                        goto next;
                }

                rb_erase(&es->rb_node, &tree->root);
                ext4_es_free_extent(inode, es);
                (*nr_shrunk)++;
next:
                if (!node)
                        goto out_wrap;
                es = rb_entry(node, struct extent_status, rb_node);
        }
        ei->i_es_shrink_lblk = es->es_lblk;
        return 1;
out_wrap:
        ei->i_es_shrink_lblk = 0;
        return 0;
}

static int es_reclaim_extents(struct ext4_inode_info *ei, int *nr_to_scan)
{
        struct inode *inode = &ei->vfs_inode;
        int nr_shrunk = 0;
        ext4_lblk_t start = ei->i_es_shrink_lblk;
        static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
                                      DEFAULT_RATELIMIT_BURST);

        if (ei->i_es_shk_nr == 0)
                return 0;

        if (ext4_test_inode_state(inode, EXT4_STATE_EXT_PRECACHED) &&
            __ratelimit(&_rs))
                ext4_warning(inode->i_sb, "forced shrink of precached extents");

        if (!es_do_reclaim_extents(ei, EXT_MAX_BLOCKS, nr_to_scan, &nr_shrunk) &&
            start != 0)
                es_do_reclaim_extents(ei, start - 1, nr_to_scan, &nr_shrunk);

        ei->i_es_tree.cache_es = NULL;
        return nr_shrunk;
}

/*
 * Called to support EXT4_IOC_CLEAR_ES_CACHE.  We can only remove
 * discretionary entries from the extent status cache.  (Some entries
 * must be present for proper operations.)
 */
void ext4_clear_inode_es(struct inode *inode)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct extent_status *es;
        struct ext4_es_tree *tree;
        struct rb_node *node;

        write_lock(&ei->i_es_lock);
        tree = &EXT4_I(inode)->i_es_tree;
        tree->cache_es = NULL;
        node = rb_first(&tree->root);
        while (node) {
                es = rb_entry(node, struct extent_status, rb_node);
                node = rb_next(node);
                if (!ext4_es_must_keep(es)) {
                        rb_erase(&es->rb_node, &tree->root);
                        ext4_es_free_extent(inode, es);
                }
        }
        ext4_clear_inode_state(inode, EXT4_STATE_EXT_PRECACHED);
        write_unlock(&ei->i_es_lock);
}

#ifdef ES_DEBUG__
static void ext4_print_pending_tree(struct inode *inode)
{
        struct ext4_pending_tree *tree;
        struct rb_node *node;
        struct pending_reservation *pr;

        printk(KERN_DEBUG "pending reservations for inode %lu:", inode->i_ino);
        tree = &EXT4_I(inode)->i_pending_tree;
        node = rb_first(&tree->root);
        while (node) {
                pr = rb_entry(node, struct pending_reservation, rb_node);
                printk(KERN_DEBUG " %u", pr->lclu);
                node = rb_next(node);
        }
        printk(KERN_DEBUG "\n");
}
#else
#define ext4_print_pending_tree(inode)
#endif

int __init ext4_init_pending(void)
{
        ext4_pending_cachep = KMEM_CACHE(pending_reservation, SLAB_RECLAIM_ACCOUNT);
        if (ext4_pending_cachep == NULL)
                return -ENOMEM;
        return 0;
}

void ext4_exit_pending(void)
{
        kmem_cache_destroy(ext4_pending_cachep);
}

void ext4_init_pending_tree(struct ext4_pending_tree *tree)
{
        tree->root = RB_ROOT;
}

/*
 * __get_pending - retrieve a pointer to a pending reservation
 *
 * @inode - file containing the pending cluster reservation
 * @lclu - logical cluster of interest
 *
 * Returns a pointer to a pending reservation if it's a member of
 * the set, and NULL if not.  Must be called holding i_es_lock.
 */
static struct pending_reservation *__get_pending(struct inode *inode,
                                                 ext4_lblk_t lclu)
{
        struct ext4_pending_tree *tree;
        struct rb_node *node;
        struct pending_reservation *pr = NULL;

        tree = &EXT4_I(inode)->i_pending_tree;
        node = (&tree->root)->rb_node;

        while (node) {
                pr = rb_entry(node, struct pending_reservation, rb_node);
                if (lclu < pr->lclu)
                        node = node->rb_left;
                else if (lclu > pr->lclu)
                        node = node->rb_right;
                else if (lclu == pr->lclu)
                        return pr;
        }
        return NULL;
}

/*
 * __insert_pending - adds a pending cluster reservation to the set of
 *                    pending reservations
 *
 * @inode - file containing the cluster
 * @lblk - logical block in the cluster to be added
 * @prealloc - preallocated pending entry
 *
 * Returns 0 on successful insertion and -ENOMEM on failure.  If the
 * pending reservation is already in the set, returns successfully.
 */
static int __insert_pending(struct inode *inode, ext4_lblk_t lblk,
                            struct pending_reservation **prealloc)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_pending_tree *tree = &EXT4_I(inode)->i_pending_tree;
        struct rb_node **p = &tree->root.rb_node;
        struct rb_node *parent = NULL;
        struct pending_reservation *pr;
        ext4_lblk_t lclu;
        int ret = 0;

        lclu = EXT4_B2C(sbi, lblk);
        /* search to find parent for insertion */
        while (*p) {
                parent = *p;
                pr = rb_entry(parent, struct pending_reservation, rb_node);

                if (lclu < pr->lclu) {
                        p = &(*p)->rb_left;
                } else if (lclu > pr->lclu) {
                        p = &(*p)->rb_right;
                } else {
                        /* pending reservation already inserted */
                        goto out;
                }
        }

        if (likely(*prealloc == NULL)) {
                pr = __alloc_pending(false);
                if (!pr) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else {
                pr = *prealloc;
                *prealloc = NULL;
        }
        pr->lclu = lclu;

        rb_link_node(&pr->rb_node, parent, p);
        rb_insert_color(&pr->rb_node, &tree->root);

out:
        return ret;
}

/*
 * __remove_pending - removes a pending cluster reservation from the set
 *                    of pending reservations
 *
 * @inode - file containing the cluster
 * @lblk - logical block in the pending cluster reservation to be removed
 *
 * Returns successfully if pending reservation is not a member of the set.
 */
static void __remove_pending(struct inode *inode, ext4_lblk_t lblk)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct pending_reservation *pr;
        struct ext4_pending_tree *tree;

        pr = __get_pending(inode, EXT4_B2C(sbi, lblk));
        if (pr != NULL) {
                tree = &EXT4_I(inode)->i_pending_tree;
                rb_erase(&pr->rb_node, &tree->root);
                __free_pending(pr);
        }
}

/*
 * ext4_remove_pending - removes a pending cluster reservation from the set
 *                       of pending reservations
 *
 * @inode - file containing the cluster
 * @lblk - logical block in the pending cluster reservation to be removed
 *
 * Locking for external use of __remove_pending.
 */
void ext4_remove_pending(struct inode *inode, ext4_lblk_t lblk)
{
        struct ext4_inode_info *ei = EXT4_I(inode);

        write_lock(&ei->i_es_lock);
        __remove_pending(inode, lblk);
        write_unlock(&ei->i_es_lock);
}

/*
 * ext4_is_pending - determine whether a cluster has a pending reservation
 *                   on it
 *
 * @inode - file containing the cluster
 * @lblk - logical block in the cluster
 *
 * Returns true if there's a pending reservation for the cluster in the
 * set of pending reservations, and false if not.
 */
bool ext4_is_pending(struct inode *inode, ext4_lblk_t lblk)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_inode_info *ei = EXT4_I(inode);
        bool ret;

        read_lock(&ei->i_es_lock);
        ret = (bool)(__get_pending(inode, EXT4_B2C(sbi, lblk)) != NULL);
        read_unlock(&ei->i_es_lock);

        return ret;
}

/*
 * ext4_es_insert_delayed_block - adds a delayed block to the extents status
 *                                tree, adding a pending reservation where
 *                                needed
 *
 * @inode - file containing the newly added block
 * @lblk - logical block to be added
 * @allocated - indicates whether a physical cluster has been allocated for
 *              the logical cluster that contains the block
 */
void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
                                  bool allocated)
{
        struct extent_status newes;
        int err1 = 0, err2 = 0, err3 = 0;
        struct extent_status *es1 = NULL;
        struct extent_status *es2 = NULL;
        struct pending_reservation *pr = NULL;

        if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
                return;

        es_debug("add [%u/1) delayed to extent status tree of inode %lu\n",
                 lblk, inode->i_ino);

        newes.es_lblk = lblk;
        newes.es_len = 1;
        ext4_es_store_pblock_status(&newes, ~0, EXTENT_STATUS_DELAYED);
        trace_ext4_es_insert_delayed_block(inode, &newes, allocated);

        ext4_es_insert_extent_check(inode, &newes);

retry:
        if (err1 && !es1)
                es1 = __es_alloc_extent(true);
        if ((err1 || err2) && !es2)
                es2 = __es_alloc_extent(true);
        if ((err1 || err2 || err3) && allocated && !pr)
                pr = __alloc_pending(true);
        write_lock(&EXT4_I(inode)->i_es_lock);

        err1 = __es_remove_extent(inode, lblk, lblk, NULL, es1);
        if (err1 != 0)
                goto error;
        /* Free preallocated extent if it didn't get used. */
        if (es1) {
                if (!es1->es_len)
                        __es_free_extent(es1);
                es1 = NULL;
        }

        err2 = __es_insert_extent(inode, &newes, es2);
        if (err2 != 0)
                goto error;
        /* Free preallocated extent if it didn't get used. */
        if (es2) {
                if (!es2->es_len)
                        __es_free_extent(es2);
                es2 = NULL;
        }

        if (allocated) {
                err3 = __insert_pending(inode, lblk, &pr);
                if (err3 != 0)
                        goto error;
                if (pr) {
                        __free_pending(pr);
                        pr = NULL;
                }
        }
error:
        write_unlock(&EXT4_I(inode)->i_es_lock);
        if (err1 || err2 || err3)
                goto retry;

        ext4_es_print_tree(inode);
        ext4_print_pending_tree(inode);
        return;
}

/*
 * __es_delayed_clu - count number of clusters containing blocks that
 *                    are delayed only
 *
 * @inode - file containing block range
 * @start - logical block defining start of range
 * @end - logical block defining end of range
 *
 * Returns the number of clusters containing only delayed (not delayed
 * and unwritten) blocks in the range specified by @start and @end.  Any
 * cluster or part of a cluster within the range and containing a delayed
 * and not unwritten block within the range is counted as a whole cluster.
 */
static unsigned int __es_delayed_clu(struct inode *inode, ext4_lblk_t start,
                                     ext4_lblk_t end)
{
        struct ext4_es_tree *tree = &EXT4_I(inode)->i_es_tree;
        struct extent_status *es;
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct rb_node *node;
        ext4_lblk_t first_lclu, last_lclu;
        unsigned long long last_counted_lclu;
        unsigned int n = 0;

        /* guaranteed to be unequal to any ext4_lblk_t value */
        last_counted_lclu = ~0ULL;

        es = __es_tree_search(&tree->root, start);

        while (es && (es->es_lblk <= end)) {
                if (ext4_es_is_delonly(es)) {
                        if (es->es_lblk <= start)
                                first_lclu = EXT4_B2C(sbi, start);
                        else
                                first_lclu = EXT4_B2C(sbi, es->es_lblk);

                        if (ext4_es_end(es) >= end)
                                last_lclu = EXT4_B2C(sbi, end);
                        else
                                last_lclu = EXT4_B2C(sbi, ext4_es_end(es));

                        if (first_lclu == last_counted_lclu)
                                n += last_lclu - first_lclu;
                        else
                                n += last_lclu - first_lclu + 1;
                        last_counted_lclu = last_lclu;
                }
                node = rb_next(&es->rb_node);
                if (!node)
                        break;
                es = rb_entry(node, struct extent_status, rb_node);
        }

        return n;
}

/*
 * ext4_es_delayed_clu - count number of clusters containing blocks that
 *                       are both delayed and unwritten
 *
 * @inode - file containing block range
 * @lblk - logical block defining start of range
 * @len - number of blocks in range
 *
 * Locking for external use of __es_delayed_clu().
 */
unsigned int ext4_es_delayed_clu(struct inode *inode, ext4_lblk_t lblk,
                                 ext4_lblk_t len)
{
        struct ext4_inode_info *ei = EXT4_I(inode);
        ext4_lblk_t end;
        unsigned int n;

        if (len == 0)
                return 0;

        end = lblk + len - 1;
        WARN_ON(end < lblk);

        read_lock(&ei->i_es_lock);

        n = __es_delayed_clu(inode, lblk, end);

        read_unlock(&ei->i_es_lock);

        return n;
}

/*
 * __revise_pending - makes, cancels, or leaves unchanged pending cluster
 *                    reservations for a specified block range depending
 *                    upon the presence or absence of delayed blocks
 *                    outside the range within clusters at the ends of the
 *                    range
 *
 * @inode - file containing the range
 * @lblk - logical block defining the start of range
 * @len  - length of range in blocks
 * @prealloc - preallocated pending entry
 *
 * Used after a newly allocated extent is added to the extents status tree.
 * Requires that the extents in the range have either written or unwritten
 * status.  Must be called while holding i_es_lock.
 */
static int __revise_pending(struct inode *inode, ext4_lblk_t lblk,
                            ext4_lblk_t len,
                            struct pending_reservation **prealloc)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        ext4_lblk_t end = lblk + len - 1;
        ext4_lblk_t first, last;
        bool f_del = false, l_del = false;
        int ret = 0;

        if (len == 0)
                return 0;

        /*
         * Two cases - block range within single cluster and block range
         * spanning two or more clusters.  Note that a cluster belonging
         * to a range starting and/or ending on a cluster boundary is treated
         * as if it does not contain a delayed extent.  The new range may
         * have allocated space for previously delayed blocks out to the
         * cluster boundary, requiring that any pre-existing pending
         * reservation be canceled.  Because this code only looks at blocks
         * outside the range, it should revise pending reservations
         * correctly even if the extent represented by the range can't be
         * inserted in the extents status tree due to ENOSPC.
         */

        if (EXT4_B2C(sbi, lblk) == EXT4_B2C(sbi, end)) {
                first = EXT4_LBLK_CMASK(sbi, lblk);
                if (first != lblk)
                        f_del = __es_scan_range(inode, &ext4_es_is_delonly,
                                                first, lblk - 1);
                if (f_del) {
                        ret = __insert_pending(inode, first, prealloc);
                        if (ret < 0)
                                goto out;
                } else {
                        last = EXT4_LBLK_CMASK(sbi, end) +
                               sbi->s_cluster_ratio - 1;
                        if (last != end)
                                l_del = __es_scan_range(inode,
                                                        &ext4_es_is_delonly,
                                                        end + 1, last);
                        if (l_del) {
                                ret = __insert_pending(inode, last, prealloc);
                                if (ret < 0)
                                        goto out;
                        } else
                                __remove_pending(inode, last);
                }
        } else {
                first = EXT4_LBLK_CMASK(sbi, lblk);
                if (first != lblk)
                        f_del = __es_scan_range(inode, &ext4_es_is_delonly,
                                                first, lblk - 1);
                if (f_del) {
                        ret = __insert_pending(inode, first, prealloc);
                        if (ret < 0)
                                goto out;
                } else
                        __remove_pending(inode, first);

                last = EXT4_LBLK_CMASK(sbi, end) + sbi->s_cluster_ratio - 1;
                if (last != end)
                        l_del = __es_scan_range(inode, &ext4_es_is_delonly,
                                                end + 1, last);
                if (l_del) {
                        ret = __insert_pending(inode, last, prealloc);
                        if (ret < 0)
                                goto out;
                } else
                        __remove_pending(inode, last);
        }
out:
        return ret;
}