#include <linux/rculist_bl.h>
#include <linux/cleancache.h>
#include <linux/fsnotify.h>
+#include <linux/lockdep.h>
#include "internal.h"
LIST_HEAD(super_blocks);
DEFINE_SPINLOCK(sb_lock);
+static char *sb_writers_name[SB_FREEZE_LEVELS] = {
+ "sb_writers",
+ "sb_pagefaults",
+ "sb_internal",
+};
+
/*
* One thing we have to be careful of with a per-sb shrinker is that we don't
* drop the last active reference to the superblock from within the shrinker.
return total_objects;
}
+static int init_sb_writers(struct super_block *s, struct file_system_type *type)
+{
+ int err;
+ int i;
+
+ for (i = 0; i < SB_FREEZE_LEVELS; i++) {
+ err = percpu_counter_init(&s->s_writers.counter[i], 0);
+ if (err < 0)
+ goto err_out;
+ lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i],
+ &type->s_writers_key[i], 0);
+ }
+ init_waitqueue_head(&s->s_writers.wait);
+ init_waitqueue_head(&s->s_writers.wait_unfrozen);
+ return 0;
+err_out:
+ while (--i >= 0)
+ percpu_counter_destroy(&s->s_writers.counter[i]);
+ return err;
+}
+
+static void destroy_sb_writers(struct super_block *s)
+{
+ int i;
+
+ for (i = 0; i < SB_FREEZE_LEVELS; i++)
+ percpu_counter_destroy(&s->s_writers.counter[i]);
+}
+
/**
* alloc_super - create new superblock
* @type: filesystem type superblock should belong to
if (s) {
if (security_sb_alloc(s)) {
+ /*
+ * We cannot call security_sb_free() without
+ * security_sb_alloc() succeeding. So bail out manually
+ */
kfree(s);
s = NULL;
goto out;
}
#ifdef CONFIG_SMP
s->s_files = alloc_percpu(struct list_head);
- if (!s->s_files) {
- security_sb_free(s);
- kfree(s);
- s = NULL;
- goto out;
- } else {
+ if (!s->s_files)
+ goto err_out;
+ else {
int i;
for_each_possible_cpu(i)
#else
INIT_LIST_HEAD(&s->s_files);
#endif
+ if (init_sb_writers(s, type))
+ goto err_out;
s->s_flags = flags;
s->s_bdi = &default_backing_dev_info;
INIT_HLIST_NODE(&s->s_instances);
}
out:
return s;
+err_out:
+ security_sb_free(s);
+#ifdef CONFIG_SMP
+ if (s->s_files)
+ free_percpu(s->s_files);
+#endif
+ destroy_sb_writers(s);
+ kfree(s);
+ s = NULL;
+ goto out;
}
/**
#ifdef CONFIG_SMP
free_percpu(s->s_files);
#endif
+ destroy_sb_writers(s);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
kfree(s->s_subtype);
{
while (1) {
struct super_block *s = get_super(bdev);
- if (!s || s->s_frozen == SB_UNFROZEN)
+ if (!s || s->s_writers.frozen == SB_UNFROZEN)
return s;
up_read(&s->s_umount);
- vfs_check_frozen(s, SB_FREEZE_WRITE);
+ wait_event(s->s_writers.wait_unfrozen,
+ s->s_writers.frozen == SB_UNFROZEN);
put_super(s);
}
}
int retval;
int remount_ro;
- if (sb->s_frozen != SB_UNFROZEN)
+ if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
#ifdef CONFIG_BLOCK
return ERR_PTR(error);
}
+/*
+ * This is an internal function, please use sb_end_{write,pagefault,intwrite}
+ * instead.
+ */
+void __sb_end_write(struct super_block *sb, int level)
+{
+ percpu_counter_dec(&sb->s_writers.counter[level-1]);
+ /*
+ * Make sure s_writers are updated before we wake up waiters in
+ * freeze_super().
+ */
+ smp_mb();
+ if (waitqueue_active(&sb->s_writers.wait))
+ wake_up(&sb->s_writers.wait);
+ rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_);
+}
+EXPORT_SYMBOL(__sb_end_write);
+
+#ifdef CONFIG_LOCKDEP
+/*
+ * We want lockdep to tell us about possible deadlocks with freezing but
+ * it's it bit tricky to properly instrument it. Getting a freeze protection
+ * works as getting a read lock but there are subtle problems. XFS for example
+ * gets freeze protection on internal level twice in some cases, which is OK
+ * only because we already hold a freeze protection also on higher level. Due
+ * to these cases we have to tell lockdep we are doing trylock when we
+ * already hold a freeze protection for a higher freeze level.
+ */
+static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock,
+ unsigned long ip)
+{
+ int i;
+
+ if (!trylock) {
+ for (i = 0; i < level - 1; i++)
+ if (lock_is_held(&sb->s_writers.lock_map[i])) {
+ trylock = true;
+ break;
+ }
+ }
+ rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip);
+}
+#endif
+
+/*
+ * This is an internal function, please use sb_start_{write,pagefault,intwrite}
+ * instead.
+ */
+int __sb_start_write(struct super_block *sb, int level, bool wait)
+{
+retry:
+ if (unlikely(sb->s_writers.frozen >= level)) {
+ if (!wait)
+ return 0;
+ wait_event(sb->s_writers.wait_unfrozen,
+ sb->s_writers.frozen < level);
+ }
+
+#ifdef CONFIG_LOCKDEP
+ acquire_freeze_lock(sb, level, !wait, _RET_IP_);
+#endif
+ percpu_counter_inc(&sb->s_writers.counter[level-1]);
+ /*
+ * Make sure counter is updated before we check for frozen.
+ * freeze_super() first sets frozen and then checks the counter.
+ */
+ smp_mb();
+ if (unlikely(sb->s_writers.frozen >= level)) {
+ __sb_end_write(sb, level);
+ goto retry;
+ }
+ return 1;
+}
+EXPORT_SYMBOL(__sb_start_write);
+
+/**
+ * sb_wait_write - wait until all writers to given file system finish
+ * @sb: the super for which we wait
+ * @level: type of writers we wait for (normal vs page fault)
+ *
+ * This function waits until there are no writers of given type to given file
+ * system. Caller of this function should make sure there can be no new writers
+ * of type @level before calling this function. Otherwise this function can
+ * livelock.
+ */
+static void sb_wait_write(struct super_block *sb, int level)
+{
+ s64 writers;
+
+ /*
+ * We just cycle-through lockdep here so that it does not complain
+ * about returning with lock to userspace
+ */
+ rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
+ rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
+
+ do {
+ DEFINE_WAIT(wait);
+
+ /*
+ * We use a barrier in prepare_to_wait() to separate setting
+ * of frozen and checking of the counter
+ */
+ prepare_to_wait(&sb->s_writers.wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ writers = percpu_counter_sum(&sb->s_writers.counter[level-1]);
+ if (writers)
+ schedule();
+
+ finish_wait(&sb->s_writers.wait, &wait);
+ } while (writers);
+}
+
/**
* freeze_super - lock the filesystem and force it into a consistent state
* @sb: the super to lock
* Syncs the super to make sure the filesystem is consistent and calls the fs's
* freeze_fs. Subsequent calls to this without first thawing the fs will return
* -EBUSY.
+ *
+ * During this function, sb->s_writers.frozen goes through these values:
+ *
+ * SB_UNFROZEN: File system is normal, all writes progress as usual.
+ *
+ * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
+ * writes should be blocked, though page faults are still allowed. We wait for
+ * all writes to complete and then proceed to the next stage.
+ *
+ * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
+ * but internal fs threads can still modify the filesystem (although they
+ * should not dirty new pages or inodes), writeback can run etc. After waiting
+ * for all running page faults we sync the filesystem which will clean all
+ * dirty pages and inodes (no new dirty pages or inodes can be created when
+ * sync is running).
+ *
+ * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
+ * modification are blocked (e.g. XFS preallocation truncation on inode
+ * reclaim). This is usually implemented by blocking new transactions for
+ * filesystems that have them and need this additional guard. After all
+ * internal writers are finished we call ->freeze_fs() to finish filesystem
+ * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
+ * mostly auxiliary for filesystems to verify they do not modify frozen fs.
+ *
+ * sb->s_writers.frozen is protected by sb->s_umount.
*/
int freeze_super(struct super_block *sb)
{
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
- if (sb->s_frozen) {
+ if (sb->s_writers.frozen != SB_UNFROZEN) {
deactivate_locked_super(sb);
return -EBUSY;
}
}
if (sb->s_flags & MS_RDONLY) {
- sb->s_frozen = SB_FREEZE_TRANS;
- smp_wmb();
+ /* Nothing to do really... */
+ sb->s_writers.frozen = SB_FREEZE_COMPLETE;
up_write(&sb->s_umount);
return 0;
}
- sb->s_frozen = SB_FREEZE_WRITE;
+ /* From now on, no new normal writers can start */
+ sb->s_writers.frozen = SB_FREEZE_WRITE;
+ smp_wmb();
+
+ /* Release s_umount to preserve sb_start_write -> s_umount ordering */
+ up_write(&sb->s_umount);
+
+ sb_wait_write(sb, SB_FREEZE_WRITE);
+
+ /* Now we go and block page faults... */
+ down_write(&sb->s_umount);
+ sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
smp_wmb();
+ sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
+
+ /* All writers are done so after syncing there won't be dirty data */
sync_filesystem(sb);
- sb->s_frozen = SB_FREEZE_TRANS;
+ /* Now wait for internal filesystem counter */
+ sb->s_writers.frozen = SB_FREEZE_FS;
smp_wmb();
+ sb_wait_write(sb, SB_FREEZE_FS);
- sync_blockdev(sb->s_bdev);
if (sb->s_op->freeze_fs) {
ret = sb->s_op->freeze_fs(sb);
if (ret) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
- sb->s_frozen = SB_UNFROZEN;
+ sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
- wake_up(&sb->s_wait_unfrozen);
+ wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return ret;
}
}
+ /*
+ * This is just for debugging purposes so that fs can warn if it
+ * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
+ */
+ sb->s_writers.frozen = SB_FREEZE_COMPLETE;
up_write(&sb->s_umount);
return 0;
}
int error;
down_write(&sb->s_umount);
- if (sb->s_frozen == SB_UNFROZEN) {
+ if (sb->s_writers.frozen == SB_UNFROZEN) {
up_write(&sb->s_umount);
return -EINVAL;
}
if (error) {
printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
- sb->s_frozen = SB_FREEZE_TRANS;
up_write(&sb->s_umount);
return error;
}
}
out:
- sb->s_frozen = SB_UNFROZEN;
+ sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
- wake_up(&sb->s_wait_unfrozen);
+ wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return 0;
projects / linux-2.6-microblaze.git / blobdiff