dax: Convert dax writeback to XArray

Use XArray iteration instead of a pagevec.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

diff --git a/fs/dax.c b/fs/dax.c
index 83a5100..de3ba82 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -997,11 +997,9 @@ unlock_pte:
        i_mmap_unlock_read(mapping);
 }
 
-static int dax_writeback_one(struct dax_device *dax_dev,
-               struct address_space *mapping, pgoff_t index, void *entry)
+static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
+               struct address_space *mapping, void *entry)
 {
-       struct radix_tree_root *pages = &mapping->i_pages;
-       void *entry2, **slot;
        unsigned long pfn;
        long ret = 0;
        size_t size;
@@ -1013,29 +1011,35 @@ static int dax_writeback_one(struct dax_device *dax_dev,
        if (WARN_ON(!xa_is_value(entry)))
                return -EIO;
 
-       xa_lock_irq(pages);
-       entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
-       /* Entry got punched out / reallocated? */
-       if (!entry2 || WARN_ON_ONCE(!xa_is_value(entry2)))
-               goto put_unlocked;
-       /*
-        * Entry got reallocated elsewhere? No need to writeback. We have to
-        * compare pfns as we must not bail out due to difference in lockbit
-        * or entry type.
-        */
-       if (dax_to_pfn(entry2) != dax_to_pfn(entry))
-               goto put_unlocked;
-       if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
-                               dax_is_zero_entry(entry))) {
-               ret = -EIO;
-               goto put_unlocked;
+       if (unlikely(dax_is_locked(entry))) {
+               void *old_entry = entry;
+
+               entry = get_unlocked_entry(xas);
+
+               /* Entry got punched out / reallocated? */
+               if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
+                       goto put_unlocked;
+               /*
+                * Entry got reallocated elsewhere? No need to writeback.
+                * We have to compare pfns as we must not bail out due to
+                * difference in lockbit or entry type.
+                */
+               if (dax_to_pfn(old_entry) != dax_to_pfn(entry))
+                       goto put_unlocked;
+               if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+                                       dax_is_zero_entry(entry))) {
+                       ret = -EIO;
+                       goto put_unlocked;
+               }
+
+               /* Another fsync thread may have already done this entry */
+               if (!xas_get_mark(xas, PAGECACHE_TAG_TOWRITE))
+                       goto put_unlocked;
        }
 
-       /* Another fsync thread may have already written back this entry */
-       if (!radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))
-               goto put_unlocked;
        /* Lock the entry to serialize with page faults */
-       entry = lock_slot(mapping, slot);
+       dax_lock_entry(xas, entry);
+
        /*
         * We can clear the tag now but we have to be careful so that concurrent
         * dax_writeback_one() calls for the same index cannot finish before we
@@ -1043,8 +1047,8 @@ static int dax_writeback_one(struct dax_device *dax_dev,
         * at the entry only under the i_pages lock and once they do that
         * they will see the entry locked and wait for it to unlock.
         */
-       radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE);
-       xa_unlock_irq(pages);
+       xas_clear_mark(xas, PAGECACHE_TAG_TOWRITE);
+       xas_unlock_irq(xas);
 
        /*
         * Even if dax_writeback_mapping_range() was given a wbc->range_start
@@ -1056,7 +1060,7 @@ static int dax_writeback_one(struct dax_device *dax_dev,
        pfn = dax_to_pfn(entry);
        size = PAGE_SIZE << dax_entry_order(entry);
 
-       dax_entry_mkclean(mapping, index, pfn);
+       dax_entry_mkclean(mapping, xas->xa_index, pfn);
        dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
        /*
         * After we have flushed the cache, we can clear the dirty tag. There
@@ -1064,16 +1068,18 @@ static int dax_writeback_one(struct dax_device *dax_dev,
         * the pfn mappings are writeprotected and fault waits for mapping
         * entry lock.
         */
-       xa_lock_irq(pages);
-       radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY);
-       xa_unlock_irq(pages);
-       trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
-       put_locked_mapping_entry(mapping, index);
+       xas_reset(xas);
+       xas_lock_irq(xas);
+       xas_store(xas, entry);
+       xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
+       dax_wake_entry(xas, entry, false);
+
+       trace_dax_writeback_one(mapping->host, xas->xa_index,
+                       size >> PAGE_SHIFT);
        return ret;
 
  put_unlocked:
-       put_unlocked_mapping_entry(mapping, index, entry2);
-       xa_unlock_irq(pages);
+       put_unlocked_entry(xas, entry);
        return ret;
 }
 
@@ -1085,13 +1091,13 @@ static int dax_writeback_one(struct dax_device *dax_dev,
 int dax_writeback_mapping_range(struct address_space *mapping,
                struct block_device *bdev, struct writeback_control *wbc)
 {
+       XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT);
        struct inode *inode = mapping->host;
-       pgoff_t start_index, end_index;
-       pgoff_t indices[PAGEVEC_SIZE];
+       pgoff_t end_index = wbc->range_end >> PAGE_SHIFT;
        struct dax_device *dax_dev;
-       struct pagevec pvec;
-       bool done = false;
-       int i, ret = 0;
+       void *entry;
+       int ret = 0;
+       unsigned int scanned = 0;
 
        if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
                return -EIO;
@@ -1103,41 +1109,29 @@ int dax_writeback_mapping_range(struct address_space *mapping,
        if (!dax_dev)
                return -EIO;
 
-       start_index = wbc->range_start >> PAGE_SHIFT;
-       end_index = wbc->range_end >> PAGE_SHIFT;
-
-       trace_dax_writeback_range(inode, start_index, end_index);
-
-       tag_pages_for_writeback(mapping, start_index, end_index);
+       trace_dax_writeback_range(inode, xas.xa_index, end_index);
 
-       pagevec_init(&pvec);
-       while (!done) {
-               pvec.nr = find_get_entries_tag(mapping, start_index,
-                               PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
-                               pvec.pages, indices);
+       tag_pages_for_writeback(mapping, xas.xa_index, end_index);
 
-               if (pvec.nr == 0)
+       xas_lock_irq(&xas);
+       xas_for_each_marked(&xas, entry, end_index, PAGECACHE_TAG_TOWRITE) {
+               ret = dax_writeback_one(&xas, dax_dev, mapping, entry);
+               if (ret < 0) {
+                       mapping_set_error(mapping, ret);
                        break;
-
-               for (i = 0; i < pvec.nr; i++) {
-                       if (indices[i] > end_index) {
-                               done = true;
-                               break;
-                       }
-
-                       ret = dax_writeback_one(dax_dev, mapping, indices[i],
-                                       pvec.pages[i]);
-                       if (ret < 0) {
-                               mapping_set_error(mapping, ret);
-                               goto out;
-                       }
                }
-               start_index = indices[pvec.nr - 1] + 1;
+               if (++scanned % XA_CHECK_SCHED)
+                       continue;
+
+               xas_pause(&xas);
+               xas_unlock_irq(&xas);
+               cond_resched();
+               xas_lock_irq(&xas);
        }
-out:
+       xas_unlock_irq(&xas);
        put_dax(dax_dev);
-       trace_dax_writeback_range_done(inode, start_index, end_index);
-       return (ret < 0 ? ret : 0);
+       trace_dax_writeback_range_done(inode, xas.xa_index, end_index);
+       return ret;
 }
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);