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-rw-r--r--fs/dax.c61
1 files changed, 39 insertions, 22 deletions
diff --git a/fs/dax.c b/fs/dax.c
index e83aa4077df4..df5c0daba698 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -618,32 +618,50 @@ static int dax_writeback_one(struct block_device *bdev,
struct address_space *mapping, pgoff_t index, void *entry)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
- struct radix_tree_node *node;
struct blk_dax_ctl dax;
- void **slot;
+ void *entry2, **slot;
int ret = 0;
- spin_lock_irq(&mapping->tree_lock);
/*
- * Regular page slots are stabilized by the page lock even
- * without the tree itself locked. These unlocked entries
- * need verification under the tree lock.
+ * A page got tagged dirty in DAX mapping? Something is seriously
+ * wrong.
*/
- if (!__radix_tree_lookup(page_tree, index, &node, &slot))
- goto unlock;
- if (*slot != entry)
- goto unlock;
-
- /* another fsync thread may have already written back this entry */
- if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
- goto unlock;
+ if (WARN_ON(!radix_tree_exceptional_entry(entry)))
+ return -EIO;
+ spin_lock_irq(&mapping->tree_lock);
+ entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
+ /* Entry got punched out / reallocated? */
+ if (!entry2 || !radix_tree_exceptional_entry(entry2))
+ goto put_unlocked;
+ /*
+ * Entry got reallocated elsewhere? No need to writeback. We have to
+ * compare sectors as we must not bail out due to difference in lockbit
+ * or entry type.
+ */
+ if (dax_radix_sector(entry2) != dax_radix_sector(entry))
+ goto put_unlocked;
if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
dax_is_zero_entry(entry))) {
ret = -EIO;
- goto unlock;
+ goto put_unlocked;
}
+ /* Another fsync thread may have already written back this entry */
+ if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
+ goto put_unlocked;
+ /* Lock the entry to serialize with page faults */
+ entry = lock_slot(mapping, slot);
+ /*
+ * 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
+ * actually flush the caches. This is achieved as the calls will look
+ * at the entry only under tree_lock and once they do that they will
+ * see the entry locked and wait for it to unlock.
+ */
+ radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
+ spin_unlock_irq(&mapping->tree_lock);
+
/*
* Even if dax_writeback_mapping_range() was given a wbc->range_start
* in the middle of a PMD, the 'index' we are given will be aligned to
@@ -653,15 +671,16 @@ static int dax_writeback_one(struct block_device *bdev,
*/
dax.sector = dax_radix_sector(entry);
dax.size = PAGE_SIZE << dax_radix_order(entry);
- spin_unlock_irq(&mapping->tree_lock);
/*
* We cannot hold tree_lock while calling dax_map_atomic() because it
* eventually calls cond_resched().
*/
ret = dax_map_atomic(bdev, &dax);
- if (ret < 0)
+ if (ret < 0) {
+ put_locked_mapping_entry(mapping, index, entry);
return ret;
+ }
if (WARN_ON_ONCE(ret < dax.size)) {
ret = -EIO;
@@ -669,15 +688,13 @@ static int dax_writeback_one(struct block_device *bdev,
}
wb_cache_pmem(dax.addr, dax.size);
-
- spin_lock_irq(&mapping->tree_lock);
- radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
- spin_unlock_irq(&mapping->tree_lock);
unmap:
dax_unmap_atomic(bdev, &dax);
+ put_locked_mapping_entry(mapping, index, entry);
return ret;
- unlock:
+ put_unlocked:
+ put_unlocked_mapping_entry(mapping, index, entry2);
spin_unlock_irq(&mapping->tree_lock);
return ret;
}
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