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-rw-r--r--fs/buffer.c12
-rw-r--r--fs/ext4/ialloc.c3
2 files changed, 13 insertions, 2 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index f8c9e5eb4685..7be23ff20b27 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -207,6 +207,15 @@ __find_get_block_slow(struct block_device *bdev, sector_t block, bool atomic)
head = folio_buffers(folio);
if (!head)
goto out_unlock;
+ /*
+ * Upon a noref migration, the folio lock serializes here;
+ * otherwise bail.
+ */
+ if (test_bit_acquire(BH_Migrate, &head->b_state)) {
+ WARN_ON(!atomic);
+ goto out_unlock;
+ }
+
bh = head;
do {
if (!buffer_mapped(bh))
@@ -1390,7 +1399,8 @@ lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
/*
* Perform a pagecache lookup for the matching buffer. If it's there, refresh
* it in the LRU and mark it as accessed. If it is not present then return
- * NULL
+ * NULL. Atomic context callers may also return NULL if the buffer is being
+ * migrated; similarly the page is not marked accessed either.
*/
static struct buffer_head *
find_get_block_common(struct block_device *bdev, sector_t block,
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 38bc8d74f4cc..e7ecc7c8a729 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -691,7 +691,8 @@ static int recently_deleted(struct super_block *sb, ext4_group_t group, int ino)
if (!bh || !buffer_uptodate(bh))
/*
* If the block is not in the buffer cache, then it
- * must have been written out.
+ * must have been written out, or, most unlikely, is
+ * being migrated - false failure should be OK here.
*/
goto out;