Avoid giving a way a buffer with __find_get_block_slow() if the
folio may be a folio migration candidate. We do this as an alternative
to the issue fixed by commit ebdf4de5642fb6 ("mm: migrate: fix reference
check race between __find_get_block() and migration"), given we've
determined that we should avoid requiring folio migration callers
from holding a spin lock while calling __migrate_folio().
This alternative simply avoids completing __find_get_block_slow()
on folio migration candidates to let us later rip out the spin_lock()
held on the buffer_migrate_folio_norefs() path.
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
fs/buffer.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/buffer.c b/fs/buffer.c
index c7abb4a029dc..6e2c3837a202 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -208,6 +208,12 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
head = folio_buffers(folio);
if (!head)
goto out_unlock;
+
+ if (folio_test_lru(folio) &&
+ folio_test_locked(folio) &&
+ !folio_test_writeback(folio))
+ goto out_unlock;
+
bh = head;
do {
if (!buffer_mapped(bh))
--
2.47.2
