[PATCH v2 4/8] buffer: Use bdev_getblk() to avoid memory reclaim in readahead path

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

__getblk() adds __GFP_NOFAIL, which is unnecessary for readahead;
we're quite comfortable with the possibility that we may not get a bh
back.  Switch to bdev_getblk() which does not include __GFP_NOFAIL.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/buffer.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 3fe293c9f3ca..58546bfd8903 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1464,7 +1464,9 @@ EXPORT_SYMBOL(__getblk_gfp);
  */
 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
 {
-	struct buffer_head *bh = __getblk(bdev, block, size);
+	struct buffer_head *bh = bdev_getblk(bdev, block, size,
+			GFP_NOWAIT | __GFP_MOVABLE);
+
 	if (likely(bh)) {
 		bh_readahead(bh, REQ_RAHEAD);
 		brelse(bh);
-- 
2.40.1