btrfs: avoid blocking when allocating context for nowait dio read/write
authorFilipe Manana <fdmanana@suse.com>
Wed, 23 Mar 2022 16:19:29 +0000 (16:19 +0000)
committerDavid Sterba <dsterba@suse.com>
Mon, 16 May 2022 15:03:10 +0000 (17:03 +0200)
commit4f208dcc6bf572fbe8178cfea703f139803863ba
tree58c998fbdae0f6dbef738d201c2d86c37b99bf1a
parent59d35c5171e65f3a208b6f44d028278f129bdeab
btrfs: avoid blocking when allocating context for nowait dio read/write

When doing a NOWAIT direct IO read/write, we allocate a context object
(struct btrfs_dio_data) with GFP_NOFS, which can result in blocking
waiting for memory allocation (GFP_NOFS is __GFP_RECLAIM | __GFP_IO).
This is undesirable for the NOWAIT semantics, so do the allocation with
GFP_NOWAIT if we are serving a NOWAIT request and if the allocation fails
return -EAGAIN, so that the caller can fallback to a blocking context and
retry with a non-blocking write.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/inode.c