From: Omar Sandoval <osandov@fb.com>
Date: Thu, 15 Aug 2019 14:04:03 -0700
Git-commit: f50cb7aff9645998b3269eac903a5e01cd6ba689
Patch-mainline: 5.4-rc1
Subject: [PATCH] btrfs: treat RWF_{,D}SYNC writes as sync for CRCs
References: bsc#1175493

The VFS indicates a synchronous write to ->write_iter() via
iocb->ki_flags. The IOCB_{,D}SYNC flags may be set based on the file
(see iocb_flags()) or the RWF_* flags passed to a syscall like
pwritev2() (see kiocb_set_rw_flags()).

However, in btrfs_file_write_iter(), we're checking if a write is
synchronous based only on the file; we use this to decide when to bump
the sync_writers counter and thus do CRCs synchronously. Make sure we do
this for all synchronous writes as determined by the VFS.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add const ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 25df5b03b591..702c30a28a43 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1882,7 +1882,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	u64 start_pos;
 	u64 end_pos;
 	ssize_t num_written = 0;
-	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
+	const bool sync = iocb->ki_flags & IOCB_DSYNC;
 	ssize_t err;
 	loff_t pos;
 	size_t count;
-- 
2.26.2