[6/7] btrfs: Make flush bios explicitely sync
diff mbox

Message ID 20170502150351.29452-7-jack@suse.cz
State New
Headers show

Commit Message

Jan Kara May 2, 2017, 3:03 p.m. UTC
Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
definitions.  generic_make_request_checks() however strips REQ_FUA and
REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
write cache and thus write effectively becomes asynchronous which can
lead to performance regressions

Fix the problem by making sure all bios which are synchronous are
properly marked with REQ_SYNC.

CC: David Sterba <dsterba@suse.com>
CC: linux-btrfs@vger.kernel.org
Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/btrfs/disk-io.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Comments

David Sterba May 2, 2017, 3:38 p.m. UTC | #1
On Tue, May 02, 2017 at 05:03:50PM +0200, Jan Kara wrote:
> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
> synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
> definitions.  generic_make_request_checks() however strips REQ_FUA and
> REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
> write cache and thus write effectively becomes asynchronous which can
> lead to performance regressions
> 
> Fix the problem by making sure all bios which are synchronous are
> properly marked with REQ_SYNC.
> 
> CC: David Sterba <dsterba@suse.com>
> CC: linux-btrfs@vger.kernel.org
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> Signed-off-by: Jan Kara <jack@suse.cz>

Acked-by: David Sterba <dsterba@suse.com>
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Liu Bo May 9, 2017, 7:09 p.m. UTC | #2
On Tue, May 02, 2017 at 05:03:50PM +0200, Jan Kara wrote:
> Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
> synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
> definitions.  generic_make_request_checks() however strips REQ_FUA and
> REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
> write cache and thus write effectively becomes asynchronous which can
> lead to performance regressions
> 
> Fix the problem by making sure all bios which are synchronous are
> properly marked with REQ_SYNC.
>

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo
> CC: David Sterba <dsterba@suse.com>
> CC: linux-btrfs@vger.kernel.org
> Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/btrfs/disk-io.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index eb1ee7b6f532..af75a9aab81e 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3488,10 +3488,12 @@ static int write_dev_supers(struct btrfs_device *device,
>  		 * we fua the first super.  The others we allow
>  		 * to go down lazy.
>  		 */
> -		if (i == 0)
> -			ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_FUA, bh);
> -		else
> +		if (i == 0) {
> +			ret = btrfsic_submit_bh(REQ_OP_WRITE,
> +						REQ_SYNC | REQ_FUA, bh);
> +		} else {
>  			ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
> +		}
>  		if (ret)
>  			errors++;
>  	}
> @@ -3555,7 +3557,7 @@ static int write_dev_flush(struct btrfs_device *device, int wait)
>  
>  	bio->bi_end_io = btrfs_end_empty_barrier;
>  	bio->bi_bdev = device->bdev;
> -	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
> +	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH;
>  	init_completion(&device->flush_wait);
>  	bio->bi_private = &device->flush_wait;
>  	device->flush_bio = bio;
> -- 
> 2.12.0
> 
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Patch
diff mbox

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index eb1ee7b6f532..af75a9aab81e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3488,10 +3488,12 @@  static int write_dev_supers(struct btrfs_device *device,
 		 * we fua the first super.  The others we allow
 		 * to go down lazy.
 		 */
-		if (i == 0)
-			ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_FUA, bh);
-		else
+		if (i == 0) {
+			ret = btrfsic_submit_bh(REQ_OP_WRITE,
+						REQ_SYNC | REQ_FUA, bh);
+		} else {
 			ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
+		}
 		if (ret)
 			errors++;
 	}
@@ -3555,7 +3557,7 @@  static int write_dev_flush(struct btrfs_device *device, int wait)
 
 	bio->bi_end_io = btrfs_end_empty_barrier;
 	bio->bi_bdev = device->bdev;
-	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
+	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH;
 	init_completion(&device->flush_wait);
 	bio->bi_private = &device->flush_wait;
 	device->flush_bio = bio;