Patch "Btrfs: disable FUA if mounted with nobarrier" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Btrfs: disable FUA if mounted with nobarrier

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     btrfs-disable-fua-if-mounted-with-nobarrier.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Feb 23 11:45:09 CET 2018
From: Omar Sandoval <osandov@fb.com>
Date: Tue, 5 Dec 2017 22:54:02 -0800
Subject: Btrfs: disable FUA if mounted with nobarrier

From: Omar Sandoval <osandov@fb.com>


[ Upstream commit 1b9e619c5bc8235cfba3dc4ced2fb0e3554a05d4 ]

I was seeing disk flushes still happening when I mounted a Btrfs
filesystem with nobarrier for testing. This is because we use FUA to
write out the first super block, and on devices without FUA support, the
block layer translates FUA to a flush. Even on devices supporting true
FUA, using FUA when we asked for no barriers is surprising.

Fixes: 387125fc722a8ed ("Btrfs: fix barrier flushes")
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/disk-io.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3391,6 +3391,7 @@ static int write_dev_supers(struct btrfs
 	int errors = 0;
 	u32 crc;
 	u64 bytenr;
+	int op_flags;
 
 	if (max_mirrors == 0)
 		max_mirrors = BTRFS_SUPER_MIRROR_MAX;
@@ -3433,13 +3434,10 @@ static int write_dev_supers(struct btrfs
 		 * we fua the first super.  The others we allow
 		 * to go down lazy.
 		 */
-		if (i == 0) {
-			ret = btrfsic_submit_bh(REQ_OP_WRITE,
-				REQ_SYNC | REQ_FUA | REQ_META | REQ_PRIO, bh);
-		} else {
-			ret = btrfsic_submit_bh(REQ_OP_WRITE,
-				REQ_SYNC | REQ_META | REQ_PRIO, bh);
-		}
+		op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
+		if (i == 0 && !btrfs_test_opt(device->fs_info, NOBARRIER))
+			op_flags |= REQ_FUA;
+		ret = btrfsic_submit_bh(REQ_OP_WRITE, op_flags, bh);
 		if (ret)
 			errors++;
 	}


Patches currently in stable-queue which might be from osandov@fb.com are

queue-4.14/btrfs-disable-fua-if-mounted-with-nobarrier.patch