Patch "btrfs: resume qgroup rescan on rw remount" has been added to the 4.9-stable tree

Patch "btrfs: resume qgroup rescan on rw remount" has been added to the 4.9-stable tree

[gregkh]

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

    btrfs: resume qgroup rescan on rw remount

to the 4.9-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-resume-qgroup-rescan-on-rw-remount.patch
and it can be found in the queue-4.9 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 6c6b5a39c4bf3dbd8cf629c9f5450e983c19dbb9 Mon Sep 17 00:00:00 2001
From: Aleksa Sarai <asarai@suse.de>
Date: Tue, 4 Jul 2017 21:49:06 +1000
Subject: btrfs: resume qgroup rescan on rw remount

From: Aleksa Sarai <asarai@suse.de>

commit 6c6b5a39c4bf3dbd8cf629c9f5450e983c19dbb9 upstream.

Several distributions mount the "proper root" as ro during initrd and
then remount it as rw before pivot_root(2). Thus, if a rescan had been
aborted by a previous shutdown, the rescan would never be resumed.

This issue would manifest itself as several btrfs ioctl(2)s causing the
entire machine to hang when btrfs_qgroup_wait_for_completion was hit
(due to the fs_info->qgroup_rescan_running flag being set but the rescan
itself not being resumed). Notably, Docker's btrfs storage driver makes
regular use of BTRFS_QUOTA_CTL_DISABLE and BTRFS_IOC_QUOTA_RESCAN_WAIT
(causing this problem to be manifested on boot for some machines).

Cc: Jeff Mahoney <jeffm@suse.com>
Fixes: b382a324b60f ("Btrfs: fix qgroup rescan resume on mount")
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/super.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1834,6 +1834,8 @@ static int btrfs_remount(struct super_bl
 			goto restore;
 		}
 
+		btrfs_qgroup_rescan_resume(fs_info);
+
 		if (!fs_info->uuid_root) {
 			btrfs_info(fs_info, "creating UUID tree");
 			ret = btrfs_create_uuid_tree(fs_info);


Patches currently in stable-queue which might be from asarai@suse.de are

queue-4.9/btrfs-resume-qgroup-rescan-on-rw-remount.patch