Commit 6c6b5a39 authored Jul 04, 2017 by Aleksa Sarai Committed by David Sterba Aug 16, 2017

btrfs: resume qgroup rescan on rw remount



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: <stable@vger.kernel.org> # v3.11+
Cc: Jeff Mahoney <jeffm@suse.com>
Fixes: b382a324 ("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>

parent 01747e92

fs/btrfs/super.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1815,6 +1815,8 @@ static int btrfs_remount(struct super_block sb, int flags, char *data)
		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);

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