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btrfs: qgroup: exit the rescan worker during umount 

I was hitting a consistent NULL pointer dereference during shutdown that
showed the trace running through end_workqueue_bio().  I traced it back to
the endio_meta_workers workqueue being poked after it had already been
destroyed.

Eventually I found that the root cause was a qgroup rescan that was still
in progress while we were stopping all the btrfs workers.

Currently we explicitly pause balance and scrub operations in
close_ctree(), but we do nothing to stop the qgroup rescan.  We should
probably be doing the same for qgroup rescan, but that's a much larger
change.  This small change is good enough to allow me to unmount without
crashing.

Signed-off-by: Justin Maggard <jmaggard@netgear.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
This commit is contained in:
Justin Maggard 2015-11-04 15:56:16 -08:00 committed by Filipe Manana
parent 9c9464cc92
commit 7343dd61fd
2 changed files with 9 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/btrfs/disk-io.c
View File

@ -3780,6 +3780,9 @@ void close_ctree(struct btrfs_root *root)
fs_info->closing = 1;
smp_mb();
/* wait for the qgroup rescan worker to stop */
btrfs_qgroup_wait_for_completion(fs_info);
/* wait for the uuid_scan task to finish */
down(&fs_info->uuid_tree_rescan_sem);
/* avoid complains from lockdep et al., set sem back to initial state */

9
fs/btrfs/qgroup.c
View File

@ -2286,7 +2286,7 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
goto out;
err = 0;
while (!err) {
while (!err && !btrfs_fs_closing(fs_info)) {
trans = btrfs_start_transaction(fs_info->fs_root, 0);
if (IS_ERR(trans)) {
err = PTR_ERR(trans);
@ -2307,7 +2307,8 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
btrfs_free_path(path);
mutex_lock(&fs_info->qgroup_rescan_lock);
fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
if (!btrfs_fs_closing(fs_info))
fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
if (err > 0 &&
fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
@ -2336,7 +2337,9 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
}
btrfs_end_transaction(trans, fs_info->quota_root);
if (err >= 0) {
if (btrfs_fs_closing(fs_info)) {
btrfs_info(fs_info, "qgroup scan paused");
} else if (err >= 0) {
btrfs_info(fs_info, "qgroup scan completed%s",
err > 0 ? " (inconsistency flag cleared)" : "");
} else {