btrfs: scrub: fix lost wakeup and hang when cancelling a scrub that is finishing

When scrub finishes, it does a wakeup on the fs_info->scrub_pause_wait
wait queue and then sets dev->scrub_sctx to NULL. On the other hand the
scrub cancel code (btrfs_scrub_cancel_dev()) waits on that wait queue
for dev->scrub_sctx to be NULL. So this means if btrfs_scrub_cancel_dev()
is called right when scrub is finishing and sees the wakeup before the
NULL is assigned to dev->scrub_sctx by btrfs_scrub_dev(), it hangs.

Fix this by doing the wakeup in btrfs_scrub_dev() after setting
dev->scrub_sctx to NULL.

Fixes: a2de733c78fa ("btrfs: scrub")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions