btrfs: scrub: add assertions for worker pointers

The scrub worker pointers are not NULL iff the scrub is running, so
reset them back once the last reference is dropped. Add assertions to
the initial phase of scrub to verify that.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 7efa1edb30cdc31e52d7ece43af69ab0be44259a..f92f97304e691e09c8eb06b0cd7a12a912c5c99a 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1075,6 +1075,10 @@ struct btrfs_fs_info {
        atomic_t scrubs_paused;
        atomic_t scrub_cancel_req;
        wait_queue_head_t scrub_pause_wait;
+       /*
+        * The worker pointers are NULL iff the refcount is 0, ie. scrub is not
+        * running.
+        */
        refcount_t scrub_workers_refcnt;
        struct btrfs_workqueue *scrub_workers;
        struct btrfs_workqueue *scrub_wr_completion_workers;

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index d20150d68a904f68086988a0ff2d8802d0f2421d..669bedfec4a9ab7be2fa3a1a5a82f924e8dd965b 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3744,17 +3744,20 @@ static noinline_for_stack int scrub_workers_get(struct btrfs_fs_info *fs_info,
        lockdep_assert_held(&fs_info->scrub_lock);
 
        if (refcount_read(&fs_info->scrub_workers_refcnt) == 0) {
+               ASSERT(fs_info->scrub_workers == NULL);
                fs_info->scrub_workers = btrfs_alloc_workqueue(fs_info, "scrub",
                                flags, is_dev_replace ? 1 : max_active, 4);
                if (!fs_info->scrub_workers)
                        goto fail_scrub_workers;
 
+               ASSERT(fs_info->scrub_wr_completion_workers == NULL);
                fs_info->scrub_wr_completion_workers =
                        btrfs_alloc_workqueue(fs_info, "scrubwrc", flags,
                                              max_active, 2);
                if (!fs_info->scrub_wr_completion_workers)
                        goto fail_scrub_wr_completion_workers;
 
+               ASSERT(fs_info->scrub_parity_workers == NULL);
                fs_info->scrub_parity_workers =
                        btrfs_alloc_workqueue(fs_info, "scrubparity", flags,
                                              max_active, 2);
@@ -3934,6 +3937,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
                scrub_workers = fs_info->scrub_workers;
                scrub_wr_comp = fs_info->scrub_wr_completion_workers;
                scrub_parity = fs_info->scrub_parity_workers;
+
+               fs_info->scrub_workers = NULL;
+               fs_info->scrub_wr_completion_workers = NULL;
+               fs_info->scrub_parity_workers = NULL;
        }
        mutex_unlock(&fs_info->scrub_lock);