Hi Josef,
thanks for addressing this.
On Mon, Aug 5, 2013 at 6:19 PM, Josef Bacik <jbacik@xxxxxxxxxxxx> wrote:
> Alex Lyakas reported a bug where wait_block_group_cache_progress() would wait
> forever if a drive failed. This is because we just bail out if there is an
> error while trying to cache a block group, we don't update anybody who may be
> waiting. So this introduces a new enum for the cache state in case of error and
> makes everybody bail out if we have an error. Alex tested and verified this
> patch fixed his problem. This fixes bz 59431. Thanks,
>
> Signed-off-by: Josef Bacik <jbacik@xxxxxxxxxxxx>
> ---
> fs/btrfs/ctree.h | 1 +
> fs/btrfs/extent-tree.c | 27 ++++++++++++++++++++-------
> 2 files changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index cbb1263..c17acbc 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1188,6 +1188,7 @@ enum btrfs_caching_type {
> BTRFS_CACHE_STARTED = 1,
> BTRFS_CACHE_FAST = 2,
> BTRFS_CACHE_FINISHED = 3,
> + BTRFS_CACHE_ERROR = 4,
> };
>
> enum btrfs_disk_cache_state {
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e868c35..e6dfa7f 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -113,7 +113,8 @@ static noinline int
> block_group_cache_done(struct btrfs_block_group_cache *cache)
> {
> smp_mb();
> - return cache->cached == BTRFS_CACHE_FINISHED;
> + return cache->cached == BTRFS_CACHE_FINISHED ||
> + cache->cached == BTRFS_CACHE_ERROR;
> }
>
> static int block_group_bits(struct btrfs_block_group_cache *cache, u64 bits)
> @@ -389,7 +390,7 @@ static noinline void caching_thread(struct btrfs_work *work)
> u64 total_found = 0;
> u64 last = 0;
> u32 nritems;
> - int ret = 0;
> + int ret = -ENOMEM;
>
> caching_ctl = container_of(work, struct btrfs_caching_control, work);
> block_group = caching_ctl->block_group;
> @@ -517,6 +518,12 @@ err:
>
> mutex_unlock(&caching_ctl->mutex);
> out:
> + if (ret) {
> + spin_lock(&block_group->lock);
> + block_group->caching_ctl = NULL;
> + block_group->cached = BTRFS_CACHE_ERROR;
> + spin_unlock(&block_group->lock);
> + }
> wake_up(&caching_ctl->wait);
>
> put_caching_control(caching_ctl);
> @@ -6035,8 +6042,11 @@ static u64 stripe_align(struct btrfs_root *root,
> * for our min num_bytes. Another option is to have it go ahead
> * and look in the rbtree for a free extent of a given size, but this
> * is a good start.
> + *
> + * Callers of this must check if cache->cached == BTRFS_CACHE_ERROR before using
> + * any of the information in this block group.
> */
> -static noinline int
> +static noinline void
> wait_block_group_cache_progress(struct btrfs_block_group_cache *cache,
> u64 num_bytes)
> {
> @@ -6044,28 +6054,29 @@ wait_block_group_cache_progress(struct btrfs_block_group_cache *cache,
>
> caching_ctl = get_caching_control(cache);
> if (!caching_ctl)
> - return 0;
> + return;
>
> wait_event(caching_ctl->wait, block_group_cache_done(cache) ||
> (cache->free_space_ctl->free_space >= num_bytes));
>
> put_caching_control(caching_ctl);
> - return 0;
> }
>
> static noinline int
> wait_block_group_cache_done(struct btrfs_block_group_cache *cache)
> {
> struct btrfs_caching_control *caching_ctl;
> + int ret = 0;
>
> caching_ctl = get_caching_control(cache);
> if (!caching_ctl)
> return 0;
In case caching_thread completes with error for this block group,
get_caching_control() will return NULL.
So this function will return success, although the block group was not
cached properly.
Currently only btrfs_trim_fs() caller checks the return value of this
function, although you didn't post the btrfs_trim_fs() change in this
patch (but you posed it in the bugzilla). Still, should we check the
cache->cached for ERROR even if there is no caching control?
>
> wait_event(caching_ctl->wait, block_group_cache_done(cache));
> -
> + if (cache->cached == BTRFS_CACHE_ERROR)
> + ret = -EIO;
> put_caching_control(caching_ctl);
> - return 0;
> + return ret;
> }
>
> int __get_raid_index(u64 flags)
> @@ -6248,6 +6259,8 @@ have_block_group:
> ret = 0;
> }
>
> + if (unlikely(block_group->cached == BTRFS_CACHE_ERROR))
> + goto loop;
> if (unlikely(block_group->ro))
> goto loop;
>
> --
> 1.7.7.6
>
> --
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Thanks,
Alex.
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