On Tue, Jun 06, 2017 at 04:45:29PM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osan...@fb.com>
>
> Currently, we only increment total_bytes_pinned in
> btrfs_free_tree_block() when dropping the last reference on the block.
> However, when the delayed ref is run later, we will decrement
> total_bytes_pinned regardless of whether it was the last reference or
> not. This causes the counter to underflow when the reference we dropped
> was not the last reference. Fix it by incrementing the counter
> unconditionally, which is what btrfs_free_extent() does. This makes
> total_bytes_pinned an overestimate when references to shared extents are
> dropped, but in the worst case this will just make us try to commit the
> transaction to try to free up space and find we didn't free enough.
>
I recognize the same problem, the patch looks good.
Reviewed-by: Liu Bo <bo.li....@oracle.com>
-liubo
> Signed-off-by: Omar Sandoval <osan...@fb.com>
> ---
> fs/btrfs/extent-tree.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 9cff937415cb..52f3a0486e64 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -7178,10 +7178,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle
> *trans,
> BUG_ON(ret); /* -ENOMEM */
> }
>
> - if (!last_ref)
> - return;
> -
> - if (btrfs_header_generation(buf) == trans->transid) {
> + if (last_ref && btrfs_header_generation(buf) == trans->transid) {
> struct btrfs_block_group_cache *cache;
>
> if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
> @@ -7212,11 +7209,13 @@ void btrfs_free_tree_block(struct btrfs_trans_handle
> *trans,
> add_pinned_bytes(fs_info, buf->len, btrfs_header_level(buf),
> root->root_key.objectid);
>
> - /*
> - * Deleting the buffer, clear the corrupt flag since it doesn't matter
> - * anymore.
> - */
> - clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + if (last_ref) {
> + /*
> + * Deleting the buffer, clear the corrupt flag since it doesn't
> + * matter anymore.
> + */
> + clear_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags);
> + }
> }
>
> /* Can return -ENOMEM */
> --
> 2.13.0
>
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