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authorLiu Bo <bo.li.liu@oracle.com>2014-07-02 12:58:01 +0400
committerChris Mason <clm@fb.com>2014-07-03 18:04:15 +0400
commitd288db5dc0110c8e0732d099aaf7a05e2ea0e0c8 (patch)
tree8f25c749e2d6199d47888278c3a22b5dc066249a /fs
parent130d5b415a091e493ac1508b9d27bbb85ba7b8c0 (diff)
downloadlinux-d288db5dc0110c8e0732d099aaf7a05e2ea0e0c8.tar.xz
Btrfs: fix race of using total_bytes_pinned
This percpu counter @total_bytes_pinned is introduced to skip unnecessary operations of 'commit transaction', it accounts for those space we may free but are stuck in delayed refs. And we zero out @space_info->total_bytes_pinned every transaction period so we have a better idea of how much space we'll actually free up by committing this transaction. However, we do the 'zero out' part a little earlier, before we actually unpin space, so we end up returning ENOSPC when we actually have free space that's just unpinned from committing transaction. xfstests/generic/074 complained then. This fixes it by actually accounting the percpu pinned number when 'unpin', and since it's protected by space_info->lock, the race is gone now. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/extent-tree.c5
1 files changed, 1 insertions, 4 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 99c253918208..813537f362f9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5678,7 +5678,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
struct btrfs_caching_control *next;
struct btrfs_caching_control *caching_ctl;
struct btrfs_block_group_cache *cache;
- struct btrfs_space_info *space_info;
down_write(&fs_info->commit_root_sem);
@@ -5701,9 +5700,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
up_write(&fs_info->commit_root_sem);
- list_for_each_entry_rcu(space_info, &fs_info->space_info, list)
- percpu_counter_set(&space_info->total_bytes_pinned, 0);
-
update_global_block_rsv(fs_info);
}
@@ -5741,6 +5737,7 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
spin_lock(&cache->lock);
cache->pinned -= len;
space_info->bytes_pinned -= len;
+ percpu_counter_add(&space_info->total_bytes_pinned, -len);
if (cache->ro) {
space_info->bytes_readonly += len;
readonly = true;