Btrfs: use percpu counter for fs_info->delalloc_bytes

fs_info->delalloc_bytes is accessed very frequently, so use percpu
counter instead of the u64 variant for it to reduce the lock
contention.

This patch also fixed the problem that we access the variant
without the lock protection.At worst, we would not flush the
delalloc inodes, and just return ENOSPC error when we still have
some free space in the fs.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4c476281b66b..50def99f5379 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1392,6 +1392,7 @@ struct btrfs_fs_info {
          */
         struct list_head ordered_extents;
 
+        spinlock_t delalloc_lock;
         /*
          * all of the inodes that have delalloc bytes.  It is possible for
          * this list to be empty even when there is still dirty data=ordered
@@ -1452,7 +1453,10 @@ struct btrfs_fs_info {
 
         /* used to keep from writing metadata until there is a nice batch */
         struct percpu_counter dirty_metadata_bytes;
+        struct percpu_counter delalloc_bytes;
         s32 dirty_metadata_batch;
+        s32 delalloc_batch;
+
         struct list_head dirty_cowonly_roots;
 
         struct btrfs_fs_devices *fs_devices;
@@ -1468,9 +1472,6 @@ struct btrfs_fs_info {
 
         struct reloc_control *reloc_ctl;
 
-        spinlock_t delalloc_lock;
-        u64 delalloc_bytes;
-
         /* data_alloc_cluster is only used in ssd mode */
         struct btrfs_free_cluster data_alloc_cluster;