Btrfs: Shrink delay allocated space in a synchronized

Shrink delayed allocation space in a synchronized manner is more
controllable than flushing all delay allocated space in an async
thread.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2bfdc641d4e3..d53cad1afe26 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5611,6 +5611,38 @@ int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
         return 0;
 }
 
+int btrfs_start_one_delalloc_inode(struct btrfs_root *root, int delay_iput)
+{
+        struct btrfs_inode *binode;
+        struct inode *inode = NULL;
+
+        spin_lock(&root->fs_info->delalloc_lock);
+        while (!list_empty(&root->fs_info->delalloc_inodes)) {
+                binode = list_entry(root->fs_info->delalloc_inodes.next,
+                                    struct btrfs_inode, delalloc_inodes);
+                inode = igrab(&binode->vfs_inode);
+                if (inode) {
+                        list_move_tail(&binode->delalloc_inodes,
+                                       &root->fs_info->delalloc_inodes);
+                        break;
+                }
+
+                list_del_init(&binode->delalloc_inodes);
+                cond_resched_lock(&root->fs_info->delalloc_lock);
+        }
+        spin_unlock(&root->fs_info->delalloc_lock);
+
+        if (inode) {
+                write_inode_now(inode, 0);
+                if (delay_iput)
+                        btrfs_add_delayed_iput(inode);
+                else
+                        iput(inode);
+                return 1;
+        }
+        return 0;
+}
+
 static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                          const char *symname)
 {