Btrfs: delay commits during fsync to allow more writers

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 18 insertions, 4 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 00b118a2db69..6933ab11a5cd 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -694,22 +694,36 @@ static int btrfs_sync_file(struct file *file,
 {
         struct inode *inode = dentry->d_inode;
         struct btrfs_root *root = BTRFS_I(inode)->root;
-        int ret;
+        int ret = 0;
         struct btrfs_trans_handle *trans;
 
         /*
-         * FIXME, use inode generation number to check if we can skip the
-         * commit
+         * check the transaction that last modified this inode
+         * and see if its already been committed
          */
         mutex_lock(&root->fs_info->fs_mutex);
+        if (!BTRFS_I(inode)->last_trans)
+                goto out;
+        mutex_lock(&root->fs_info->trans_mutex);
+        if (BTRFS_I(inode)->last_trans <=
+            root->fs_info->last_trans_committed) {
+                BTRFS_I(inode)->last_trans = 0;
+                mutex_unlock(&root->fs_info->trans_mutex);
+                goto out;
+        }
+        mutex_unlock(&root->fs_info->trans_mutex);
+
+        /*
+         * ok we haven't committed the transaction yet, lets do a commit
+         */
         trans = btrfs_start_transaction(root, 1);
         if (!trans) {
                 ret = -ENOMEM;
                 goto out;
         }
         ret = btrfs_commit_transaction(trans, root);
-        mutex_unlock(&root->fs_info->fs_mutex);
 out:
+        mutex_unlock(&root->fs_info->fs_mutex);
         return ret > 0 ? EIO : ret;
 }