Btrfs: fix joining the same transaction handler more than 2 times

If we flush inodes with pending delalloc in a transaction, we may join
the same transaction handler more than 2 times.

The reason is:
  Task						use_count of trans handle
  commit_transaction				1
    |-> btrfs_start_delalloc_inodes		1
	  |-> run_delalloc_nocow		1
		|-> join_transaction		2
		|-> cow_file_range		2
			|-> join_transaction	3

In fact, cow_file_range needn't join the transaction again because the caller
have joined the transaction, so we fix this problem by this way.

Reported-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 47 insertions, 30 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index dce9e218b845..96d20903beeb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -804,14 +804,14 @@ static u64 get_extent_allocation_hint(struct inode *inode, u64 start,
  * required to start IO on it.  It may be clean and already done with
  * IO when we return.
  */
-static noinline int cow_file_range(struct inode *inode,
-                                   struct page *locked_page,
-                                   u64 start, u64 end, int *page_started,
-                                   unsigned long *nr_written,
-                                   int unlock)
+static noinline int __cow_file_range(struct btrfs_trans_handle *trans,
+                                     struct inode *inode,
+                                     struct btrfs_root *root,
+                                     struct page *locked_page,
+                                     u64 start, u64 end, int *page_started,
+                                     unsigned long *nr_written,
+                                     int unlock)
 {
-        struct btrfs_root *root = BTRFS_I(inode)->root;
-        struct btrfs_trans_handle *trans;
         u64 alloc_hint = 0;
         u64 num_bytes;
         unsigned long ram_size;
@@ -824,25 +824,10 @@ static noinline int cow_file_range(struct inode *inode,
         int ret = 0;
 
         BUG_ON(btrfs_is_free_space_inode(inode));
-        trans = btrfs_join_transaction(root);
-        if (IS_ERR(trans)) {
-                extent_clear_unlock_delalloc(inode,
-                             &BTRFS_I(inode)->io_tree,
-                             start, end, locked_page,
-                             EXTENT_CLEAR_UNLOCK_PAGE |
-                             EXTENT_CLEAR_UNLOCK |
-                             EXTENT_CLEAR_DELALLOC |
-                             EXTENT_CLEAR_DIRTY |
-                             EXTENT_SET_WRITEBACK |
-                             EXTENT_END_WRITEBACK);
-                return PTR_ERR(trans);
-        }
-        trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
         num_bytes = (end - start + blocksize) & ~(blocksize - 1);
         num_bytes = max(blocksize,  num_bytes);
         disk_num_bytes = num_bytes;
-        ret = 0;
 
         /* if this is a small write inside eof, kick off defrag */
         if (num_bytes < 64 * 1024 &&
@@ -953,11 +938,9 @@ static noinline int cow_file_range(struct inode *inode,
                 alloc_hint = ins.objectid + ins.offset;
                 start += cur_alloc_size;
         }
-        ret = 0;
 out:
-        btrfs_end_transaction(trans, root);
-
         return ret;
+
 out_unlock:
         extent_clear_unlock_delalloc(inode,
                      &BTRFS_I(inode)->io_tree,
@@ -972,6 +955,39 @@ out_unlock:
         goto out;
 }
 
+static noinline int cow_file_range(struct inode *inode,
+                                   struct page *locked_page,
+                                   u64 start, u64 end, int *page_started,
+                                   unsigned long *nr_written,
+                                   int unlock)
+{
+        struct btrfs_trans_handle *trans;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        int ret;
+
+        trans = btrfs_join_transaction(root);
+        if (IS_ERR(trans)) {
+                extent_clear_unlock_delalloc(inode,
+                             &BTRFS_I(inode)->io_tree,
+                             start, end, locked_page,
+                             EXTENT_CLEAR_UNLOCK_PAGE |
+                             EXTENT_CLEAR_UNLOCK |
+                             EXTENT_CLEAR_DELALLOC |
+                             EXTENT_CLEAR_DIRTY |
+                             EXTENT_SET_WRITEBACK |
+                             EXTENT_END_WRITEBACK);
+                return PTR_ERR(trans);
+        }
+        trans->block_rsv = &root->fs_info->delalloc_block_rsv;
+
+        ret = __cow_file_range(trans, inode, root, locked_page, start, end,
+                               page_started, nr_written, unlock);
+
+        btrfs_end_transaction(trans, root);
+
+        return ret;
+}
+
 /*
  * work queue call back to started compression on a file and pages
  */
@@ -1282,9 +1298,9 @@ out_check:
 
                 btrfs_release_path(path);
                 if (cow_start != (u64)-1) {
-                        ret = cow_file_range(inode, locked_page, cow_start,
-                                        found_key.offset - 1, page_started,
-                                        nr_written, 1);
+                        ret = __cow_file_range(trans, inode, root, locked_page,
+                                               cow_start, found_key.offset - 1,
+                                               page_started, nr_written, 1);
                         if (ret) {
                                 btrfs_abort_transaction(trans, root, ret);
                                 goto error;
@@ -1353,8 +1369,9 @@ out_check:
         }
 
         if (cow_start != (u64)-1) {
-                ret = cow_file_range(inode, locked_page, cow_start, end,
-                                     page_started, nr_written, 1);
+                ret = __cow_file_range(trans, inode, root, locked_page,
+                                       cow_start, end,
+                                       page_started, nr_written, 1);
                 if (ret) {
                         btrfs_abort_transaction(trans, root, ret);
                         goto error;