1 files changed, 40 insertions, 28 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index fb0f99dc8c22..32f2c22c7ef2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -100,29 +100,40 @@ static int ext4_split_extent_at(handle_t *handle,
 static int ext4_find_delayed_extent(struct inode *inode,
 				    struct extent_status *newes);
 
-static int ext4_ext_truncate_extend_restart(handle_t *handle,
-					    struct inode *inode,
-					    int needed)
+static int ext4_ext_trunc_restart_fn(struct inode *inode, int *dropped)
 {
-	int err;
-
-	if (!ext4_handle_valid(handle))
-		return 0;
-	if (handle->h_buffer_credits >= needed)
-		return 0;
 	/*
-	 * If we need to extend the journal get a few extra blocks
-	 * while we're at it for efficiency's sake.
+	 * Drop i_data_sem to avoid deadlock with ext4_map_blocks.  At this
+	 * moment, get_block can be called only for blocks inside i_size since
+	 * page cache has been already dropped and writes are blocked by
+	 * i_mutex. So we can safely drop the i_data_sem here.
 	 */
-	needed += 3;
-	err = ext4_journal_extend(handle, needed - handle->h_buffer_credits);
-	if (err <= 0)
-		return err;
-	err = ext4_truncate_restart_trans(handle, inode, needed);
-	if (err == 0)
-		err = -EAGAIN;
+	BUG_ON(EXT4_JOURNAL(inode) == NULL);
+	ext4_discard_preallocations(inode);
+	up_write(&EXT4_I(inode)->i_data_sem);
+	*dropped = 1;
+	return 0;
+}
 
-	return err;
+/*
+ * Make sure 'handle' has at least 'check_cred' credits. If not, restart
+ * transaction with 'restart_cred' credits. The function drops i_data_sem
+ * when restarting transaction and gets it after transaction is restarted.
+ *
+ * The function returns 0 on success, 1 if transaction had to be restarted,
+ * and < 0 in case of fatal error.
+ */
+int ext4_datasem_ensure_credits(handle_t *handle, struct inode *inode,
+				int check_cred, int restart_cred)
+{
+	int ret;
+	int dropped = 0;
+
+	ret = ext4_journal_ensure_credits_fn(handle, check_cred, restart_cred,
+			ext4_ext_trunc_restart_fn(inode, &dropped));
+	if (dropped)
+		down_write(&EXT4_I(inode)->i_data_sem);
+	return ret;
 }
 
 /*
@@ -2820,9 +2831,13 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
 		}
 		credits += EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb);
 
-		err = ext4_ext_truncate_extend_restart(handle, inode, credits);
-		if (err)
+		err = ext4_datasem_ensure_credits(handle, inode, credits,
+						  credits);
+		if (err) {
+			if (err > 0)
+				err = -EAGAIN;
 			goto out;
+		}
 
 		err = ext4_ext_get_access(handle, inode, path + depth);
 		if (err)
@@ -5206,13 +5221,10 @@ ext4_access_path(handle_t *handle, struct inode *inode,
 	 * descriptor) for each block group; assume two block
 	 * groups
 	 */
-	if (handle->h_buffer_credits < 7) {
-		credits = ext4_writepage_trans_blocks(inode);
-		err = ext4_ext_truncate_extend_restart(handle, inode, credits);
-		/* EAGAIN is success */
-		if (err && err != -EAGAIN)
-			return err;
-	}
+	credits = ext4_writepage_trans_blocks(inode);
+	err = ext4_datasem_ensure_credits(handle, inode, 7, credits);
+	if (err < 0)
+		return err;
 
 	err = ext4_ext_get_access(handle, inode, path);
 	return err;