---

yaml
---
r: 166684
b: refs/heads/master
c: ab93dbe
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 35d62a942db5ae03104929fe7397835b572c4bc4
+refs/heads/master: ab93dbecfba72bbc04b7036343d180aaff1b61a3

trunk/fs/btrfs/file.c

@@ -920,26 +920,35 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
 	start_pos = pos;
 
 	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+
+	/* do the reserve before the mutex lock in case we have to do some
+	 * flushing.  We wouldn't deadlock, but this is more polite.
+	 */
+	err = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
+	if (err)
+		goto out_nolock;
+
+	mutex_lock(&inode->i_mutex);
+
 	current->backing_dev_info = inode->i_mapping->backing_dev_info;
 	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
 	if (err)
-		goto out_nolock;
+		goto out;
+
 	if (count == 0)
-		goto out_nolock;
+		goto out;
 
 	err = file_remove_suid(file);
 	if (err)
-		goto out_nolock;
-
-	err = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
-	if (err)
-		goto out_nolock;
+		goto out;
 
 	file_update_time(file);
 
 	pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
 
-	mutex_lock(&inode->i_mutex);
+	/* generic_write_checks can change our pos */
+	start_pos = pos;
+
 	BTRFS_I(inode)->sequence++;
 	first_index = pos >> PAGE_CACHE_SHIFT;
 	last_index = (pos + count) >> PAGE_CACHE_SHIFT;