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authorChris Mason <chris.mason@oracle.com>2009-10-01 12:29:10 -0400
committerChris Mason <chris.mason@oracle.com>2009-10-01 12:29:10 -0400
commitab93dbecfba72bbc04b7036343d180aaff1b61a3 (patch)
tree6bb523dcf9be0885b6fa9cb6cc9ac694ee089028
parent35d62a942db5ae03104929fe7397835b572c4bc4 (diff)
Btrfs: take i_mutex before generic_write_checks
btrfs_file_write was incorrectly calling generic_write_checks without taking i_mutex. This lead to problems with racing around i_size when doing O_APPEND writes. The fix here is to move i_mutex higher. Signed-off-by: Chris Mason <chris.mason@oracle.com>
-rw-r--r--fs/btrfs/file.c25
1 files changed, 17 insertions, 8 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1be96ba6f6b..f155179877a 100644
--- a/fs/btrfs/file.c
+++ b/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;