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Commit ab93dbec authored by Chris Mason's avatar Chris Mason
Browse files

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: default avatarChris Mason <chris.mason@oracle.com>
parent 35d62a94

fs/btrfs/file.c

+17 −8
Original line number Diff line number Diff line
@@ -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;