Re: [PATCH 1/2] ext4: introduce new i_write_mutex to protect fallocate

[Theodore Ts'o <tytso@mit.edu>]

On Mon, May 26, 2014 at 12:29:00PM -0400, Theodore Ts'o wrote:
> On Tue, May 13, 2014 at 09:19:17AM +0900, Namjae Jeon wrote:
> > Introduce new i_write_mutex to protect new writes from coming while doing
> > fallocate operations. Also, get rid of aio_mutex as it is covered by
> > i_write_mutex.
> > 
> Thanks, applied.
> 

I had to apply the following fix up patch, or else running generic/308
using the ext3 config would end up returning to userspace with
i_write_mutex still locked.

For all ext4 developers: please consider running at least
"kvm-xfstests -g quick" (which would have shown this issue), or better
yet, "kvm-xfstests -g auto" before sending patches.  It finds problems
like this.  :-)

Cheers,

					- Ted

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 8c39305..e5cd87f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -135,8 +135,8 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 		if ((pos > sbi->s_bitmap_maxbytes) ||
 		    (pos == sbi->s_bitmap_maxbytes && length > 0)) {
 			mutex_unlock(&inode->i_mutex);
-			ret = -EFBIG;
-			goto errout;
+			mutex_unlock(&EXT4_I(inode)->i_write_mutex);
+			return -EFBIG;
 		}
 
 		if (pos + length > sbi->s_bitmap_maxbytes) {
@@ -196,7 +196,6 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 	if (o_direct)
 		blk_finish_plug(&plug);
 
-errout:
 	if (unaligned_direct_aio)
 		mutex_unlock(&EXT4_I(inode)->i_write_mutex);
 	return ret;