ext3: retry failed direct IO allocations

On a 256M 4k block filesystem, doing this in a loop:

dd if=/dev/zero of=test oflag=direct bs=1M count=64
rm -f test

eventually leads to spurious ENOSPC:

dd: writing `test': No space left on device

As with other block allocation callers, it looks like we need to
potentially retry the allocations on the initial ENOSPC.

A similar patch went into ext4 (commit
fbbf69456619de5d251cb9f1df609069178c62d5)

Signed-off-by: Eric Sandeen <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ext3/inode.c

···
 	ssize_t ret;
 	int orphan = 0;
 	size_t count = iov_length(iov, nr_segs);
+	int retries = 0;
 
 	if (rw == WRITE) {
 		loff_t final_size = offset + count;
···
 		}
 	}
 
+retry:
 	ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
 				 offset, nr_segs,
 				 ext3_get_block, NULL);
+	if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
+		goto retry;
 
 	if (orphan) {
 		int err;