[Cluster-devel] [GFS2 PATCH] GFS2: Fix direct IO write rounding error

[Bob Peterson <rpeterso@redhat.com>]

Hi,

The fsx test in xfstests was failing because it was using direct IO
writes which were using a bad calculation. It was using
loff_t lstart = offset & (PAGE_CACHE_SIZE - 1); when it should be
loff_t lstart = offset & ~(PAGE_CACHE_SIZE - 1);
Thus, the write at offset 0x67e00 was calculating lstart to be
0xe00, the address of our corruption. Instead, it should have been
0x67000. This patch fixes the calculation.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 93f0746..aa016e4 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -1082,7 +1082,7 @@ static ssize_t gfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 	 * the first place, mapping->nr_pages will always be zero.
 	 */
 	if (mapping->nrpages) {
-		loff_t lstart = offset & (PAGE_CACHE_SIZE - 1);
+		loff_t lstart = offset & ~(PAGE_CACHE_SIZE - 1);
 		loff_t len = iov_iter_count(iter);
 		loff_t end = PAGE_ALIGN(offset + len) - 1;