On 03/17/2013 11:01 AM, Jeff Liu wrote:
On 32-bit system, if the request pos is 64-bit and evaluate block_offset
with (pos & PAGE_MASK) will result in overflows, therefore the assertion
will failed. We have to check the write offset against (pos & ~0UL) to
avoid this issue as it can evaluate the highest 20 bits on 32-bit correctly
if the pos request is 64-bit and keep the expected result of 64-bit pos request
on 64-bit system unchanged.
Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
Reported-by: Michael L. Semon <mlsemon35@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
fs/xfs/xfs_aops.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 5f707e5..2fc7367 100644
@@ -1501,7 +1501,12 @@ xfs_vm_write_failed(
loff_t to = from + len;
struct buffer_head *bh, *head;
- ASSERT(block_offset + from == pos);
+ * Evaluate block_offset via (pos & PAGE_MASK) on 32-bit system
+ * can cause overflow if the request pos is 64-bit. Hence we
+ * have to verify the write offset with (pos & ~0UL) to avoid it.
+ ASSERT(block_offset + from == (pos & ~0UL));
head = page_buffers(page);
block_start = 0;
Thanks! I can't help but admire the effort. That stated, I did read
Dave's review and now understand the "..." that he left as comments to
the original bug report...
My original reason for writing was to refine the test case a little bit.
On this 32-bit Pentium III PC, xfstests #078 succeeds on a 560MB
device-mapper linear target (1146880 sectors), but it fails with an oops
on a 544MB dm-linear target (1114112 sectors). Looking at the output of
the `df` command over and over during the test, the data does stop
growing at a point between those two numbers, proving Dave's initial