async_xor: increase src_offs when dropping destination page

BugLink: https://bugs.launchpad.net/bugs/1929455
commit ceaf2966ab082bbc4d26516f97b3ca8a676e2af8 upstream.

Now we support sharing one page if PAGE_SIZE is not equal stripe size. To
support this, it needs to support calculating xor value with different
offsets for each r5dev. One offset array is used to record those offsets.

In RMW mode, parity page is used as a source page. It sets
ASYNC_TX_XOR_DROP_DST before calculating xor value in ops_run_prexor5.
So it needs to add src_list and src_offs at the same time. Now it only
needs src_list. So the xor value which is calculated is wrong. It can
cause data corruption problem.

I can reproduce this problem 100% on a POWER8 machine. The steps are:

  mdadm -CR /dev/md0 -l5 -n3 /dev/sdb1 /dev/sdc1 /dev/sdd1 --size=3G
  mkfs.xfs /dev/md0
  mount /dev/md0 /mnt/test
  mount: /mnt/test: mount(2) system call failed: Structure needs cleaning.

Fixes: 29bcff787a25 ("md/raid5: add new xor function to support different page offset")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/crypto/async_tx/async_xor.c b/crypto/async_tx/async_xor.c
index a057ecb1288d2d8f55dedf513c7310c47d0303ed..6cd7f7025df47873261988e29532ef4938de0481 100644 (file)
--- a/crypto/async_tx/async_xor.c
+++ b/crypto/async_tx/async_xor.c
@@ -233,6 +233,7 @@ async_xor_offs(struct page *dest, unsigned int offset,
                if (submit->flags & ASYNC_TX_XOR_DROP_DST) {
                        src_cnt--;
                        src_list++;
+                       src_offs++;
                }
 
                /* wait for any prerequisite operations */