dm: revert 8f50e358153d ("dm: limit the max bio size as BIO_MAX_PAGES * PAGE_SIZE")

The limit was already incorporated to dm-crypt with commit 4e870e948fba
("dm crypt: fix error with too large bios"), so we don't need to apply
it globally to all targets. The quantity BIO_MAX_PAGES * PAGE_SIZE is
wrong anyway because the variable ti->max_io_len it is supposed to be in
the units of 512-byte sectors not in bytes.

Reduction of the limit to 1048576 sectors could even cause data
corruption in rare cases - suppose that we have a dm-striped device with
stripe size 768MiB. The target will call dm_set_target_max_io_len with
the value 1572864. The buggy code would reduce it to 1048576. Now, the
dm-core will errorneously split the bios on 1048576-sector boundary
insetad of 1572864-sector boundary and pass these stripe-crossing bios
to the striped target.

Cc: stable@vger.kernel.org # v4.16+
Fixes: 8f50e358153d ("dm: limit the max bio size as BIO_MAX_PAGES * PAGE_SIZE")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 68d24056d0b1c17d7fa0c271d1d5582d7eb72c89..89b04169658d262b4ddf6e5c275b263e37ff151a 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1042,15 +1042,7 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
                return -EINVAL;
        }
 
-       /*
-        * BIO based queue uses its own splitting. When multipage bvecs
-        * is switched on, size of the incoming bio may be too big to
-        * be handled in some targets, such as crypt.
-        *
-        * When these targets are ready for the big bio, we can remove
-        * the limit.
-        */
-       ti->max_io_len = min_t(uint32_t, len, BIO_MAX_PAGES * PAGE_SIZE);
+       ti->max_io_len = (uint32_t) len;
 
        return 0;
 }