[220/272] md_make_request: dont touch the bio after calling make_request

Greg KH
2011-02-16T00:36:06Z

From: Chris Mason <chris.mason@oracle.com>

commit e91ece5590b3c728624ab57043fc7a05069c604a upstream.

md_make_request was calling bio_sectors() for part_stat_add
after it was calling the make_request function. This is
bad because the make_request function can free the bio and
because the bi_size field can change around.

The fix here was suggested by Jens Axboe. It saves the
sector count before the make_request call. I hit this
with CONFIG_DEBUG_PAGEALLOC turned on while trying to break
his pretty fusionio card.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/md/md.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -287,6 +287,7 @@ static int md_make_request(struct reques
mddev_t *mddev = q->queuedata;
int rv;
int cpu;
+ unsigned int sectors;

if (mddev == NULL || mddev->pers == NULL
|| !mddev->ready) {
@@ -311,12 +312,16 @@ static int md_make_request(struct reques
atomic_inc(&mddev->active_io);
rcu_read_unlock();

+ /*
+ * save the sectors now since our bio can
+ * go away inside make_request
+ */
+ sectors = bio_sectors(bio);
rv = mddev->pers->make_request(mddev, bio);

cpu = part_stat_lock();
part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
- part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
- bio_sectors(bio));
+ part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw], sectors);
part_stat_unlock();

if (atomic_dec_and_test(&mddev->active_io) && mddev->suspended)