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md: Ensure no IO request to get md device before it is properly initialised.

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When an md device is in the process of coming on line it is possible
for an IO request (typically a partition table probe) to get through
before the array is fully initialised, which can cause unexpected
behaviour (e.g. a crash).

So explicitly record when the array is ready for IO and don't allow IO
through until then.

There is no possibility for a similar problem when the array is going
off-line as there must only be one 'open' at that time, and it is busy
off-lining the array and so cannot send IO requests.  So no memory
barrier is needed in md_stop()

This has been a bug since commit 409c57f380 in 2.6.30 which
introduced md_make_request.  Before then, each personality would
register its own make_request_fn when it was ready.
This is suitable for any stable kernel from 2.6.30.y onwards.

Cc: <stable@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Reported-by:  "Hawrylewicz Czarnowski, Przemyslaw" <przemyslaw.hawrylewicz.czarnowski@intel.com>
This commit is contained in:
NeilBrown 2011-01-14 09:14:33 +11:00
parent 067032bc62
commit 0ca69886a8
2 changed files with 8 additions and 3 deletions
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8
drivers/md/md.c
View file

@ -288,10 +288,12 @@ static int md_make_request(struct request_queue *q, struct bio *bio)
int rv;
int cpu;
if (mddev == NULL || mddev->pers == NULL) {
if (mddev == NULL || mddev->pers == NULL
|| !mddev->ready) {
bio_io_error(bio);
return 0;
}
smp_rmb(); /* Ensure implications of 'active' are visible */
rcu_read_lock();
if (mddev->suspended) {
DEFINE_WAIT(__wait);
@ -4564,7 +4566,8 @@ int md_run(mddev_t *mddev)
mddev->safemode_timer.data = (unsigned long) mddev;
mddev->safemode_delay = (200 * HZ)/1000 +1; /* 200 msec delay */
mddev->in_sync = 1;
smp_wmb();
mddev->ready = 1;
list_for_each_entry(rdev, &mddev->disks, same_set)
if (rdev->raid_disk >= 0) {
char nm[20];
@ -4725,6 +4728,7 @@ EXPORT_SYMBOL_GPL(md_stop_writes);
void md_stop(mddev_t *mddev)
{
mddev->ready = 0;
mddev->pers->stop(mddev);
if (mddev->pers->sync_request && mddev->to_remove == NULL)
mddev->to_remove = &md_redundancy_group;

3
drivers/md/md.h
View file

@ -148,7 +148,8 @@ struct mddev_s
* are happening, so run/
* takeover/stop are not safe
*/
int ready; /* See when safe to pass
* IO requests down */
struct gendisk *gendisk;
struct kobject kobj;