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md: split mddev_find

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commit 65aa97c4d2bfd76677c211b9d03ef05a98c6d68e upstream.

Split mddev_find into a simple mddev_find that just finds an existing
mddev by the unit number, and a more complicated mddev_find that deals
with find or allocating a mddev.

This turns out to fix this bug reported by Zhao Heming.

----------------------------- snip ------------------------------
commit d3374825ce ("md: make devices disappear when they are no longer
needed.") introduced protection between mddev creating & removing. The
md_open shouldn't create mddev when all_mddevs list doesn't contain
mddev. With currently code logic, there will be very easy to trigger
soft lockup in non-preempt env.
This commit is contained in:
Christoph Hellwig 2021-04-03 18:15:29 +02:00 • committed by Greg Kroah-Hartman
commit afa4de0926
1 changed files with 19 additions and 5 deletions
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24
drivers/md/md.c
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@ -648,6 +648,22 @@ void mddev_init(struct mddev *mddev)
EXPORT_SYMBOL_GPL(mddev_init);
static struct mddev *mddev_find(dev_t unit)
{
struct mddev *mddev;
if (MAJOR(unit) != MD_MAJOR)
unit &= ~((1 << MdpMinorShift) - 1);
spin_lock(&all_mddevs_lock);
mddev = mddev_find_locked(unit);
if (mddev)
mddev_get(mddev);
spin_unlock(&all_mddevs_lock);
return mddev;
}
static struct mddev *mddev_find_or_alloc(dev_t unit)
{
struct mddev *mddev, *new = NULL;
@ -5436,7 +5452,7 @@ static int md_alloc(dev_t dev, char *name)
* writing to /sys/module/md_mod/parameters/new_array.
*/
static DEFINE_MUTEX(disks_mutex);
struct mddev *mddev = mddev_find(dev);
struct mddev *mddev = mddev_find_or_alloc(dev);
struct gendisk *disk;
int partitioned;
int shift;
@ -6312,11 +6328,9 @@ static void autorun_devices(int part)
md_probe(dev, NULL, NULL);
mddev = mddev_find(dev);
if (!mddev || !mddev->gendisk) {
if (mddev)
mddev_put(mddev);
if (!mddev)
break;
}
if (mddev_lock(mddev))
pr_warn("md: %s locked, cannot run\n", mdname(mddev));
else if (mddev->raid_disks || mddev->major_version