[PATCH 5.10 048/530] md: split mddev_find
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2021-05-12 15:28:03
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From: Christoph Hellwig <hch@lst.de>
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 d3374825ce57 ("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.
---
drivers/md/md.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c@@ -750,6 +750,22 @@ 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; if (unit && MAJOR(unit) != MD_MAJOR)
@@ -5656,7 +5672,7 @@ static int md_alloc(dev_t dev, char *nam * 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;
@@ -6539,11 +6555,9 @@ 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