From 565e0450129647df5112bff3df3ffd02b0c08e32 Mon Sep 17 00:00:00 2001 From: Aliaksei Karaliou Date: Sat, 23 Dec 2017 21:20:31 +0300 Subject: md/raid5: simplify uninitialization of shrinker Don't use shrinker.nr_deferred to check whether shrinker was initialized or not. Now this check was integrated into unregister_shrinker(), so it is safe to call it against unregistered shrinker. Signed-off-by: Aliaksei Karaliou Signed-off-by: Shaohua Li --- drivers/md/raid5.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'drivers/md/raid5.c') diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 50d01144b805..36e050678f5a 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -6764,9 +6764,7 @@ static void free_conf(struct r5conf *conf) log_exit(conf); - if (conf->shrinker.nr_deferred) - unregister_shrinker(&conf->shrinker); - + unregister_shrinker(&conf->shrinker); free_thread_groups(conf); shrink_stripes(conf); raid5_free_percpu(conf); -- cgit v1.2.3 From 53b8d89ddbdbb0e4625a46d2cdbb6f106c52f801 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 20 Feb 2018 14:09:11 +0100 Subject: md: raid5: avoid string overflow warning gcc warns about a possible overflow of the kmem_cache string, when adding four characters to a string of the same length: drivers/md/raid5.c: In function 'setup_conf': drivers/md/raid5.c:2207:34: error: '-alt' directive writing 4 bytes into a region of size between 1 and 32 [-Werror=format-overflow=] sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); ^~~~ drivers/md/raid5.c:2207:2: note: 'sprintf' output between 5 and 36 bytes into a destination of size 32 sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If I'm counting correctly, we need 11 characters for the fixed part of the string and 18 characters for a 64-bit pointer (when no gendisk is used), so that leaves three characters for conf->level, which should always be sufficient. This makes the code use snprintf() with the correct length, to make the code more robust against changes, and to get the compiler to shut up. In commit f4be6b43f1ac ("md/raid5: ensure we create a unique name for kmem_cache when mddev has no gendisk") from 2010, Neil said that the pointer could be removed "shortly" once devices without gendisk are disallowed. I have no idea if that happened, but if it did, that should probably be changed as well. Signed-off-by: Arnd Bergmann Signed-off-by: Shaohua Li --- drivers/md/raid5.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'drivers/md/raid5.c') diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 36e050678f5a..e3b0f799fbfa 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2196,15 +2196,16 @@ static int grow_one_stripe(struct r5conf *conf, gfp_t gfp) static int grow_stripes(struct r5conf *conf, int num) { struct kmem_cache *sc; + size_t namelen = sizeof(conf->cache_name[0]); int devs = max(conf->raid_disks, conf->previous_raid_disks); if (conf->mddev->gendisk) - sprintf(conf->cache_name[0], + snprintf(conf->cache_name[0], namelen, "raid%d-%s", conf->level, mdname(conf->mddev)); else - sprintf(conf->cache_name[0], + snprintf(conf->cache_name[0], namelen, "raid%d-%p", conf->level, conf->mddev); - sprintf(conf->cache_name[1], "%s-alt", conf->cache_name[0]); + snprintf(conf->cache_name[1], namelen, "%.27s-alt", conf->cache_name[0]); conf->active_name = 0; sc = kmem_cache_create(conf->cache_name[conf->active_name], -- cgit v1.2.3 From 8876391e440ba615b10eef729576e111f0315f87 Mon Sep 17 00:00:00 2001 From: BingJing Chang Date: Thu, 22 Feb 2018 13:34:46 +0800 Subject: md: fix a potential deadlock of raid5/raid10 reshape There is a potential deadlock if mount/umount happens when raid5_finish_reshape() tries to grow the size of emulated disk. How the deadlock happens? 1) The raid5 resync thread finished reshape (expanding array). 2) The mount or umount thread holds VFS sb->s_umount lock and tries to write through critical data into raid5 emulated block device. So it waits for raid5 kernel thread handling stripes in order to finish it I/Os. 3) In the routine of raid5 kernel thread, md_check_recovery() will be called first in order to reap the raid5 resync thread. That is, raid5_finish_reshape() will be called. In this function, it will try to update conf and call VFS revalidate_disk() to grow the raid5 emulated block device. It will try to acquire VFS sb->s_umount lock. The raid5 kernel thread cannot continue, so no one can handle mount/ umount I/Os (stripes). Once the write-through I/Os cannot be finished, mount/umount will not release sb->s_umount lock. The deadlock happens. The raid5 kernel thread is an emulated block device. It is responible to handle I/Os (stripes) from upper layers. The emulated block device should not request any I/Os on itself. That is, it should not call VFS layer functions. (If it did, it will try to acquire VFS locks to guarantee the I/Os sequence.) So we have the resync thread to send resync I/O requests and to wait for the results. For solving this potential deadlock, we can put the size growth of the emulated block device as the final step of reshape thread. 2017/12/29: Thanks to Guoqing Jiang , we confirmed that there is the same deadlock issue in raid10. It's reproducible and can be fixed by this patch. For raid10.c, we can remove the similar code to prevent deadlock as well since they has been called before. Reported-by: Alex Wu Reviewed-by: Alex Wu Reviewed-by: Chung-Chiang Cheng Signed-off-by: BingJing Chang Signed-off-by: Shaohua Li --- drivers/md/raid5.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'drivers/md/raid5.c') diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index e3b0f799fbfa..b5d2601483e3 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -8000,13 +8000,7 @@ static void raid5_finish_reshape(struct mddev *mddev) if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) { - if (mddev->delta_disks > 0) { - md_set_array_sectors(mddev, raid5_size(mddev, 0, 0)); - if (mddev->queue) { - set_capacity(mddev->gendisk, mddev->array_sectors); - revalidate_disk(mddev->gendisk); - } - } else { + if (mddev->delta_disks <= 0) { int d; spin_lock_irq(&conf->device_lock); mddev->degraded = raid5_calc_degraded(conf); -- cgit v1.2.3