Hi

I submit this upstream patch for the stable branches 6.6 and 6.11.

Matthew Sakai from the DM-VDO team found out that there is a very narrow race condition in the slub sysfs code and it could cause crashes if caches with the same name are rapidly created and deleted. In order to work around these crashes, we need to have unique slab cache names.

Mikulas

commit 346dbf1b1345476a6524512892cceb931bee3039 Author: Mikulas Patocka mpatocka@redhat.com Date: Mon Nov 11 16:51:02 2024 +0100

dm-cache: fix warnings about duplicate slab caches

The commit 4c39529663b9 adds a warning about duplicate cache names if CONFIG_DEBUG_VM is selected. These warnings are triggered by the dm-cache code.

The dm-cache code allocates a slab cache for each device. This commit changes it to allocate just one slab cache in the module init function.

Signed-off-by: Mikulas Patocka mpatocka@redhat.com Fixes: 4c39529663b9 ("slab: Warn on duplicate cache names when DEBUG_VM=y")

diff --git a/drivers/md/dm-cache-background-tracker.c b/drivers/md/dm-cache-background-tracker.c index 9c5308298cf1..f3051bd7d2df 100644 --- a/drivers/md/dm-cache-background-tracker.c +++ b/drivers/md/dm-cache-background-tracker.c @@ -11,12 +11,6 @@

#define DM_MSG_PREFIX "dm-background-tracker"

-struct bt_work { - struct list_head list; - struct rb_node node; - struct policy_work work; -}; - struct background_tracker { unsigned int max_work; atomic_t pending_promotes; @@ -26,10 +20,10 @@ struct background_tracker { struct list_head issued; struct list_head queued; struct rb_root pending; - - struct kmem_cache *work_cache; };

+struct kmem_cache *btracker_work_cache = NULL; + struct background_tracker *btracker_create(unsigned int max_work) { struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL); @@ -48,12 +42,6 @@ struct background_tracker *btracker_create(unsigned int max_work) INIT_LIST_HEAD(&b->queued);

b->pending = RB_ROOT; - b->work_cache = KMEM_CACHE(bt_work, 0); - if (!b->work_cache) { - DMERR("couldn't create mempool for background work items"); - kfree(b); - b = NULL; - }

return b; } @@ -66,10 +54,9 @@ void btracker_destroy(struct background_tracker *b) BUG_ON(!list_empty(&b->issued)); list_for_each_entry_safe (w, tmp, &b->queued, list) { list_del(&w->list); - kmem_cache_free(b->work_cache, w); + kmem_cache_free(btracker_work_cache, w); }

- kmem_cache_destroy(b->work_cache); kfree(b); } EXPORT_SYMBOL_GPL(btracker_destroy); @@ -180,7 +167,7 @@ static struct bt_work *alloc_work(struct background_tracker *b) if (max_work_reached(b)) return NULL;

- return kmem_cache_alloc(b->work_cache, GFP_NOWAIT); + return kmem_cache_alloc(btracker_work_cache, GFP_NOWAIT); }

int btracker_queue(struct background_tracker *b, @@ -203,7 +190,7 @@ int btracker_queue(struct background_tracker *b, * There was a race, we'll just ignore this second * bit of work for the same oblock. */ - kmem_cache_free(b->work_cache, w); + kmem_cache_free(btracker_work_cache, w); return -EINVAL; }

@@ -244,7 +231,7 @@ void btracker_complete(struct background_tracker *b, update_stats(b, &w->work, -1); rb_erase(&w->node, &b->pending); list_del(&w->list); - kmem_cache_free(b->work_cache, w); + kmem_cache_free(btracker_work_cache, w); } EXPORT_SYMBOL_GPL(btracker_complete);

diff --git a/drivers/md/dm-cache-background-tracker.h b/drivers/md/dm-cache-background-tracker.h index 5b8f5c667b81..09c8fc59f7bb 100644 --- a/drivers/md/dm-cache-background-tracker.h +++ b/drivers/md/dm-cache-background-tracker.h @@ -26,6 +26,14 @@ * protected with a spinlock. */

+struct bt_work { + struct list_head list; + struct rb_node node; + struct policy_work work; +}; + +extern struct kmem_cache *btracker_work_cache; + struct background_work; struct background_tracker;

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 40709310e327..849eb6333e98 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -10,6 +10,7 @@ #include "dm-bio-record.h" #include "dm-cache-metadata.h" #include "dm-io-tracker.h" +#include "dm-cache-background-tracker.h"

#include <linux/dm-io.h> #include <linux/dm-kcopyd.h> @@ -2263,7 +2264,7 @@ static int parse_cache_args(struct cache_args *ca, int argc, char **argv,

/*----------------------------------------------------------------*/

-static struct kmem_cache *migration_cache; +static struct kmem_cache *migration_cache = NULL;

#define NOT_CORE_OPTION 1

@@ -3445,22 +3446,36 @@ static int __init dm_cache_init(void) int r;

migration_cache = KMEM_CACHE(dm_cache_migration, 0); - if (!migration_cache) - return -ENOMEM; + if (!migration_cache) { + r = -ENOMEM; + goto err; + } + + btracker_work_cache = kmem_cache_create("dm_cache_bt_work", + sizeof(struct bt_work), __alignof__(struct bt_work), 0, NULL); + if (!btracker_work_cache) { + r = -ENOMEM; + goto err; + }

r = dm_register_target(&cache_target); if (r) { - kmem_cache_destroy(migration_cache); - return r; + goto err; }

return 0; + +err: + kmem_cache_destroy(migration_cache); + kmem_cache_destroy(btracker_work_cache); + return r; }

static void __exit dm_cache_exit(void) { dm_unregister_target(&cache_target); kmem_cache_destroy(migration_cache); + kmem_cache_destroy(btracker_work_cache); }

module_init(dm_cache_init);