On 11/8/24 17:49, Yang Shi wrote:
> On Wed, Nov 6, 2024 at 3:35 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
>>
>> On 11/6/24 12:19, Mikulas Patocka wrote:
>> > Hi
>>
>> Hi,
>>
>> > The commit 4c39529663b93165953ecf9b1a9ea817358dcd06 ("slab: Warn on
>> > duplicate cache names when DEBUG_VM=y") is causing large number of
>> > warnings about "dm_bufio_buffer", "dm_bufio_buffer-%u" (and other) device
>> > mapper caches.
>>
>> Hmm wonder why nobody run into this before. We thought the code that would
>> cause the warning would be all fixed before introducing it, but we missed
>> some, sorry.
>
> Another data point, I also saw such warning when booting 6.12-rcX (rc1
> and rc6), but from mlx5 driver. I thought it was mlx driver specific
> issue, it seems not.
Well this particular issue is mlx driver specific.
The caches it creates (per device?) don't seem to be have specific size or
anything to that device, so it should be relatively simple to fix.
> [ 63.537874] kmem_cache of name 'mlx5_fs_ftes' already exists
> [ 63.546399] WARNING: CPU: 0 PID: 9 at mm/slab_common.c:107
> __kmem_cache_create_args+0xb4/0x330
> [ 63.557839] Modules linked in: vfat fat mlx5_core(+) dax_hmem
> cxl_acpi ampere_cspmu cxl_port cxl_core mlxfw psample einj arm_spe_pmu
> arm_cspmu_module tls pci_hyperv_intf acpi_ipmi acpi_tad ipmi_ssif
> ipmi_devintf arm_cmn ipmi_msghandler cppc_cpufreq(+) fuse loop
> nfnetlink zram xfs crct10dif_ce polyval_ce polyval_generic ghash_ce
> sha3_ce nvme sha512_ce nvme_core sha512_arm64 sbsa_gwdt nvme_auth
> xgene_hwmon
> [ 63.596473] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Tainted: G
> W 6.12.0-rc6 #80
> [ 63.609156] Tainted: [W]=WARN
> [ 63.614976] Hardware name: ZOLLNER SUNMOONLAKE/SunMoon Lake, BIOS
> 00.00. 2024-10-30 13:48:02 11/06/2024
> [ 63.624359] Workqueue: events work_for_cpu_fn
> [ 63.631569] pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [ 63.638523] pc : __kmem_cache_create_args+0xb4/0x330
> [ 63.646340] lr : __kmem_cache_create_args+0xb4/0x330
> [ 63.654158] sp : ffff800080d1bc00
> [ 63.660330] x29: ffff800080d1bc00 x28: 0000000000000000 x27: 0000000000000000
> [ 63.670318] x26: 0000000000000000 x25: ffffbf101f234410 x24: 00000000000002d8
> [ 63.677446] x23: 0000000000000000 x22: ffff800080d1bc58 x21: ffffbf101f2344b8
> [ 63.687436] x20: ffffbf0ff94870a8 x19: ffff2001053a1700 x18: 0000000000000014
> [ 63.694563] x17: 00000000a871ae29 x16: ffffbf101c282f18 x15: 000000007773661b
> [ 63.704552] x14: 0000000000000000 x13: 7374736978652079 x12: 646165726c612027
> [ 63.714539] x11: 736574665f73665f x10: 35786c6d2720656d x9 : ffffbf101c1722f0
> [ 63.724531] x8 : ffff800080d1b890 x7 : 0000000000000001 x6 : 0000000000000001
> [ 63.734518] x5 : ffff001f7d803448 x4 : 0000000000000000 x3 : 0000000000000000
> [ 63.741646] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000108e3a440
> [ 63.751634] Call trace:
> [ 63.754072] __kmem_cache_create_args+0xb4/0x330
> [ 63.761542] mlx5_fs_core_alloc+0x158/0x1a8 [mlx5_core]
> [ 63.769708] mlx5_init_once+0x13c/0x520 [mlx5_core]
> [ 63.777528] mlx5_init_one_devl_locked+0xa8/0x280 [mlx5_core]
> [ 63.786127] probe_one+0xe0/0x200 [mlx5_core]
> [ 63.790569] local_pci_probe+0x48/0xc0
> [ 63.794307] work_for_cpu_fn+0x24/0x40
> [ 63.798044] process_one_work+0x180/0x430
> [ 63.802042] worker_thread+0x25c/0x380
> [ 63.805778] kthread+0xf4/0x108
> [ 63.808907] ret_from_fork+0x10/0x20
>
>>
>> > I'd like to ask - how to properly fix it?
>> >
>> > We create a "dm_bufio_buffer" or "dm_bufio_buffer-%u" cache with every dm
>> > bufio client. It used to work (and the duplicate caches are merged), but
>>
>> Note the merging can be disabled so then it's really several caches with
>> exactly same name in /proc/slabinfo and inability to create their
>> sysfs/debugfs directories.
>>
>> > now it warns.
>> >
>> > Should I append a pointer to the dm_bufio structure to the slab cache name
>> > to make them different? Or is there any other preferred solution?
>>
>> Anything that uniquely identifies the client should be ok, but beware e.g.
>> device names that can have slashes, see commit a360f311f57a36 (also for the
>> simplest possible fix that is an incremented number).
>>
>> > Note that it is not possible to pre-create the cache "dm_bufio_buffer-%u"
>> > in the module's init function, because the size of per-buffer auxiliary
>> > data is not known at this point.
>>
>> Looks like some chose to solve this the harder way, see 4d784c042d164f
>>
>> > Mikulas
>> >
>>
>>
