lkml.org 
[lkml]   [2021]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v7] mm: slub: move sysfs slab alloc/free interfaces to debugfs
From
Date


On 5/26/2021 5:08 PM, Vlastimil Babka wrote:
> On 5/25/21 9:38 AM, Faiyaz Mohammed wrote:
>> alloc_calls and free_calls implementation in sysfs have two issues,
>> one is PAGE_SIZE limitiation of sysfs and other is it does not adhere
>> to "one value per file" rule.
>>
>> To overcome this issues, move the alloc_calls and free_calls implemeation
>> to debugfs.
>>
>> Rename the alloc_calls/free_calls to alloc_traces/free_traces,
>> to be inline with what it does.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> These were IIRC bot reports for some bugs in the previous versions, so keeping
> the Reported-by: for the whole patch is misleading - these were not reports for
> the sysfs issues this patch fixes by moving the files to debugfs.
>
Yes, I will update in next patch version.
>> Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
>> ---
>> changes in V7:
>> - Drop the older alloc_calls and free_calls interface.
>> changes in v6:
>> - https://lore.kernel.org/linux-mm/1621341949-26762-1-git-send-email-faiyazm@codeaurora.org/
>>
>> changes in v5:
>> - https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@codeaurora.org/
>>
>> changes in v4:
>> - https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@codeaurora.org/
>>
>> changes in v3:
>> - https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@codeaurora.org/
>>
>> changes in v2:
>> - https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@codeaurora.org/
>>
>> changes in v1:
>> - https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@codeaurora.org/
>>
>> include/linux/slub_def.h | 8 ++
>> mm/slab_common.c | 9 ++
>> mm/slub.c | 353 ++++++++++++++++++++++++++++++++++-------------
>> 3 files changed, 276 insertions(+), 94 deletions(-)
>
> I don't see any of the symlinks under /sys/kernel/debug/slab/, so I think the
> aliases handling code is wrong, and I can see at least two reasons why it could be:
>

I think I missed one thing, when CONFIG_SLUB_DEBUG_ON enable or
slub_debug is pass through command line __kmem_cache_alias() will return
null, so no symlinks will be created even if CONFIG_SLAB_MERGE_DEFAULT
is enable and to store user data we need to enable CONFIG_SLUB_DEBUG_ON
or pass slub_debug through command line.

>> @@ -4525,6 +4535,8 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>> s->refcount--;
>> s = NULL;
>> }
>> +
>> + debugfs_slab_alias(s, name);
>
> Here you might be calling debugfs_slab_alias() with NULL if the
> sysfs_slab_alias() above returned true.
>
I think we can drop debugfs_slab_alias implementation.
>> }
>>
>> return s;
>
> ...
>
>> +static int __init slab_debugfs_init(void)
>> +{
>> + struct kmem_cache *s;
>> +
>> + slab_debugfs_root = debugfs_create_dir("slab", NULL);
>> +
>> + slab_state = FULL;
>> +
>> + list_for_each_entry(s, &slab_caches, list)
>> + debugfs_slab_add(s);
>> +
>> + while (alias_list) {
>> + struct saved_alias *al = alias_list;
>
> alias_list a single list and both slab_sysfs_init() and slab_debugfs_init()
> flush it. So only the init call that happens to be called first, does actually
> find an unflushed list. I think you
> need to use a separate list for debugfs (simpler) or a shared list with both
> sysfs and debugfs processing (probably more complicated).
>
same here, I think we can drop the debugfs alias change.

> And finally a question, perhaps also for Greg. With sysfs, we hand out the
> lifecycle of struct kmem_cache to sysfs, to ensure we are not reading sysfs
> files of a cache that has been removed.
>
> But with debugfs, what are the guarantees that things won't blow up when a
> debugfs file is being read while somebody calls kmem_cache_destroy() on the cache?
>
>> +
>> + alias_list = alias_list->next;
>> +
>> + debugfs_slab_alias(al->s, al->name);
>> +
>> + kfree(al);
>> + }
>> +
>> + return 0;
>> +
>> +}
>> +__initcall(slab_debugfs_init);
>> +#endif
>> /*
>> * The /proc/slabinfo ABI
>> */
>>
>

\
 
 \ /
  Last update: 2021-05-31 08:56    [W:0.121 / U:0.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site