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@xxxxxxxxx> >> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > 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@xxxxxxxxxxxxxx> >> --- >> 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@xxxxxxxxxxxxxx/ >> >> changes in v5: >> - https://lore.kernel.org/linux-mm/1620296523-21922-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v4: >> - https://lore.kernel.org/linux-mm/1618583239-18124-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v3: >> - https://lore.kernel.org/linux-mm/1617712064-12264-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> changes in v2: >> - https://lore.kernel.org/linux-mm/3ac1d3e6-6207-96ad-16a1-0f5139d8b2b5@xxxxxxxxxxxxxx/ >> >> changes in v1: >> - https://lore.kernel.org/linux-mm/1610443287-23933-1-git-send-email-faiyazm@xxxxxxxxxxxxxx/ >> >> 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 >> */ >> >
