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Date: Thu, 25 Feb 2010 08:50:15 +0300
From: Dmitry Monakhov <dmonakhov@...nvz.org>
To: David Rientjes <rientjes@...gle.com>
Cc: linux-kernel@...r.kernel.org, akinobu.mita@...il.com
Subject: Re: [PATCH] failslab: add ability to filter slab caches
David Rientjes <rientjes@...gle.com> writes:
> On Wed, 24 Feb 2010, Dmitry Monakhov wrote:
>
>> >> Example:
>> >> echo 1 > /sys/kernel/slab/skbuff_head_cache/failslab
>> >> echo 1 > /sys/kernel/debug/failslab/cache-filter
>> >>
>> >
>> > Where's the changelog?
>> I've hoped than subject is enough. But if you want more verbose
>> changelog, take following version.
>>
Ohh... i'm sorry i've missed other comments in your previous review.
It will be fixed in second version. Also see major note about
slab flags later in the text.
>
> Please do not attach patches to emails when sending to LKML, they are
> preferred to be inline. See Documentation/SubmittingPatches.
Yeah, In fact i've chose inline option but my mailer by unknown reason
change it.
>
>> This patch allow to inject faults only for specific slabs.
>> In order to preserve default behavior cache filter is off by
>> default (all caches are faulty).
>>
>> One may define specific set of slabs like this:
>> # mark skbuff_head_cache as faulty
>> echo 1 > /sys/kernel/slab/skbuff_head_cache/failslab
>> # Turn on cache filter (off by default)
>> echo 1 > /sys/kernel/debug/failslab/cache-filter
>> # Turn on fault injection
>> echo 1 > /sys/kernel/debug/failslab/times
>> echo 1 > /sys/kernel/debug/failslab/probability
>>
>
> Please describe your new slub_debug=a option here as well as in an update
> to Documentation/vm/slub.txt.
Done
>
>> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
>> ---
>> include/linux/fault-inject.h | 4 ++--
>> include/linux/slab.h | 4 +++-
>> mm/failslab.c | 18 +++++++++++++++---
>> mm/slab.c | 2 +-
>> mm/slub.c | 31 +++++++++++++++++++++++++++++--
>> 5 files changed, 50 insertions(+), 9 deletions(-)
>>
>> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
>> index 06ca9b2..d935647 100644
>> --- a/include/linux/fault-inject.h
>> +++ b/include/linux/fault-inject.h
>> @@ -82,9 +82,9 @@ static inline void cleanup_fault_attr_dentries(struct fault_attr *attr)
>> #endif /* CONFIG_FAULT_INJECTION */
>>
>> #ifdef CONFIG_FAILSLAB
>> -extern bool should_failslab(size_t size, gfp_t gfpflags);
>> +extern bool should_failslab(size_t size, gfp_t gfpflags, unsigned long c_flags);
>> #else
>> -static inline bool should_failslab(size_t size, gfp_t gfpflags)
>> +static inline bool should_failslab(size_t size, gfp_t gfpflags, unsigned long f)
>> {
>> return false;
>> }
>
> As I said in the first review, these need to be more descriptive: 'flags'
> would be better.
done
>
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 2da8372..9e03a81 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -70,7 +70,9 @@
>> #else
>> # define SLAB_NOTRACK 0x00000000UL
>> #endif
>> -
>> +#ifdef CONFIG_FAILSLAB
>> +# define SLAB_FAILSLAB 0x02000000UL /* Fault injection filter mark */
>> +#endif
>
> Trailing whitespace on your #endif.
Sorry. fixed
>
>> /* The following flags affect the page allocator grouping pages by mobility */
>> #define SLAB_RECLAIM_ACCOUNT 0x00020000UL /* Objects are reclaimable */
>> #define SLAB_TEMPORARY SLAB_RECLAIM_ACCOUNT /* Objects are short-lived */
>> diff --git a/mm/failslab.c b/mm/failslab.c
>> index 9339de5..bb41f98 100644
>> --- a/mm/failslab.c
>> +++ b/mm/failslab.c
>> @@ -1,18 +1,22 @@
>> #include <linux/fault-inject.h>
>> #include <linux/gfp.h>
>> +#include <linux/slab.h>
>>
>> static struct {
>> struct fault_attr attr;
>> u32 ignore_gfp_wait;
>> + int cache_filter;
>> #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>> struct dentry *ignore_gfp_wait_file;
>> + struct dentry *cache_filter_file;
>> #endif
>> } failslab = {
>> .attr = FAULT_ATTR_INITIALIZER,
>> .ignore_gfp_wait = 1,
>> + .cache_filter = 0,
>> };
>>
>> -bool should_failslab(size_t size, gfp_t gfpflags)
>> +bool should_failslab(size_t size, gfp_t gfpflags, unsigned long cache_flags)
>> {
>> if (gfpflags & __GFP_NOFAIL)
>> return false;
>> @@ -20,6 +24,9 @@ bool should_failslab(size_t size, gfp_t gfpflags)
>> if (failslab.ignore_gfp_wait && (gfpflags & __GFP_WAIT))
>> return false;
>>
>> + if (failslab.cache_filter && !(cache_flags & SLAB_FAILSLAB))
>> + return false;
>> +
>> return should_fail(&failslab.attr, size);
>> }
>>
>> @@ -30,7 +37,6 @@ static int __init setup_failslab(char *str)
>> __setup("failslab=", setup_failslab);
>>
>> #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>> -
>> static int __init failslab_debugfs_init(void)
>> {
>> mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
>> @@ -46,8 +52,14 @@ static int __init failslab_debugfs_init(void)
>> debugfs_create_bool("ignore-gfp-wait", mode, dir,
>> &failslab.ignore_gfp_wait);
>>
>> - if (!failslab.ignore_gfp_wait_file) {
>> + failslab.cache_filter_file =
>> + debugfs_create_bool("cache-filter", mode, dir,
>> + &failslab.cache_filter);
>> +
>> + if (!failslab.ignore_gfp_wait_file ||
>> + !failslab.cache_filter_file) {
>> err = -ENOMEM;
>> + debugfs_remove(failslab.cache_filter_file);
>> debugfs_remove(failslab.ignore_gfp_wait_file);
>> cleanup_fault_attr_dentries(&failslab.attr);
>> }
>> diff --git a/mm/slab.c b/mm/slab.c
>> index 7451bda..33496b7 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -3101,7 +3101,7 @@ static bool slab_should_failslab(struct kmem_cache *cachep, gfp_t flags)
>> if (cachep == &cache_cache)
>> return false;
>>
>> - return should_failslab(obj_size(cachep), flags);
>> + return should_failslab(obj_size(cachep), flags, cachep->flags);
>> }
>>
>
> cachep->flags for CONFIG_SLAB is of type unsigned int and
> should_failslab() takes an unsigned long.
Strange story, seems that flag definition in slab_def.h is differ
from slub_def.h and slob_def.h (unsigned long long)
Need to be fixed. Will send as separate patch.
>
>> static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 8d71aaf..64114fa 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -151,7 +151,8 @@
>> * Set of flags that will prevent slab merging
>> */
>> #define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
>> - SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE)
>> + SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
>> + SLAB_FAILSLAB)
>>
>> #define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
>> SLAB_CACHE_DMA | SLAB_NOTRACK)
>
> As I mentioned in my first review of your patch, this breaks for
> CONFIG_FAILSLAB=n. Please make sure your patch compiles for the
> defconfig.
fixed.
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