Re: [PATCH] failslab for SLUB

[Johannes Weiner <hannes@cmpxchg.org>]

On Tue, Dec 23, 2008 at 03:00:43PM +0200, Pekka J Enberg wrote:
> Hi Akinobu,
> 
> On Tue, 23 Dec 2008, Akinobu Mita wrote:
> > Currently fault-injection capability for SLAB allocator is only available
> > to SLAB. This patch makes it available to SLUB, too.
> 
> The code duplication in your patch is unfortunate. What do you think of 
> this patch instead?
> 
> 		Pekka
> 
> >>From 98bb6a5dade01ab007b3994a1456b7cac6b1f905 Mon Sep 17 00:00:00 2001
> From: Akinobu Mita <akinobu.mita@gmail.com>
> Date: Tue, 23 Dec 2008 19:37:01 +0900
> Subject: [PATCH] SLUB: failslab support
> 
> Currently fault-injection capability for SLAB allocator is only
> available to SLAB. This patch makes it available to SLUB, too.
> 
> [penberg@cs.helsinki.fi: unify slab and slub implementations]
> Cc: Christoph Lameter <cl@linux-foundation.org>
> Cc: Matt Mackall <mpm@selenic.com>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
> ---
>  include/linux/fault-inject.h |    9 +++++
>  lib/Kconfig.debug            |    1 +
>  mm/Makefile                  |    1 +
>  mm/failslab.c                |   59 +++++++++++++++++++++++++++++++++
>  mm/slab.c                    |   75 +++---------------------------------------
>  mm/slub.c                    |    4 ++
>  6 files changed, 79 insertions(+), 70 deletions(-)
>  create mode 100644 mm/failslab.c
> 
[...]
> diff --git a/mm/failslab.c b/mm/failslab.c
> new file mode 100644
> index 0000000..7c6ea64
> --- /dev/null
> +++ b/mm/failslab.c
> @@ -0,0 +1,59 @@
> +#include <linux/fault-inject.h>
> +
> +static struct {
> +	struct fault_attr attr;
> +	u32 ignore_gfp_wait;
> +#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> +	struct dentry *ignore_gfp_wait_file;
> +#endif
> +} failslab = {
> +	.attr = FAULT_ATTR_INITIALIZER,
> +	.ignore_gfp_wait = 1,
> +};
> +
> +bool should_failslab(size_t size, gfp_t gfpflags)
> +{
> +	if (gfpflags & __GFP_NOFAIL)
> +		return false;
> +
> +        if (failslab.ignore_gfp_wait && (gfpflags & __GFP_WAIT))
> +		return false;
> +
> +	return should_fail(&failslab.attr, size);
> +}
> +
> +static int __init setup_failslab(char *str)
> +{
> +	return setup_fault_attr(&failslab.attr, 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;
> +	struct dentry *dir;
> +	int err;
> +
> +	err = init_fault_attr_dentries(&failslab.attr, "failslab");
> +	if (err)
> +		return err;
> +	dir = failslab.attr.dentries.dir;
> +
> +	failslab.ignore_gfp_wait_file =
> +		debugfs_create_bool("ignore-gfp-wait", mode, dir,
> +				      &failslab.ignore_gfp_wait);
> +
> +	if (!failslab.ignore_gfp_wait_file) {
> +		err = -ENOMEM;
> +		debugfs_remove(failslab.ignore_gfp_wait_file);
> +		cleanup_fault_attr_dentries(&failslab.attr);
> +	}
> +
> +	return err;
> +}
> +
> +late_initcall(failslab_debugfs_init);
> +
> +#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
> diff --git a/mm/slab.c b/mm/slab.c
> index 0918751..c347dd8 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3106,79 +3106,14 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
>  #define cache_alloc_debugcheck_after(a,b,objp,d) (objp)
>  #endif
>  
> -#ifdef CONFIG_FAILSLAB
> -
> -static struct failslab_attr {
> -
> -	struct fault_attr attr;
> -
> -	u32 ignore_gfp_wait;
> -#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> -	struct dentry *ignore_gfp_wait_file;
> -#endif
> -
> -} failslab = {
> -	.attr = FAULT_ATTR_INITIALIZER,
> -	.ignore_gfp_wait = 1,
> -};
> -
> -static int __init setup_failslab(char *str)
> -{
> -	return setup_fault_attr(&failslab.attr, str);
> -}
> -__setup("failslab=", setup_failslab);
> -
> -static int should_failslab(struct kmem_cache *cachep, gfp_t flags)
> +static bool slab_should_failslab(struct kmem_cache *cachep, gfp_t flags)
>  {
>  	if (cachep == &cache_cache)
> -		return 0;
> -	if (flags & __GFP_NOFAIL)
> -		return 0;
> -	if (failslab.ignore_gfp_wait && (flags & __GFP_WAIT))
> -		return 0;
> +		return false;
>  
> -	return should_fail(&failslab.attr, obj_size(cachep));
> +	return should_failslab(obj_size(cachep), flags);
>  }
>  
> -#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> -
> -static int __init failslab_debugfs(void)
> -{
> -	mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
> -	struct dentry *dir;
> -	int err;
> -
> -	err = init_fault_attr_dentries(&failslab.attr, "failslab");
> -	if (err)
> -		return err;
> -	dir = failslab.attr.dentries.dir;
> -
> -	failslab.ignore_gfp_wait_file =
> -		debugfs_create_bool("ignore-gfp-wait", mode, dir,
> -				      &failslab.ignore_gfp_wait);
> -
> -	if (!failslab.ignore_gfp_wait_file) {
> -		err = -ENOMEM;
> -		debugfs_remove(failslab.ignore_gfp_wait_file);
> -		cleanup_fault_attr_dentries(&failslab.attr);
> -	}
> -
> -	return err;
> -}
> -
> -late_initcall(failslab_debugfs);
> -
> -#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
> -
> -#else /* CONFIG_FAILSLAB */
> -
> -static inline int should_failslab(struct kmem_cache *cachep, gfp_t flags)
> -{
> -	return 0;
> -}
> -
> -#endif /* CONFIG_FAILSLAB */
> -
>  static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>  {
>  	void *objp;
> @@ -3381,7 +3316,7 @@ __cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
>  	unsigned long save_flags;
>  	void *ptr;
>  
> -	if (should_failslab(cachep, flags))
> +	if (slab_should_failslab(cachep, flags))

should_failslab()?

>  		return NULL;
>  
>  	cache_alloc_debugcheck_before(cachep, flags);
> @@ -3457,7 +3392,7 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
>  	unsigned long save_flags;
>  	void *objp;
>  
> -	if (should_failslab(cachep, flags))
> +	if (slab_should_failslab(cachep, flags))

should_failslab()?

	Hannes

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