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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Sk8nuKUV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Sk8nuKUV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9D58C4CEC2; Wed, 4 Sep 2024 16:53:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1725468785; bh=u1tfE+6LTF/AZPaX62ARJpFZTaHNZWfbhWhv90/bG3s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Sk8nuKUVpGPOYGgLAnFueUUTfsYVEYnDPrpSv0ecfRmwV4ID2QN+6CZJ52PZeMEyq PffZmkN9T3tcvABDERA/L7KuP7H8bebBjTBxS/80+7ZQoZ/mJTcpmqMsXFy19uLc5K LMioyZDfR5rkW+6LYJKFZaYxWLLOEkZ2i837+cd5rx0YUy3zxqPV1xP+Z1VzTCJocl 5qASXHEvlnPlb7v7ql6jHpsBWHUy3DEZKm/37slbHE/n6FuB+HqXWEu7RqRea4lAHC SiNfmh2JSl6Tpbudo2zc35pkpcISRqR3lipSVgE5e0I3mfNYSqnFdCUNzh/cpzx/zM QCNtmUd5TDutw== Date: Wed, 4 Sep 2024 18:53:00 +0200 From: Christian Brauner To: Mike Rapoport Cc: Vlastimil Babka , Jens Axboe , Jann Horn , Linus Torvalds , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2 02/15] slab: add struct kmem_cache_args Message-ID: <20240904-warfen-labyrinth-f16ea368a200@brauner> References: <20240903-work-kmem_cache_args-v2-0-76f97e9a4560@kernel.org> <20240903-work-kmem_cache_args-v2-2-76f97e9a4560@kernel.org> <20240904-bauaufsicht-gewohnheit-a70bd9266986@brauner> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Wed, Sep 04, 2024 at 07:16:07PM GMT, Mike Rapoport wrote: > On Wed, Sep 04, 2024 at 05:48:31PM +0200, Christian Brauner wrote: > > On Wed, Sep 04, 2024 at 06:16:16PM GMT, Mike Rapoport wrote: > > > On Tue, Sep 03, 2024 at 04:20:43PM +0200, Christian Brauner wrote: > > > > Signed-off-by: Christian Brauner > > > > --- > > > > include/linux/slab.h | 21 ++++++++++++++++ > > > > mm/slab_common.c | 67 +++++++++++++++++++++++++++++++++++++++------------- > > > > 2 files changed, 72 insertions(+), 16 deletions(-) > > > > > > > > diff --git a/include/linux/slab.h b/include/linux/slab.h > > > > index 5b2da2cf31a8..79d8c8bca4a4 100644 > > > > --- a/include/linux/slab.h > > > > +++ b/include/linux/slab.h > > > > @@ -240,6 +240,27 @@ struct mem_cgroup; > > > > */ > > > > bool slab_is_available(void); > > > > > > > > +/** > > > > + * @align: The required alignment for the objects. > > > > + * @useroffset: Usercopy region offset > > > > + * @usersize: Usercopy region size > > > > + * @freeptr_offset: Custom offset for the free pointer in RCU caches > > > > + * @use_freeptr_offset: Whether a @freeptr_offset is used > > > > + * @ctor: A constructor for the objects. > > > > + */ > > > > +struct kmem_cache_args { > > > > + unsigned int align; > > > > + unsigned int useroffset; > > > > + unsigned int usersize; > > > > + unsigned int freeptr_offset; > > > > + bool use_freeptr_offset; > > > > + void (*ctor)(void *); > > > > +}; > > > > + > > > > +struct kmem_cache *__kmem_cache_create_args(const char *name, > > > > + unsigned int object_size, > > > > + struct kmem_cache_args *args, > > > > + slab_flags_t flags); > > > > struct kmem_cache *kmem_cache_create(const char *name, unsigned int size, > > > > unsigned int align, slab_flags_t flags, > > > > void (*ctor)(void *)); > > > > diff --git a/mm/slab_common.c b/mm/slab_common.c > > > > index 91e0e36e4379..0f13c045b8d1 100644 > > > > --- a/mm/slab_common.c > > > > +++ b/mm/slab_common.c > > > > @@ -248,14 +248,24 @@ static struct kmem_cache *create_cache(const char *name, > > > > return ERR_PTR(err); > > > > } > > > > > > > > -static struct kmem_cache * > > > > -do_kmem_cache_create_usercopy(const char *name, > > > > - unsigned int size, unsigned int freeptr_offset, > > > > - unsigned int align, slab_flags_t flags, > > > > - unsigned int useroffset, unsigned int usersize, > > > > - void (*ctor)(void *)) > > > > +/** > > > > + * __kmem_cache_create_args - Create a kmem cache > > > > + * @name: A string which is used in /proc/slabinfo to identify this cache. > > > > + * @object_size: The size of objects to be created in this cache. > > > > + * @args: Arguments for the cache creation (see struct kmem_cache_args). > > > > + * @flags: See %SLAB_* flags for an explanation of individual @flags. > > > > + * > > > > + * Cannot be called within a interrupt, but can be interrupted. > > > > + * > > > > + * Return: a pointer to the cache on success, NULL on failure. > > > > + */ > > > > +struct kmem_cache *__kmem_cache_create_args(const char *name, > > > > + unsigned int object_size, > > > > + struct kmem_cache_args *args, > > > > + slab_flags_t flags) > > > > { > > > > struct kmem_cache *s = NULL; > > > > + unsigned int freeptr_offset = UINT_MAX; > > > > const char *cache_name; > > > > int err; > > > > > > > > @@ -275,7 +285,7 @@ do_kmem_cache_create_usercopy(const char *name, > > > > > > > > mutex_lock(&slab_mutex); > > > > > > > > - err = kmem_cache_sanity_check(name, size); > > > > + err = kmem_cache_sanity_check(name, object_size); > > > > if (err) { > > > > goto out_unlock; > > > > } > > > > @@ -296,12 +306,14 @@ do_kmem_cache_create_usercopy(const char *name, > > > > > > > > /* Fail closed on bad usersize of useroffset values. */ > > > > if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) || > > > > - WARN_ON(!usersize && useroffset) || > > > > - WARN_ON(size < usersize || size - usersize < useroffset)) > > > > - usersize = useroffset = 0; > > > > - > > > > - if (!usersize) > > > > - s = __kmem_cache_alias(name, size, align, flags, ctor); > > > > + WARN_ON(!args->usersize && args->useroffset) || > > > > + WARN_ON(object_size < args->usersize || > > > > + object_size - args->usersize < args->useroffset)) > > > > + args->usersize = args->useroffset = 0; > > > > + > > > > + if (!args->usersize) > > > > + s = __kmem_cache_alias(name, object_size, args->align, flags, > > > > + args->ctor); > > > > > > Sorry I missed it in the previous review, but nothing guaranties that > > > nobody will call kmem_cache_create_args with args != NULL. > > > > > > I think there should be a check for args != NULL and a substitution of args > > > with defaults if it actually was NULL. > > > > I think that callers that pass NULL should all be switched to > > KMEM_CACHE() and passing NULL should simply not be supported. And the > > few callers that need some very special alignment need to pass struct > > kmem_cache_args anyway. So there should never be a need to pass NULL. > > But you can't guarantee that some random driver won't call > > __kmem_cache_create_args("name", size, NULL, flags); > > At least we'd need > > if (!args) > return -EINVAL; Calling __kmem_cache_create_args() directly is a bug. That's why it's __*(). And we don't check for non-NULL @name either. In fact we almost never do such checks. Plus, if someone did: kmem_cache_create("foo", sizeof(foo), NULL, flags); they'd get a compile time error due to _Generic().