linux-kernel - Re: [PATCH] mm, vmalloc: properly track vmalloc users

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Date:   Tue, 9 May 2017 13:19:34 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     kbuild-all@...org, kbuild test robot <lkp@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm, vmalloc: properly track vmalloc users

On Wed 03-05-17 08:37:50, Michal Hocko wrote:
> From 33a6239135cb444654f48d5e942e7f34898e24ea Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.com>
> Date: Tue, 2 May 2017 11:18:29 +0200
> Subject: [PATCH] mm, vmalloc: properly track vmalloc users
> 
> __vmalloc_node_flags used to be static inline but this has changed by
> "mm: introduce kv[mz]alloc helpers" because kvmalloc_node needs to use
> it as well and the code is outside of the vmalloc proper. I haven't
> realized that changing this will lead to a subtle bug though. The
> function is responsible to track the caller as well. This caller is
> then printed by /proc/vmallocinfo. If __vmalloc_node_flags is not inline
> then we would get only direct users of __vmalloc_node_flags as callers
> (e.g. v[mz]alloc) which reduces usefulness of this debugging feature
> considerably. It simply doesn't help to see that the given range belongs
> to vmalloc as a caller:
> 0xffffc90002c79000-0xffffc90002c7d000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N0=3
> 0xffffc90002c81000-0xffffc90002c85000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3
> 0xffffc90002c8d000-0xffffc90002c91000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3
> 0xffffc90002c95000-0xffffc90002c99000   16384 vmalloc+0x16/0x18 pages=3 vmalloc N1=3
> 
> We really want to catch the _caller_ of the vmalloc function. Fix this
> issue by making __vmalloc_node_flags static inline again and export
> __vmalloc_node_flags_caller for kvmalloc_node().
> 

The "mm: introduce kv[mz]alloc helpers" got merged in the mean time so I
believe the patch should mention

Fixes: a7c3e901a46f ("mm: introduce kv[mz]alloc helpers")

> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
>  include/linux/vmalloc.h | 16 +++++++++++++++-
>  mm/util.c               |  3 ++-
>  mm/vmalloc.c            |  8 +++++++-
>  3 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 46991ad3ddd5..4a0fabeb1e92 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -80,7 +80,21 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
>  			unsigned long start, unsigned long end, gfp_t gfp_mask,
>  			pgprot_t prot, unsigned long vm_flags, int node,
>  			const void *caller);
> -extern void *__vmalloc_node_flags(unsigned long size, int node, gfp_t flags);
> +#ifndef CONFIG_MMU
> +extern void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags);
> +static inline void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags, void* caller)
> +{
> +	return __vmalloc_node_flags(size, node, flags);
> +}
> +#else
> +/*
> + * We really want to have this inlined due to caller tracking. This
> + * function is used by the highlevel vmalloc apis and so we want to track
> + * their callers and inlining will achieve that.
> + */
> +extern void *__vmalloc_node_flags_caller(unsigned long size,
> +					int node, gfp_t flags, void* caller);
> +#endif
>  
>  extern void vfree(const void *addr);
>  extern void vfree_atomic(const void *addr);
> diff --git a/mm/util.c b/mm/util.c
> index 3022051da938..c35e5870921d 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -380,7 +380,8 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
>  	if (ret || size <= PAGE_SIZE)
>  		return ret;
>  
> -	return __vmalloc_node_flags(size, node, flags);
> +	return __vmalloc_node_flags_caller(size, node, flags,
> +			__builtin_return_address(0));
>  }
>  EXPORT_SYMBOL(kvmalloc_node);
>  
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 65912eb93a2c..1a97d4a31406 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1809,13 +1809,19 @@ void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
>  }
>  EXPORT_SYMBOL(__vmalloc);
>  
> -void *__vmalloc_node_flags(unsigned long size,
> +static inline void *__vmalloc_node_flags(unsigned long size,
>  					int node, gfp_t flags)
>  {
>  	return __vmalloc_node(size, 1, flags, PAGE_KERNEL,
>  					node, __builtin_return_address(0));
>  }
>  
> +
> +void *__vmalloc_node_flags_caller(unsigned long size, int node, gfp_t flags, void *caller)
> +{
> +	return __vmalloc_node(size, 1, flags, PAGE_KERNEL, node, caller);
> +}
> +
>  /**
>   *	vmalloc  -  allocate virtually contiguous memory
>   *	@size:		allocation size
> -- 
> 2.11.0
> 
> -- 
> Michal Hocko
> SUSE Labs

-- 
Michal Hocko
SUSE Labs