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From: Dave Hansen <dave.hansen@intel.com>
To: Liu Song <fishland@aliyun.com>,
	gregkh@linuxfoundation.org, jroedel@suse.de,
	dave.hansen@linux.intel.com, tglx@linutronix.de
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, liu.song11@zte.com.cn
Subject: Re: [RFC PATCH] mm/vmalloc: make sure to traverse from the beginning when overflow occur
Date: Mon, 13 Apr 2020 08:02:49 -0700	[thread overview]
Message-ID: <b295ec51-56fd-a377-95c9-a88cf5b151bc@intel.com> (raw)
In-Reply-To: <20200412143803.43931-1-fishland@aliyun.com>

On 4/12/20 7:38 AM, Liu Song wrote:
> If overflow, should ensure that "free_vmap_cache" is set to NULL,
> so as to ensure that it can be traversed from the beginning.

This changelog is a bit sparse.

Does this fix a demonstrated problem?  Or was it just discovered via
code review and assumed to help a theoretical problem?

Which tree is it against?  'free_vmap_cache' doesn't show up in Linus's
tree.
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index d8e877365f9f..2638a20d36ce 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -441,7 +441,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  	if (!free_vmap_cache ||
>  			size < cached_hole_size ||
>  			vstart < cached_vstart ||
> -			align < cached_align) {
> +			align < cached_align || purged) {
>  nocache:
>  		cached_hole_size = 0;
>  		free_vmap_cache = NULL;

Is 'purged' the right way to do this?

There is a path through the overflow code that also sets purged=0.  Does
'free_vmap_cache' *not* need to get reset in that case?

It also seems more natural to me that the code mucking with the rbtree
would be the one to reset the cache.

       reply	other threads:[~2020-04-13 15:02 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200412143803.43931-1-fishland@aliyun.com>
2020-04-13 15:02 ` Dave Hansen [this message]
2020-04-14 19:02   ` [RFC PATCH] mm/vmalloc: make sure to traverse from the beginning when overflow occur Uladzislau Rezki

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