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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id j15sm5887lja.71.2020.04.14.12.02.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 12:02:25 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 14 Apr 2020 21:02:15 +0200 To: Dave Hansen , Liu Song Cc: Liu Song , gregkh@linuxfoundation.org, jroedel@suse.de, dave.hansen@linux.intel.com, tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "liu.song11@zte.com.cnhange-folder>?" Subject: Re: [RFC PATCH] mm/vmalloc: make sure to traverse from the beginning when overflow occur Message-ID: <20200414190215.GA1531@pc636> References: <20200412143803.43931-1-fishland@aliyun.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 13, 2020 at 08:02:49AM -0700, Dave Hansen wrote: > 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; > > We do not have such code since 5.2 kernel or so, nor things like cached_hole_size, free_vmap_cache and so on. It was totally reworked. -- Vlad Rezki