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AJvYcCXfiHKQaK+tSxskc6D9KnxlhI87tdIgkLYLGu++zQelXwcZXzE52r8BR+jdJxfOejtQ0cDVeepDlw==@kvack.org X-Gm-Message-State: AOJu0Yx6vAFd2IIQb7ruf4eXqc5BQJeJJtZLhQAOqePD9+eVz08H7d1x eEel7hVd9FN2N30pJyWcvSWdXR2RFhaCCpMuN9sPlN2gzg2vnlXl X-Google-Smtp-Source: AGHT+IH9N9ss4gLA9dtSroKcF0iRQVrztkQFXO7hpDDQhs906SODYmbH4iVhovUli9GLBSLsClihzA== X-Received: by 2002:a17:906:c10c:b0:a9a:9df:5581 with SMTP id a640c23a62f3a-a9abf8b2561mr869024666b.38.1729845148105; Fri, 25 Oct 2024 01:32:28 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9b3a081d59sm42711566b.189.2024.10.25.01.32.27 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 25 Oct 2024 01:32:27 -0700 (PDT) Date: Fri, 25 Oct 2024 08:32:27 +0000 From: Wei Yang To: Lorenzo Stoakes Cc: Wei Yang , akpm@linux-foundation.org, Liam.Howlett@oracle.com, vbabka@suse.cz, jannh@google.com, linux-mm@kvack.org Subject: Re: [PATCH 1/3] mm/vma: miss to restore vmi.index on expansion failure Message-ID: <20241025083227.nt3twr5mgq7ssg3d@master> Reply-To: Wei Yang References: <20241025031847.6274-1-richard.weiyang@gmail.com> <20241025031847.6274-2-richard.weiyang@gmail.com> <848b5701-9dec-4c69-bcca-f9186090978a@lucifer.local> <20241025075955.hczpuimxcfqhjv5x@master> <978e1d13-bb8b-437e-adc2-8af389064ae3@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <978e1d13-bb8b-437e-adc2-8af389064ae3@lucifer.local> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 615B24001B X-Stat-Signature: uk6dt7mmq5unys3gxs76mdqn4r3rqxb8 X-HE-Tag: 1729845135-586874 X-HE-Meta: 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 KudbIvWH 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.007937, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 25, 2024 at 09:10:09AM +0100, Lorenzo Stoakes wrote: >On Fri, Oct 25, 2024 at 07:59:55AM +0000, Wei Yang wrote: >> On Fri, Oct 25, 2024 at 08:06:06AM +0100, Lorenzo Stoakes wrote: >> >> vmg->vma = NULL; >> >> vmg->start = start; >> >> vmg->end = end; >> >> vmg->pgoff = pgoff; >> >> - if (vmg->vma == prev) >> >> - vma_iter_set(vmg->vmi, start); >> > >> >So please replace this whole series with a patch that just removes these >> >lines, thanks! >> > >> >Also what tree are you making this change against? All mm changes should be >> >against akpm's tree in the mm-unstable branch. This change looks like it's >> >against another tree, as the code for this function has changed. >> > >> >> For mm-unstable, this is what you expect? >> >> diff --git a/mm/vma.c b/mm/vma.c >> index b5c1adcb6992..03b4838026ab 100644 >> --- a/mm/vma.c >> +++ b/mm/vma.c >> @@ -1003,16 +1003,6 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg) >> return vmg->vma; >> } >> >> - /* If expansion failed, reset state. Allows us to retry merge later. */ >> - if (!just_expand) { >> - vmg->vma = NULL; >> - vmg->start = start; >> - vmg->end = end; >> - vmg->pgoff = pgoff; >> - if (vmg->vma == prev) >> - vma_iter_set(vmg->vmi, start); >> - } >> - > >Noooo! Sorry I wasn't clear :) We need this. > >I mean: > > - if (vmg->vma == prev) > - vma_iter_set(vmg->vmi, start); > >And with an explanation like: > > We incorrectly set vmg->vma = NULL before checking to see if we > must reset the VMA iterator. However, since the only use case for > this reset is mmap_region() and we always reset iterators there > anyway, there is simply no need to do this. > > However, we absolutely do need to reset the vmg parameters to what > they originally were, as well as resetting vmg->vma, as these may > have been mutated to attempt a merge. > > There will be no change in behaviour, rather we simply avoid a > pointless compare and, for cases where the VMA was the first in the > mm, a pointless assignment to mas parameters. > Ok, I get what you want. But I have a question on your introduction of VMG_FLAG_JUST_EXPAND. Lets say just_expand is true and can_merge_left is true. Now we will adjust vmg->start/vma/pgoff in if (can_merge_left). If we fail expansion, we won't restore vmg->vma/start/pgoff, since just_expand is true. Is this what you expect? >> return NULL; >> } >> >> >> >> >> >> return NULL; >> >> } >> >> -- >> >> 2.34.1 >> >> >> >> >> >> -- >> Wei Yang >> Help you, Help me >> > >I want to refactor this further, but only after recent mmap_region() >changes have settled down. > >Thanks! -- Wei Yang Help you, Help me