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Tue, 03 Nov 2026 03:08:41 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e71b8011csm27509475f8f.31.2026.11.03.03.08.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 03:08:38 -0800 (PST) Message-ID: <9ffda863-507e-4911-8d4e-dbb7f0e26544@gmail.com> Date: Tue, 3 Nov 2026 12:08:36 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] mm/mremap: restore VMA_ACCOUNT_BIT if the unmap fails To: Josef Bacik , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , David Hildenbrand Cc: Vlastimil Babka , Jann Horn , Pedro Falcato , Muchun Song , Oscar Salvador , linux-mm@kvack.org References: <20261102-b4-mremap-pre-split-v2-0-d281dd11ad7d@toxicpanda.com> <20261102-b4-mremap-pre-split-v2-4-d281dd11ad7d@toxicpanda.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261102-b4-mremap-pre-split-v2-4-d281dd11ad7d@toxicpanda.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: uceunkp14my6fdy6ps51ka5o1fubhren X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-8.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: E9A391C0002 X-HE-Tag: 1793704122-70366 X-HE-Meta: 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 ZLCc0hSZ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/3/26 12:46 AM, Josef Bacik wrote: > If the unmap at the end of an mremap() move fails, the source VMA stays > without VMA_ACCOUNT_BIT. Neither munmap() nor exit_mmap() uncharges it > then, so the charge for all of its pages stays in vm_committed_as after > the process is gone. > > unmap_source_vma() clears the flag on the whole source VMA before the unmap > and sets it again on the remaining parts afterwards, but its error path > returns without doing so. > > This was reproduced with fault injection: each failure on an anonymous > mapping left Committed_AS higher by the size of the whole VMA after > everything was unmapped. > > Fix by setting the flag again on everything in the range of the original > VMA, on both paths, with a new helper. A failed unmap may have split the > VMA already, so the helper walks the range. > > Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure") > Signed-off-by: Josef Bacik nice! Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a