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b=QMW8zha/pnUwa3tfZUaFK2bT4lDcoBh/DY32ySXAvx11GfxnxoQT76C+mWa83vMqn 5dgf8xFQbeRRXfbsboE5M/KFKQz47hbPo+EnqmXiHpYBYZT/iaCMtvy2d2ha8kC2jD kgCM8jiflgzODz8WMWnAkyrMK8wZZiWSJ/y3RPWdIflBININGH3XfgJt3QlL3aOh04 VQeOoh5daKWcZcWfgeCKy1wVXRC06BIkFwwa+6zb6ouw5miTUoZ6wRq1INFRkKwBf7 9vBqWHAjIFRuHZBjJkRpVvwlCaqTdHMs8ANOEvnniMBCsaiTXLvOqKY52FCYC86mjb KIPEY48x9nSeg== Message-ID: <28a5b824-f415-461c-af88-cb474ed37df1@kernel.org> Date: Mon, 3 Nov 2025 18:08:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/5] mm: Document lenient map_count checks To: Kalesh Singh , akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, david@redhat.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de Cc: rostedt@goodmis.org, hughd@google.com, kernel-team@android.com, android-mm@google.com, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jann Horn , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20251028212528.681081-1-kaleshsingh@google.com> <20251028212528.681081-2-kaleshsingh@google.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251028212528.681081-2-kaleshsingh@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: C42BF2001C X-Stat-Signature: x38auwdj19tpc6ptmh3dcho4xfnauj49 X-Rspam-User: X-HE-Tag: 1762189693-14449 X-HE-Meta: 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 t5j6nn0o /OL2tZqMgZ6PeCYxO1jPGfnLGkyJ0dCDaVh4D4JHF1AJGQUHshfNs+z7fzYsFEWlH0EBuOvMNYRu20blFTE6kw72HeYocEpGKdij/Qs3YxGBfV+Sj4iqU0iyPBm7ZP5OdZwnq1UDTSuXkPTCLOVeTbCe2/VTfSUgfZR1THHYoX7b2DyQjlOY583hFTmjmQbmIpQyYWP25sM85uXDBm3G4aC2WGbgL4tVLo+oEEvDlk7pLIf/izr5jkDBKOH2kH8r4HGqnmHrQqcW2NPBM80LzBLGerkK2PFG3F7A6aRgj1AIy2J0gY58u5WfSWNOQuYoZbmtAOGdmlLAnIZbGjQ5CF/VNLPP9n6zXRfFu X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 28.10.25 22:24, Kalesh Singh wrote: > Add comments to the map_count limit checks in do_mmap() and > do_brk_flags() to clarify their intended behavior. > > The use of a strict inequality ('>') in these checks is intentional but > non-obvious. It allows these functions to succeed when the VMA count is > exactly at the sysctl_max_map_count limit. This historical behavior > accounts for cases where the operation might not create a new VMA, but > instead merge with or expand an existing one, in which case the VMA > count does not increase. > > These comments clarify the long-standing behavior and will help prevent > future misinterpretation as an off-by-one error. > > Signed-off-by: Kalesh Singh > --- Acked-by: David Hildenbrand (Red Hat) -- Cheers David