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AJvYcCWRfK2RM4yHiA5gMjlxyrqxHhzqhkFQ1TJtmLL/Ko04NEj5QD5kwHME5QxZ9+ZBSQm6LkKbOwHE4g==@kvack.org X-Gm-Message-State: AOJu0Yxkfk7iVIbi3zLh1OaxMZuaJN4MMN9vVA2FrAlZn2e+bVQSAPrK IF3HTpaejZj/OdXV6+yl/nIYhZwlY9A1eZfNPGzxGrPhCHGC5abVtt5EfachEyqNH9ROYKGhwwU sqQcSO9ykGwabc9y+OiTVzR5qf9KZY9H8l4+c3oJm X-Gm-Gg: ASbGnctNq5fqmmnGH0OPnQ0yUvClhsKZz8ApCyPJ7mzU7NSj6IyALHEXwZ2+9oo79FN T/q31IS78v48BNbH8cUuvk/YHXJySYrjFkwnMzVgDCPMeO2K0eDWu493HC4Q8zMQ9DG9859JBQ/ za9hrTszAZ3L1M1ATK2eiTFSELVbPV6eQWxnFW0k/0SHmN+GppJ+tGL1XIBzIe5RqlIcTBljSDu w== X-Google-Smtp-Source: AGHT+IEU/TvuWoEbQ4te2ysqypswU5dT7NndQazyOFRc4vkSO/Fq1Wv/2Ic2ztMR6HHz0WqYXvto3hPD9kQ7BwMTx3U= X-Received: by 2002:a05:622a:306:b0:48d:8f6e:ece7 with SMTP id d75a77b69052e-4a9de07279bmr3534091cf.3.1752072232239; Wed, 09 Jul 2025 07:43:52 -0700 (PDT) MIME-Version: 1.0 References: <20250704060727.724817-1-surenb@google.com> <20250704060727.724817-8-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 9 Jul 2025 07:43:40 -0700 X-Gm-Features: Ac12FXxjAN0XIip7JsJyjMywVS_OrT44fU8TqxqHaIiIlNUJxwEx3Zvd-AP4Q2Q Message-ID: Subject: Re: [PATCH v6 7/8] fs/proc/task_mmu: read proc/pid/maps under per-vma lock To: Vlastimil Babka Cc: akpm@linux-foundation.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, peterx@redhat.com, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, paulmck@kernel.org, shuah@kernel.org, adobriyan@gmail.com, brauner@kernel.org, josef@toxicpanda.com, yebin10@huawei.com, linux@weissschuh.net, willy@infradead.org, osalvador@suse.de, andrii@kernel.org, ryan.roberts@arm.com, christophe.leroy@csgroup.eu, tjmercier@google.com, kaleshsingh@google.com, aha310510@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B23C918001A X-Stat-Signature: qfjkyy6yo1mnhs6u54r99gemgihzuz8j X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1752072233-850245 X-HE-Meta: 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 donGzlXv D16oNz9O/BKNcaGpaXRn5rwdqrrcgCfWFSiRfNpuAKx5mQkn8R/ucDNSCWtQUieJqpRF+bGYeW7n4CLaIVE3S6DgjN7Qtw8rJjGDc9cxotteYHzLfDSuWHEE+/DCEwpbh3iogj8KmtfY5bHuSIjaXRct9nPL5IA4BIsUCo0PswbWtXBXUtf/taZN533IKm8RBUYwX0/U+wQgm26acL8KTdVe+CeRokByZcvhHRnwS5eZrBkwLqb7u2dXksG20hg4qsOYpg26HyI/nv9Mu4DBzdB0EMg== 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 Wed, Jul 9, 2025 at 3:03=E2=80=AFAM Vlastimil Babka wro= te: > > On 7/4/25 08:07, Suren Baghdasaryan wrote: > > --- a/mm/mmap_lock.c > > +++ b/mm/mmap_lock.c > > @@ -178,6 +178,94 @@ struct vm_area_struct *lock_vma_under_rcu(struct m= m_struct *mm, > > count_vm_vma_lock_event(VMA_LOCK_ABORT); > > return NULL; > > } > > + > > +static struct vm_area_struct *lock_vma_under_mmap_lock(struct mm_struc= t *mm, > > + struct vma_iterato= r *iter, > > + unsigned long addr= ess) > > +{ > > + struct vm_area_struct *vma; > > + int ret; > > + > > + ret =3D mmap_read_lock_killable(mm); > > + if (ret) > > + return ERR_PTR(ret); > > + > > + /* Lookup the vma at the last position again under mmap_read_lock= */ > > + vma_iter_init(iter, mm, address); > > + vma =3D vma_next(iter); > > + if (vma) > > + vma_start_read_locked(vma); > > This can in theory return false (refcount overflow?) so it should be hand= led? Yes, I should handle it by falling back to mmap_lock. Thanks! > > > + > > + mmap_read_unlock(mm); > > + > > + return vma; > > +} > > +