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Mon, 17 Apr 2023 15:48:08 -0700 (PDT) MIME-Version: 1.0 References: <20230415000818.1955007-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 17 Apr 2023 15:47:57 -0700 Message-ID: Subject: Re: [PATCH v2 1/1] mm: do not increment pgfault stats when page fault handler retries To: Peter Xu Cc: akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 31EC118000A X-Stat-Signature: dbpkcad6gp46jh7qcnnfkz7q1sb8ykxn X-Rspam-User: X-HE-Tag: 1681771688-53408 X-HE-Meta: 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 2VrQl1ZD uSlFHtZVRZ6jvmnIKhpSy2IClbAVLRQkSThvUIDNtt2sCb/q2lC6ECCgH59R6P6+iV7Kvm8CdjzKhulWfPsTCPG9p3anJBQRaDFIHKi9k5QpwbORRdOP1lMpJHsmqtTrNtVWDhNdVVWFYeR3SiCMskESMZOl20U6p6Tg95yFbtHBCjc7XQSowEiVqE6CLtJreFrEQFWpdlXB5/EFqxh/TP3ywF2r3Ia5GF7OclBORkOY+tpZSN/aHbilI8mb5hde3envFEsvnn7LLCmLdzCcHyzFokjqRbFYRartlhWoDRDtNvgY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000035, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Apr 17, 2023 at 2:26=E2=80=AFPM Peter Xu wrote: > > On Fri, Apr 14, 2023 at 05:08:18PM -0700, Suren Baghdasaryan wrote: > > @@ -5223,8 +5230,8 @@ vm_fault_t handle_mm_fault(struct vm_area_struct = *vma, unsigned long address, > > if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM)) > > mem_cgroup_oom_synchronize(false); > > } > > - > > - mm_account_fault(regs, address, flags, ret); > > +out: > > + mm_account_fault(mm, regs, address, flags, ret); > > Ah, one more question.. can this cached mm race with a destroying mm (jus= t > like the vma race we wanted to avoid)? Still a question only applies to > COMPLETE case when mmap read lock can be released. Thanks, I believe that is impossible because whoever is calling the page fault handler has stabilized the mm by getting a refcount. > > > > > return ret; > > } > > -- > Peter Xu >