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AJvYcCUqX74ehbBaRZ3Cz4Z9EQSNkZBxbcNG7ftb89Ult+6AxTF0kEzwXswLnf0WEuO02MqDq59pxo8ttw==@kvack.org X-Gm-Message-State: AOJu0Yy9OOiBcFEo8Ka7U78NqGEkM3xm2cplkV6QOFvpNQ3Y+AJPeMeq Ga1M/IR2PRIs8w+fYijokoFEkxeXMvDC3TK608rW+jafsASu5BC2IcTQptReuzqBPJILlWoifNp AaDPr6auSoo08om9A1xoknZfTtqraEtHwBN+B X-Gm-Gg: ASbGncswP5P3Hl23n5VsdZL+259Ob/NAK8RP4nDqGI85SnCUkuzdRnGDeWt0wS7GQql vVPykXhJzWxY67oz1qDQLaxvUgptGRCljrFOn4A== X-Google-Smtp-Source: AGHT+IEpQzRLxiuB1jT2vUBbfAuBb9/GSt/nwSklPLPGLl27yYB31UvM3A4BKyGUvxnVdYUKLclC1LLsTAejqH31Slw= X-Received: by 2002:a05:622a:1828:b0:466:8906:159a with SMTP id d75a77b69052e-46c71fe2df2mr326951cf.19.1736292142325; Tue, 07 Jan 2025 15:22:22 -0800 (PST) MIME-Version: 1.0 References: <20250107030415.721474-1-surenb@google.com> <20250107122809.ofddv3yw44ciaklm@master> In-Reply-To: <20250107122809.ofddv3yw44ciaklm@master> From: Suren Baghdasaryan Date: Tue, 7 Jan 2025 15:22:11 -0800 X-Gm-Features: AbW1kvZaHO58vTfeT2La7AQFhN5fnTYAxeBfUL2fEXNVTiP-y8o8EvksqfqJbF8 Message-ID: Subject: Re: [PATCH 1/1] mm: remove extra check for VMA_LOCK_OFFSET when read-locking a vma To: Wei Yang Cc: akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, 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: rspam02 X-Rspamd-Queue-Id: 82DBBA0007 X-Stat-Signature: 454cfzqf5x4oyxf143fyt1aidck4f3ti X-Rspam-User: X-HE-Tag: 1736292143-193306 X-HE-Meta: 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 ZrqmGwtJ 7uNDFu6AQogWN4Q1N+7Fpxi8z9sA9eBJqEW1XUJcLNO1xMXGK3b3S4/lNzZGZ9T7VIL/pXhRy/wL4vzBU7ECUfbTY7MgzSVPuIcDcGjGhiehufplyDagbriKX6S1T7xG11bgOionezLtwIKlyk7pb8Su/48s9+VozEWb2c3Zvd1R4a7+HTrBvB83WvEKtwKjdoMHO7JY6nkIXrMB8H0WiCiW5/Lkbg9Enl56oCd16XdezGyPkzWkTuAp0fIB8LYdPdjHXGoi3K7MWVsCeO5X8mKruXFsnL46PMFKTOeHDT3c2uGq7sBEZiPKK9JS4vWfpJ+FFMz8o5YnEkHfg51THg9/Vgyf5dWPcKquQHQKdlTSdrVc= 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 Tue, Jan 7, 2025 at 4:28=E2=80=AFAM Wei Yang = wrote: > > On Mon, Jan 06, 2025 at 07:04:15PM -0800, Suren Baghdasaryan wrote: > >Since we limit vm_refcnt at VMA_REF_LIMIT and it's smaller than > >VMA_LOCK_OFFSET, there is no need to check again if VMA_LOCK_OFFSET bit > >is set. Remove the extra check and add a clarifying comment. > > > >Fixes: e8f32ff00a66 ("mm: replace vm_lock and detached flag with a refer= ence count") > >Suggested-by: Wei Yang > >Signed-off-by: Suren Baghdasaryan > > Reviewed-by: Wei Yang Since I have to respin v8, I'll fold this fix into the original patch. > > >--- > >Applies over mm-unstable > > > > include/linux/mm.h | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > >diff --git a/include/linux/mm.h b/include/linux/mm.h > >index 486638d22fc6..b5f262fc7dc5 100644 > >--- a/include/linux/mm.h > >+++ b/include/linux/mm.h > >@@ -747,7 +747,11 @@ static inline bool vma_start_read(struct mm_struct = *mm, struct vm_area_struct *v > > > > > > rwsem_acquire_read(&vma->vmlock_dep_map, 0, 0, _RET_IP_); > >- /* Limit at VMA_REF_LIMIT to leave one count for a writer */ > >+ /* > >+ * Limit at VMA_REF_LIMIT to leave one count for a writer. > >+ * If VMA_LOCK_OFFSET is set, __refcount_inc_not_zero_limited() w= ill fail > >+ * because VMA_REF_LIMIT is less than VMA_LOCK_OFFSET. > >+ */ > > if (unlikely(!__refcount_inc_not_zero_limited(&vma->vm_refcnt, &o= ldcnt, > > VMA_REF_LIMIT))) { > > rwsem_release(&vma->vmlock_dep_map, _RET_IP_); > >@@ -766,8 +770,7 @@ static inline bool vma_start_read(struct mm_struct *= mm, struct vm_area_struct *v > > * after it has been unlocked. > > * This pairs with RELEASE semantics in vma_end_write_all(). > > */ > >- if (unlikely(oldcnt & VMA_LOCK_OFFSET || > >- vma->vm_lock_seq =3D=3D raw_read_seqcount(&mm->mm_lo= ck_seq))) { > >+ if (unlikely(vma->vm_lock_seq =3D=3D raw_read_seqcount(&mm->mm_lo= ck_seq))) { > > vma_refcount_put(vma); > > return false; > > } > > > >base-commit: f349e79bfbf3abfade8011797ff6d0d47b67dab7 > >-- > >2.47.1.613.gc27f4b7a9f-goog > > -- > Wei Yang > Help you, Help me