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AJvYcCVJtj6gDqGcbEb8DKh9lnPyiim/Qk5jzgUdqKX4wpe8YAFK98f69K6keAPoefMxn7UfntBZfHB7jOHIHdE=@vger.kernel.org X-Gm-Message-State: AOJu0Yzsde143dw2cMD+K/77y+QyBQ6RQGSKXe0+2zUOzlPZF1dyrCb+ nJnzr2/9U+z0oEyE7Nr26eb5Fx465+FX17K3VmATl/8zBvpQ4/P2yLAkUm4S88jOyuVz+1pu9FB 4Xg== X-Google-Smtp-Source: AGHT+IF/E1FLpmQ9hujXfDz8ah1g4xzG4PooG2XovTR77om7ynRlxwPBbvaTMprv3cmEsfAU/D0wit+tFCw= X-Received: from pfbeg17.prod.google.com ([2002:a05:6a00:8011:b0:724:edad:f712]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:cc2:b0:71e:55e2:2c58 with SMTP id d2e1a72fcca58-725b812e375mr6388253b3a.15.1733525538875; Fri, 06 Dec 2024 14:52:18 -0800 (PST) Date: Fri, 6 Dec 2024 14:52:03 -0800 In-Reply-To: <20241206225204.4008261-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241206225204.4008261-1-surenb@google.com> X-Mailer: git-send-email 2.47.0.338.g60cca15819-goog Message-ID: <20241206225204.4008261-7-surenb@google.com> Subject: [PATCH v5 6/6] docs/mm: document latest changes to vm_lock From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: 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, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Change the documentation to reflect that vm_lock is integrated into vma. Document newly introduced vma_start_read_locked{_nested} functions. Signed-off-by: Suren Baghdasaryan Reviewed-by: Lorenzo Stoakes --- Documentation/mm/process_addrs.rst | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/Documentation/mm/process_addrs.rst b/Documentation/mm/process_= addrs.rst index 81417fa2ed20..92cf497a9e3c 100644 --- a/Documentation/mm/process_addrs.rst +++ b/Documentation/mm/process_addrs.rst @@ -716,7 +716,11 @@ calls :c:func:`!rcu_read_lock` to ensure that the VMA = is looked up in an RCU critical section, then attempts to VMA lock it via :c:func:`!vma_start_rea= d`, before releasing the RCU lock via :c:func:`!rcu_read_unlock`. =20 -VMA read locks hold the read lock on the :c:member:`!vma->vm_lock` semapho= re for +In cases when the user already holds mmap read lock, :c:func:`!vma_start_r= ead_locked` +and :c:func:`!vma_start_read_locked_nested` can be used. These functions a= lways +succeed in acquiring VMA read lock. + +VMA read locks hold the read lock on the :c:member:`!vma.vm_lock` semaphor= e for their duration and the caller of :c:func:`!lock_vma_under_rcu` must releas= e it via :c:func:`!vma_end_read`. =20 @@ -780,7 +784,7 @@ keep VMAs locked across entirely separate write operati= ons. It also maintains correct lock ordering. =20 Each time a VMA read lock is acquired, we acquire a read lock on the -:c:member:`!vma->vm_lock` read/write semaphore and hold it, while checking= that +:c:member:`!vma.vm_lock` read/write semaphore and hold it, while checking = that the sequence count of the VMA does not match that of the mm. =20 If it does, the read lock fails. If it does not, we hold the lock, excludi= ng @@ -790,7 +794,7 @@ Importantly, maple tree operations performed in :c:func= :`!lock_vma_under_rcu` are also RCU safe, so the whole read lock operation is guaranteed to funct= ion correctly. =20 -On the write side, we acquire a write lock on the :c:member:`!vma->vm_lock` +On the write side, we acquire a write lock on the :c:member:`!vma.vm_lock` read/write semaphore, before setting the VMA's sequence number under this = lock, also simultaneously holding the mmap write lock. =20 --=20 2.47.0.338.g60cca15819-goog