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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4907eae9898sm18844735e9.4.2026.05.27.02.18.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 May 2026 02:18:43 -0700 (PDT) Date: Wed, 27 May 2026 10:18:42 +0100 From: David Laight To: Steven Rostedt Cc: =?UTF-8?B?QW5kcsOp?= Almeida , Peter Zijlstra , Juri Lelli , Vincent Guittot , Christian Brauner , Kees Cook , Shuah Khan , willy@infradead.org, mathieu.desnoyers@efficios.com, Linus Torvalds , akpm@linux-foundation.org, Yafang Shao , andrii.nakryiko@gmail.com, arnaldo.melo@gmail.com, Petr Mladek , linux-kernel@vger.kernel.org, kernel-dev@igalia.com, linux-mm@kvack.org, linux-api@vger.kernel.org Subject: Re: [PATCH v2 3/6] treewide: Replace memcpy(..., current->comm) with strscpy() Message-ID: <20260527101842.376d567f@pumpkin> In-Reply-To: <20260526190625.3f4aca0a@gandalf.local.home> References: <20260524-tonyk-long_name-v2-0-332f6bd041c4@igalia.com> <20260524-tonyk-long_name-v2-3-332f6bd041c4@igalia.com> <20260526190625.3f4aca0a@gandalf.local.home> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: ojz7gzyuc6tib6jmsf5txcumojjgrr5d X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C91A92000F X-Rspam-User: X-HE-Tag: 1779873525-743867 X-HE-Meta: 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 j+jCYBuz thLaLZWZIg1pV5xM3jPvBJEB8UkLWo51tTrs5wCDFBRls6OH33FvFf7WdamTr0OvqyxiU3DfWPNYxzYW+j6rCjI1riTr5XXhF+LRp9jNX4Yr5//5Tac3sAd02GkNqy5b+BnVtCkuoaKu41FLkFMDOsbk5/NsYnoJYV+ia73QZRleag3IgbYkmDfDok41HO2aMeu7T38bkqPjQb5y74H6DcNipy1MlwKE2XkYQIBjonCHZLRDAP93nZz9JouLBjmgNLPvAJIPiENSBRukcpr+sQhsDSQQzJNseO3myFZFty/gYKwGVWfE7owbgW2TzFUP0+2+6cqr1nUgGFQGULnmfoUFlsQVJmJ3A3I0J0FcxrVz/edZd3HKflYSitV/3wuk3IfiFlrdaBHKyLRcE2Vq15mwKdGNM/IPTZ9/ebVp5dL7pnHDCjVdpqbUnp8VNOh/ZPV07x9Dd9x8Cdye7xRc3SV9ndgnwKzrk8AkuM7DmTzoGMhAC5WniIlw+9B/1ewJuRji62fBSDF8evzVmfSy/bmH9mXcE8tfVnv8VxIbQ2+l41iF46mNpzaO+8N24ego3g2tbkaCpgFiknK3HRmWMBKWONvXhbtjZduLWTfbbqKZmJhSDSYEfAkMX9Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 26 May 2026 19:06:25 -0400 Steven Rostedt wrote: > On Sun, 24 May 2026 19:38:53 -0300 > Andr=C3=A9 Almeida wrote: >=20 > > In order to increase the size of current->comm[] and to avoid breaking = any > > existing code, replace memcpy() with strscpy(). The later function makes > > sure that the copy is NUL terminated. This is crucial given that the > > source buffer might be larger than the destination buffer and could > > truncate the NUL character out of it. ... > As tracing now slows it down by 3.9% which is a significant increase from= 2.7% >=20 > I really rather keep memcpy() here. I suspect the copies could/should be replaced by a copy_task_comm() function that can perform optimisations that strscpy[_pad]() can't do because it can (for example) assume that the source is terminated. When the src and dst are the same size it can also degenerate to memcpy() - which should get inlined. The cost of copying 64 bytes might still be rather more than copying just 16. A compromise of 32 may be better. -- David >=20 > -- Steve