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Mon, 05 Jan 2026 07:10:55 -0800 (PST) From: Breno Leitao Date: Mon, 05 Jan 2026 07:10:27 -0800 Subject: [PATCH] fs/namei: Remove redundant DCACHE_MANAGED_DENTRY check in __follow_mount_rcu Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260105-dcache-v1-1-f0d904b4a7c2@debian.org> X-B4-Tracking: v=1; b=H4sIAGPUW2kC/yXMQQqDMBBG4asM/9pAErHQXKV0ESejjgtbEhVBv Luoy7f43o4iWaUg0I4sqxb9TQjkKgIPcerFaEIgeOtf1tnGJI48iLEuxiY5fre1R0X4Z+l0u0e f79NlaUfh+dI4jhPjwM1uagAAAA== X-Change-ID: 20260105-dcache-01aa5d1c9b32 To: Alexander Viro , Christian Brauner , Jan Kara Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, jlayton@kernel.org, rostedt@goodmis.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; a=openpgp-sha256; l=1279; i=leitao@debian.org; h=from:subject:message-id; bh=u36PWBh4yDI8ZT2iUBF75swI9f7/OKlVQSDrJTnmZos=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBpW9R/KC2HMUGNVhVBtyaw/Mx3J36QvTGMTN2Wk b9SP1g0X8iJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCaVvUfwAKCRA1o5Of/Hh3 bdGZD/9aC/VOpoYXOQtb4qzpoLcHBMPATE96DyLEW3RWFRFVR8cbijyap9GV47cubaWQEjT9oor BkgmhOcntEvtEG4bvT66ZdDaN85S7AGyTTg33AAxNzxWXsrHCEWBluR+KPVZamcLM7kP+kBkuU9 vM3N4Ma/qLGH58tiqA+sjrSyJLvTuJY6jvy3LJoF2OpXmIPIWLC5tl4Efg1Gpyy/+/cokbrBnXP yDTyTROSQjW/Yjm+qwtXOJTZ00mUoEvl3m6nLO2bkS0a4cOURlbM12JXIxJB4Jo60wxVjrD1hLm 3yubvi6G0D7Wty2XI8mShy4oRjELlHyVICVcRXLKsHjwVvfV01PbVDCJX04B6YpPS644nvMXTJH WqsDUw45JEqswX0sKyGWywcb4DcxwRnhRKjPAh5UrJpr0BkqCciiZPn4d0IxMV2/m9fiJkJ5GTX rKUq1Zexu8cNV8cjOwjjUDc9/pY2OE4zmAOKRHlxtbgiQDHJZ0JNtuKfNIs/4geK+xxKEagLHp/ ML9P2EfAiDeld3vKoDN8xqg8oZAiTzhYQpn9CLmdtyG44dZuowE0Ym9LG8UW/8qdxVfb2Y6A3P5 9joASX5VYhxZFLMckA2NT6DDC9vIvzfo3t+49ee9pAS55atlJvVEzBfzhgYLJ4386H8AgLcbAYd SfCEwayilAR6tgA== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D The check for DCACHE_MANAGED_DENTRY at the start of __follow_mount_rcu() is redundant because the only caller (handle_mounts) already verifies d_managed(dentry) before calling this function, so, dentry in __follow_mount_rcu() has always DCACHE_MANAGED_DENTRY set. This early-out optimization never fires in practice - but it is marking as likely(). This was detected with branch profiling, which shows 100% misprediction in this likely. Remove the whole if clause instead of removing the likely, given we know for sure that dentry is not DCACHE_MANAGED_DENTRY. Signed-off-by: Breno Leitao Acked-by: Al Viro --- fs/namei.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index bf0f66f0e9b9..774a2f5b0a10 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1623,9 +1623,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, = struct path *path) struct dentry *dentry =3D path->dentry; unsigned int flags =3D dentry->d_flags; =20 - if (likely(!(flags & DCACHE_MANAGED_DENTRY))) - return true; - if (unlikely(nd->flags & LOOKUP_NO_XDEV)) return false; =20 --- base-commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c change-id: 20260105-dcache-01aa5d1c9b32 Best regards, -- =20 Breno Leitao