linux-kernel - [PATCH] fs: mark lookup

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Message-ID: <20251119144930.2911698-1-mjguzik@gmail.com>
Date: Wed, 19 Nov 2025 15:49:30 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: brauner@...nel.org
Cc: viro@...iv.linux.org.uk,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH] fs: mark lookup_slow() as noinline

Otherwise it gets inlined notably in walk_component(), which convinces
the compiler to push/pop additional registers in the fast path to
accomodate existence of the inlined version.

Shortens the fast path of that routine from 87 to 71 bytes.

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---

The intent is to get to a point where I can inline walk_component and
step_into. This is probably the last patch of the sort before I write a
patchset + provide bench results.

 fs/namei.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index 11295fcf877c..667360deef48 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1863,7 +1863,7 @@ static struct dentry *__lookup_slow(const struct qstr *name,
 	return dentry;
 }

-static struct dentry *lookup_slow(const struct qstr *name,
+static noinline struct dentry *lookup_slow(const struct qstr *name,
 				  struct dentry *dir,
 				  unsigned int flags)
 {
-- 
2.48.1