linux-kernel - [PATCH 2/7] follow_dotdot{,_rcu}(): change calling conventions

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Message-ID: <YsN0Qy5d69q6YWhS@ZenIV>
Date:   Tue, 5 Jul 2022 00:14:11 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Vitaly Buka <vitalybuka@...gle.com>,
        linux-toolchains <linux-toolchains@...r.kernel.org>
Subject: [PATCH 2/7] follow_dotdot{,_rcu}(): change calling conventions

Instead of returning NULL when we are in root, just make it return
the current position (and set *seqp and *inodep accordingly).
That collapses the calls of step_into() in handle_dots()

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 4dbf55b37ec6..ecdb9ac21ece 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1909,7 +1909,9 @@ static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
 		return ERR_PTR(-ECHILD);
 	if (unlikely(nd->flags & LOOKUP_BENEATH))
 		return ERR_PTR(-ECHILD);
-	return NULL;
+	*seqp = nd->seq;
+	*inodep = nd->path.dentry->d_inode;
+	return nd->path.dentry;
 }
 
 static struct dentry *follow_dotdot(struct nameidata *nd,
@@ -1945,8 +1947,9 @@ static struct dentry *follow_dotdot(struct nameidata *nd,
 in_root:
 	if (unlikely(nd->flags & LOOKUP_BENEATH))
 		return ERR_PTR(-EXDEV);
-	dget(nd->path.dentry);
-	return NULL;
+	*seqp = 0;
+	*inodep = nd->path.dentry->d_inode;
+	return dget(nd->path.dentry);
 }
 
 static const char *handle_dots(struct nameidata *nd, int type)
@@ -1968,12 +1971,7 @@ static const char *handle_dots(struct nameidata *nd, int type)
 			parent = follow_dotdot(nd, &inode, &seq);
 		if (IS_ERR(parent))
 			return ERR_CAST(parent);
-		if (unlikely(!parent))
-			error = step_into(nd, WALK_NOFOLLOW,
-					 nd->path.dentry, nd->inode, nd->seq);
-		else
-			error = step_into(nd, WALK_NOFOLLOW,
-					 parent, inode, seq);
+		error = step_into(nd, WALK_NOFOLLOW, parent, inode, seq);
 		if (unlikely(error))
 			return error;
 
-- 
2.30.2