linux-kernel - [PATCH 5/7] follow_dotdot{,_rcu}(): don't bother with inode

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Date:   Tue, 5 Jul 2022 00:15:38 +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 5/7] follow_dotdot{,_rcu}(): don't bother with inode

step_into() will fetch it, TYVM.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index dddbebf92b48..fe95fe39634c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1880,8 +1880,7 @@ static const char *step_into(struct nameidata *nd, int flags,
 	return pick_link(nd, &path, inode, flags);
 }
 
-static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
-					struct inode **inodep)
+static struct dentry *follow_dotdot_rcu(struct nameidata *nd)
 {
 	struct dentry *parent, *old;
 
@@ -1905,7 +1904,6 @@ static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
 	}
 	old = nd->path.dentry;
 	parent = old->d_parent;
-	*inodep = parent->d_inode;
 	nd->next_seq = read_seqcount_begin(&parent->d_seq);
 	// makes sure that non-RCU pathwalk could reach this state
 	if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
@@ -1919,12 +1917,10 @@ static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
 	if (unlikely(nd->flags & LOOKUP_BENEATH))
 		return ERR_PTR(-ECHILD);
 	nd->next_seq = nd->seq;
-	*inodep = nd->path.dentry->d_inode;
 	return nd->path.dentry;
 }
 
-static struct dentry *follow_dotdot(struct nameidata *nd,
-				 struct inode **inodep)
+static struct dentry *follow_dotdot(struct nameidata *nd)
 {
 	struct dentry *parent;
 
@@ -1948,13 +1944,11 @@ static struct dentry *follow_dotdot(struct nameidata *nd,
 		dput(parent);
 		return ERR_PTR(-ENOENT);
 	}
-	*inodep = parent->d_inode;
 	return parent;
 
 in_root:
 	if (unlikely(nd->flags & LOOKUP_BENEATH))
 		return ERR_PTR(-EXDEV);
-	*inodep = nd->path.dentry->d_inode;
 	return dget(nd->path.dentry);
 }
 
@@ -1963,7 +1957,6 @@ static const char *handle_dots(struct nameidata *nd, int type)
 	if (type == LAST_DOTDOT) {
 		const char *error = NULL;
 		struct dentry *parent;
-		struct inode *inode;
 
 		if (!nd->root.mnt) {
 			error = ERR_PTR(set_root(nd));
@@ -1971,9 +1964,9 @@ static const char *handle_dots(struct nameidata *nd, int type)
 				return error;
 		}
 		if (nd->flags & LOOKUP_RCU)
-			parent = follow_dotdot_rcu(nd, &inode);
+			parent = follow_dotdot_rcu(nd);
 		else
-			parent = follow_dotdot(nd, &inode);
+			parent = follow_dotdot(nd);
 		if (IS_ERR(parent))
 			return ERR_CAST(parent);
 		error = step_into(nd, WALK_NOFOLLOW, parent);
-- 
2.30.2