linux-kernel - [PATCH 3/9] merging pick_link() with get

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Message-Id: <20200119031738.2681033-20-viro@ZenIV.linux.org.uk>
Date:   Sun, 19 Jan 2020 03:17:32 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     linux-fsdevel@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Aleksa Sarai <cyphar@...har.com>,
        David Howells <dhowells@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 3/9] merging pick_link() with get_link(), part 3

From: Al Viro <viro@...iv.linux.org.uk>

After a pure jump ("/" or procfs-style symlink) we don't need to
hold the link anymore.  link_path_walk() dropped it if such case
had been detected, lookup_last/do_last() (i.e. old trailing_symlink())
left it on the stack - it ended up calling terminate_walk() shortly
anyway, which would've purged the entire stack.

Do it in get_link() itself instead.  Simpler logics that way...

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index d93e155caded..fe03e4d1144b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1153,7 +1153,9 @@ const char *get_link(struct nameidata *nd)
 		} else {
 			res = get(dentry, inode, &last->done);
 		}
-		if (IS_ERR_OR_NULL(res))
+		if (!res)
+			goto all_done;
+		if (IS_ERR(res))
 			return res;
 	}
 	if (*res == '/') {
@@ -1163,9 +1165,11 @@ const char *get_link(struct nameidata *nd)
 		while (unlikely(*++res == '/'))
 			;
 	}
-	if (!*res)
-		res = NULL;
-	return res;
+	if (*res)
+		return res;
+all_done: // pure jump
+	put_link(nd);
+	return NULL;
 }
 
 /*
@@ -2210,11 +2214,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 
 			if (IS_ERR(s))
 				return PTR_ERR(s);
-			err = 0;
-			if (unlikely(!s)) {
-				/* jumped */
-				put_link(nd);
-			} else {
+			if (likely(s)) {
 				nd->stack[nd->depth - 1].name = name;
 				name = s;
 				continue;
-- 
2.20.1