linux-kernel - [RFC][PATCH v4 19/69] merging pick_link() with get

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Message-Id: <20200313235357.2646756-19-viro@ZenIV.linux.org.uk>
Date:   Fri, 13 Mar 2020 23:53:07 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [RFC][PATCH v4 19/69] merging pick_link() with get_link(), part 1

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

Move restoring LOOKUP_PARENT and zeroing nd->stack.name[0] past
the call of get_link() (nothing _currently_ uses them in there).
That allows to moved the call of may_follow_link() into get_link()
as well, since now the presence of LOOKUP_PARENT distinguishes
the callers from each other (link_path_walk() has it, trailing_symlink()
doesn't).

Preparations for folding trailing_symlink() into callers (lookup_last()
and do_last()) and changing the calling conventions of those.  Next
stage after that will have get_link() call migrate into walk_component(),
then - into step_into().  It's tricky enough to warrant doing that
in stages, unfortunately...

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index db55de1b580b..cd91fc970830 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1115,6 +1115,12 @@ const char *get_link(struct nameidata *nd)
 	int error;
 	const char *res;

+	if (!(nd->flags & LOOKUP_PARENT)) {
+		error = may_follow_link(nd);
+		if (unlikely(error))
+			return ERR_PTR(error);
+	}
+
 	if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS))
 		return ERR_PTR(-ELOOP);

@@ -2329,13 +2335,9 @@ static const char *path_init(struct nameidata *nd, unsigned flags)

 static const char *trailing_symlink(struct nameidata *nd)
 {
-	const char *s;
-	int error = may_follow_link(nd);
-	if (unlikely(error))
-		return ERR_PTR(error);
+	const char *s = get_link(nd);
 	nd->flags |= LOOKUP_PARENT;
 	nd->stack[0].name = NULL;
-	s = get_link(nd);
 	return s ? s : "";
 }

-- 
2.11.0