From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: [PATCH 52/79] link_path_walk: nd->depth massage, part 1 Date: Tue, 5 May 2015 06:22:26 +0100 Message-ID: <1430803373-4948-52-git-send-email-viro@ZenIV.linux.org.uk> References: <20150505052205.GS889@ZenIV.linux.org.uk> Cc: Neil Brown , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Linus Torvalds Return-path: In-Reply-To: <20150505052205.GS889@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org From: Al Viro nd->stack[0] is unused until the handling of trailing symlinks and we want to get rid of that. Having fucked that transformation up several times, I went for bloody pedantic series of provably equivalent transformations. Sorry. Step 1: keep nd->depth higher by one in link_path_walk() - increment upon entry, decrement on exits, adjust the arithmetics inside and surround the calls of functions that care about nd->depth value (nd_alloc_stack(), get_link(), put_link()) with decrement/increment pairs. Signed-off-by: Al Viro --- fs/namei.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 078db1d..da23835 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1755,6 +1755,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) if (!*name) return 0; + nd->depth++; /* At this point we know we have a real path component. */ for(;;) { u64 hash_len; @@ -1815,15 +1816,18 @@ Walked: if (err) { const char *s; + nd->depth--; err = nd_alloc_stack(nd); + nd->depth++; if (unlikely(err)) { path_to_nameidata(&nd->link, nd); break; } nd->depth++; - + nd->depth--; s = get_link(nd); + nd->depth++; if (unlikely(IS_ERR(s))) { err = PTR_ERR(s); @@ -1833,7 +1837,9 @@ Walked: err = 0; if (unlikely(!s)) { /* jumped */ + nd->depth--; put_link(nd); + nd->depth++; nd->depth--; } else { if (*s == '/') { @@ -1847,7 +1853,7 @@ Walked: ; } nd->inode = nd->path.dentry->d_inode; - nd->stack[nd->depth].name = name; + nd->stack[nd->depth - 1].name = name; if (!*s) goto OK; name = s; @@ -1861,19 +1867,25 @@ Walked: } terminate_walk(nd); Err: - while (unlikely(nd->depth)) { + while (unlikely(nd->depth > 1)) { + nd->depth--; put_link(nd); + nd->depth++; nd->depth--; } + nd->depth--; return err; OK: - if (unlikely(nd->depth)) { - name = nd->stack[nd->depth].name; + if (unlikely(nd->depth > 1)) { + name = nd->stack[nd->depth - 1].name; err = walk_component(nd, LOOKUP_FOLLOW); + nd->depth--; put_link(nd); + nd->depth++; nd->depth--; goto Walked; } + nd->depth--; return 0; } -- 2.1.4