From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH] kernfs: make kernfs_walk_ns() use kernfs_pr_cont_buf[] Date: Fri, 15 Jan 2016 12:30:14 -0500 Message-ID: <20160115173014.GI3520@mtj.duckdns.org> References: <1449527935-27056-1-git-send-email-tj@kernel.org> <1449527935-27056-3-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , pablo@netfilter.org, Patrick McHardy , kadlec@blackhole.kfki.hu, Daniel Borkmann , daniel.wagner@bmw-carit.de, nhorman@tuxdriver.com, Zefan Li , Johannes Weiner , "netdev@vger.kernel.org" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, cgroups@vger.kernel.org, "linux-kernel@vger.kernel.org" , kernel-team@fb.com, ninasc@fb.com, Josh Triplett To: Greg Kroah-Hartman , Geert Uytterhoeven Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org kernfs_walk_ns() uses a static path_buf[PATH_MAX] to separate out path components. Keeping around the 4k buffer just for kernfs_walk_ns() is wasteful. This patch makes it piggyback on kernfs_pr_cont_buf[] instead. This requires kernfs_walk_ns() to hold kernfs_rename_lock. Signed-off-by: Tejun Heo Reported-by: Geert Uytterhoeven --- Hello, Greg, can you please route this one? Thanks. fs/kernfs/dir.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -698,15 +698,22 @@ static struct kernfs_node *kernfs_walk_n const unsigned char *path, const void *ns) { - static char path_buf[PATH_MAX]; /* protected by kernfs_mutex */ - size_t len = strlcpy(path_buf, path, PATH_MAX); - char *p = path_buf; - char *name; + size_t len; + char *p, *name; lockdep_assert_held(&kernfs_mutex); - if (len >= PATH_MAX) + /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */ + spin_lock_irq(&kernfs_rename_lock); + + len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf)); + + if (len >= sizeof(kernfs_pr_cont_buf)) { + spin_unlock_irq(&kernfs_rename_lock); return NULL; + } + + p = kernfs_pr_cont_buf; while ((name = strsep(&p, "/")) && parent) { if (*name == '\0') @@ -714,6 +721,8 @@ static struct kernfs_node *kernfs_walk_n parent = kernfs_find_ns(parent, name, ns); } + spin_unlock_irq(&kernfs_rename_lock); + return parent; }