From: Ian Kent <raven@themaw.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: autofs mailing list <autofs@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Omar Sandoval <osandov@osandov.com>,
Al Viro <viro@ZenIV.linux.org.uk>
Subject: [PATCH 2/8] vfs - add path_is_mountpoint() helper
Date: Tue, 11 Oct 2016 13:33:58 +0800 [thread overview]
Message-ID: <20161011053358.27645.9729.stgit@pluto.themaw.net> (raw)
In-Reply-To: <20161011053352.27645.83962.stgit@pluto.themaw.net>
From: Ian Kent <ikent@redhat.com>
d_mountpoint() can only be used reliably to establish if a dentry is
not mounted in any namespace. It isn't aware of the possibility there
may be multiple mounts using a given dentry that may be in a different
namespace.
Add helper functions, path_is_mountpoint() and an rcu version , that
checks if a struct path is a mountpoint for this case.
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Omar Sandoval <osandov@osandov.com>
---
fs/namespace.c | 43 +++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 2 ++
2 files changed, 45 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c
index ff1cd14..5ef9618 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1160,6 +1160,49 @@ struct vfsmount *mntget(struct vfsmount *mnt)
}
EXPORT_SYMBOL(mntget);
+static bool __path_is_mountpoint(struct path *path)
+{
+ struct mount *mount;
+ struct vfsmount *mnt;
+ unsigned seq;
+
+ do {
+ seq = read_seqbegin(&mount_lock);
+ mount = __lookup_mnt(path->mnt, path->dentry);
+ mnt = mount ? &mount->mnt : NULL;
+ } while (mnt &&
+ !(mnt->mnt_flags & MNT_SYNC_UMOUNT) &&
+ read_seqretry(&mount_lock, seq));
+
+ return mnt != NULL;
+}
+
+/* Check if path is a mount in current namespace */
+bool path_is_mountpoint(struct path *path)
+{
+ bool res;
+
+ if (!d_mountpoint(path->dentry))
+ return 0;
+
+ rcu_read_lock();
+ res = __path_is_mountpoint(path);
+ rcu_read_unlock();
+
+ return res;
+}
+EXPORT_SYMBOL(path_is_mountpoint);
+
+/* Check if path is a mount in current namespace */
+bool path_is_mountpoint_rcu(struct path *path)
+{
+ if (!d_mountpoint(path->dentry))
+ return 0;
+
+ return __path_is_mountpoint(path);
+}
+EXPORT_SYMBOL(path_is_mountpoint_rcu);
+
struct vfsmount *mnt_clone_internal(struct path *path)
{
struct mount *p;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 09a8c41..deaf08b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2142,6 +2142,8 @@ extern int vfs_ustat(dev_t, struct kstatfs *);
extern int freeze_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
extern bool our_mnt(struct vfsmount *mnt);
+extern bool path_is_mountpoint(struct path *);
+extern bool path_is_mountpoint_rcu(struct path *);
extern int current_umask(void);
next prev parent reply other threads:[~2016-10-11 5:34 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 5:33 [PATCH 1/8] vfs - change d_manage() to take a struct path Ian Kent
2016-10-11 5:33 ` Ian Kent [this message]
2016-10-11 5:34 ` [PATCH 3/8] vfs - add path_has_submounts() Ian Kent
2016-10-11 5:34 ` [PATCH 4/8] autofs - change autofs4_expire_wait() to take struct path Ian Kent
2016-10-11 5:34 ` [PATCH 5/8] autofs - change autofs4_wait() " Ian Kent
2016-10-11 5:34 ` [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks Ian Kent
2016-10-27 2:17 ` Al Viro
2016-10-27 2:51 ` Ian Kent
2016-10-11 5:34 ` [PATCH 7/8] autofs - use path_has_submounts() to fix unreliable have_submount() checks Ian Kent
2016-10-11 5:34 ` [PATCH 8/8] vfs - remove unused have_submounts() function Ian Kent
2016-10-11 16:04 ` [PATCH 1/8] vfs - change d_manage() to take a struct path Eric W. Biederman
2016-10-11 23:47 ` Ian Kent
2016-10-19 19:40 ` Andrew Morton
2016-10-20 23:39 ` Ian Kent
2016-10-27 2:11 ` Al Viro
2016-10-27 2:47 ` Ian Kent
2016-10-27 6:50 ` Ian Kent
2016-11-01 2:02 ` Ian Kent
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