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Subject[PATCH 1/7] vfs - merge path_is_mountpoint() and path_is_mountpoint_rcu()
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From: Ian Kent <ikent@redhat.com>

Forgetting that the rcu lock allows nesting I added a superfluous rcu
version of path_is_mountpoint().

Merge it and the rcu version, make the common case (d_mountpoint()
returning true) inline and change the path parameter to a const.

Also move the function definition to include/linux/mount.h as it
seems a more sensible place for it.

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/autofs4/root.c | 11 +++--------
fs/namespace.c | 41 ++++++++++++++---------------------------
include/linux/fs.h | 2 --
include/linux/mount.h | 11 +++++++++++
4 files changed, 28 insertions(+), 37 deletions(-)

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index c4df881..dd2ea5d 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -437,13 +437,8 @@ static int autofs4_d_manage(struct path *path, bool rcu_walk)

/* The daemon never waits. */
if (autofs4_oz_mode(sbi)) {
- if (rcu_walk) {
- if (!path_is_mountpoint_rcu(path))
- return -EISDIR;
- } else {
- if (!path_is_mountpoint(path))
- return -EISDIR;
- }
+ if (!path_is_mountpoint(path))
+ return -EISDIR;
return 0;
}

@@ -471,7 +466,7 @@ static int autofs4_d_manage(struct path *path, bool rcu_walk)

if (ino->flags & AUTOFS_INF_WANT_EXPIRE)
return 0;
- if (path_is_mountpoint_rcu(path))
+ if (path_is_mountpoint(path))
return 0;
inode = d_inode_rcu(dentry);
if (inode && S_ISLNK(inode->i_mode))
diff --git a/fs/namespace.c b/fs/namespace.c
index 79473ee..da1cd87 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1160,12 +1160,23 @@ struct vfsmount *mntget(struct vfsmount *mnt)
}
EXPORT_SYMBOL(mntget);

-static bool __path_is_mountpoint(struct path *path)
+/* __path_is_mountpoint() - Check if path is a mount in the current
+ * namespace.
+ *
+ * d_mountpoint() can only be used reliably to establish if a dentry is
+ * not mounted in any namespace and that common case is handled inline.
+ * d_mountpoint() isn't aware of the possibility there may be multiple
+ * mounts using a given dentry in a different namespace. This function
+ * checks if the passed in path is a mountpoint rather than the dentry
+ * alone.
+ */
+bool __path_is_mountpoint(const struct path *path)
{
struct mount *mount;
struct vfsmount *mnt;
unsigned seq;

+ rcu_read_lock();
do {
seq = read_seqbegin(&mount_lock);
mount = __lookup_mnt(path->mnt, path->dentry);
@@ -1173,35 +1184,11 @@ static bool __path_is_mountpoint(struct path *path)
} 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 false;
-
- 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 false;
-
- return __path_is_mountpoint(path);
+ return mnt != NULL;
}
-EXPORT_SYMBOL(path_is_mountpoint_rcu);
+EXPORT_SYMBOL(__path_is_mountpoint);

struct vfsmount *mnt_clone_internal(struct path *path)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 03a5a39..83de8b6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2095,8 +2095,6 @@ 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);

diff --git a/include/linux/mount.h b/include/linux/mount.h
index 1172cce..42dc62b 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -15,6 +15,8 @@
#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/atomic.h>
+#include <linux/path.h>
+#include <linux/dcache.h>

struct super_block;
struct vfsmount;
@@ -98,4 +100,13 @@ extern dev_t name_to_dev_t(const char *name);

extern unsigned int sysctl_mount_max;

+extern bool __path_is_mountpoint(const struct path *path);
+static inline bool path_is_mountpoint(const struct path *path)
+{
+ if (!d_mountpoint(path->dentry))
+ return 0;
+
+ return __path_is_mountpoint(path);
+}
+
#endif /* _LINUX_MOUNT_H */
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