The patch titled
Subject: vfs: add path_has_submounts()
has been added to the -mm tree. Its filename is
vfs-add-path_has_submounts.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/vfs-add-path_has_submounts.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/vfs-add-path_has_submounts.patch
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------------------------------------------------------
From: Ian Kent <ikent@xxxxxxxxxx>
Subject: vfs: add path_has_submounts()
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 the given dentry, possibly in a different
namespace.
Add function, path_has_submounts(), that checks is a struct path contains
mounts (or is a mountpoint itself) to handle this case.
Link: http://lkml.kernel.org/r/20161011053403.27645.55242.stgit@xxxxxxxxxxxxxxxx
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Omar Sandoval <osandov@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/dcache.c | 35 +++++++++++++++++++++++++++++++++++
include/linux/dcache.h | 1 +
2 files changed, 36 insertions(+)
diff -puN fs/dcache.c~vfs-add-path_has_submounts fs/dcache.c
--- a/fs/dcache.c~vfs-add-path_has_submounts
+++ a/fs/dcache.c
@@ -1306,6 +1306,41 @@ int have_submounts(struct dentry *parent
}
EXPORT_SYMBOL(have_submounts);
+struct check_mount {
+ struct vfsmount *mnt;
+ unsigned int mounted;
+};
+
+static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
+{
+ struct check_mount *info = data;
+ struct path path = { .mnt = info->mnt, .dentry = dentry };
+
+ if (path_is_mountpoint(&path)) {
+ info->mounted = 1;
+ return D_WALK_QUIT;
+ }
+ return D_WALK_CONTINUE;
+}
+
+/**
+ * path_has_submounts - check for mounts over a dentry in the
+ * current namespace.
+ * @parent: path to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point in the current namespace.
+ */
+int path_has_submounts(struct path *parent)
+{
+ struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
+
+ d_walk(parent->dentry, &data, path_check_mount, NULL);
+
+ return data.mounted;
+}
+EXPORT_SYMBOL(path_has_submounts);
+
/*
* Called by mount code to set a mountpoint and check if the mountpoint is
* reachable (e.g. NFS can unhash a directory dentry and then the complete
diff -puN include/linux/dcache.h~vfs-add-path_has_submounts include/linux/dcache.h
--- a/include/linux/dcache.h~vfs-add-path_has_submounts
+++ a/include/linux/dcache.h
@@ -255,6 +255,7 @@ extern void d_prune_aliases(struct inode
/* test whether we have any submounts in a subdir tree */
extern int have_submounts(struct dentry *);
+extern int path_has_submounts(struct path *);
/*
* This adds the entry to the hash queues.
_
Patches currently in -mm which might be from ikent@xxxxxxxxxx are
vfs-change-d_manage-to-take-a-struct-path.patch
vfs-add-path_is_mountpoint-helper.patch
vfs-add-path_has_submounts.patch
autofs-change-autofs4_expire_wait-to-take-struct-path.patch
autofs-change-autofs4_wait-to-take-struct-path.patch
autofs-use-path_is_mountpoint-to-fix-unreliable-d_mountpoint-checks.patch
autofs-use-path_has_submounts-to-fix-unreliable-have_submount-checks.patch
vfs-remove-unused-have_submounts-function.patch
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