redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

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@pluto.themaw.net
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
hifive-unleashed-5.1
Ian Kent 2016-11-24 08:03:41 +11:00 committed by Al Viro
parent c6609c0a1c
commit 01619491a5
2 changed files with 40 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
fs/dcache.c
View File

@ -1306,6 +1306,45 @@ 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 (likely(!d_mountpoint(dentry)))
return D_WALK_CONTINUE;
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(const struct path *parent)
{
struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
read_seqlock_excl(&mount_lock);
d_walk(parent->dentry, &data, path_check_mount, NULL);
read_sequnlock_excl(&mount_lock);
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

1
include/linux/dcache.h
View File

@ -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(const struct path *);
/*
* This adds the entry to the hash queues.