br_read_unlock(&vfsmount_lock);
}
-/*
- * When we move over from the RCU domain to properly refcounted
- * long-lived dentries, we need to check the sequence numbers
- * we got before lookup very carefully.
- *
- * We cannot blindly increment a dentry refcount - even if it
- * is not locked - if it is zero, because it may have gone
- * through the final d_kill() logic already.
- *
- * So for a zero refcount, we need to get the spinlock (which is
- * safe even for a dead dentry because the de-allocation is
- * RCU-delayed), and check the sequence count under the lock.
- *
- * Once we have checked the sequence count, we know it is live,
- * and since we hold the spinlock it cannot die from under us.
- *
- * In contrast, if the reference count wasn't zero, we can just
- * increment the lockref without having to take the spinlock.
- * Even if the sequence number ends up being stale, we haven't
- * gone through the final dput() and killed the dentry yet.
- */
-static inline int d_rcu_to_refcount(struct dentry *dentry, seqcount_t *validate, unsigned seq)
-{
- int gotref;
-
- gotref = lockref_get_or_lock(&dentry->d_lockref);
-
- /* Does the sequence number still match? */
- if (read_seqcount_retry(validate, seq)) {
- if (gotref)
- dput(dentry);
- else
- spin_unlock(&dentry->d_lock);
- return -ECHILD;
- }
-
- /* Get the ref now, if we couldn't get it originally */
- if (!gotref) {
- dentry->d_lockref.count++;
- spin_unlock(&dentry->d_lock);
- }
- return 0;
-}
-
/**
* unlazy_walk - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
{
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
- int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
- if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
- want_root = 1;
- spin_lock(&fs->lock);
- if (nd->root.mnt != fs->root.mnt ||
- nd->root.dentry != fs->root.dentry)
- goto err_root;
- }
+
+ /*
+ * Get a reference to the parent first: we're
+ * going to make "path_put(nd->path)" valid in
+ * non-RCU context for "terminate_walk()".
+ *
+ * If this doesn't work, return immediately with
+ * RCU walking still active (and then we will do
+ * the RCU walk cleanup in terminate_walk()).
+ */
+ if (!lockref_get_not_dead(&parent->d_lockref))
+ return -ECHILD;
+
+ /*
+ * After the mntget(), we terminate_walk() will do
+ * the right thing for non-RCU mode, and all our
+ * subsequent exit cases should unlock_rcu_walk()
+ * before returning.
+ */
+ mntget(nd->path.mnt);
+ nd->flags &= ~LOOKUP_RCU;
/*
* For a negative lookup, the lookup sequence point is the parents
* be valid if the child sequence number is still valid.
*/
if (!dentry) {
- if (d_rcu_to_refcount(parent, &parent->d_seq, nd->seq) < 0)
- goto err_root;
+ if (read_seqcount_retry(&parent->d_seq, nd->seq))
+ goto out;
BUG_ON(nd->inode != parent->d_inode);
} else {
- if (d_rcu_to_refcount(dentry, &dentry->d_seq, nd->seq) < 0)
- goto err_root;
- if (d_rcu_to_refcount(parent, &dentry->d_seq, nd->seq) < 0)
- goto err_parent;
+ if (!lockref_get_not_dead(&dentry->d_lockref))
+ goto out;
+ if (read_seqcount_retry(&dentry->d_seq, nd->seq))
+ goto drop_dentry;
}
- if (want_root) {
+
+ /*
+ * Sequence counts matched. Now make sure that the root is
+ * still valid and get it if required.
+ */
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ spin_lock(&fs->lock);
+ if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry)
+ goto unlock_and_drop_dentry;
path_get(&nd->root);
spin_unlock(&fs->lock);
}
- mntget(nd->path.mnt);
unlock_rcu_walk();
- nd->flags &= ~LOOKUP_RCU;
return 0;
-err_parent:
+unlock_and_drop_dentry:
+ spin_unlock(&fs->lock);
+drop_dentry:
+ unlock_rcu_walk();
dput(dentry);
-err_root:
- if (want_root)
- spin_unlock(&fs->lock);
+ goto drop_root_mnt;
+out:
+ unlock_rcu_walk();
+drop_root_mnt:
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
return -ECHILD;
}
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
- if (d_rcu_to_refcount(dentry, &dentry->d_seq, nd->seq) < 0) {
+ if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
+ unlock_rcu_walk();
+ return -ECHILD;
+ }
+ if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
unlock_rcu_walk();
+ dput(dentry);
return -ECHILD;
}
mntget(nd->path.mnt);
}
}
-static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
-{
- int ret;
-
- if (IS_ERR(link))
- goto fail;
-
- if (*link == '/') {
- set_root(nd);
- path_put(&nd->path);
- nd->path = nd->root;
- path_get(&nd->root);
- nd->flags |= LOOKUP_JUMPED;
- }
- nd->inode = nd->path.dentry->d_inode;
-
- ret = link_path_walk(link, nd);
- return ret;
-fail:
- path_put(&nd->path);
- return PTR_ERR(link);
-}
-
static void path_put_conditional(struct path *path, struct nameidata *nd)
{
dput(path->dentry);
error = 0;
s = nd_get_link(nd);
if (s) {
- error = __vfs_follow_link(nd, s);
+ if (unlikely(IS_ERR(s))) {
+ path_put(&nd->path);
+ put_link(nd, link, *p);
+ return PTR_ERR(s);
+ }
+ if (*s == '/') {
+ set_root(nd);
+ path_put(&nd->path);
+ nd->path = nd->root;
+ path_get(&nd->root);
+ nd->flags |= LOOKUP_JUMPED;
+ }
+ nd->inode = nd->path.dentry->d_inode;
+ error = link_path_walk(s, nd);
if (unlikely(error))
put_link(nd, link, *p);
}
return s;
}
+/**
+ * mountpoint_last - look up last component for umount
+ * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
+ * @path: pointer to container for result
+ *
+ * This is a special lookup_last function just for umount. In this case, we
+ * need to resolve the path without doing any revalidation.
+ *
+ * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
+ * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
+ * in almost all cases, this lookup will be served out of the dcache. The only
+ * cases where it won't are if nd->last refers to a symlink or the path is
+ * bogus and it doesn't exist.
+ *
+ * Returns:
+ * -error: if there was an error during lookup. This includes -ENOENT if the
+ * lookup found a negative dentry. The nd->path reference will also be
+ * put in this case.
+ *
+ * 0: if we successfully resolved nd->path and found it to not to be a
+ * symlink that needs to be followed. "path" will also be populated.
+ * The nd->path reference will also be put.
+ *
+ * 1: if we successfully resolved nd->last and found it to be a symlink
+ * that needs to be followed. "path" will be populated with the path
+ * to the link, and nd->path will *not* be put.
+ */
+static int
+mountpoint_last(struct nameidata *nd, struct path *path)
+{
+ int error = 0;
+ struct dentry *dentry;
+ struct dentry *dir = nd->path.dentry;
+
+ /* If we're in rcuwalk, drop out of it to handle last component */
+ if (nd->flags & LOOKUP_RCU) {
+ if (unlazy_walk(nd, NULL)) {
+ error = -ECHILD;
+ goto out;
+ }
+ }
+
+ nd->flags &= ~LOOKUP_PARENT;
+
+ if (unlikely(nd->last_type != LAST_NORM)) {
+ error = handle_dots(nd, nd->last_type);
+ if (error)
+ goto out;
+ dentry = dget(nd->path.dentry);
+ goto done;
+ }
+
+ mutex_lock(&dir->d_inode->i_mutex);
+ dentry = d_lookup(dir, &nd->last);
+ if (!dentry) {
+ /*
+ * No cached dentry. Mounted dentries are pinned in the cache,
+ * so that means that this dentry is probably a symlink or the
+ * path doesn't actually point to a mounted dentry.
+ */
+ dentry = d_alloc(dir, &nd->last);
+ if (!dentry) {
+ error = -ENOMEM;
+ mutex_unlock(&dir->d_inode->i_mutex);
+ goto out;
+ }
+ dentry = lookup_real(dir->d_inode, dentry, nd->flags);
+ error = PTR_ERR(dentry);
+ if (IS_ERR(dentry)) {
+ mutex_unlock(&dir->d_inode->i_mutex);
+ goto out;
+ }
+ }
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+done:
+ if (!dentry->d_inode) {
+ error = -ENOENT;
+ dput(dentry);
+ goto out;
+ }
+ path->dentry = dentry;
+ path->mnt = mntget(nd->path.mnt);
+ if (should_follow_link(dentry->d_inode, nd->flags & LOOKUP_FOLLOW))
+ return 1;
+ follow_mount(path);
+ error = 0;
+out:
+ terminate_walk(nd);
+ return error;
+}
+
+/**
+ * path_mountpoint - look up a path to be umounted
+ * @dfd: directory file descriptor to start walk from
+ * @name: full pathname to walk
+ * @flags: lookup flags
+ *
+ * Look up the given name, but don't attempt to revalidate the last component.
+ * Returns 0 and "path" will be valid on success; Retuns error otherwise.
+ */
+static int
+path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags)
+{
+ struct file *base = NULL;
+ struct nameidata nd;
+ int err;
+
+ err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base);
+ if (unlikely(err))
+ return err;
+
+ current->total_link_count = 0;
+ err = link_path_walk(name, &nd);
+ if (err)
+ goto out;
+
+ err = mountpoint_last(&nd, path);
+ while (err > 0) {
+ void *cookie;
+ struct path link = *path;
+ err = may_follow_link(&link, &nd);
+ if (unlikely(err))
+ break;
+ nd.flags |= LOOKUP_PARENT;
+ err = follow_link(&link, &nd, &cookie);
+ if (err)
+ break;
+ err = mountpoint_last(&nd, path);
+ put_link(&nd, &link, cookie);
+ }
+out:
+ if (base)
+ fput(base);
+
+ if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT))
+ path_put(&nd.root);
+
+ return err;
+}
+
+static int
+filename_mountpoint(int dfd, struct filename *s, struct path *path,
+ unsigned int flags)
+{
+ int error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_RCU);
+ if (unlikely(error == -ECHILD))
+ error = path_mountpoint(dfd, s->name, path, flags);
+ if (unlikely(error == -ESTALE))
+ error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_REVAL);
+ if (likely(!error))
+ audit_inode(s, path->dentry, 0);
+ return error;
+}
+
+/**
+ * user_path_mountpoint_at - lookup a path from userland in order to umount it
+ * @dfd: directory file descriptor
+ * @name: pathname from userland
+ * @flags: lookup flags
+ * @path: pointer to container to hold result
+ *
+ * A umount is a special case for path walking. We're not actually interested
+ * in the inode in this situation, and ESTALE errors can be a problem. We
+ * simply want track down the dentry and vfsmount attached at the mountpoint
+ * and avoid revalidating the last component.
+ *
+ * Returns 0 and populates "path" on success.
+ */
+int
+user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
+ struct path *path)
+{
+ struct filename *s = getname(name);
+ int error;
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ error = filename_mountpoint(dfd, s, path, flags);
+ putname(s);
+ return error;
+}
+
+int
+kern_path_mountpoint(int dfd, const char *name, struct path *path,
+ unsigned int flags)
+{
+ struct filename s = {.name = name};
+ return filename_mountpoint(dfd, &s, path, flags);
+}
+EXPORT_SYMBOL(kern_path_mountpoint);
+
/*
* It's inline, so penalty for filesystems that don't use sticky bit is
* minimal.
return res;
}
-int vfs_follow_link(struct nameidata *nd, const char *link)
-{
- return __vfs_follow_link(nd, link);
-}
-
/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
EXPORT_SYMBOL(inode_permission);
EXPORT_SYMBOL(unlock_rename);
EXPORT_SYMBOL(vfs_create);
-EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
EXPORT_SYMBOL(vfs_mknod);
projects / ~andy / linux / blobdiff