namei: handle absolute symlinks without dropping out of RCU mode
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index bf46e10..a5ed0d0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -499,7 +499,7 @@
struct path root;
struct inode *inode; /* path.dentry.d_inode */
unsigned int flags;
- unsigned seq, m_seq;
+ unsigned seq, m_seq, root_seq;
int last_type;
unsigned depth;
int total_link_count;
@@ -788,14 +788,14 @@
static __always_inline unsigned set_root_rcu(struct nameidata *nd)
{
struct fs_struct *fs = current->fs;
- unsigned seq, res;
+ unsigned seq;
do {
seq = read_seqcount_begin(&fs->seq);
nd->root = fs->root;
- res = __read_seqcount_begin(&nd->root.dentry->d_seq);
+ nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
- return res;
+ return nd->root_seq;
}
static void path_put_conditional(struct path *path, struct nameidata *nd)
@@ -995,15 +995,23 @@
}
if (*res == '/') {
if (nd->flags & LOOKUP_RCU) {
- if (unlikely(unlazy_walk(nd, NULL, 0)))
+ struct dentry *d;
+ if (!nd->root.mnt)
+ set_root_rcu(nd);
+ nd->path = nd->root;
+ d = nd->path.dentry;
+ nd->inode = d->d_inode;
+ nd->seq = nd->root_seq;
+ if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
return ERR_PTR(-ECHILD);
+ } else {
+ if (!nd->root.mnt)
+ set_root(nd);
+ path_put(&nd->path);
+ nd->path = nd->root;
+ path_get(&nd->root);
+ nd->inode = nd->path.dentry->d_inode;
}
- if (!nd->root.mnt)
- set_root(nd);
- path_put(&nd->path);
- nd->path = nd->root;
- path_get(&nd->root);
- nd->inode = nd->path.dentry->d_inode;
nd->flags |= LOOKUP_JUMPED;
while (unlikely(*++res == '/'))
;
@@ -1979,6 +1987,7 @@
if (flags & LOOKUP_RCU) {
rcu_read_lock();
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ nd->root_seq = nd->seq;
nd->m_seq = read_seqbegin(&mount_lock);
} else {
path_get(&nd->path);
