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authorAl Viro <viro@zeniv.linux.org.uk>2020-02-26 19:19:05 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2020-04-02 01:09:22 -0400
commit2aa38470853a65dc9b1b4bd0989d34cd3fc57ebd (patch)
treed445f35666a55d6af1cfbc0b105f47632975c750 /fs
parent7ef482fa65513b18eed05a5c5f00413aad137810 (diff)
non-RCU analogue of the previous commit
new helper: choose_mountpoint(). Wrapper around choose_mountpoint_rcu(), similar to lookup_mnt() vs. __lookup_mnt(). follow_dotdot() switched to it. Now we don't grab mount_lock exclusive anymore; note that the primitive used non-RCU mount traversals in other direction (lookup_mnt()) doesn't bother with that either - it uses mount_lock seqcount instead. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/namei.c56
1 files changed, 39 insertions, 17 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 6529c2506491..669a0dfa3012 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -605,10 +605,9 @@ static void terminate_walk(struct nameidata *nd)
}
/* path_put is needed afterwards regardless of success or failure */
-static bool legitimize_path(struct nameidata *nd,
- struct path *path, unsigned seq)
+static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
{
- int res = __legitimize_mnt(path->mnt, nd->m_seq);
+ int res = __legitimize_mnt(path->mnt, mseq);
if (unlikely(res)) {
if (res > 0)
path->mnt = NULL;
@@ -622,6 +621,12 @@ static bool legitimize_path(struct nameidata *nd,
return !read_seqcount_retry(&path->dentry->d_seq, seq);
}
+static inline bool legitimize_path(struct nameidata *nd,
+ struct path *path, unsigned seq)
+{
+ return __legitimize_path(path, nd->m_seq, seq);
+}
+
static bool legitimize_links(struct nameidata *nd)
{
int i;
@@ -1154,6 +1159,31 @@ static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
return false;
}
+static bool choose_mountpoint(struct mount *m, const struct path *root,
+ struct path *path)
+{
+ bool found;
+
+ rcu_read_lock();
+ while (1) {
+ unsigned seq, mseq = read_seqbegin(&mount_lock);
+
+ found = choose_mountpoint_rcu(m, root, path, &seq);
+ if (unlikely(!found)) {
+ if (!read_seqretry(&mount_lock, mseq))
+ break;
+ } else {
+ if (likely(__legitimize_path(path, seq, mseq)))
+ break;
+ rcu_read_unlock();
+ path_put(path);
+ rcu_read_lock();
+ }
+ }
+ rcu_read_unlock();
+ return found;
+}
+
/*
* Perform an automount
* - return -EISDIR to tell follow_managed() to stop and return the path we
@@ -1756,22 +1786,14 @@ static struct dentry *follow_dotdot(struct nameidata *nd,
if (path_equal(&nd->path, &nd->root))
goto in_root;
if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
- struct path path = nd->path;
- path_get(&path);
- while (1) {
- if (!follow_up(&path)) {
- path_put(&path);
- goto in_root;
- }
- if (path_equal(&path, &nd->root)) {
- path_put(&path);
- goto in_root;
- }
- if (path.dentry != nd->path.mnt->mnt_root)
- break;
- }
+ struct path path;
+
+ if (!choose_mountpoint(real_mount(nd->path.mnt),
+ &nd->root, &path))
+ goto in_root;
path_put(&nd->path);
nd->path = path;
+ nd->inode = path.dentry->d_inode;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return ERR_PTR(-EXDEV);
}