[PATCH 12/14] d_path: prepend_path(): lift the inner loop into a new helper

Al Viro
2021-05-19T00:51:15Z

... and leave the rename_lock/mount_lock handling in prepend_path()
itself

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/d_path.c | 77 ++++++++++++++++++++++++++++++-------------------------------
1 file changed, 38 insertions(+), 39 deletions(-)

diff --git a/fs/d_path.c b/fs/d_path.c
index 9a0356cc98d3..ba629879a4bf 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -68,6 +68,42 @@ static bool prepend_name(struct prepend_buffer *p, const struct qstr *name)
return true;
}

+static int __prepend_path(const struct dentry *dentry, const struct mount *mnt,
+ const struct path *root, struct prepend_buffer *p)
+{
+ while (dentry != root->dentry || &mnt->mnt != root->mnt) {
+ const struct dentry *parent = READ_ONCE(dentry->d_parent);
+
+ if (dentry == mnt->mnt.mnt_root) {
+ struct mount *m = READ_ONCE(mnt->mnt_parent);
+ struct mnt_namespace *mnt_ns;
+
+ if (likely(mnt != m)) {
+ dentry = READ_ONCE(mnt->mnt_mountpoint);
+ mnt = m;
+ continue;
+ }
+ /* Global root */
+ mnt_ns = READ_ONCE(mnt->mnt_ns);
+ /* open-coded is_mounted() to use local mnt_ns */
+ if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns))
+ return 1; // absolute root
+ else
+ return 2; // detached or not attached yet
+ }
+
+ if (unlikely(dentry == parent))
+ /* Escaped? */
+ return 3;
+
+ prefetch(parent);
+ if (!prepend_name(p, &dentry->d_name))
+ break;
+ dentry = parent;
+ }
+ return 0;
+}
+
/**
* prepend_path - Prepend path string to a buffer
* @path: the dentry/vfsmount to report
@@ -89,11 +125,9 @@ static int prepend_path(const struct path *path,
const struct path *root,
struct prepend_buffer *p)
{
- struct dentry *dentry;
- struct mount *mnt;
- int error = 0;
unsigned seq, m_seq = 0;
struct prepend_buffer b;
+ int error;

rcu_read_lock();
restart_mnt:
@@ -102,43 +136,8 @@ static int prepend_path(const struct path *path,
rcu_read_lock();
restart:
b = *p;
- error = 0;
- dentry = path->dentry;
- mnt = real_mount(path->mnt);
read_seqbegin_or_lock(&rename_lock, &seq);
- while (dentry != root->dentry || &mnt->mnt != root->mnt) {
- struct dentry * parent;
-
- if (dentry == mnt->mnt.mnt_root || IS_ROOT(dentry)) {
- struct mount *parent = READ_ONCE(mnt->mnt_parent);
- struct mnt_namespace *mnt_ns;
-
- /* Escaped? */
- if (dentry != mnt->mnt.mnt_root) {
- error = 3;
- break;
- }
- /* Global root? */
- if (mnt != parent) {
- dentry = READ_ONCE(mnt->mnt_mountpoint);
- mnt = parent;
- continue;
- }
- mnt_ns = READ_ONCE(mnt->mnt_ns);
- /* open-coded is_mounted() to use local mnt_ns */
- if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns))
- error = 1; // absolute root
- else
- error = 2; // detached or not attached yet
- break;
- }
- parent = dentry->d_parent;
- prefetch(parent);
- if (!prepend_name(&b, &dentry->d_name))
- break;
-
- dentry = parent;
- }
+ error = __prepend_path(path->dentry, real_mount(path->mnt), root, &b);
if (!(seq & 1))
rcu_read_unlock();
if (need_seqretry(&rename_lock, seq)) {
--
2.11.0