[RFC][PATCH v3 49/55] lift all calls of step_into() out of follow_dotdot/follow_dotdot_rcu

Al Viro
2020-03-01T21:53:45Z

lift step_into() into handle_dots() (where they merge with each other);
have follow_... return dentry and pass inode/seq to the caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 74 +++++++++++++++++++++++++++++++-------------------------------
1 file changed, 37 insertions(+), 37 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index cc01bca2266c..cf7b7a6c08fc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1689,31 +1689,29 @@ static const char *step_into(struct nameidata *nd, int flags,
return pick_link(nd, &path, inode, seq, flags);
}

-static const char *follow_dotdot_rcu(struct nameidata *nd, int flags)
+static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
+ struct inode **inodep,
+ unsigned *seqp)
{
- struct dentry *parent = NULL;
- struct inode *inode = nd->inode;
- unsigned seq;
-
while (1) {
if (path_equal(&nd->path, &nd->root))
break;
if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry;
+ struct dentry *parent = old->d_parent;

- parent = old->d_parent;
- inode = parent->d_inode;
- seq = read_seqcount_begin(&parent->d_seq);
+ *inodep = parent->d_inode;
+ *seqp = read_seqcount_begin(&parent->d_seq);
if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
return ERR_PTR(-ECHILD);
if (unlikely(!path_connected(nd->path.mnt, parent)))
return ERR_PTR(-ECHILD);
- break;
+ return parent;
} else {
struct mount *mnt = real_mount(nd->path.mnt);
struct mount *mparent = mnt->mnt_parent;
struct dentry *mountpoint = mnt->mnt_mountpoint;
- struct inode *inode2 = mountpoint->d_inode;
+ struct inode *inode = mountpoint->d_inode;
unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
return ERR_PTR(-ECHILD);
@@ -1724,56 +1722,51 @@ static const char *follow_dotdot_rcu(struct nameidata *nd, int flags)
/* we know that mountpoint was pinned */
nd->path.dentry = mountpoint;
nd->path.mnt = &mparent->mnt;
- inode = nd->inode = inode2;
+ nd->inode = inode;
nd->seq = seq;
}
}
- if (unlikely(!parent)) {
- if (unlikely(nd->flags & LOOKUP_BENEATH))
- return ERR_PTR(-ECHILD);
- return step_into(nd, flags | WALK_NOFOLLOW,
- nd->path.dentry, nd->inode, nd->seq);
- } else {
- return step_into(nd, flags | WALK_NOFOLLOW,
- parent, inode, seq);
- }
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return ERR_PTR(-ECHILD);
+ return NULL;
}

-static const char *follow_dotdot(struct nameidata *nd, int flags)
+static struct dentry *follow_dotdot(struct nameidata *nd,
+ struct inode **inodep,
+ unsigned *seqp)
{
- struct dentry *parent = NULL;
while (1) {
if (path_equal(&nd->path, &nd->root))
break;
if (nd->path.dentry != nd->path.mnt->mnt_root) {
/* rare case of legitimate dget_parent()... */
- parent = dget_parent(nd->path.dentry);
+ struct dentry *parent = dget_parent(nd->path.dentry);
if (unlikely(!path_connected(nd->path.mnt, parent))) {
dput(parent);
return ERR_PTR(-ENOENT);
}
- break;
+ *seqp = 0;
+ *inodep = parent->d_inode;
+ return parent;
}
if (!follow_up(&nd->path))
break;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return ERR_PTR(-EXDEV);
}
- if (unlikely(!parent)) {
- if (unlikely(nd->flags & LOOKUP_BENEATH))
- return ERR_PTR(-EXDEV);
- return step_into(nd, flags | WALK_NOFOLLOW,
- dget(nd->path.dentry), nd->inode, nd->seq);
- } else {
- return step_into(nd, flags | WALK_NOFOLLOW,
- parent, parent->d_inode, 0);
- }
+ if (unlikely(nd->flags & LOOKUP_BENEATH))
+ return ERR_PTR(-EXDEV);
+ dget(nd->path.dentry);
+ return NULL;
}

static const char *handle_dots(struct nameidata *nd, int type, int flags)
{
if (type == LAST_DOTDOT) {
const char *error = NULL;
+ struct dentry *parent;
+ struct inode *inode;
+ unsigned seq;

if (!nd->root.mnt) {
error = ERR_PTR(set_root(nd));
@@ -1781,11 +1774,18 @@ static const char *handle_dots(struct nameidata *nd, int type, int flags)
return error;
}
if (nd->flags & LOOKUP_RCU)
- error = follow_dotdot_rcu(nd, flags);
+ parent = follow_dotdot_rcu(nd, &inode, &seq);
else
- error = follow_dotdot(nd, flags);
- if (error)
- return error;
+ parent = follow_dotdot(nd, &inode, &seq);
+ if (IS_ERR(parent))
+ return ERR_CAST(parent);
+ if (unlikely(!parent)) {
+ error = step_into(nd, flags | WALK_NOFOLLOW,
+ nd->path.dentry, nd->inode, nd->seq);
+ } else {
+ error = step_into(nd, flags | WALK_NOFOLLOW,
+ parent, inode, seq);
+ }

if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
/*
--
2.11.0