[RFC][PATCH v3 47/55] follow_dotdot{,_rcu}(): preparation to switch to step_into()

Al Viro
2020-03-01T21:53:35Z

Right now the tail ends of follow_dotdot{,_rcu}() are pretty
much the open-coded analogues of step_into(). The differences:
* the lack of proper LOOKUP_NO_XDEV handling in non-RCU case
(arguably a bug)
* the lack of ->d_manage() handling (again, arguably a bug)
* the lack of (conditional) put_link() - that sits in
handle_dots() right now.

Bring the put_link() in, adjust the calling conventions so that
on the next step with could just switch those functions to
returning step_into().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 49 +++++++++++++++++++++++++++----------------------
1 file changed, 27 insertions(+), 22 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 1bfefb99cbca..3e3bf11ee3d7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1689,7 +1689,7 @@ static const char *step_into(struct nameidata *nd, int flags,
return pick_link(nd, &path, inode, seq, flags);
}

-static int follow_dotdot_rcu(struct nameidata *nd)
+static const char *follow_dotdot_rcu(struct nameidata *nd, int flags)
{
struct dentry *parent = NULL;
struct inode *inode = nd->inode;
@@ -1705,9 +1705,9 @@ static int follow_dotdot_rcu(struct nameidata *nd)
inode = parent->d_inode;
seq = read_seqcount_begin(&parent->d_seq);
if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
if (unlikely(!path_connected(nd->path.mnt, parent)))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
break;
} else {
struct mount *mnt = real_mount(nd->path.mnt);
@@ -1716,11 +1716,11 @@ static int follow_dotdot_rcu(struct nameidata *nd)
struct inode *inode2 = mountpoint->d_inode;
unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
if (&mparent->mnt == nd->path.mnt)
break;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
/* we know that mountpoint was pinned */
nd->path.dentry = mountpoint;
nd->path.mnt = &mparent->mnt;
@@ -1730,7 +1730,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
}
if (unlikely(!parent)) {
if (unlikely(nd->flags & LOOKUP_BENEATH))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
} else {
nd->path.dentry = parent;
nd->seq = seq;
@@ -1739,21 +1739,23 @@ static int follow_dotdot_rcu(struct nameidata *nd)
struct mount *mounted;
mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
if (!mounted)
break;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
- return -ECHILD;
+ return ERR_PTR(-ECHILD);
nd->path.mnt = &mounted->mnt;
nd->path.dentry = mounted->mnt.mnt_root;
inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
}
nd->inode = inode;
- return 0;
+ if (!(flags & WALK_MORE) && nd->depth)
+ put_link(nd);
+ return NULL;
}

-static int follow_dotdot(struct nameidata *nd)
+static const char *follow_dotdot(struct nameidata *nd, int flags)
{
struct dentry *parent = NULL;
while (1) {
@@ -1764,43 +1766,45 @@ static int follow_dotdot(struct nameidata *nd)
parent = dget_parent(nd->path.dentry);
if (unlikely(!path_connected(nd->path.mnt, parent))) {
dput(parent);
- return -ENOENT;
+ return ERR_PTR(-ENOENT);
}
break;
}
if (!follow_up(&nd->path))
break;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
- return -EXDEV;
+ return ERR_PTR(-EXDEV);
}
if (unlikely(!parent)) {
if (unlikely(nd->flags & LOOKUP_BENEATH))
- return -EXDEV;
+ return ERR_PTR(-EXDEV);
} else {
dput(nd->path.dentry);
nd->path.dentry = parent;
}
follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode;
- return 0;
+ if (!(flags & WALK_MORE) && nd->depth)
+ put_link(nd);
+ return NULL;
}

static const char *handle_dots(struct nameidata *nd, int type, int flags)
{
if (type == LAST_DOTDOT) {
- int error = 0;
+ const char *error = NULL;

if (!nd->root.mnt) {
- error = set_root(nd);
+ error = ERR_PTR(set_root(nd));
if (error)
- return ERR_PTR(error);
+ return error;
}
if (nd->flags & LOOKUP_RCU)
- error = follow_dotdot_rcu(nd);
+ error = follow_dotdot_rcu(nd, flags);
else
- error = follow_dotdot(nd);
+ error = follow_dotdot(nd, flags);
if (error)
- return ERR_PTR(error);
+ return error;

if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
/*
@@ -1815,9 +1819,10 @@ static const char *handle_dots(struct nameidata *nd, int type, int flags)
if (unlikely(__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)))
return ERR_PTR(-EAGAIN);
}
+ } else { // LAST_DOT
+ if (!(flags & WALK_MORE) && nd->depth)
+ put_link(nd);
}
- if (!(flags & WALK_MORE) && nd->depth)
- put_link(nd);
return NULL;
}

--
2.11.0