[RFC][PATCH v4 47/69] handle_dots(), follow_dotdot{,_rcu}(): preparation to switch to step_into()

Al Viro
2020-03-13T23:56:07Z

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)

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 | 52 +++++++++++++++++++++++++---------------------------
1 file changed, 25 insertions(+), 27 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 3ee3b8719505..1749e435edc7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1687,7 +1687,7 @@ 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)
{
struct dentry *parent = NULL;
struct inode *inode = nd->inode;
@@ -1703,9 +1703,9 @@ 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);
@@ -1714,11 +1714,11 @@ 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;
@@ -1728,7 +1728,7 @@ 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;
@@ -1737,21 +1737,21 @@ 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;
+ return NULL;
}

-static int follow_dotdot(struct nameidata *nd)
+static const char *follow_dotdot(struct nameidata *nd)
{
struct dentry *parent = NULL;
while (1) {
@@ -1762,34 +1762,34 @@ 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;
+ return NULL;
}

-static inline int handle_dots(struct nameidata *nd, int type)
+static const char *handle_dots(struct nameidata *nd, int type)
{
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 error;
}
@@ -1809,12 +1809,12 @@ static inline int handle_dots(struct nameidata *nd, int type)
*/
smp_rmb();
if (unlikely(__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)))
- return -EAGAIN;
+ return ERR_PTR(-EAGAIN);
if (unlikely(__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)))
- return -EAGAIN;
+ return ERR_PTR(-EAGAIN);
}
}
- return 0;
+ return NULL;
}

static const char *walk_component(struct nameidata *nd, int flags)
@@ -1822,7 +1822,6 @@ static const char *walk_component(struct nameidata *nd, int flags)
struct dentry *dentry;
struct inode *inode;
unsigned seq;
- int err;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
@@ -1831,8 +1830,7 @@ static const char *walk_component(struct nameidata *nd, int flags)
if (unlikely(nd->last_type != LAST_NORM)) {
if (!(flags & WALK_MORE) && nd->depth)
put_link(nd);
- err = handle_dots(nd, nd->last_type);
- return ERR_PTR(err);
+ return handle_dots(nd, nd->last_type);
}
dentry = lookup_fast(nd, &inode, &seq);
if (IS_ERR(dentry))
@@ -3128,10 +3126,10 @@ static const char *open_last_lookups(struct nameidata *nd,
if (nd->last_type != LAST_NORM) {
if (nd->depth)
put_link(nd);
- error = handle_dots(nd, nd->last_type);
- if (likely(!error))
- error = complete_walk(nd);
- return ERR_PTR(error);
+ res = handle_dots(nd, nd->last_type);
+ if (likely(!res))
+ res = ERR_PTR(complete_walk(nd));
+ return res;
}

if (!(open_flag & O_CREAT)) {
--
2.11.0