On Fri, Jul 12, 2019 at 01:55:52PM +0100, Al Viro wrote:
On Fri, Jul 12, 2019 at 01:39:24PM +0100, Al Viro wrote:
On Fri, Jul 12, 2019 at 08:57:45PM +1000, Aleksa Sarai wrote:
@@ -2350,9 +2400,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
s = ERR_PTR(error);
return s;
}
- error = dirfd_path_init(nd);
- if (unlikely(error))
- return ERR_PTR(error);
+ if (likely(!nd->path.mnt)) {
Is that a weird way of saying "if we hadn't already called dirfd_path_init()"?
Yes. I did it to be more consistent with the other "have we got the
root" checks elsewhere. Is there another way you'd prefer I do it?
"Have we got the root" checks are inevitable evil; here you are making the
control flow in a single function hard to follow.
I *think* what you are doing is
absolute pathname, no LOOKUP_BENEATH:
set_root
error = nd_jump_root(nd)
else
error = dirfd_path_init(nd)
return unlikely(error) ? ERR_PTR(error) : s;
which should be a lot easier to follow (not to mention shorter), but I might
be missing something in all of that.
PS: if that's what's going on, I would be tempted to turn the entire
path_init() part into this:
if (flags & LOOKUP_BENEATH)
while (*s == '/')
s++;
in the very beginning (plus the handling of nd_jump_root() prototype
change, but that belongs with nd_jump_root() change itself, obviously).
Again, I might be missing something here...
Argh... I am, at that - you have setting path->root (and grabbing it)
in LOOKUP_BENEATH cases and you do it after dirfd_path_init(). So
how about
if (flags & LOOKUP_BENEATH)
while (*s == '/')
s++;
before the whole thing and
if (*s == '/') { /* can happen only without LOOKUP_BENEATH */
set_root(nd);
error = nd_jump_root(nd);
if (unlikely(error))
return ERR_PTR(error);
} else if (nd->dfd == AT_FDCWD) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
do {
seq = read_seqcount_begin(&fs->seq);
nd->path = fs->pwd;
nd->inode = nd->path.dentry->d_inode;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
} else {
get_fs_pwd(current->fs, &nd->path);
nd->inode = nd->path.dentry->d_inode;
}
} else {
/* Caller must check execute permissions on the starting path component */
struct fd f = fdget_raw(nd->dfd);
struct dentry *dentry;
if (!f.file)
return ERR_PTR(-EBADF);
dentry = f.file->f_path.dentry;
if (*s && unlikely(!d_can_lookup(dentry))) {
fdput(f);
return ERR_PTR(-ENOTDIR);
}
nd->path = f.file->f_path;
if (flags & LOOKUP_RCU) {
nd->inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
} else {
path_get(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
fdput(f);
}
if (flags & LOOKUP_BENEATH) {
nd->root = nd->path;
if (!(flags & LOOKUP_RCU))
path_get(&nd->root);
else
nd->root_seq = nd->seq;
}
return s;
replacing the part in the end? Makes for much smaller change; it might
very well still make sense to add dirfd_path_init() as a separate
cleanup (perhaps with the *s == '/' case included), though.
