Miklos Szeredi wrote:
> > Three differences compared to d_path().
> > (1) Ignores current process's root directory.
>
> I'd suggest calling __d_path() and passing in the namespace root
> instead of the process root. That would be a lot simpler and result
> in less code duplication.
>
Yes, that'll be possible. But I won't do so. See (3).
> > (2) Trailing '/' is added if the pathname refers to a directory.
>
> Caller can do this.
>
Yes. But I'd like to add trailing '/' here.
Appending trailing '/' have to worry about buffer size, but removing trailing
'/' needn't to. Thus, I think it is more convenient for callers that trailing
'/' is automatically added.
> > (3) /proc/PID/ is represented as /proc/self/ if PID equals current->tgid.
>
> This too. Such hacks really don't belong in generic VFS functions.
>
No.
How can the caller of __d_path() detect the /PID/ part and convert
to /self/ from returned string? You might think that I can use
strstr(returned_path, "/proc/") and strict_strtoul() .
The procfs is mounted on /proc/ by convention, but that is not guaranteed.
Some systems might mount procfs on /proc2/ , /p/ or /var/tmp/proc/100/proc/ .
Also, a pathname like /var/tmp/proc/100/file1.txt is possible.
In this case, /var/tmp/proc/ is not the mount point of the procfs.
Thus, it is too late for the caller of __d_path() to detect the /PID/ part.
If the caller of __d_path() traverses {dentry,mount} tree for checking
dentry->d_sb->s_magic == PROC_SUPER_MAGIC, the reason to call __d_path()
disappears.
Thus, I need to detect /proc/PID/ and convert it to /proc/self/ in
d_realpath().
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