Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Miklos Szeredi]

On Mon, 13 Sep 2010, Aneesh Kumar K. V wrote:
> As per your suggestion i started looking at handlefs details and below
> is my take on the approach.
> 
> handlefs would be an internal kernel mount like pipefs and would have
> inode object mapping to the returned file descriptor of
> open_by_handle_at syscall for symlinks. For regular files we can do what
> we already does and for symlinks we will create inodes in handlefs and
> their inode operation will in turn result in call out of inode operations
> of the actual symlinks. Based on the above
> 
> a) We still need open_by_handle_at syscall
> b) We still need handle based link syscall, because we need to support
>    creating hardlinks based on handle, and the existing linkat syscall
>    takes the oldpath name.
> c) We still need handle based readlink syscall, because the existing
>    readlinkat syscall takes pathname.

You can implement ->read() on the symlink file instead.

> d) we can drop stat, chown and xattr syscall because they are introduced
>    specially for symlinks as we don't allow open on symlinks.
> e) It would be nice to have handle based stat syscall to avoid two
>    syscall overhead for fetching file attributes when implementing a
>    file server, where fetching file attribute is a common operation. 

Syscall overhead is generally insignificant compared to other effects.
The server can also cache open files for commonly used handles.

> 
> With the above from the current patch series we can drop chown and
> xattr syscalls. Would it be ok if we get the series with the those two
> syscall patches dropped upstream as i work on supporting symlinks with
> handlefs approach ?

Try it.

Al seems to only be active to the outside world around the merge
window, so that's the best time to ask him to pull.

Thanks,
Miklos
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