Re: [Qemu-devel] Re: [V9fs-developer] [PATCH] virtio-9p: getattr server implementation for 9P2000.L protocol.

[Sripathi Kodi <sripathik@in.ibm.com>]

On Thu, 01 Jul 2010 11:01:15 +0530
"Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

> On Fri, 28 May 2010 16:08:43 +0530, Sripathi Kodi <sripathik@in.ibm.com> wrote:
> > From: M. Mohan Kumar <mohan@in.ibm.com>
> > 
> > SYNOPSIS
> > 
> >       size[4] Tgetattr tag[2] fid[4]
> > 
> >       size[4] Rgetattr tag[2] lstat[n]
> > 
> >    DESCRIPTION
> > 
> >       The getattr transaction inquires about the file identified by fid.
> >       The reply will contain a machine-independent directory entry,
> >       laid out as follows:
> > 
> >          qid.type[1]
> >             the type of the file (directory, etc.), represented as a bit
> >             vector corresponding to the high 8 bits of the file's mode
> >             word.
> > 
> >          qid.vers[4]
> >             version number for given path
> > 
> >          qid.path[8]
> >             the file server's unique identification for the file
> > 
> >          st_mode[4]
> >             Permission and flags
> > 
> >          st_nlink[8]
> >             Number of hard links
> > 
> >          st_uid[4]
> >             User id of owner
> > 
> >          st_gid[4]
> >             Group ID of owner
> > 
> >          st_rdev[8]
> >             Device ID (if special file)
> > 
> >          st_size[8]
> >             Size, in bytes
> > 
> >          st_blksize[8]
> >             Block size for file system IO
> > 
> >          st_blocks[8]
> >             Number of file system blocks allocated
> > 
> >          st_atime_sec[8]
> >             Time of last access, seconds
> > 
> >          st_atime_nsec[8]
> >             Time of last access, nanoseconds
> > 
> >          st_mtime_sec[8]
> >             Time of last modification, seconds
> > 
> >          st_mtime_nsec[8]
> >             Time of last modification, nanoseconds
> > 
> >          st_ctime_sec[8]
> >             Time of last status change, seconds
> > 
> >          st_ctime_nsec[8]
> >             Time of last status change, nanoseconds
> > 
> > 
> > This patch implements the client side of getattr implementation for 9P2000.L.
> > It introduces a new structure p9_stat_dotl for getting Linux stat information
> > along with QID. The data layout is similar to stat structure in Linux user
> > space with the following major differences:
> > 
> > inode (st_ino) is not part of data. Instead qid is.
> > 
> > device (st_dev) is not part of data because this doesn't make sense on the
> > client.
> > 
> > All time variables are 64 bit wide on the wire. The kernel seems to use
> > 32 bit variables for these variables. However, some of the architectures
> > have used 64 bit variables and glibc exposes 64 bit variables to user
> > space on some architectures. Hence to be on the safer side we have made
> > these 64 bit in the protocol. Refer to the comments in
> > include/asm-generic/stat.h
> > 
> > 
> 
> Can we just hold on this patch. There is a discussion to add
> i_generation and inode create time to a variant of stat. So may be the
> protocol bits need those
> 

IMHO, we can put this in now and change it later if needed based on how
the discussion about VFS changes go because:
a) 9P2000.L is still at experimental stage, so it allows us to change
the protocol later. 
b) The kernel patch for this is already in linux-next. Without these
patches in QEMU it won't be possible to use 9P2000.L.

Thanks,
Sripathi.

> -aneesh
>