linux-kernel - Re: request for patches: showing mount options

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Date:	Fri, 27 Jul 2007 15:43:01 -0400
From:	Chuck Lever <chuck.lever@...cle.com>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, kzak@...hat.com, ericvh@...il.com,
	lucho@...kov.net, zippel@...ux-m68k.org, hpa@...or.com,
	raven@...maw.net, rathamahata@...4.ru, dhowells@...hat.com,
	sfrench@...ba.org, mhalcrow@...ibm.com,
	phillip@...lewell.homeip.net, hirofumi@...l.parknet.co.jp,
	mikulas@...ax.karlin.mff.cuni.cz, wli@...omorphy.com,
	shaggy@...tin.ibm.com, vandrove@...cvut.cz,
	trond.myklebust@....uio.no, aia21@...tab.net,
	mark.fasheh@...cle.com, kurt.hackel@...cle.com,
	reiserfs-devel@...r.kernel.org, bfennema@...con.csc.calpoly.edu,
	dushistov@...l.ru, xfs-masters@....sgi.com, arnd@...db.de,
	holzheu@...ibm.com
Subject: Re: request for patches: showing mount options

Miklos:

Some mount options are never passed to the kernel, and thus can't appear 
in /proc/mounts.  Examples include user, users, and _netdev for NFS.

Miklos Szeredi wrote:
> [please consider pruning the CC list if discussing some aspect, which
> doesn't concern all]
> 
> I've done an audit of all filesystems with regards to showing mount
> options in /proc/<pid>/mounts.  Unfortunately most of them show none
> or only a part of all accepted options (for details see list of
> filesystems at the end of the mail).
> 
> This is currently not a big problem, because mount(8) stores the given
> options in /etc/mtab.  However we want to get rid of mtab, and this
> requires, that the option showing be fixed up.
> 
> It would be easiest if this was done by the VFS instead of having to
> deal with it in filesystems.  However there are differences in how
> filesytems handle options during mount and remount, and it would be
> impossible to take this into account in all cases.
> 
> If you are CC-ed, and responsible for one of these filesystems, please
> take a moment to fully implement the ->show_options() method.  In most
> cases it should be an easy task.
> 
> If for some reason you are unable to do this, please let me know and
> I'll fix it up.
> 
> Here are some guidelines for showing options.  I'll also add these to
> Documentation/filesystems/vfs.txt
> 
> +   If a filesystem accepts mount options, it must define show_options()
> +   to show all the currently active options.  The rules are:
> +
> +     - options MUST be shown which are not default or their values differ
> +       from the default
> +
> +     - options MAY be shown which are enabled by default or have their
> +       default value
> +
> +   Options used only internally between a mount helper and the kernel
> +   (such as file descriptors), or which only have an effect during the
> +   mounting (such as ones controlling the creation of a journal) are exempt
> +   from the above rules.
> 
> Thanks,
> Miklos
> 
> -------
> legend:
> 
>   all - fs has options, but doesn't define ->show_options()
>   some - fs defines ->show_options(), but some options are not shown
>   noopt - fs does not have options
>   good - fs shows all options
>   patch - I have a patch
> 
> 
> 9p          some
> adfs        all (maintainer?)
> affs        all
> afs         all
> autofs      all
> autofs4     some
> befs        all
> bfs         noopt
> cifs        some (odd parser)
> coda        noopt
> configfs    noopt
> cramfs      noopt
> debugfs     noopt
> devpts      patch
> ecryptfs    some
> efs         noopt
> ext2        patch
> ext3        patch
> ext4        patch
> fat         some
> freevxfs    noopt
> fuse        patch
> gfs2        good
> hfs         good
> hfsplus     good
> hostfs      patch
> hpfs        all
> hppfs       noopt
> hugetlbfs   all
> isofs       all (maintainer?)
> jffs2       noopt
> jfs         some
> minix       noopt
> msdos       ->fat
> ncpfs       all (FS_BINARY_MOUNTDATA?)
> nfs         some
> nfsd        noopt
> ntfs        good (odd parser)
> ocfs2       all
> openpromfs  noopt
> proc        noopt
> qnx4        noopt
> ramfs       noopt
> reiserfs    all
> romfs       noopt
> smbfs       good (odd parser) (maintainer?)
> sysfs       noopt
> sysv        noopt
> udf         all
> ufs         all
> vfat        ->fat
> xfs         some (odd parser)
> 
> mm/shmem.c                                    patch
> drivers/oprofile/oprofilefs.c                 noopt
> drivers/infiniband/hw/ipath/ipath_fs.c        noopt
> drivers/misc/ibmasm/ibmasmfs.c                noopt
> drivers/usb/core (usbfs)                      noopt
> drivers/usb/gadget (gadgetfs)                 noopt
> drivers/isdn/capi/capifs.c                    noopt
> kernel/cpuset.c                               noopt
> fs/binfmt_misc.c                              noopt
> net/sunrpc/rpc_pipe.c                         noopt
> arch/powerpc/platforms/cell/spufs             all
> arch/s390/hypfs                               all
> ipc/mqueue.c                                  noopt
> security (securityfs)                         noopt
> security/selinux/selinuxfs.c                  noopt
> 
> in -mm:
> 
> reiser4                some (odd parser)
> kernel/container.c     good (odd parser)
> -
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