Re: [PATCH] fix mount option parsing in remount

[Christoph Hellwig <hch@lst.de>]

ping^2

On Tue, Jun 03, 2008 at 10:00:19AM +0200, Christoph Hellwig wrote:
> ping?  silently ignoring wrong options causes a lot of confusion for
> users, and the patch sould simple enough.  Anyone take 10 minutes to
> review it and check it in?
> 
> On Sun, May 18, 2008 at 05:35:39PM +0200, Christoph Hellwig wrote:
> > Remount currently happily accept any option thrown at it, although the
> > only filesystem specific option it actually handles is barrier/nobarrier.
> > And it actually doesn't handle these correctly either because it only
> > uses the value it parsed when we're doing a ro->rw transition.  In
> > addition to that there's also a bad bug in xfs_parseargs which doesn't
> > touch the actual option in the mount point except for a single one,
> > XFS_MOUNT_SMALL_INUMS and thus forced any filesystem that's every
> > remounted in some way to not support 64bit inodes with no way to recover
> > unless unmounted.
> > 
> > This patch changes xfs_fs_remount to use it's own linux/parser.h based
> > options parse instead of xfs_parseargs and reject all options except
> > for barrier/nobarrier and to the right thing in general.  Eventually
> > I'd like to have a single big option table used for mount aswell but
> > that can wait for a while.
> > 
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > 
> > Index: linux-2.6-xfs/fs/xfs/linux-2.6/xfs_super.c
> > ===================================================================
> > --- linux-2.6-xfs.orig/fs/xfs/linux-2.6/xfs_super.c	2008-05-18 15:22:23.000000000 +0200
> > +++ linux-2.6-xfs/fs/xfs/linux-2.6/xfs_super.c	2008-05-18 15:59:32.000000000 +0200
> > @@ -67,6 +67,7 @@
> >  #include <linux/writeback.h>
> >  #include <linux/kthread.h>
> >  #include <linux/freezer.h>
> > +#include <linux/parser.h>
> >  
> >  static struct quotactl_ops xfs_quotactl_operations;
> >  static struct super_operations xfs_super_operations;
> > @@ -1255,6 +1256,19 @@ xfs_fs_statfs(
> >  	return 0;
> >  }
> >  
> > +/*
> > + * Eventually we should extend this table and use it for mount, too.
> > + */
> > +enum {
> > +	Opt_barrier, Opt_nobarrier, Opt_err
> > +};
> > +
> > +static match_table_t tokens = {
> > +	{Opt_barrier, "barrier"},
> > +	{Opt_nobarrier, "nobarrier"},
> > +	{Opt_err, NULL}
> > +};
> > +
> >  STATIC int
> >  xfs_fs_remount(
> >  	struct super_block	*sb,
> > @@ -1262,36 +1276,54 @@ xfs_fs_remount(
> >  	char			*options)
> >  {
> >  	struct xfs_mount	*mp = XFS_M(sb);
> > -	struct xfs_mount_args	*args;
> > -	int			error;
> > +	substring_t		args[MAX_OPT_ARGS];
> > +	char			*p;
> >  
> > -	args = xfs_args_allocate(sb, 0);
> > -	if (!args)
> > -		return -ENOMEM;
> > +	while ((p = strsep(&options, ",")) != NULL) {
> > +		int token;
> >  
> > -	error = xfs_parseargs(mp, options, args, 1);
> > -	if (error)
> > -		goto out_free_args;
> > +		if (!*p)
> > +			continue;
> >  
> > -	if (!(*flags & MS_RDONLY)) {			/* rw/ro -> rw */
> > -		if (mp->m_flags & XFS_MOUNT_RDONLY)
> > -		mp->m_flags &= ~XFS_MOUNT_RDONLY;
> > -		if (args->flags & XFSMNT_BARRIER) {
> > +		token = match_token(p, tokens, args);
> > +		switch (token) {
> > +		case Opt_barrier:
> >  			mp->m_flags |= XFS_MOUNT_BARRIER;
> > -			xfs_mountfs_check_barriers(mp);
> > -		} else {
> > +
> > +			/*
> > +			 * Test if barriers are actually working if we can,
> > +			 * else delay this check until the filesystem is
> > +			 * marked writeable.
> > +			 */
> > +			if (!(mp->m_flags & XFS_MOUNT_RDONLY))
> > +				xfs_mountfs_check_barriers(mp);
> > +			break;
> > +		case Opt_nobarrier:
> >  			mp->m_flags &= ~XFS_MOUNT_BARRIER;
> > +			break;
> > +		default:
> > +			printk(KERN_INFO
> > +	"XFS: mount option \"%s\" not support for remount\n", p);
> > +			return -EINVAL;
> >  		}
> > -	} else if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {	/* rw -> ro */
> > +	}
> > +
> > +	/* rw/ro -> rw */
> > +	if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(*flags & MS_RDONLY)) {
> > +		mp->m_flags &= ~XFS_MOUNT_RDONLY;
> > +		if (mp->m_flags & XFS_MOUNT_BARRIER)
> > +			xfs_mountfs_check_barriers(mp);
> > +	}
> > +
> > +	/* rw -> ro */
> > +	if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (*flags & MS_RDONLY)) {
> >  		xfs_filestream_flush(mp);
> >  		xfs_sync(mp, SYNC_DATA_QUIESCE);
> >  		xfs_attr_quiesce(mp);
> >  		mp->m_flags |= XFS_MOUNT_RDONLY;
> >  	}
> >  
> > - out_free_args:
> > -	kfree(args);
> > -	return -error;
> > +	return 0;
> >  }
> >  
> >  /*
> ---end quoted text---
---end quoted text---