Re: [PATCH 7/9] vfs: protect remounting superblock read-only

[Al Viro]

On Tue, Oct 05, 2010 at 12:31:15PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@xxxxxxx>
> 
> Currently remouting superblock read-only is racy in a major way.
> 
> With the per mount read-only infrastructure it is now possible to
> prevent most races, which this patch attempts.
> 
> Before starting the remount read-only, set MNT_WRITE_HOLD on all
> mounts so that writes are held off until the remount either succeeds
> or fails.

Umm...  What'll happen if your remount will say mnt_want_write() on
e.g. internal vfsmount over that sb?  Or, more subtle, tries to
update atime on some opened struct file on that sb.
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