On Wed 29-01-20 01:29:29, Al Viro wrote:
> On Tue, Jan 28, 2020 at 11:06:31AM +0100, Sascha Hauer wrote:
> > Hi Jan,
>
> > @@ -810,6 +811,36 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
> > #endif
> > }
> >
> > +static struct super_block *quotactl_path(const char __user *special, int cmd,
> > + struct path *path)
> > +{
> > + struct super_block *sb;
> > + int ret;
> > +
> > + ret = user_path_at(AT_FDCWD, special, LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT,
> > + path);
> > + if (ret)
> > + return ERR_PTR(ret);
> > +
> > + sb = path->mnt->mnt_sb;
> > +restart:
> > + if (quotactl_cmd_onoff(cmd))
> > + down_write(&sb->s_umount);
> > + else
> > + down_read(&sb->s_umount);
> > +
> > + if (quotactl_cmd_write(cmd) && sb->s_writers.frozen != SB_UNFROZEN) {
> > + if (quotactl_cmd_onoff(cmd))
> > + up_write(&sb->s_umount);
> > + else
> > + up_read(&sb->s_umount);
> > + wait_event(sb->s_writers.wait_unfrozen,
> > + sb->s_writers.frozen == SB_UNFROZEN);
> > + goto restart;
> > + }
> > +
> > + return sb;
> > +}
>
> This partial duplicate of __get_super_thawed() guts does *not* belong here,
> especially not interleaved with quota-specific checks.
OK, so some primitive in fs/super.c like:
void hold_super_thawed(struct super_block *sb, bool excl);
that would implement the above functionality and grab passive reference?
> > + if (q_path) {
> > + if (quotactl_cmd_onoff(cmd))
> > + up_write(&sb->s_umount);
> > + else
> > + up_read(&sb->s_umount);
> > +
> > + path_put(&sb_path);
> > + } else {
> > + if (!quotactl_cmd_onoff(cmds))
> > + drop_super(sb);
> > + else
> > + drop_super_exclusive(sb);
> > + }
>
> Er... Why not have the same code that you've used to lock the damn thing
> (needs to be moved to fs/super.c) simply get a passive ref to it? Then
> you could do the same thing, q_path or no q_path...
Yes.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
