On Thu, Dec 11, 2008 at 01:51:47PM -0800, Andrew Morton wrote:
> On Wed, 10 Dec 2008 08:27:07 +0100
> Nick Piggin <npiggin@xxxxxxx> wrote:
>
> > + if (sync) {
> > + struct inode *inode, *old_inode = NULL;
> > +
> > + /*
> > + * Data integrity sync. Must wait for all pages under writeback,
> > + * because there may have been pages dirtied before our sync
> > + * call, but which had writeout started before we write it out.
> > + * In which case, the inode may not be on the dirty list, but
> > + * we still have to wait for that writeout.
> > + */
> > + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
> > + struct address_space *mapping;
> > +
> > + if (inode->i_state & (I_FREEING|I_WILL_FREE))
> > + continue;
> > + mapping = inode->i_mapping;
> > + if (mapping->nrpages == 0)
> > + continue;
> > + __iget(inode);
> > + spin_unlock(&inode_lock);
> > + /*
> > + * We hold a reference to 'inode' so it couldn't have
> > + * been removed from s_inodes list while we dropped the
> > + * inode_lock. We cannot iput the inode now as we can
> > + * be holding the last reference and we cannot iput it
> > + * under inode_lock. So we keep the reference and iput
> > + * it later.
> > + */
>
> hm, tricky.
>
> Can umount run concurrently with this? What will it say about the busy
> inode?
AFAIKS umount shouldn't because we've taken a reference on the superblock
higher up.
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