Re: [Ocfs2-devel] [PATCH] fix crash on ocfs2_duplicate_clusters_by_page

[Larry Chen]

Hi Andrew and Changwei,

Thanks for your review, I'll propose a new version with comments corrected.

Thanks,
Larry
On 08/30/2018 10:29 AM, Changwei Ge wrote:
> Hi Larry,
>
> Besides Andrew's comments, other parts of this patch look good to me.
>
> Thanks,
>
> Changwei
>
>
> On 2018/8/30 6:25, Andrew Morton wrote:
> > On Wed, 29 Aug 2018 15:47:40 +0800 Larry Chen <lchen@xxxxxxxx> wrote:
> >
> > > ocfs2_duplicate_clusters_by_page may crash if one of extent's pages is dirty.
> > > When a page has not been written back, it is still in dirty state. If
> > > ocfs2_duplicate_clusters_by_page is called against the
> > > dirty page, the crash happens.
> > >
> > > To fix this bug, we can just unlock the page and wait the page until
> > > it's not dirty.
> > >
> > > The following is the buck trace dump:
> > >
> > > kernel BUG at /root/code/ocfs2/refcounttree.c:2961!
> > > [exception RIP: ocfs2_duplicate_clusters_by_page+822]
> > > __ocfs2_move_extent+0x80/0x450 [ocfs2]
> > > ? __ocfs2_claim_clusters+0x130/0x250 [ocfs2]
> > > ocfs2_defrag_extent+0x5b8/0x5e0 [ocfs2]
> > > __ocfs2_move_extents_range+0x2a4/0x470 [ocfs2]
> > > ocfs2_move_extents+0x180/0x3b0 [ocfs2]
> > > ? ocfs2_wait_for_recovery+0x13/0x70 [ocfs2]
> > > ocfs2_ioctl_move_extents+0x133/0x2d0 [ocfs2]
> > > ocfs2_ioctl+0x253/0x640 [ocfs2]
> > > do_vfs_ioctl+0x90/0x5f0
> > > SyS_ioctl+0x74/0x80
> > > do_syscall_64+0x74/0x140
> > > entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> > >
> > > --- a/fs/ocfs2/refcounttree.c
> > > +++ b/fs/ocfs2/refcounttree.c
> > > @@ -2946,6 +2946,7 @@ int ocfs2_duplicate_clusters_by_page(handle_t *handle,
> > >    		if (map_end & (PAGE_SIZE - 1))
> > >    			to = map_end & (PAGE_SIZE - 1);
> > >    
> > > +retry:
> > >    		page = find_or_create_page(mapping, page_index, GFP_NOFS);
> > >    		if (!page) {
> > >    			ret = -ENOMEM;
> > > @@ -2957,8 +2958,15 @@ int ocfs2_duplicate_clusters_by_page(handle_t *handle,
> > >    		 * In case PAGE_SIZE <= CLUSTER_SIZE, This page
> > >    		 * can't be dirtied before we CoW it out.
> > >    		 */
> > Looks sane, but the below change shows that the above comment is
> > untrue.  Can we please update the comment as well?
> >
> >
> > > -		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize)
> > > -			BUG_ON(PageDirty(page));
> > > +		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize) {
> > > +			if (PageDirty(page)) {
> > > +				/*
> > > +				 * write_on_page will unlock the page on return
> > > +				 */
> > > +				ret = write_one_page(page);
> > > +				goto retry;
> > > +			}
> > > +		}
> > >    
> > >    		if (!PageUptodate(page)) {
> > >    			ret = block_read_full_page(page, ocfs2_get_block);
> >
> > _______________________________________________
> > Ocfs2-devel mailing list
> > Ocfs2-devel@xxxxxxxxxxxxxx
> > https://oss.oracle.com/mailman/listinfo/ocfs2-devel