Re: [PATCH v2 1/2] mm, thp: check page mapping when truncating page cache

[Rongwei Wang]

On 10/5/21 3:05 AM, Matthew Wilcox wrote:
> On Tue, Oct 05, 2021 at 01:26:50AM +0800, Rongwei Wang wrote:
> > Hi,
> > I have run our cases these two days to stress test new Patch #1. The new
> > Patch #1 mainly add filemap_invalidate_{un}lock before and after
> > truncate_pagecache(), basing on original Patch #1. And the crash has not
> > happened.
>
> You shouldn't need most of patch 1.
>
> In fact, the only two patches you should need would be this:
>
> +++ b/mm/filemap.c
> @@ -2093,7 +2093,6 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
>                  if (!xa_is_value(page)) {
>                          if (page->index < start)
>                                  goto put;
> -                       VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
>                          if (page->index + thp_nr_pages(page) - 1 > end)
>                                  goto put;
>                          if (!trylock_page(page))
>
> (already in Andrew's tree) and:
>
> > -               if (filemap_nr_thps(inode->i_mapping))
> > +               if (filemap_nr_thps(inode->i_mapping)) {
> > +                       filemap_invalidate_lock(inode->i_mapping);
> >                          truncate_pagecache(inode, 0);
> > +                       filemap_invalidate_unlock(inode->i_mapping);
> > +               }
>
> If you can still hit a bug with just those two patches, then something
> else is going wrong, and needs to be investigated.
OK, I see what your mean. I will send Patch v3 and only keep 
filemap_invalidate_{un}lock in Patch #1.

Thanks!
>