On Mon 12-11-18 12:57:34, Pavel Tikhomirov wrote:
> If all pages are deleted from the mapping by memory reclaim and also
> moved to the cleancache:
>
> __delete_from_page_cache
> (no shadow case)
> unaccount_page_cache_page
> cleancache_put_page
> page_cache_delete
> mapping->nrpages -= nr
> (nrpages becomes 0)
>
> We don't clean the cleancache for an inode after final file truncation
> (removal).
>
> truncate_inode_pages_final
> check (nrpages || nrexceptional) is false
> no truncate_inode_pages
> no cleancache_invalidate_inode(mapping)
>
> These way when reading the new file created with same inode we may get
> these trash leftover pages from cleancache and see wrong data instead of
> the contents of the new file.
>
> Fix it by always doing truncate_inode_pages which is already ready for
> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
>
> Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")
> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Reviewed-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> Signed-off-by: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx>
> ---
> mm/truncate.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
The patch looks good but can you add a short comment before the
truncate_inode_pages() call explaining why it needs to be called always?
Something like:
/*
* Cleancache needs notification even if there are no pages or
* shadow entries...
*/
Otherwise you can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
>
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 45d68e90b703..4c56c19e76eb 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -517,9 +517,9 @@ void truncate_inode_pages_final(struct address_space *mapping)
> */
> xa_lock_irq(&mapping->i_pages);
> xa_unlock_irq(&mapping->i_pages);
> -
> - truncate_inode_pages(mapping, 0);
> }
> +
> + truncate_inode_pages(mapping, 0);
> }
> EXPORT_SYMBOL(truncate_inode_pages_final);
>
> --
> 2.17.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
