On Tue 27-11-18 13:16:33, Matthew Wilcox wrote:
> If we race with inode destroy, it's possible for page->mapping to be
> NULL before we even enter this routine, as well as after having slept
> waiting for the dax entry to become unlocked.
>
> Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Thanks for writing this fix. The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/dax.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 9bcce89ea18e..e69fc231833b 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -365,7 +365,7 @@ bool dax_lock_mapping_entry(struct page *page)
> struct address_space *mapping = READ_ONCE(page->mapping);
>
> locked = false;
> - if (!dax_mapping(mapping))
> + if (!mapping || !dax_mapping(mapping))
> break;
>
> /*
> --
> 2.19.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
