ao? 2011a1'11ae??29ae?JPY 14:02, KAMEZAWA Hiroyuki a??e??:
>
> You can't know whether the 'page' is allocated by alloc_page() in fallocate()
> or just found as exiting one.
> Then, yourwill corrupt existing pages in error path.
> Is it allowed ?
>

According to the comment,

/*
  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
  *
  * If we allocate a new one we do not mark it dirty. That's up to the
  * vm. If we swap it in we mark it dirty since we also free the swap
  * entry since a page cannot live in both the swap and page cache
  */

so we can know if the page is newly allocated by checking page dirty bit.
Or am I missing something?

But whoops, I sent a wrong version of this patch, the below one is
the correct one. Sorry for this.