On Mon, Feb 06, 2023 at 08:28:56PM +0900, David Stevens wrote:
> @@ -1747,6 +1748,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> int nr_none = 0, result = SCAN_SUCCEED;
> bool is_shmem = shmem_file(file);
> + bool i_mmap_locked = false;
you don't need this ...
> + * While iterating, we may drop the page cache lock multiple times. It
> + * is safe to replace pages in the page cache with hpage while doing so
> + * because nobody is able to map or otherwise access the content of
> + * hpage until we unlock it. However, we cannot insert hpage into empty
> + * indicies until we know we won't have to drop the page cache lock
"indices".
> @@ -1967,6 +1974,46 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> put_page(page);
> goto xa_unlocked;
> }
> +
> + if (nr_none) {
> + struct vm_area_struct *vma;
> + int nr_none_check = 0;
> +
> + xas_unlock_irq(&xas);
> + i_mmap_lock_read(mapping);
> + i_mmap_locked = true;
> + xas_lock_irq(&xas);
> +
> + xas_set(&xas, start);
> + for (index = start; index < end; index++) {
> + if (!xas_next(&xas))
> + nr_none_check++;
> + }
> +
> + if (nr_none != nr_none_check) {
> + result = SCAN_PAGE_FILLED;
... you can unlock the i_mmap_lock here before the goto.
I think you need to add a case in madvise_collapse_errno(). It should
probably return -EBUSY, I would think?
