On Fri 16-03-18 13:59:08, Kirill A. Shutemov wrote:
[..]
> @@ -498,31 +498,42 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
> continue;
> }
>
> - page = find_lock_page(inode->i_mapping,
> + page = find_get_page(inode->i_mapping,
> (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
> if (!page)
> goto drop;
>
> + /* No huge page at the end of the file: nothing to split */
> if (!PageTransHuge(page)) {
> - unlock_page(page);
> put_page(page);
> goto drop;
> }
>
> + /*
> + * Leave the inode on the list if we failed to lock
> + * the page at this time.
> + *
> + * Waiting for the lock may lead to deadlock in the
> + * reclaim path.
> + */
> + if (!trylock_page(page)) {
> + put_page(page);
> + goto leave;
> + }
Can somebody split the huge page after the PageTransHuge check and
before we lock it?
> +
> ret = split_huge_page(page);
> unlock_page(page);
> put_page(page);
>
> - if (ret) {
> - /* split failed: leave it on the list */
> - iput(inode);
> - continue;
> - }
> + /* If split failed leave the inode on the list */
> + if (ret)
> + goto leave;
>
> split++;
> drop:
> list_del_init(&info->shrinklist);
> removed++;
> +leave:
> iput(inode);
> }
>
> --
> 2.16.1
--
Michal Hocko
SUSE Labs