Commit f530ed0e authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

shmem: convert shmem_writepage() to use a folio throughout 

Even though we will split any large folio that comes in, write the code to
handle large folios so as to not leave a trap for whoever tries to handle
large folios in the swap cache.

Link: https://lkml.kernel.org/r/20220902194653.1739778-7-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 681ecf63

mm/shmem.c

+24 −23
Original line number Diff line number Diff line
@@ -1328,17 +1328,18 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
	 * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,

	 * and its shmem_writeback() needs them to be split when swapping.

	 */

	if (PageTransCompound(page)) {

	if (folio_test_large(folio)) {

		/* Ensure the subpages are still dirty */

		SetPageDirty(page);

		folio_test_set_dirty(folio);

		if (split_huge_page(page) < 0)

			goto redirty;

		ClearPageDirty(page);

		folio = page_folio(page);

		folio_clear_dirty(folio);

	}



	BUG_ON(!PageLocked(page));

	mapping = page->mapping;

	index = page->index;

	BUG_ON(!folio_test_locked(folio));

	mapping = folio->mapping;

	index = folio->index;

	inode = mapping->host;

	info = SHMEM_I(inode);

	if (info->flags & VM_LOCKED)
@@ -1361,15 +1362,15 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
	/*

	 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC

	 * value into swapfile.c, the only way we can correctly account for a

	 * fallocated page arriving here is now to initialize it and write it.

	 * fallocated folio arriving here is now to initialize it and write it.

	 *

	 * That's okay for a page already fallocated earlier, but if we have

	 * That's okay for a folio already fallocated earlier, but if we have

	 * not yet completed the fallocation, then (a) we want to keep track

	 * of this page in case we have to undo it, and (b) it may not be a

	 * of this folio in case we have to undo it, and (b) it may not be a

	 * good idea to continue anyway, once we're pushing into swap.  So

	 * reactivate the page, and let shmem_fallocate() quit when too many.

	 * reactivate the folio, and let shmem_fallocate() quit when too many.

	 */

	if (!PageUptodate(page)) {

	if (!folio_test_uptodate(folio)) {

		if (inode->i_private) {

			struct shmem_falloc *shmem_falloc;

			spin_lock(&inode->i_lock);
@@ -1385,9 +1386,9 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
			if (shmem_falloc)

				goto redirty;

		}

		clear_highpage(page);

		flush_dcache_page(page);

		SetPageUptodate(page);

		folio_zero_range(folio, 0, folio_size(folio));

		flush_dcache_folio(folio);

		folio_mark_uptodate(folio);

	}



	swap = folio_alloc_swap(folio);
@@ -1396,7 +1397,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 


	/*

	 * Add inode to shmem_unuse()'s list of swapped-out inodes,

	 * if it's not already there.  Do it now before the page is

	 * if it's not already there.  Do it now before the folio is

	 * moved to swap cache, when its pagelock no longer protects

	 * the inode from eviction.  But don't unlock the mutex until

	 * we've incremented swapped, because shmem_unuse_inode() will
@@ -1406,7 +1407,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
	if (list_empty(&info->swaplist))

		list_add(&info->swaplist, &shmem_swaplist);



	if (add_to_swap_cache(page, swap,

	if (add_to_swap_cache(&folio->page, swap,

			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,

			NULL) == 0) {

		spin_lock_irq(&info->lock);
@@ -1415,21 +1416,21 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
		spin_unlock_irq(&info->lock);



		swap_shmem_alloc(swap);

		shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));

		shmem_delete_from_page_cache(&folio->page, swp_to_radix_entry(swap));



		mutex_unlock(&shmem_swaplist_mutex);

		BUG_ON(page_mapped(page));

		swap_writepage(page, wbc);

		BUG_ON(folio_mapped(folio));

		swap_writepage(&folio->page, wbc);

		return 0;

	}



	mutex_unlock(&shmem_swaplist_mutex);

	put_swap_page(page, swap);

	put_swap_page(&folio->page, swap);

redirty:

	set_page_dirty(page);

	folio_mark_dirty(folio);

	if (wbc->for_reclaim)

		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */

	unlock_page(page);

		return AOP_WRITEPAGE_ACTIVATE;	/* Return with folio locked */

	folio_unlock(folio);

	return 0;

}