Commit 8897277a authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm: support order-1 folios in the page cache 

Folios of order 1 have no space to store the deferred list.  This is not a
problem for the page cache as file-backed folios are never placed on the
deferred list.  All we need to do is prevent the core MM from touching the
deferred list for order 1 folios and remove the code which prevented us
from allocating order 1 folios.

Link: https://lore.kernel.org/linux-mm/90344ea7-4eec-47ee-5996-0c22f42d6a6a@google.com/
Link: https://lkml.kernel.org/r/20240226205534.1603748-3-zi.yan@sent.com


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 319a624e

mm/filemap.c

+0 −2
Original line number Diff line number Diff line
@@ -1912,8 +1912,6 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, 
			gfp_t alloc_gfp = gfp;



			err = -ENOMEM;

			if (order == 1)

				order = 0;

			if (order > 0)

				alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;

			folio = filemap_alloc_folio(alloc_gfp, order);

mm/huge_memory.c

+15 −4
Original line number Diff line number Diff line
@@ -790,7 +790,9 @@ struct deferred_split *get_deferred_split_queue(struct folio *folio) 


void folio_prep_large_rmappable(struct folio *folio)

{

	VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);

	if (!folio || !folio_test_large(folio))

		return;

	if (folio_order(folio) > 1)

		INIT_LIST_HEAD(&folio->_deferred_list);

	folio_set_large_rmappable(folio);

}
@@ -3114,7 +3116,8 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) 
	/* Prevent deferred_split_scan() touching ->_refcount */

	spin_lock(&ds_queue->split_queue_lock);

	if (folio_ref_freeze(folio, 1 + extra_pins)) {

		if (!list_empty(&folio->_deferred_list)) {

		if (folio_order(folio) > 1 &&

		    !list_empty(&folio->_deferred_list)) {

			ds_queue->split_queue_len--;

			list_del(&folio->_deferred_list);

		}
@@ -3165,6 +3168,9 @@ void folio_undo_large_rmappable(struct folio *folio) 
	struct deferred_split *ds_queue;

	unsigned long flags;



	if (folio_order(folio) <= 1)

		return;



	/*

	 * At this point, there is no one trying to add the folio to

	 * deferred_list. If folio is not in deferred_list, it's safe
@@ -3190,7 +3196,12 @@ void deferred_split_folio(struct folio *folio) 
#endif

	unsigned long flags;



	VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);

	/*

	 * Order 1 folios have no space for a deferred list, but we also

	 * won't waste much memory by not adding them to the deferred list.

	 */

	if (folio_order(folio) <= 1)

		return;



	/*

	 * The try_to_unmap() in page reclaim path might reach here too,

mm/internal.h

+1 −2
Original line number Diff line number Diff line
@@ -420,7 +420,6 @@ static inline struct folio *page_rmappable_folio(struct page *page) 
{

	struct folio *folio = (struct folio *)page;



	if (folio && folio_order(folio) > 1)

	folio_prep_large_rmappable(folio);

	return folio;

}

mm/readahead.c

+0 −3
Original line number Diff line number Diff line
@@ -514,9 +514,6 @@ void page_cache_ra_order(struct readahead_control *ractl, 
		/* Don't allocate pages past EOF */

		while (index + (1UL << order) - 1 > limit)

			order--;

		/* THP machinery does not support order-1 */

		if (order == 1)

			order = 0;

		err = ra_alloc_folio(ractl, index, mark, order, gfp);

		if (err)

			break;