[v2,2/4] mm/readahead: Limit page cache size in page_cache_ra_order()

Commit Message

Gavin Shan June 27, 2024, 12:39 a.m. UTC

In page_cache_ra_order(), the maximal order of the page cache to be
allocated shouldn't be larger than MAX_PAGECACHE_ORDER. Otherwise,
it's possible the large page cache can't be supported by xarray when
the corresponding xarray entry is split.

For example, HPAGE_PMD_ORDER is 13 on ARM64 when the base page size
is 64KB. The PMD-sized page cache can't be supported by xarray.

Fixes: 793917d997df ("mm/readahead: Add large folio readahead")
Cc: [e-mail] # v5.18+
Signed-off-by: Gavin Shan <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
---
 mm/readahead.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Patch

diff --git a/mm/readahead.c b/mm/readahead.c
index c1b23989d9ca..817b2a352d78 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -503,11 +503,11 @@  void page_cache_ra_order(struct readahead_control *ractl,
 
 	limit = min(limit, index + ra->size - 1);
 
-	if (new_order < MAX_PAGECACHE_ORDER) {
+	if (new_order < MAX_PAGECACHE_ORDER)
 		new_order += 2;
-		new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order);
-		new_order = min_t(unsigned int, new_order, ilog2(ra->size));
-	}
+
+	new_order = min_t(unsigned int, MAX_PAGECACHE_ORDER, new_order);
+	new_order = min_t(unsigned int, new_order, ilog2(ra->size));
 
 	/* See comment in page_cache_ra_unbounded() */
 	nofs = memalloc_nofs_save();