Re: [PATCH 3/4] mm/readahead: Limit page cache size in page_cache_ra_order()

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On 6/26/24 4:45 AM, David Hildenbrand wrote:
On 25.06.24 11:06, Gavin Shan wrote:
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.

Suggested-by: David Hildenbrand <david@xxxxxxxxxx>

Heh, you came up with this yourself concurrently :) so feel free to drop that.

Acked-by: David Hildenbrand <david@xxxxxxxxxx>


David, thanks for your follow-up and reviews. I will drop that tag in next respin :)

Thanks,
Gavin

Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
  mm/readahead.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

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();






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