linux-kernel - [RFC 04/23] filemap: set the order of the index in page_cache_delete

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Date:   Fri, 15 Sep 2023 20:38:29 +0200
From:   Pankaj Raghav <kernel@...kajraghav.com>
To:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:     p.raghav@...sung.com, david@...morbit.com, da.gomez@...sung.com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        willy@...radead.org, djwong@...nel.org, linux-mm@...ck.org,
        chandan.babu@...cle.com, mcgrof@...nel.org, gost.dev@...sung.com
Subject: [RFC 04/23] filemap: set the order of the index in page_cache_delete_batch()

From: Luis Chamberlain <mcgrof@...nel.org>

Similar to page_cache_delete(), call xas_set_order for non-hugetlb pages
while deleting an entry from the page cache. Also put BUG_ON if the
order of the folio is less than the mapping min_order.

Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 mm/filemap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index b1ce63143df5..2c47729dc8b0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -126,6 +126,7 @@
 static void page_cache_delete(struct address_space *mapping,
 				   struct folio *folio, void *shadow)
 {
+	unsigned int min_order = mapping_min_folio_order(mapping);
 	XA_STATE(xas, &mapping->i_pages, folio->index);
 	long nr = 1;
 
@@ -134,6 +135,7 @@ static void page_cache_delete(struct address_space *mapping,
 	xas_set_order(&xas, folio->index, folio_order(folio));
 	nr = folio_nr_pages(folio);
 
+	VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio);
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
 	xas_store(&xas, shadow);
@@ -276,6 +278,7 @@ void filemap_remove_folio(struct folio *folio)
 static void page_cache_delete_batch(struct address_space *mapping,
 			     struct folio_batch *fbatch)
 {
+	unsigned int min_order = mapping_min_folio_order(mapping);
 	XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
 	long total_pages = 0;
 	int i = 0;
@@ -304,6 +307,11 @@ static void page_cache_delete_batch(struct address_space *mapping,
 
 		WARN_ON_ONCE(!folio_test_locked(folio));
 
+		/* hugetlb pages are represented by a single entry in the xarray */
+		if (!folio_test_hugetlb(folio)) {
+			VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio);
+			xas_set_order(&xas, folio->index, folio_order(folio));
+		}
 		folio->mapping = NULL;
 		/* Leave folio->index set: truncation lookup relies on it */
 
-- 
2.40.1