linux-kernel - [RFC 05/23] filemap: align index to mapping_min_order in filemap_range_has

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Date:   Fri, 15 Sep 2023 20:38:30 +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 05/23] filemap: align index to mapping_min_order in filemap_range_has_page()

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

page cache is mapping min_folio_order aligned. Use mapping min_folio_order
to align the start_byte and end_byte in filemap_range_has_page().

Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 mm/filemap.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 2c47729dc8b0..4dee24b5b61c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -477,9 +477,12 @@ EXPORT_SYMBOL(filemap_flush);
 bool filemap_range_has_page(struct address_space *mapping,
 			   loff_t start_byte, loff_t end_byte)
 {
+	unsigned int min_order = mapping_min_folio_order(mapping);
+	unsigned int nrpages = 1UL << min_order;
+	pgoff_t index = round_down(start_byte >> PAGE_SHIFT, nrpages);
 	struct folio *folio;
-	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
-	pgoff_t max = end_byte >> PAGE_SHIFT;
+	XA_STATE(xas, &mapping->i_pages, index);
+	pgoff_t max = round_down(end_byte >> PAGE_SHIFT, nrpages);
 
 	if (end_byte < start_byte)
 		return false;
-- 
2.40.1