linux-kernel - [PATCH AUTOSEL 6.12 268/486] fs/mpage: avoid negative shift for large blocksize

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Message-Id: <20250505223922.2682012-268-sashal@kernel.org>
Date: Mon,  5 May 2025 18:35:44 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Hannes Reinecke <hare@...nel.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Hannes Reinecke <hare@...e.de>,
	Christian Brauner <brauner@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.12 268/486] fs/mpage: avoid negative shift for large blocksize

From: Hannes Reinecke <hare@...nel.org>

[ Upstream commit 86c60efd7c0ede43bd677f2eee1d84200528df1e ]

For large blocksizes the number of block bits is larger than PAGE_SHIFT,
so calculate the sector number from the byte offset instead. This is
required to enable large folios with buffer-heads.

Reviewed-by: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
Signed-off-by: Hannes Reinecke <hare@...nel.org>
Link: https://lore.kernel.org/r/20250221223823.1680616-4-mcgrof@kernel.org
Reviewed-by: Hannes Reinecke <hare@...e.de>
Signed-off-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/mpage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index 82aecf3727437..a3c82206977f6 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -181,7 +181,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	if (folio_buffers(folio))
 		goto confused;
 
-	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
+	block_in_file = folio_pos(folio) >> blkbits;
 	last_block = block_in_file + args->nr_pages * blocks_per_page;
 	last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
 	if (last_block > last_block_in_file)
@@ -527,7 +527,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 	 * The page has no buffers: map it to disk
 	 */
 	BUG_ON(!folio_test_uptodate(folio));
-	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
+	block_in_file = folio_pos(folio) >> blkbits;
 	/*
 	 * Whole page beyond EOF? Skip allocating blocks to avoid leaking
 	 * space.
-- 
2.39.5