diff mbox series

[2/5] fs/mpage: avoid negative shift for large blocksize

Message ID 20240510102906.51844-3-hare@kernel.org (mailing list archive)
State New
Headers show
Series enable bs > ps for block devices | expand

Commit Message

Hannes Reinecke May 10, 2024, 10:29 a.m. UTC 
From: Hannes Reinecke <hare@kernel.org>

For large blocksizes the number of block bits is larger than PAGE_SHIFT,
so use shift to calculate the sector number from the page cache index.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
---
 fs/mpage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Matthew Wilcox May 10, 2024, 10:24 p.m. UTC | #1 
On Fri, May 10, 2024 at 12:29:03PM +0200, hare@kernel.org wrote:
> -	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
> +	block_in_file = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);

	block_in_file = folio_pos(folio) >> blkbits;
Hannes Reinecke May 11, 2024, 9:13 a.m. UTC | #2 
On 5/11/24 00:24, Matthew Wilcox wrote:
> On Fri, May 10, 2024 at 12:29:03PM +0200, hare@kernel.org wrote:
>> -	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
>> +	block_in_file = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);
> 
> 	block_in_file = folio_pos(folio) >> blkbits;
> 
> 
I know there was a better way. Will be fixing it up.

Cheers,

Hannes
diff mbox series

Patch

diff --git a/fs/mpage.c b/fs/mpage.c
index 379a71475c42..e3732686e65f 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -188,7 +188,7 @@  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 = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);
 	last_block = block_in_file + args->nr_pages * blocks_per_folio;
 	last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
 	if (last_block > last_block_in_file)
@@ -534,7 +534,7 @@  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 = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);
 	/*
 	 * Whole page beyond EOF? Skip allocating blocks to avoid leaking
 	 * space.