[RFC v2 06/11] fs/mpage: avoid negative shift for large blocksize

Luis Chamberlain
2024-12-14T03:11:06Z

From: Hannes Reinecke <hare@kernel.org>

For large blocksizes the number of block bits is larger than PAGE_SHIFT,
so use instead use folio_pos(folio) >> blkbits to calculate the sector
number.

With this in place we can now enable large folios on with buffer-heads.

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

diff --git a/fs/mpage.c b/fs/mpage.c
index eb6fee7de529..c6bb2a9706a1 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_folio;
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.
--
2.43.0