If i_blkbits is larger than PAGE_SHIFT, we shift by a negative number,
which is undefined. It is safe to shift the block left as a block
device must be smaller than MAX_LFS_FILESIZE, which is guaranteed to
fit in loff_t.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
---
fs/buffer.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index ab345fd4da12..faf1916200c2 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -199,7 +199,7 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
int all_mapped = 1;
static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
- index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
+ index = ((loff_t)block << bd_inode->i_blkbits) / PAGE_SIZE;
folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
if (IS_ERR(folio))
goto out;
@@ -1693,13 +1693,13 @@ void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
struct inode *bd_inode = bdev->bd_inode;
struct address_space *bd_mapping = bd_inode->i_mapping;
struct folio_batch fbatch;
- pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
+ pgoff_t index = ((loff_t)block << bd_inode->i_blkbits) / PAGE_SIZE;
pgoff_t end;
int i, count;
struct buffer_head *bh;
struct buffer_head *head;
- end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
+ end = ((loff_t)(block + len - 1) << bd_inode->i_blkbits) / PAGE_SIZE;
folio_batch_init(&fbatch);
while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
count = folio_batch_count(&fbatch);
@@ -2660,8 +2660,8 @@ int block_truncate_page(struct address_space *mapping,
return 0;
length = blocksize - length;
- iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
-
+ iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
+
folio = filemap_grab_folio(mapping, index);
if (IS_ERR(folio))
return PTR_ERR(folio);
--
2.42.0
