buffer: fix various functions for block size > PAGE_SIZE

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.

Link: https://lkml.kernel.org/r/20231109210608.2252323-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/buffer.c b/fs/buffer.c
index ab345fd4da12ad3cb89bb7e59cf4c8efac8e6374..faf1916200c2d35901b6ee6fe04625c5be34b9c5 100644 (file)
--- 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);