erofs: avoid using generic_block_bmap

Surprisingly, `block' in sector_t indicates the number of
i_blkbits-sized blocks rather than sectors for bmap.

In addition, considering buffer_head limits mapped size to 32-bits,
should avoid using generic_block_bmap.

Link: https://lore.kernel.org/r/20201209115740.18802-1-huangjianan@oppo.com
Fixes: 9da681e017a3 ("staging: erofs: support bmap")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
[ Gao Xiang: slightly update the commit message description. ]
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 347be14..ea4f693 100644 (file)
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -312,27 +312,12 @@ static void erofs_raw_access_readahead(struct readahead_control *rac)
                submit_bio(bio);
 }
 
-static int erofs_get_block(struct inode *inode, sector_t iblock,
-                          struct buffer_head *bh, int create)
-{
-       struct erofs_map_blocks map = {
-               .m_la = iblock << 9,
-       };
-       int err;
-
-       err = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
-       if (err)
-               return err;
-
-       if (map.m_flags & EROFS_MAP_MAPPED)
-               bh->b_blocknr = erofs_blknr(map.m_pa);
-
-       return err;
-}
-
 static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
 {
        struct inode *inode = mapping->host;
+       struct erofs_map_blocks map = {
+               .m_la = blknr_to_addr(block),
+       };
 
        if (EROFS_I(inode)->datalayout == EROFS_INODE_FLAT_INLINE) {
                erofs_blk_t blks = i_size_read(inode) >> LOG_BLOCK_SIZE;
@@ -341,7 +326,10 @@ static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
                        return 0;
        }
 
-       return generic_block_bmap(mapping, block, erofs_get_block);
+       if (!erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW))
+               return erofs_blknr(map.m_pa);
+
+       return 0;
 }
 
 /* for uncompressed (aligned) files and raw access for other files */