erofs: implement fscache-based data read for inline layout

Implement the data plane of reading data from data blobs over fscache
for inline layout.

For the heading non-inline part, the data plane for non-inline layout is
reused, while only the tail packing part needs special handling.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220425122143.56815-20-jefflexu@linux.alibaba.com
Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index b3af72af7c888196609ecc0cc8c67b118b06341d..5b779812a5eecd49b2bdfcb50058486b4a734b76 100644 (file)
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -83,6 +83,33 @@ out:
        return ret;
 }
 
+static int erofs_fscache_readpage_inline(struct folio *folio,
+                                        struct erofs_map_blocks *map)
+{
+       struct super_block *sb = folio_mapping(folio)->host->i_sb;
+       struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
+       erofs_blk_t blknr;
+       size_t offset, len;
+       void *src, *dst;
+
+       /* For tail packing layout, the offset may be non-zero. */
+       offset = erofs_blkoff(map->m_pa);
+       blknr = erofs_blknr(map->m_pa);
+       len = map->m_llen;
+
+       src = erofs_read_metabuf(&buf, sb, blknr, EROFS_KMAP);
+       if (IS_ERR(src))
+               return PTR_ERR(src);
+
+       dst = kmap_local_folio(folio, 0);
+       memcpy(dst, src + offset, len);
+       memset(dst + len, 0, PAGE_SIZE - len);
+       kunmap_local(dst);
+
+       erofs_put_metabuf(&buf);
+       return 0;
+}
+
 static int erofs_fscache_readpage(struct file *file, struct page *page)
 {
        struct folio *folio = page_folio(page);
@@ -108,6 +135,11 @@ static int erofs_fscache_readpage(struct file *file, struct page *page)
                goto out_uptodate;
        }
 
+       if (map.m_flags & EROFS_MAP_META) {
+               ret = erofs_fscache_readpage_inline(folio, &map);
+               goto out_uptodate;
+       }
+
        mdev = (struct erofs_map_dev) {
                .m_deviceid = map.m_deviceid,
                .m_pa = map.m_pa,