[PATCH v4 17/21] erofs: implement fscache-based data read for inline layout

Jeffle Xu
2022-03-07T12:34:40Z

This patch implements the data plane of reading data from bootstrap blob
file over fscache for inline layout.

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

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
fs/erofs/fscache.c | 43 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index ff69698948ad..4da148cc4484 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -85,8 +85,9 @@ static int erofs_fscache_readpage_noinline(struct page *page,
{
struct fscache_cookie *cookie = fsmap->m_ctx->cookie;
/*
- * 1) For FLAT_PLAIN layout, the output map.m_la shall be equal to o_la,
- * and the output map.m_pa is exactly the physical address of o_la.
+ * 1) For FLAT_PLAIN and FLAT_INLINE (the heading non tail packing part)
+ * layout, the output map.m_la shall be equal to o_la, and the output
+ * map.m_pa is exactly the physical address of o_la.
* 2) For CHUNK_BASED layout, the output map.m_la is rounded down to the
* nearest chunk boundary, and the output map.m_pa is actually the
* physical address of this chunk boundary. So we need to recalculate
@@ -97,6 +98,40 @@ static int erofs_fscache_readpage_noinline(struct page *page,
return erofs_fscache_read_page(cookie, page, start);
}

+static int erofs_fscache_readpage_inline(struct page *page,
+ struct erofs_fscache_map *fsmap)
+{
+ struct inode *inode = page->mapping->host;
+ struct super_block *sb = inode->i_sb;
+ struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
+ erofs_blk_t blknr;
+ size_t offset, len;
+ void *src, *dst;
+
+ /*
+ * For inline (tail packing) layout, the offset may be non-zero, which
+ * can be calculated from corresponding physical address directly.
+ * Currently only flat layout supports inline (FLAT_INLINE), and the
+ * output map.m_pa is exactly the physical address of o_la in this case.
+ */
+ offset = erofs_blkoff(fsmap->m_pa);
+ blknr = erofs_blknr(fsmap->m_pa);
+ len = fsmap->m_llen;
+
+ src = erofs_read_metabuf(&buf, sb, blknr, EROFS_KMAP);
+ if (IS_ERR(src))
+ return PTR_ERR(src);
+
+ dst = kmap(page);
+ memcpy(dst, src + offset, len);
+ memset(dst + len, 0, PAGE_SIZE - len);
+ kunmap(page);
+
+ erofs_put_metabuf(&buf);
+
+ return 0;
+}
+
static int erofs_fscache_do_readpage(struct page *page)
{
struct inode *inode = page->mapping->host;
@@ -126,8 +161,12 @@ static int erofs_fscache_do_readpage(struct page *page)
if (ret)
return ret;

+ if (map.m_flags & EROFS_MAP_META)
+ return erofs_fscache_readpage_inline(page, &fsmap);
+
switch (vi->datalayout) {
case EROFS_INODE_FLAT_PLAIN:
+ case EROFS_INODE_FLAT_INLINE:
case EROFS_INODE_CHUNK_BASED:
return erofs_fscache_readpage_noinline(page, &fsmap);
default:
--
2.27.0