[PATCH v4 16/21] erofs: implement fscache-based data read for non-inline layout

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

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

Be noted that compressed layout is not supported yet.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
fs/erofs/fscache.c | 94 +++++++++++++++++++++++++++++++++++++++++++++
fs/erofs/inode.c | 6 ++-
fs/erofs/internal.h | 1 +
3 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 3f75c1b679e0..ff69698948ad 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -4,6 +4,12 @@
*/
#include "internal.h"

+struct erofs_fscache_map {
+ struct erofs_fscache_context *m_ctx;
+ erofs_off_t m_pa, m_la, o_la;
+ u64 m_llen;
+};
+
static struct fscache_volume *volume;

/*
@@ -60,10 +66,98 @@ static int erofs_fscache_readpage_blob(struct file *data, struct page *page)
return ret;
}

+static inline int erofs_fscache_get_map(struct erofs_fscache_map *fsmap,
+ struct erofs_map_blocks *map,
+ struct super_block *sb)
+{
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+ fsmap->m_ctx = sbi->bootstrap;
+ fsmap->m_la = map->m_la;
+ fsmap->m_pa = map->m_pa;
+ fsmap->m_llen = map->m_llen;
+
+ return 0;
+}
+
+static int erofs_fscache_readpage_noinline(struct page *page,
+ struct erofs_fscache_map *fsmap)
+{
+ 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.
+ * 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
+ * the actual physical address of o_la.
+ */
+ loff_t start = fsmap->m_pa + (fsmap->o_la - fsmap->m_la);
+
+ return erofs_fscache_read_page(cookie, page, start);
+}
+
+static int erofs_fscache_do_readpage(struct page *page)
+{
+ struct inode *inode = page->mapping->host;
+ struct erofs_inode *vi = EROFS_I(inode);
+ struct super_block *sb = inode->i_sb;
+ struct erofs_map_blocks map;
+ struct erofs_fscache_map fsmap;
+ int ret;
+
+ if (erofs_inode_is_data_compressed(vi->datalayout)) {
+ erofs_info(sb, "compressed layout not supported yet");
+ return -EOPNOTSUPP;
+ }
+
+ map.m_la = fsmap.o_la = page_offset(page);
+
+ ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
+ if (ret)
+ return ret;
+
+ if (!(map.m_flags & EROFS_MAP_MAPPED)) {
+ zero_user(page, 0, PAGE_SIZE);
+ return 0;
+ }
+
+ ret = erofs_fscache_get_map(&fsmap, &map, sb);
+ if (ret)
+ return ret;
+
+ switch (vi->datalayout) {
+ case EROFS_INODE_FLAT_PLAIN:
+ case EROFS_INODE_CHUNK_BASED:
+ return erofs_fscache_readpage_noinline(page, &fsmap);
+ default:
+ DBG_BUGON(1);
+ return -EOPNOTSUPP;
+ }
+}
+
+static int erofs_fscache_readpage(struct file *file, struct page *page)
+{
+ int ret;
+
+ ret = erofs_fscache_do_readpage(page);
+ if (!ret)
+ SetPageUptodate(page);
+ else
+ SetPageError(page);
+
+ unlock_page(page);
+ return ret;
+}
+
static const struct address_space_operations erofs_fscache_blob_aops = {
.readpage = erofs_fscache_readpage_blob,
};

+const struct address_space_operations erofs_fscache_access_aops = {
+ .readpage = erofs_fscache_readpage,
+};
+
struct page *erofs_fscache_read_cache_page(struct erofs_fscache_context *ctx,
pgoff_t index)
{
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index ff62f84f47d3..2f450cb3a7b9 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -296,7 +296,11 @@ static int erofs_fill_inode(struct inode *inode, int isdir)
err = z_erofs_fill_inode(inode);
goto out_unlock;
}
- inode->i_mapping->a_ops = &erofs_raw_access_aops;
+
+ if (erofs_bdev_mode(inode->i_sb))
+ inode->i_mapping->a_ops = &erofs_raw_access_aops;
+ else
+ inode->i_mapping->a_ops = &erofs_fscache_access_aops;

out_unlock:
erofs_put_metabuf(&buf);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index fca706cfaf72..548f928b0ded 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -393,6 +393,7 @@ struct page *erofs_grab_cache_page_nowait(struct address_space *mapping,
extern const struct super_operations erofs_sops;

extern const struct address_space_operations erofs_raw_access_aops;
+extern const struct address_space_operations erofs_fscache_access_aops;
extern const struct address_space_operations z_erofs_aops;

/*
--
2.27.0