[PATCH v6 17/22] erofs: implement fscache-based data read for non-inline layout

Jeffle Xu
2022-03-25T12:23:45Z

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 | 83 +++++++++++++++++++++++++++++++++++++++++++++
fs/erofs/inode.c | 8 ++++-
fs/erofs/internal.h | 5 +++
3 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 91377939b4f7..4a9a4e60c15d 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -60,10 +60,93 @@ static int erofs_fscache_readpage_blob(struct file *data, struct page *page)
return ret;
}

+static inline int erofs_fscache_get_map(struct erofs_map_blocks *map,
+ struct super_block *sb)
+{
+ struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+ map->m_fscache = sbi->bootstrap;
+ return 0;
+}
+
+static int erofs_fscache_readpage_noinline(struct folio *folio,
+ struct erofs_map_blocks *map)
+{
+ struct fscache_cookie *cookie = map->m_fscache->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 = map->m_pa + (map->o_la - map->m_la);
+
+ return erofs_fscache_read_folio(cookie, folio, start);
+}
+
+static int erofs_fscache_do_readpage(struct folio *folio)
+{
+ struct inode *inode = folio_file_mapping(folio)->host;
+ struct erofs_inode *vi = EROFS_I(inode);
+ struct super_block *sb = inode->i_sb;
+ struct erofs_map_blocks map;
+ int ret;
+
+ if (erofs_inode_is_data_compressed(vi->datalayout)) {
+ erofs_info(sb, "compressed layout not supported yet");
+ return -EOPNOTSUPP;
+ }
+
+ DBG_BUGON(folio_size(folio) != EROFS_BLKSIZ);
+
+ map.m_la = map.o_la = folio_pos(folio);
+
+ ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
+ if (ret)
+ return ret;
+
+ if (!(map.m_flags & EROFS_MAP_MAPPED)) {
+ folio_zero_range(folio, 0, folio_size(folio));
+ return 0;
+ }
+
+ ret = erofs_fscache_get_map(&map, sb);
+ if (ret)
+ return ret;
+
+ switch (vi->datalayout) {
+ case EROFS_INODE_FLAT_PLAIN:
+ case EROFS_INODE_CHUNK_BASED:
+ return erofs_fscache_readpage_noinline(folio, &map);
+ default:
+ DBG_BUGON(1);
+ return -EOPNOTSUPP;
+ }
+}
+
+static int erofs_fscache_readpage(struct file *file, struct page *page)
+{
+ struct folio *folio = page_folio(page);
+ int ret;
+
+ ret = erofs_fscache_do_readpage(folio);
+ if (!ret)
+ folio_mark_uptodate(folio);
+
+ folio_unlock(folio);
+ 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,
+};
+
/*
* erofs_fscache_get_folio - find and read page cache of blob file
* @ctx: the context of the blob file
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index ff62f84f47d3..744faf3ef9f4 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -296,7 +296,13 @@ 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;
+
+#ifdef CONFIG_EROFS_FS_ONDEMAND
+ if (erofs_is_nodev_mode(inode->i_sb))
+ inode->i_mapping->a_ops = &erofs_fscache_access_aops;
+#endif
+ if (!erofs_is_nodev_mode(inode->i_sb))
+ inode->i_mapping->a_ops = &erofs_raw_access_aops;

out_unlock:
erofs_put_metabuf(&buf);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index fa89a1e3012f..6537ededed51 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -442,6 +442,9 @@ struct erofs_map_blocks {
unsigned short m_deviceid;
char m_algorithmformat;
unsigned int m_flags;
+
+ struct erofs_fscache *m_fscache;
+ erofs_off_t o_la;
};

/* Flags used by erofs_map_blocks_flatmode() */
@@ -634,6 +637,8 @@ struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path,
void erofs_fscache_put(struct erofs_fscache *ctx);

struct folio *erofs_fscache_get_folio(struct erofs_fscache *ctx, pgoff_t index);
+
+extern const struct address_space_operations erofs_fscache_access_aops;
#else
static inline int erofs_init_fscache(void) { return 0; }
static inline void erofs_exit_fscache(void) {}
--
2.27.0