This patch implements the data plane of reading data from bootstrap blob
file over fscache.
Be noted that currently compressed layout is not supported yet.
Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
fs/erofs/fscache.c | 91 +++++++++++++++++++++++++++++++++++++++++++++
fs/erofs/inode.c | 6 ++-
fs/erofs/internal.h | 1 +
3 files changed, 97 insertions(+), 1 deletion(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 325f5663836b..bfcec831d58a 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -65,6 +65,97 @@ struct page *erofs_readpage_from_fscache(struct erofs_cookie_ctx *ctx,
return page;
}
+static inline void do_copy_page(struct page *from, struct page *to,
+ size_t offset, size_t len)
+{
+ char *vfrom, *vto;
+
+ vfrom = kmap_atomic(from);
+ vto = kmap_atomic(to);
+ memcpy(vto, vfrom + offset, len);
+ kunmap_atomic(vto);
+ kunmap_atomic(vfrom);
+}
+
+static int erofs_fscache_do_readpage(struct file *file, 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;
+ erofs_off_t o_la, pa;
+ size_t offset, len;
+ struct page *ipage;
+ int ret;
+
+ if (erofs_inode_is_data_compressed(vi->datalayout)) {
+ erofs_info(sb, "compressed layout not supported yet");
+ return -EOPNOTSUPP;
+ }
+
+ o_la = page_offset(page);
+ map.m_la = o_la;
+
+ 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;
+ }
+
+ /*
+ * 1) For FLAT_PLAIN/FLAT_INLINE 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.
+ */
+ pa = map.m_pa + o_la - map.m_la;
+
+ ipage = erofs_get_meta_page(sb, erofs_blknr(pa));
+ if (IS_ERR(ipage))
+ return PTR_ERR(ipage);
+
+ /*
+ * @offset refers to the page offset inside @ipage.
+ * 1) Except for the inline layout, the offset shall all be 0, and @pa
+ * shall be aligned with EROFS_BLKSIZ in this case. Thus we can
+ * conveniently get the offset from @pa.
+ * 2) While for the inline layout, the offset may be non-zero. Since
+ * currently only flat layout supports inline, we can calculate the
+ * offset from the corresponding physical address.
+ */
+ offset = erofs_blkoff(pa);
+ len = min_t(u64, map.m_llen, PAGE_SIZE);
+
+ do_copy_page(ipage, page, offset, len);
+
+ unlock_page(ipage);
+ return 0;
+}
+
+static int erofs_fscache_readpage(struct file *file, struct page *page)
+{
+ int ret;
+
+ ret = erofs_fscache_do_readpage(file, page);
+ if (ret)
+ SetPageError(page);
+ else
+ SetPageUptodate(page);
+
+ unlock_page(page);
+ return ret;
+}
+
+const struct address_space_operations erofs_fscache_access_aops = {
+ .readpage = erofs_fscache_readpage,
+};
+
static int erofs_fscache_init_cookie(struct erofs_cookie_ctx *ctx, char *path)
{
struct fscache_cookie *cookie;
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index 2345f1de438e..452d147277c4 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -299,7 +299,11 @@ 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 (inode->i_sb->s_bdev)
+ inode->i_mapping->a_ops = &erofs_raw_access_aops;
+ else
+ inode->i_mapping->a_ops = &erofs_fscache_access_aops;
out_unlock:
unlock_page(page);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 10fb7ef26ddf..f3a1aa429a93 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -357,6 +357,7 @@ 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
