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From:   Jeffle Xu <jefflexu@linux.alibaba.com>
To:     dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org
Cc:     torvalds@linux-foundation.org, gregkh@linuxfoundation.org,
        willy@infradead.org, linux-fsdevel@vger.kernel.org,
        joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com,
        tao.peng@linux.alibaba.com, gerry@linux.alibaba.com,
        eguan@linux.alibaba.com, linux-kernel@vger.kernel.org,
        luodaowen.backend@bytedance.com, tianzichen@kuaishou.com,
        fannaihao@baidu.com, zhangjiachen.jaycee@bytedance.com,
        zhujia.zj@bytedance.com
Subject: [PATCH v10 19/21] erofs: implement fscache-based data read for inline layout
Date:   Mon, 25 Apr 2022 20:21:41 +0800
Message-Id: <20220425122143.56815-20-jefflexu@linux.alibaba.com>
In-Reply-To: <20220425122143.56815-1-jefflexu@linux.alibaba.com>
References: <20220425122143.56815-1-jefflexu@linux.alibaba.com>
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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>
---
 fs/erofs/fscache.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index b3af72af7c88..5b779812a5ee 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -83,6 +83,33 @@ static int erofs_fscache_meta_readpage(struct file *data, struct page *page)
 	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,
-- 
2.27.0