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Date: Thu, 7 Apr 2022 22:19:28 +0800
From: Gao Xiang <xiang@...nel.org>
To: Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc: dhowells@...hat.com, linux-cachefs@...hat.com, xiang@...nel.org,
chao@...nel.org, linux-erofs@...ts.ozlabs.org,
torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
willy@...radead.org, linux-fsdevel@...r.kernel.org,
joseph.qi@...ux.alibaba.com, bo.liu@...ux.alibaba.com,
tao.peng@...ux.alibaba.com, gerry@...ux.alibaba.com,
eguan@...ux.alibaba.com, linux-kernel@...r.kernel.org,
luodaowen.backend@...edance.com, tianzichen@...ishou.com,
fannaihao@...du.com
Subject: Re: [PATCH v8 16/20] erofs: implement fscache-based metadata read
On Wed, Apr 06, 2022 at 03:56:08PM +0800, Jeffle Xu wrote:
> Implement the data plane of reading metadata from primary data blob
> over fscache.
>
> Signed-off-by: Jeffle Xu <jefflexu@...ux.alibaba.com>
> ---
> fs/erofs/data.c | 20 ++++++++++++++++++--
> fs/erofs/fscache.c | 38 ++++++++++++++++++++++++++++++++++++++
> fs/erofs/internal.h | 9 +++++++++
> 3 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 14b64d960541..cb8fe299ad67 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -31,15 +31,26 @@ void erofs_put_metabuf(struct erofs_buf *buf)
> void *erofs_bread(struct erofs_buf *buf, struct inode *inode,
> erofs_blk_t blkaddr, enum erofs_kmap_type type)
> {
> - struct address_space *const mapping = inode->i_mapping;
> erofs_off_t offset = blknr_to_addr(blkaddr);
> pgoff_t index = offset >> PAGE_SHIFT;
> struct page *page = buf->page;
>
> if (!page || page->index != index) {
> erofs_put_metabuf(buf);
> - page = read_cache_page_gfp(mapping, index,
> + if (buf->sb) {
> + struct folio *folio;
> +
> + folio = erofs_fscache_get_folio(buf->sb, index);
> + if (IS_ERR(folio))
> + page = ERR_CAST(folio);
> + else
> + page = folio_page(folio, 0);
> + } else {
> + struct address_space *const mapping = inode->i_mapping;
> +
> + page = read_cache_page_gfp(mapping, index,
> mapping_gfp_constraint(mapping, ~__GFP_FS));
> + }
> if (IS_ERR(page))
> return page;
> /* should already be PageUptodate, no need to lock page */
> @@ -63,6 +74,11 @@ void *erofs_bread(struct erofs_buf *buf, struct inode *inode,
> void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
> erofs_blk_t blkaddr, enum erofs_kmap_type type)
> {
> + if (erofs_is_fscache_mode(sb)) {
> + buf->sb = sb;
> + return erofs_bread(buf, NULL, blkaddr, type);
> + }
> +
> return erofs_bread(buf, sb->s_bdev->bd_inode, blkaddr, type);
> }
>
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index d38a6efc8e50..158cc273f8fb 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -34,9 +34,47 @@ static int erofs_fscache_read_folios(struct fscache_cookie *cookie,
> return ret;
> }
>
> +static int erofs_fscache_meta_readpage(struct file *data, struct page *page)
> +{
> + int ret;
> + struct super_block *sb = (struct super_block *)data;
> + struct folio *folio = page_folio(page);
> + struct erofs_map_dev mdev = {
> + .m_deviceid = 0,
> + .m_pa = folio_pos(folio),
> + };
> +
> + ret = erofs_map_dev(sb, &mdev);
> + if (ret)
> + goto out;
> +
> + ret = erofs_fscache_read_folios(mdev.m_fscache->cookie,
> + folio_file_mapping(folio), folio_pos(folio),
> + folio_size(folio), mdev.m_pa);
> + if (ret)
> + goto out;
> +
> + folio_mark_uptodate(folio);
> +out:
> + folio_unlock(folio);
> + return ret;
> +}
> +
> static const struct address_space_operations erofs_fscache_meta_aops = {
> + .readpage = erofs_fscache_meta_readpage,
> };
>
> +/*
> + * Get the page cache of data blob at the index offset.
> + * Return: up to date page on success, ERR_PTR() on failure.
> + */
Unnecessary comment and even unnecessary helper.
Thanks,
Gao Xiang
> +struct folio *erofs_fscache_get_folio(struct super_block *sb, pgoff_t index)
> +{
> + struct erofs_fscache *ctx = EROFS_SB(sb)->s_fscache;
> +
> + return read_mapping_folio(ctx->inode->i_mapping, index, (void *)sb);
> +}
> +
> /*
> * Create an fscache context for data blob.
> * Return: 0 on success and allocated fscache context is assigned to @fscache,
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 90f7d6286a4f..e186051f0640 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -276,6 +276,7 @@ enum erofs_kmap_type {
> };
>
> struct erofs_buf {
> + struct super_block *sb;
> struct page *page;
> void *base;
> enum erofs_kmap_type kmap_type;
> @@ -639,6 +640,8 @@ int erofs_fscache_register_cookie(struct super_block *sb,
> struct erofs_fscache **fscache,
> char *name, bool need_inode);
> void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
> +
> +struct folio *erofs_fscache_get_folio(struct super_block *sb, pgoff_t index);
> #else
> static inline int erofs_fscache_register_fs(struct super_block *sb) { return 0; }
> static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
> @@ -653,6 +656,12 @@ static inline int erofs_fscache_register_cookie(struct super_block *sb,
> static inline void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
> {
> }
> +
> +static inline struct folio *erofs_fscache_get_folio(struct super_block *sb,
> + pgoff_t index)
> +{
> + return ERR_PTR(-EOPNOTSUPP);
> +}
> #endif
>
> #define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */
> --
> 2.27.0
>
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