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Message-ID: <20220102074806.GC40650@rsjd01523.et2sqa>
Date: Sun, 2 Jan 2022 15:48:06 +0800
From: Liu Bo <bo.liu@...ux.alibaba.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc: linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, Yue Hu <huyue2@...ong.com>
Subject: Re: [PATCH v2 1/5] erofs: introduce meta buffer operations
On Sun, Jan 02, 2022 at 12:00:13PM +0800, Gao Xiang wrote:
> In order to support subpage and folio for all uncompressed files,
> introduce meta buffer descriptors, which can be effectively stored
> on stack, in place of meta page operations.
>
> This converts the uncompressed data path to meta buffers.
>
Reviewed-by: Liu Bo <bo.liu@...ux.alibaba.com>
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> ---
> fs/erofs/data.c | 97 +++++++++++++++++++++++++++++++++++----------
> fs/erofs/internal.h | 13 ++++++
> 2 files changed, 89 insertions(+), 21 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 4f98c76ec043..6495e16a50a9 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -22,6 +22,56 @@ struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr)
> return page;
> }
>
> +void erofs_unmap_metabuf(struct erofs_buf *buf)
> +{
> + if (buf->kmap_type == EROFS_KMAP)
> + kunmap(buf->page);
> + else if (buf->kmap_type == EROFS_KMAP_ATOMIC)
> + kunmap_atomic(buf->base);
> + buf->kmap_type = EROFS_NO_KMAP;
> +}
> +
> +void erofs_put_metabuf(struct erofs_buf *buf)
> +{
> + if (!buf->page)
> + return;
> + erofs_unmap_metabuf(buf);
> + put_page(buf->page);
> + buf->page = NULL;
> +}
> +
> +void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
> + erofs_blk_t blkaddr, enum erofs_kmap_type type)
> +{
> + struct address_space *const mapping = sb->s_bdev->bd_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,
> + mapping_gfp_constraint(mapping, ~__GFP_FS));
> + if (IS_ERR(page))
> + return page;
> + /* should already be PageUptodate, no need to lock page */
> + buf->page = page;
> + }
> + if (buf->kmap_type == EROFS_NO_KMAP) {
> + if (type == EROFS_KMAP)
> + buf->base = kmap(page);
> + else if (type == EROFS_KMAP_ATOMIC)
> + buf->base = kmap_atomic(page);
> + buf->kmap_type = type;
> + } else if (buf->kmap_type != type) {
> + DBG_BUGON(1);
> + return ERR_PTR(-EFAULT);
> + }
> + if (type == EROFS_NO_KMAP)
> + return NULL;
> + return buf->base + (offset & ~PAGE_MASK);
> +}
> +
> static int erofs_map_blocks_flatmode(struct inode *inode,
> struct erofs_map_blocks *map,
> int flags)
> @@ -31,7 +81,7 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
> struct erofs_inode *vi = EROFS_I(inode);
> bool tailendpacking = (vi->datalayout == EROFS_INODE_FLAT_INLINE);
>
> - nblocks = DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
> + nblocks = DIV_ROUND_UP(inode->i_size, EROFS_BLKSIZ);
> lastblk = nblocks - tailendpacking;
>
> /* there is no hole in flatmode */
> @@ -72,10 +122,11 @@ static int erofs_map_blocks(struct inode *inode,
> struct super_block *sb = inode->i_sb;
> struct erofs_inode *vi = EROFS_I(inode);
> struct erofs_inode_chunk_index *idx;
> - struct page *page;
> + struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
> u64 chunknr;
> unsigned int unit;
> erofs_off_t pos;
> + void *kaddr;
> int err = 0;
>
> trace_erofs_map_blocks_enter(inode, map, flags);
> @@ -101,9 +152,9 @@ static int erofs_map_blocks(struct inode *inode,
> pos = ALIGN(iloc(EROFS_SB(sb), vi->nid) + vi->inode_isize +
> vi->xattr_isize, unit) + unit * chunknr;
>
> - page = erofs_get_meta_page(inode->i_sb, erofs_blknr(pos));
> - if (IS_ERR(page)) {
> - err = PTR_ERR(page);
> + kaddr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos), EROFS_KMAP);
> + if (IS_ERR(kaddr)) {
> + err = PTR_ERR(kaddr);
> goto out;
> }
> map->m_la = chunknr << vi->chunkbits;
> @@ -112,7 +163,7 @@ static int erofs_map_blocks(struct inode *inode,
>
> /* handle block map */
> if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)) {
> - __le32 *blkaddr = page_address(page) + erofs_blkoff(pos);
> + __le32 *blkaddr = kaddr + erofs_blkoff(pos);
>
> if (le32_to_cpu(*blkaddr) == EROFS_NULL_ADDR) {
> map->m_flags = 0;
> @@ -123,7 +174,7 @@ static int erofs_map_blocks(struct inode *inode,
> goto out_unlock;
> }
> /* parse chunk indexes */
> - idx = page_address(page) + erofs_blkoff(pos);
> + idx = kaddr + erofs_blkoff(pos);
> switch (le32_to_cpu(idx->blkaddr)) {
> case EROFS_NULL_ADDR:
> map->m_flags = 0;
> @@ -136,8 +187,7 @@ static int erofs_map_blocks(struct inode *inode,
> break;
> }
> out_unlock:
> - unlock_page(page);
> - put_page(page);
> + erofs_put_metabuf(&buf);
> out:
> if (!err)
> map->m_llen = map->m_plen;
> @@ -226,16 +276,16 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> }
>
> if (map.m_flags & EROFS_MAP_META) {
> - struct page *ipage;
> + void *ptr;
> + struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
>
> iomap->type = IOMAP_INLINE;
> - ipage = erofs_get_meta_page(inode->i_sb,
> - erofs_blknr(mdev.m_pa));
> - if (IS_ERR(ipage))
> - return PTR_ERR(ipage);
> - iomap->inline_data = page_address(ipage) +
> - erofs_blkoff(mdev.m_pa);
> - iomap->private = ipage;
> + ptr = erofs_read_metabuf(&buf, inode->i_sb,
> + erofs_blknr(mdev.m_pa), EROFS_KMAP);
> + if (IS_ERR(ptr))
> + return PTR_ERR(ptr);
> + iomap->inline_data = ptr + erofs_blkoff(mdev.m_pa);
> + iomap->private = buf.base;
> } else {
> iomap->type = IOMAP_MAPPED;
> iomap->addr = mdev.m_pa;
> @@ -246,12 +296,17 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> static int erofs_iomap_end(struct inode *inode, loff_t pos, loff_t length,
> ssize_t written, unsigned int flags, struct iomap *iomap)
> {
> - struct page *ipage = iomap->private;
> + void *ptr = iomap->private;
> +
> + if (ptr) {
> + struct erofs_buf buf = {
> + .page = kmap_to_page(ptr),
> + .base = ptr,
> + .kmap_type = EROFS_KMAP,
> + };
>
> - if (ipage) {
> DBG_BUGON(iomap->type != IOMAP_INLINE);
> - unlock_page(ipage);
> - put_page(ipage);
> + erofs_put_metabuf(&buf);
> } else {
> DBG_BUGON(iomap->type == IOMAP_INLINE);
> }
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index fca3747d97be..7053f1c4171d 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -251,6 +251,19 @@ static inline int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
> #error erofs cannot be used in this platform
> #endif
>
> +enum erofs_kmap_type {
> + EROFS_NO_KMAP, /* don't map the buffer */
> + EROFS_KMAP, /* use kmap() to map the buffer */
> + EROFS_KMAP_ATOMIC, /* use kmap_atomic() to map the buffer */
> +};
> +
> +struct erofs_buf {
> + struct page *page;
> + void *base;
> + enum erofs_kmap_type kmap_type;
> +};
> +#define __EROFS_BUF_INITIALIZER ((struct erofs_buf){ .page = NULL })
> +
> #define ROOT_NID(sb) ((sb)->root_nid)
>
> #define erofs_blknr(addr) ((addr) / EROFS_BLKSIZ)
> --
> 2.24.4
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