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Message-ID: <5ed798da-4f01-17d4-cba2-dda50728bd25@kernel.org>
Date: Tue, 4 Jan 2022 16:15:05 +0800
From: Chao Yu <chao@...nel.org>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>,
linux-erofs@...ts.ozlabs.org, Liu Bo <bo.liu@...ux.alibaba.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Yue Hu <huyue2@...ong.com>
Subject: Re: [PATCH v2 5/5] erofs: use meta buffers for zmap operations
On 2022/1/2 12:00, Gao Xiang wrote:
> Get rid of old erofs_get_meta_page() within zmap operations by
> using on-stack meta buffers in order to prepare subpage and folio
> features.
>
> Finally, erofs_get_meta_page() is useless. Get rid of it!
>
> Reviewed-by: Yue Hu <huyue2@...ong.com>
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> ---
> fs/erofs/data.c | 13 -----------
> fs/erofs/internal.h | 6 ++---
> fs/erofs/zdata.c | 23 ++++++++-----------
> fs/erofs/zmap.c | 56 +++++++++++++--------------------------------
> 4 files changed, 28 insertions(+), 70 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 6495e16a50a9..187f19f8a9a1 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -9,19 +9,6 @@
> #include <linux/dax.h>
> #include <trace/events/erofs.h>
>
> -struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr)
> -{
> - struct address_space *const mapping = sb->s_bdev->bd_inode->i_mapping;
> - struct page *page;
> -
> - page = read_cache_page_gfp(mapping, blkaddr,
> - mapping_gfp_constraint(mapping, ~__GFP_FS));
> - /* should already be PageUptodate */
> - if (!IS_ERR(page))
> - lock_page(page);
> - return page;
> -}
> -
> void erofs_unmap_metabuf(struct erofs_buf *buf)
> {
> if (buf->kmap_type == EROFS_KMAP)
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index f1e4eb3025f6..3db494a398b2 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -419,14 +419,14 @@ enum {
> #define EROFS_MAP_FULL_MAPPED (1 << BH_FullMapped)
>
> struct erofs_map_blocks {
> + struct erofs_buf buf;
> +
> erofs_off_t m_pa, m_la;
> u64 m_plen, m_llen;
>
> unsigned short m_deviceid;
> char m_algorithmformat;
> unsigned int m_flags;
> -
> - struct page *mpage;
> };
>
> /* Flags used by erofs_map_blocks_flatmode() */
> @@ -474,7 +474,7 @@ struct erofs_map_dev {
>
> /* data.c */
> extern const struct file_operations erofs_file_fops;
> -struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr);
> +void erofs_unmap_metabuf(struct erofs_buf *buf);
> void erofs_put_metabuf(struct erofs_buf *buf);
> void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
> erofs_blk_t blkaddr, enum erofs_kmap_type type);
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 49da3931b2e3..498b7666efe8 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -698,20 +698,18 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> goto err_out;
>
> if (z_erofs_is_inline_pcluster(clt->pcl)) {
> - struct page *mpage;
> + void *mp;
>
> - mpage = erofs_get_meta_page(inode->i_sb,
> - erofs_blknr(map->m_pa));
> - if (IS_ERR(mpage)) {
> - err = PTR_ERR(mpage);
> + mp = erofs_read_metabuf(&fe->map.buf, inode->i_sb,
> + erofs_blknr(map->m_pa), EROFS_NO_KMAP);
> + if (IS_ERR(mp)) {
> + err = PTR_ERR(mp);
> erofs_err(inode->i_sb,
> "failed to get inline page, err %d", err);
> goto err_out;
> }
> - /* TODO: new subpage feature will get rid of it */
> - unlock_page(mpage);
> -
> - WRITE_ONCE(clt->pcl->compressed_pages[0], mpage);
> + get_page(fe->map.buf.page);
Comparing to previous implementation, it adds an extra reference on the page, why?
Thanks,
> + WRITE_ONCE(clt->pcl->compressed_pages[0], fe->map.buf.page);
> clt->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
> } else {
> /* preload all compressed pages (can change mode if needed) */
> @@ -1529,9 +1527,7 @@ static int z_erofs_readpage(struct file *file, struct page *page)
> if (err)
> erofs_err(inode->i_sb, "failed to read, err [%d]", err);
>
> - if (f.map.mpage)
> - put_page(f.map.mpage);
> -
> + erofs_put_metabuf(&f.map.buf);
> erofs_release_pages(&pagepool);
> return err;
> }
> @@ -1576,8 +1572,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
>
> z_erofs_runqueue(inode->i_sb, &f, &pagepool,
> z_erofs_get_sync_decompress_policy(sbi, nr_pages));
> - if (f.map.mpage)
> - put_page(f.map.mpage);
> + erofs_put_metabuf(&f.map.buf);
> erofs_release_pages(&pagepool);
> }
>
> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> index 1037ac17b7a6..18d7fd1a5064 100644
> --- a/fs/erofs/zmap.c
> +++ b/fs/erofs/zmap.c
> @@ -35,7 +35,7 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
> struct super_block *const sb = inode->i_sb;
> int err, headnr;
> erofs_off_t pos;
> - struct page *page;
> + struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
> void *kaddr;
> struct z_erofs_map_header *h;
>
> @@ -61,14 +61,13 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
>
> pos = ALIGN(iloc(EROFS_SB(sb), vi->nid) + vi->inode_isize +
> vi->xattr_isize, 8);
> - page = erofs_get_meta_page(sb, erofs_blknr(pos));
> - if (IS_ERR(page)) {
> - err = PTR_ERR(page);
> + kaddr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos),
> + EROFS_KMAP_ATOMIC);
> + if (IS_ERR(kaddr)) {
> + err = PTR_ERR(kaddr);
> goto out_unlock;
> }
>
> - kaddr = kmap_atomic(page);
> -
> h = kaddr + erofs_blkoff(pos);
> vi->z_advise = le16_to_cpu(h->h_advise);
> vi->z_algorithmtype[0] = h->h_algorithmtype & 15;
> @@ -101,20 +100,19 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
> goto unmap_done;
> }
> unmap_done:
> - kunmap_atomic(kaddr);
> - unlock_page(page);
> - put_page(page);
> + erofs_put_metabuf(&buf);
> if (err)
> goto out_unlock;
>
> if (vi->z_advise & Z_EROFS_ADVISE_INLINE_PCLUSTER) {
> - struct erofs_map_blocks map = { .mpage = NULL };
> + struct erofs_map_blocks map = {
> + .buf = __EROFS_BUF_INITIALIZER
> + };
>
> vi->z_idata_size = le16_to_cpu(h->h_idata_size);
> err = z_erofs_do_map_blocks(inode, &map,
> EROFS_GET_BLOCKS_FINDTAIL);
> - if (map.mpage)
> - put_page(map.mpage);
> + erofs_put_metabuf(&map.buf);
>
> if (!map.m_plen ||
> erofs_blkoff(map.m_pa) + map.m_plen > EROFS_BLKSIZ) {
> @@ -151,31 +149,11 @@ static int z_erofs_reload_indexes(struct z_erofs_maprecorder *m,
> erofs_blk_t eblk)
> {
> struct super_block *const sb = m->inode->i_sb;
> - struct erofs_map_blocks *const map = m->map;
> - struct page *mpage = map->mpage;
> -
> - if (mpage) {
> - if (mpage->index == eblk) {
> - if (!m->kaddr)
> - m->kaddr = kmap_atomic(mpage);
> - return 0;
> - }
>
> - if (m->kaddr) {
> - kunmap_atomic(m->kaddr);
> - m->kaddr = NULL;
> - }
> - put_page(mpage);
> - }
> -
> - mpage = erofs_get_meta_page(sb, eblk);
> - if (IS_ERR(mpage)) {
> - map->mpage = NULL;
> - return PTR_ERR(mpage);
> - }
> - m->kaddr = kmap_atomic(mpage);
> - unlock_page(mpage);
> - map->mpage = mpage;
> + m->kaddr = erofs_read_metabuf(&m->map->buf, sb, eblk,
> + EROFS_KMAP_ATOMIC);
> + if (IS_ERR(m->kaddr))
> + return PTR_ERR(m->kaddr);
> return 0;
> }
>
> @@ -711,8 +689,7 @@ static int z_erofs_do_map_blocks(struct inode *inode,
> map->m_flags |= EROFS_MAP_FULL_MAPPED;
> }
> unmap_out:
> - if (m.kaddr)
> - kunmap_atomic(m.kaddr);
> + erofs_unmap_metabuf(&m.map->buf);
>
> out:
> erofs_dbg("%s, m_la %llu m_pa %llu m_llen %llu m_plen %llu m_flags 0%o",
> @@ -759,8 +736,7 @@ static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset,
> struct erofs_map_blocks map = { .m_la = offset };
>
> ret = z_erofs_map_blocks_iter(inode, &map, EROFS_GET_BLOCKS_FIEMAP);
> - if (map.mpage)
> - put_page(map.mpage);
> + erofs_put_metabuf(&map.buf);
> if (ret < 0)
> return ret;
>
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