Re: [PATCH 07/16] erofs: switch compressed_pages[] to bufvec

From: Yue Hu
Date: Fri Jul 15 2022 - 03:52:08 EST

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In reply to: Gao Xiang: "[PATCH 07/16] erofs: switch compressed_pages[] to bufvec"
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On Thu, 14 Jul 2022 21:20:42 +0800
Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> wrote:

> Convert compressed_pages[] to bufvec in order to avoid using
> page->private to keep onlinepage_index (decompressed offset)
> for inplace I/O pages.
>
> In the future, we only rely on folio->private to keep a countdown
> to unlock folios and set folio_uptodate.
>
> Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
> ---
> fs/erofs/zdata.c | 113 +++++++++++++++++++++++------------------------
> fs/erofs/zdata.h | 4 +-
> 2 files changed, 57 insertions(+), 60 deletions(-)
>
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 757d352bc2c7..f2e3f07baad7 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -134,7 +134,7 @@ static int z_erofs_create_pcluster_pool(void)
>
> for (pcs = pcluster_pool;
> pcs < pcluster_pool + ARRAY_SIZE(pcluster_pool); ++pcs) {
> - size = struct_size(a, compressed_pages, pcs->maxpages);
> + size = struct_size(a, compressed_bvecs, pcs->maxpages);
>
> sprintf(pcs->name, "erofs_pcluster-%u", pcs->maxpages);
> pcs->slab = kmem_cache_create(pcs->name, size, 0,
> @@ -287,16 +287,16 @@ struct z_erofs_decompress_frontend {
>
> struct page *candidate_bvpage;
> struct z_erofs_pcluster *pcl, *tailpcl;
> - /* a pointer used to pick up inplace I/O pages */
> - struct page **icpage_ptr;
> z_erofs_next_pcluster_t owned_head;
> -
> enum z_erofs_collectmode mode;
>
> bool readahead;
> /* used for applying cache strategy on the fly */
> bool backmost;
> erofs_off_t headoffset;
> +
> + /* a pointer used to pick up inplace I/O pages */
> + unsigned int icur;

not a pointer?

> };
>
> #define DECOMPRESS_FRONTEND_INIT(__i) { \
> @@ -319,24 +319,21 @@ static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe,
> */
> gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
> __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
> - struct page **pages;
> - pgoff_t index;
> + unsigned int i;
>
> if (fe->mode < COLLECT_PRIMARY_FOLLOWED)
> return;
>
> - pages = pcl->compressed_pages;
> - index = pcl->obj.index;
> - for (; index < pcl->obj.index + pcl->pclusterpages; ++index, ++pages) {
> + for (i = 0; i < pcl->pclusterpages; ++i) {
> struct page *page;
> compressed_page_t t;
> struct page *newpage = NULL;
>
> /* the compressed page was loaded before */
> - if (READ_ONCE(*pages))
> + if (READ_ONCE(pcl->compressed_bvecs[i].page))
> continue;
>
> - page = find_get_page(mc, index);
> + page = find_get_page(mc, pcl->obj.index + i);
>
> if (page) {
> t = tag_compressed_page_justfound(page);
> @@ -357,7 +354,8 @@ static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe,
> }
> }
>
> - if (!cmpxchg_relaxed(pages, NULL, tagptr_cast_ptr(t)))
> + if (!cmpxchg_relaxed(&pcl->compressed_bvecs[i].page, NULL,
> + tagptr_cast_ptr(t)))
> continue;
>
> if (page)
> @@ -388,7 +386,7 @@ int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
> * therefore no need to worry about available decompression users.
> */
> for (i = 0; i < pcl->pclusterpages; ++i) {
> - struct page *page = pcl->compressed_pages[i];
> + struct page *page = pcl->compressed_bvecs[i].page;
>
> if (!page)
> continue;
> @@ -401,7 +399,7 @@ int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
> continue;
>
> /* barrier is implied in the following 'unlock_page' */
> - WRITE_ONCE(pcl->compressed_pages[i], NULL);
> + WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
> detach_page_private(page);
> unlock_page(page);
> }
> @@ -411,36 +409,39 @@ int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
> int erofs_try_to_free_cached_page(struct page *page)
> {
> struct z_erofs_pcluster *const pcl = (void *)page_private(page);
> - int ret = 0; /* 0 - busy */
> + int ret, i;
>
> - if (erofs_workgroup_try_to_freeze(&pcl->obj, 1)) {
> - unsigned int i;
> + if (!erofs_workgroup_try_to_freeze(&pcl->obj, 1))
> + return 0;
>
> - DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
> - for (i = 0; i < pcl->pclusterpages; ++i) {
> - if (pcl->compressed_pages[i] == page) {
> - WRITE_ONCE(pcl->compressed_pages[i], NULL);
> - ret = 1;
> - break;
> - }
> + ret = 0;
> + DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
> + for (i = 0; i < pcl->pclusterpages; ++i) {
> + if (pcl->compressed_bvecs[i].page == page) {
> + WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
> + ret = 1;
> + break;
> }
> - erofs_workgroup_unfreeze(&pcl->obj, 1);
> -
> - if (ret)
> - detach_page_private(page);
> }
> + erofs_workgroup_unfreeze(&pcl->obj, 1);
> + if (ret)
> + detach_page_private(page);
> return ret;
> }
>
> /* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
> static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
> - struct page *page)
> + struct z_erofs_bvec *bvec)
> {
> struct z_erofs_pcluster *const pcl = fe->pcl;
>
> - while (fe->icpage_ptr > pcl->compressed_pages)
> - if (!cmpxchg(--fe->icpage_ptr, NULL, page))
> + while (fe->icur > 0) {
> + if (!cmpxchg(&pcl->compressed_bvecs[--fe->icur].page,
> + NULL, bvec->page)) {
> + pcl->compressed_bvecs[fe->icur] = *bvec;
> return true;
> + }
> + }
> return false;
> }
>
> @@ -454,7 +455,7 @@ static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
> if (fe->mode >= COLLECT_PRIMARY &&
> type == Z_EROFS_PAGE_TYPE_EXCLUSIVE) {
> /* give priority for inplaceio to use file pages first */
> - if (z_erofs_try_inplace_io(fe, bvec->page))
> + if (z_erofs_try_inplace_io(fe, bvec))
> return 0;
> /* otherwise, check if it can be used as a bvpage */
> if (fe->mode >= COLLECT_PRIMARY_FOLLOWED &&
> @@ -648,8 +649,7 @@ static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
> z_erofs_bvec_iter_begin(&fe->biter, &fe->pcl->bvset,
> Z_EROFS_INLINE_BVECS, fe->pcl->vcnt);
> /* since file-backed online pages are traversed in reverse order */
> - fe->icpage_ptr = fe->pcl->compressed_pages +
> - z_erofs_pclusterpages(fe->pcl);
> + fe->icur = z_erofs_pclusterpages(fe->pcl);
> return 0;
> }
>
> @@ -769,7 +769,8 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> goto err_out;
> }
> get_page(fe->map.buf.page);
> - WRITE_ONCE(fe->pcl->compressed_pages[0], fe->map.buf.page);
> + WRITE_ONCE(fe->pcl->compressed_bvecs[0].page,
> + fe->map.buf.page);
> fe->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
> } else {
> /* bind cache first when cached decompression is preferred */
> @@ -927,8 +928,9 @@ static struct page **z_erofs_parse_in_bvecs(struct erofs_sb_info *sbi,
> *overlapped = false;
>
> for (i = 0; i < pclusterpages; ++i) {
> - unsigned int pagenr;
> - struct page *page = pcl->compressed_pages[i];
> + struct z_erofs_bvec *bvec = &pcl->compressed_bvecs[i];
> + struct page *page = bvec->page;
> + unsigned int pgnr;
>
> /* compressed pages ought to be present before decompressing */
> if (!page) {
> @@ -951,21 +953,15 @@ static struct page **z_erofs_parse_in_bvecs(struct erofs_sb_info *sbi,
> continue;
> }
>
> - /*
> - * only if non-head page can be selected
> - * for inplace decompression
> - */
> - pagenr = z_erofs_onlinepage_index(page);
> -
> - DBG_BUGON(pagenr >= pcl->nr_pages);
> - if (pages[pagenr]) {
> + pgnr = (bvec->offset + pcl->pageofs_out) >> PAGE_SHIFT;
> + DBG_BUGON(pgnr >= pcl->nr_pages);
> + if (pages[pgnr]) {
> DBG_BUGON(1);
> - SetPageError(pages[pagenr]);
> - z_erofs_onlinepage_endio(pages[pagenr]);
> + SetPageError(pages[pgnr]);
> + z_erofs_onlinepage_endio(pages[pgnr]);
> err = -EFSCORRUPTED;
> }
> - pages[pagenr] = page;
> -
> + pages[pgnr] = page;
> *overlapped = true;
> }
>
> @@ -1067,19 +1063,19 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
> out:
> /* must handle all compressed pages before actual file pages */
> if (z_erofs_is_inline_pcluster(pcl)) {
> - page = pcl->compressed_pages[0];
> - WRITE_ONCE(pcl->compressed_pages[0], NULL);
> + page = pcl->compressed_bvecs[0].page;
> + WRITE_ONCE(pcl->compressed_bvecs[0].page, NULL);
> put_page(page);
> } else {
> for (i = 0; i < pclusterpages; ++i) {
> - page = pcl->compressed_pages[i];
> + page = pcl->compressed_bvecs[i].page;
>
> if (erofs_page_is_managed(sbi, page))
> continue;
>
> /* recycle all individual short-lived pages */
> (void)z_erofs_put_shortlivedpage(pagepool, page);
> - WRITE_ONCE(pcl->compressed_pages[i], NULL);
> + WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
> }
> }
> kfree(compressed_pages);
> @@ -1193,7 +1189,7 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
> int justfound;
>
> repeat:
> - page = READ_ONCE(pcl->compressed_pages[nr]);
> + page = READ_ONCE(pcl->compressed_bvecs[nr].page);
> oldpage = page;
>
> if (!page)
> @@ -1209,7 +1205,7 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
> * otherwise, it will go inplace I/O path instead.
> */
> if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
> - WRITE_ONCE(pcl->compressed_pages[nr], page);
> + WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
> set_page_private(page, 0);
> tocache = true;
> goto out_tocache;
> @@ -1235,14 +1231,14 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
>
> /* the page is still in manage cache */
> if (page->mapping == mc) {
> - WRITE_ONCE(pcl->compressed_pages[nr], page);
> + WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
>
> ClearPageError(page);
> if (!PagePrivate(page)) {
> /*
> * impossible to be !PagePrivate(page) for
> * the current restriction as well if
> - * the page is already in compressed_pages[].
> + * the page is already in compressed_bvecs[].
> */
> DBG_BUGON(!justfound);
>
> @@ -1271,7 +1267,8 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
> put_page(page);
> out_allocpage:
> page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
> - if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
> + if (oldpage != cmpxchg(&pcl->compressed_bvecs[nr].page,
> + oldpage, page)) {
> erofs_pagepool_add(pagepool, page);
> cond_resched();
> goto repeat;
> diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
> index a755c5a44d87..a70f1b73e901 100644
> --- a/fs/erofs/zdata.h
> +++ b/fs/erofs/zdata.h
> @@ -87,8 +87,8 @@ struct z_erofs_pcluster {
> /* I: compression algorithm format */
> unsigned char algorithmformat;
>
> - /* A: compressed pages (can be cached or inplaced pages) */
> - struct page *compressed_pages[];
> + /* A: compressed bvecs (can be cached or inplaced pages) */
> + struct z_erofs_bvec compressed_bvecs[];
> };
>
> /* let's avoid the valid 32-bit kernel addresses */

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In reply to: Gao Xiang: "[PATCH 07/16] erofs: switch compressed_pages[] to bufvec"
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