From 5169b844b7dd5934cd4f22ab66de0cc669abf0b0 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 9 May 2022 18:20:49 -0700 Subject: mm: submit multipage reads for SWP_FS_OPS swap-space swap_readpage() is given one page at a time, but may be called repeatedly in succession. For block-device swap-space, the blk_plug functionality allows the multiple pages to be combined together at lower layers. That cannot be used for SWP_FS_OPS as blk_plug may not exist - it is only active when CONFIG_BLOCK=y. Consequently all swap reads over NFS are single page reads. With this patch we pass in a pointer-to-pointer when swap_readpage can store state between calls - much like the effect of blk_plug. After calling swap_readpage() some number of times, the state will be passed to swap_read_unplug() which can submit the combined request. Link: https://lkml.kernel.org/r/164859778127.29473.14059420492644907783.stgit@noble.brown Signed-off-by: NeilBrown Reviewed-by: Christoph Hellwig Tested-by: David Howells Tested-by: Geert Uytterhoeven Cc: Hugh Dickins Cc: Mel Gorman Cc: Trond Myklebust Cc: Miaohe Lin Signed-off-by: Andrew Morton --- mm/swap_state.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) (limited to 'mm/swap_state.c') diff --git a/mm/swap_state.c b/mm/swap_state.c index f3ab01801629..d41746a572a2 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -520,14 +520,16 @@ fail_unlock: * the swap entry is no longer in use. */ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, - struct vm_area_struct *vma, unsigned long addr, bool do_poll) + struct vm_area_struct *vma, + unsigned long addr, bool do_poll, + struct swap_iocb **plug) { bool page_was_allocated; struct page *retpage = __read_swap_cache_async(entry, gfp_mask, vma, addr, &page_was_allocated); if (page_was_allocated) - swap_readpage(retpage, do_poll); + swap_readpage(retpage, do_poll, plug); return retpage; } @@ -621,6 +623,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, unsigned long mask; struct swap_info_struct *si = swp_swap_info(entry); struct blk_plug plug; + struct swap_iocb *splug = NULL; bool do_poll = true, page_allocated; struct vm_area_struct *vma = vmf->vma; unsigned long addr = vmf->address; @@ -647,7 +650,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, if (!page) continue; if (page_allocated) { - swap_readpage(page, false); + swap_readpage(page, false, &splug); if (offset != entry_offset) { SetPageReadahead(page); count_vm_event(SWAP_RA); @@ -656,10 +659,12 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, put_page(page); } blk_finish_plug(&plug); + swap_read_unplug(splug); lru_add_drain(); /* Push any new pages onto the LRU now */ skip: - return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll); + /* The page was likely read above, so no need for plugging here */ + return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll, NULL); } int init_swap_address_space(unsigned int type, unsigned long nr_pages) @@ -790,6 +795,7 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, struct vm_fault *vmf) { struct blk_plug plug; + struct swap_iocb *splug = NULL; struct vm_area_struct *vma = vmf->vma; struct page *page; pte_t *pte, pentry; @@ -820,7 +826,7 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, if (!page) continue; if (page_allocated) { - swap_readpage(page, false); + swap_readpage(page, false, &splug); if (i != ra_info.offset) { SetPageReadahead(page); count_vm_event(SWAP_RA); @@ -829,10 +835,12 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, put_page(page); } blk_finish_plug(&plug); + swap_read_unplug(splug); lru_add_drain(); skip: + /* The page was likely read above, so no need for plugging here */ return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address, - ra_info.win == 1); + ra_info.win == 1, NULL); } /** -- cgit v1.2.3-59-g8ed1b