From 2282679fb20bf036a714ed49fadd0230c278a203 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 9 May 2022 18:20:49 -0700 Subject: mm: submit multipage write for SWP_FS_OPS swap-space swap_writepage() is given one page at a time, but may be called repeatedly in succession. For block-device swapspace, 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 a pointer-to-pointer via the wbc. swap_writepage can store state between calls - much like the pointer passed explicitly to swap_readpage. After calling swap_writepage() some number of times, the state will be passed to swap_write_unplug() which can submit the combined request. Link: https://lkml.kernel.org/r/164859778128.29473.5191868522654408537.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/vmscan.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 95ebcb5b3e12e6..a9761b04564c4f 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1156,7 +1156,8 @@ typedef enum { * pageout is called by shrink_page_list() for each dirty page. * Calls ->writepage(). */ -static pageout_t pageout(struct folio *folio, struct address_space *mapping) +static pageout_t pageout(struct folio *folio, struct address_space *mapping, + struct swap_iocb **plug) { /* * If the folio is dirty, only perform writeback if that write @@ -1201,6 +1202,7 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping) .range_start = 0, .range_end = LLONG_MAX, .for_reclaim = 1, + .swap_plug = plug, }; folio_set_reclaim(folio); @@ -1533,6 +1535,7 @@ static unsigned int shrink_page_list(struct list_head *page_list, unsigned int nr_reclaimed = 0; unsigned int pgactivate = 0; bool do_demote_pass; + struct swap_iocb *plug = NULL; memset(stat, 0, sizeof(*stat)); cond_resched(); @@ -1814,7 +1817,7 @@ static unsigned int shrink_page_list(struct list_head *page_list, * starts and then write it out here. */ try_to_unmap_flush_dirty(); - switch (pageout(folio, mapping)) { + switch (pageout(folio, mapping, &plug)) { case PAGE_KEEP: goto keep_locked; case PAGE_ACTIVATE: @@ -1968,6 +1971,8 @@ static unsigned int shrink_page_list(struct list_head *page_list, list_splice(&ret_pages, page_list); count_vm_events(PGACTIVATE, pgactivate); + if (plug) + swap_write_unplug(plug); return nr_reclaimed; } -- cgit 1.2.3-korg