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Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH v2 5/5] mm: Remove swap BIO paths and only use DIO paths [BROKEN] From: David Howells To: willy@infradead.org Cc: dhowells@redhat.com, dhowells@redhat.com, trond.myklebust@primarydata.com, darrick.wong@oracle.com, hch@lst.de, viro@zeniv.linux.org.uk, jlayton@kernel.org, sfrench@samba.org, torvalds@linux-foundation.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 12 Aug 2021 21:22:41 +0100 Message-ID: <162879976139.3306668.12495248062404308890.stgit@warthog.procyon.org.uk> In-Reply-To: <162879971699.3306668.8977537647318498651.stgit@warthog.procyon.org.uk> References: <162879971699.3306668.8977537647318498651.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Rspamd-Queue-Id: 8A51930071D2 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Izku0CvW; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf09.hostedemail.com: domain of dhowells@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=dhowells@redhat.com X-Rspamd-Server: rspam04 X-Stat-Signature: iic8zjzb75uhexicebnz6ua6abtkz856 X-HE-Tag: 1628799770-417102 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [!] NOTE: This doesn't work and might damage your disk's contents. Delete the BIO-generating swap read/write paths and always use ->direct_IO(). This puts the mapping layer in the filesystem. This doesn't work - probably due to ki_pos being set to page_file_offset(page) which then gets remapped. Suggested-by: Matthew Wilcox (Oracle) Signed-off-by: David Howells --- fs/direct-io.c | 2 + include/linux/bio.h | 2 + mm/page_io.c | 156 ++------------------------------------------------- 3 files changed, 9 insertions(+), 151 deletions(-) diff --git a/fs/direct-io.c b/fs/direct-io.c index b2e86e739d7a..76eec0a68fa4 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -1216,6 +1216,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, } if (iocb->ki_flags & IOCB_HIPRI) dio->op_flags |= REQ_HIPRI; + if (iocb->ki_flags & IOCB_SWAP) + dio->op_flags |= REQ_SWAP; /* * For AIO O_(D)SYNC writes we need to defer completions to a workqueue diff --git a/include/linux/bio.h b/include/linux/bio.h index 2203b686e1f0..da75cfa72ed3 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -816,6 +816,8 @@ static inline void bio_set_polled(struct bio *bio, struct kiocb *kiocb) bio->bi_opf |= REQ_HIPRI; if (!is_sync_kiocb(kiocb)) bio->bi_opf |= REQ_NOWAIT; + if (kiocb->ki_flags & IOCB_SWAP) + bio->bi_opf |= REQ_SWAP; } struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp); diff --git a/mm/page_io.c b/mm/page_io.c index dae7bbd7a842..fb260d9c3973 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -44,30 +44,6 @@ static void swapfile_put_kiocb(struct swapfile_kiocb *ki) } } -static void end_swap_bio_write(struct bio *bio) -{ - struct page *page = bio_first_page_all(bio); - - if (bio->bi_status) { - SetPageError(page); - /* - * We failed to write the page out to swap-space. - * Re-dirty the page in order to avoid it being reclaimed. - * Also print a dire warning that things will go BAD (tm) - * very quickly. - * - * Also clear PG_reclaim to avoid folio_rotate_reclaimable() - */ - set_page_dirty(page); - pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n", - MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), - (unsigned long long)bio->bi_iter.bi_sector); - ClearPageReclaim(page); - } - end_page_writeback(page); - bio_put(bio); -} - static void swap_slot_free_notify(struct page *page) { struct swap_info_struct *sis; @@ -116,32 +92,6 @@ static void swap_slot_free_notify(struct page *page) } } -static void end_swap_bio_read(struct bio *bio) -{ - struct page *page = bio_first_page_all(bio); - struct task_struct *waiter = bio->bi_private; - - if (bio->bi_status) { - SetPageError(page); - ClearPageUptodate(page); - pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n", - MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), - (unsigned long long)bio->bi_iter.bi_sector); - goto out; - } - - SetPageUptodate(page); - swap_slot_free_notify(page); -out: - unlock_page(page); - WRITE_ONCE(bio->bi_private, NULL); - bio_put(bio); - if (waiter) { - blk_wake_io_task(waiter); - put_task_struct(waiter); - } -} - int generic_swapfile_activate(struct swap_info_struct *sis, struct file *swap_file, sector_t *span) @@ -281,31 +231,12 @@ static inline void count_swpout_vm_event(struct page *page) count_vm_events(PSWPOUT, thp_nr_pages(page)); } -#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) -static void bio_associate_blkg_from_page(struct bio *bio, struct page *page) -{ - struct cgroup_subsys_state *css; - struct mem_cgroup *memcg; - - memcg = page_memcg(page); - if (!memcg) - return; - - rcu_read_lock(); - css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys); - bio_associate_blkg_from_css(bio, css); - rcu_read_unlock(); -} -#else -#define bio_associate_blkg_from_page(bio, page) do { } while (0) -#endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ - static void __swapfile_write_complete(struct kiocb *iocb, long ret, long ret2) { struct page *page = iocb->ki_swap_page; if (ret == thp_size(page)) { - count_vm_event(PSWPOUT); + count_swpout_vm_event(page); ret = 0; } else { /* @@ -401,34 +332,10 @@ static int swapfile_write(struct swap_info_struct *sis, int __swap_writepage(struct page *page, struct writeback_control *wbc) { - struct bio *bio; - int ret; struct swap_info_struct *sis = page_swap_info(page); VM_BUG_ON_PAGE(!PageSwapCache(page), page); - if (data_race(sis->flags & SWP_FS_OPS)) - return swapfile_write(sis, page, wbc); - - ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); - if (!ret) { - count_swpout_vm_event(page); - return 0; - } - - bio = bio_alloc(GFP_NOIO, 1); - bio_set_dev(bio, sis->bdev); - bio->bi_iter.bi_sector = swap_page_sector(page); - bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); - bio->bi_end_io = end_swap_bio_write; - bio_add_page(bio, page, thp_size(page), 0); - - bio_associate_blkg_from_page(bio, page); - count_swpout_vm_event(page); - set_page_writeback(page); - unlock_page(page); - submit_bio(bio); - - return 0; + return swapfile_write(sis, page, wbc); } static void __swapfile_read_complete(struct kiocb *iocb, long ret, long ret2) @@ -437,6 +344,7 @@ static void __swapfile_read_complete(struct kiocb *iocb, long ret, long ret2) if (ret == PAGE_SIZE) { count_vm_event(PSWPIN); + swap_slot_free_notify(page); SetPageUptodate(page); } else { SetPageError(page); @@ -522,12 +430,9 @@ static int swapfile_read(struct swap_info_struct *sis, struct page *page, int swap_readpage(struct page *page, bool synchronous) { - struct bio *bio; - int ret = 0; struct swap_info_struct *sis = page_swap_info(page); - blk_qc_t qc; - struct gendisk *disk; unsigned long pflags; + int ret = 0; VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); VM_BUG_ON_PAGE(!PageLocked(page), page); @@ -543,60 +448,9 @@ int swap_readpage(struct page *page, bool synchronous) if (frontswap_load(page) == 0) { SetPageUptodate(page); unlock_page(page); - goto out; - } - - if (data_race(sis->flags & SWP_FS_OPS)) { + } else { ret = swapfile_read(sis, page, synchronous); - goto out; - } - - if (sis->flags & SWP_SYNCHRONOUS_IO) { - ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); - if (!ret) { - if (trylock_page(page)) { - swap_slot_free_notify(page); - unlock_page(page); - } - - count_vm_event(PSWPIN); - goto out; - } } - - ret = 0; - bio = bio_alloc(GFP_KERNEL, 1); - bio_set_dev(bio, sis->bdev); - bio->bi_opf = REQ_OP_READ; - bio->bi_iter.bi_sector = swap_page_sector(page); - bio->bi_end_io = end_swap_bio_read; - bio_add_page(bio, page, thp_size(page), 0); - - disk = bio->bi_bdev->bd_disk; - /* - * Keep this task valid during swap readpage because the oom killer may - * attempt to access it in the page fault retry time check. - */ - if (synchronous) { - bio->bi_opf |= REQ_HIPRI; - get_task_struct(current); - bio->bi_private = current; - } - count_vm_event(PSWPIN); - bio_get(bio); - qc = submit_bio(bio); - while (synchronous) { - set_current_state(TASK_UNINTERRUPTIBLE); - if (!READ_ONCE(bio->bi_private)) - break; - - if (!blk_poll(disk->queue, qc, true)) - blk_io_schedule(); - } - __set_current_state(TASK_RUNNING); - bio_put(bio); - -out: psi_memstall_leave(&pflags); return ret; }