[PATCH v3 9/9] mm: Remove swap BIO paths and only use DIO paths
From: David Howells <dhowells@redhat.com>
Date: 2021-09-24 17:20:29
Also in:
linux-block, linux-fsdevel, linux-mm, linux-xfs, lkml
Subsystem:
memory management, memory management - swap, the rest · Maintainers:
Andrew Morton, Chris Li, Kairui Song, Linus Torvalds
Delete the BIO-generating swap read/write paths and always use ->swap_rw().
This puts the mapping layer in the filesystem.
[!] ALSO: Add a compile-time knob to disable swap by asynchronous DIO, only
using synchronous DIO. Async DIO doesn't seem to work, with ATA errors
being chucked out by the swap-on-blockdev and swapfile-on-XFS. It also
misbehaves on NFS.
I have tested this with sync DIO on ext4-swapfile, xfs-swapfile, a raw
blockdev and NFS. The first three work; NFS works for a while then grinds to
a halt, chucking out lists of blocked sunrpc operations (I suspect it can't
allocate memory somewhere).
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Darrick J. Wong <djwong@kernel.org>
cc: linux-block@vger.kernel.org
cc: linux-xfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
mm/page_io.c | 156 +++------------------------------------------------------
mm/swapfile.c | 4 +
2 files changed, 10 insertions(+), 150 deletions(-)
diff --git a/mm/page_io.c b/mm/page_io.c
index 8f1199d59162..b48318951380 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c@@ -26,6 +26,8 @@ #include <linux/uio.h> #include <linux/sched/task.h> +#define ONLY_USE_SYNC_DIO 1 + /* * Keep track of the kiocb we're using to do async DIO. We have to * refcount it until various things stop looking at the kiocb *after*
@@ -42,30 +44,6 @@ static void swapfile_put_kiocb(struct swapfile_kiocb *ki) kfree(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 rotate_reclaimable_page() - */ - 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;
@@ -114,32 +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)
@@ -279,25 +231,6 @@ 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 page *page, long ret) { if (ret == thp_size(page)) {
@@ -364,7 +297,7 @@ static int swapfile_write(struct swap_info_struct *sis, iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); - if (wbc->sync_mode == WB_SYNC_ALL) + if (ONLY_USE_SYNC_DIO || wbc->sync_mode == WB_SYNC_ALL) return swapfile_write_sync(sis, page, wbc, &from); ki = kzalloc(sizeof(*ki), GFP_KERNEL);
@@ -390,40 +323,17 @@ 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 page *page, long ret) { if (ret == page_size(page)) { count_vm_event(PSWPIN); + swap_slot_free_notify(page); SetPageUptodate(page); } else { SetPageError(page);
@@ -473,7 +383,7 @@ static void swapfile_read(struct swap_info_struct *sis, struct page *page, iov_iter_bvec(&to, READ, &bv, 1, thp_size(page)); - if (synchronous) + if (ONLY_USE_SYNC_DIO || synchronous) return swapfile_read_sync(sis, page, &to); ki = kzalloc(sizeof(*ki), GFP_KERNEL);
@@ -495,10 +405,7 @@ static void swapfile_read(struct swap_info_struct *sis, struct page *page, void swap_readpage(struct page *page, bool synchronous) { - struct bio *bio; struct swap_info_struct *sis = page_swap_info(page); - blk_qc_t qc; - struct gendisk *disk; unsigned long pflags; VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
@@ -515,58 +422,9 @@ void 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 { swapfile_read(sis, page, synchronous); - goto out; } - - if (sis->flags & SWP_SYNCHRONOUS_IO) { - if (!bdev_read_page(sis->bdev, swap_page_sector(page), page)) { - if (trylock_page(page)) { - swap_slot_free_notify(page); - unlock_page(page); - } - - count_vm_event(PSWPIN); - goto out; - } - } - - 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); }
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 22d10f713848..95d2571e3727 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c@@ -2918,6 +2918,8 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) return -EINVAL; p->flags |= SWP_BLKDEV; } else if (S_ISREG(inode->i_mode)) { + if (!inode->i_mapping->a_ops->swap_rw) + return -EINVAL; p->bdev = inode->i_sb->s_bdev; }
@@ -3165,7 +3167,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) name = NULL; goto bad_swap; } - swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0); + swap_file = file_open_name(name, O_RDWR | O_LARGEFILE | O_DIRECT, 0); if (IS_ERR(swap_file)) { error = PTR_ERR(swap_file); swap_file = NULL;