// SPDX-License-Identifier: GPL-2.0 /* * linux/mm/page_io.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds * * Swap reorganised 29.12.95, * Asynchronous swapping added 30.12.95. Stephen Tweedie * Removed race in async swapping. 14.4.1996. Bruno Haible * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman */ #include <linux/mm.h> #include <linux/kernel_stat.h> #include <linux/gfp.h> #include <linux/pagemap.h> #include <linux/swap.h> #include <linux/bio.h> #include <linux/swapops.h> #include <linux/writeback.h> #include <linux/blkdev.h> #include <linux/psi.h> #include <linux/uio.h> #include <linux/sched/task.h> #include <linux/delayacct.h> #include <linux/zswap.h> #include "swap.h" static void __end_swap_bio_write(struct bio *bio) { struct folio *folio = bio_first_folio_all(bio); if (bio->bi_status) { /* * 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() */ folio_mark_dirty(folio); 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); folio_clear_reclaim(folio); } folio_end_writeback(folio); } static void end_swap_bio_write(struct bio *bio) { __end_swap_bio_write(bio); bio_put(bio); } static void __end_swap_bio_read(struct bio *bio) { struct folio *folio = bio_first_folio_all(bio); if (bio->bi_status) { 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); } else { folio_mark_uptodate(folio); } folio_unlock(folio); } static void end_swap_bio_read(struct bio *bio) { __end_swap_bio_read(bio); bio_put(bio); } int generic_swapfile_activate(struct swap_info_struct *sis, struct file *swap_file, sector_t *span) { struct address_space *mapping = swap_file->f_mapping; struct inode *inode = mapping->host; unsigned blocks_per_page; unsigned long page_no; unsigned blkbits; sector_t probe_block; sector_t last_block; sector_t lowest_block = -1; sector_t highest_block = 0; int nr_extents = 0; int ret; blkbits = inode->i_blkbits; blocks_per_page = PAGE_SIZE >> blkbits; /* * Map all the blocks into the extent tree. This code doesn't try * to be very smart. */ probe_block = 0; page_no = 0; last_block = i_size_read(inode) >> blkbits; while ((probe_block + blocks_per_page) <= last_block && page_no < sis->max) { unsigned block_in_page; sector_t first_block; cond_resched(); first_block = probe_block; ret = bmap(inode, &first_block); if (ret || !first_block) goto bad_bmap; /* * It must be PAGE_SIZE aligned on-disk */ if (first_block & (blocks_per_page - 1)) { probe_block++; goto reprobe; } for (block_in_page = 1; block_in_page < blocks_per_page; block_in_page++) { sector_t block; block = probe_block + block_in_page; ret = bmap(inode, &block); if (ret || !block) goto bad_bmap; if (block != first_block + block_in_page) { /* Discontiguity */ probe_block++; goto reprobe; } } first_block >>= (PAGE_SHIFT - blkbits); if (page_no) { /* exclude the header page */ if (first_block < lowest_block) lowest_block = first_block; if (first_block > highest_block) highest_block = first_block; } /* * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks */ ret = add_swap_extent(sis, page_no, 1, first_block); if (ret < 0) goto out; nr_extents += ret; page_no++; probe_block += blocks_per_page; reprobe: continue; } ret = nr_extents; *span = 1 + highest_block - lowest_block; if (page_no == 0) page_no = 1; /* force Empty message */ sis->max = page_no; sis->pages = page_no - 1; sis->highest_bit = page_no - 1; out: return ret; bad_bmap: pr_err("swapon: swapfile has holes\n"); ret = -EINVAL; goto out; } /* * We may have stale swap cache pages in memory: notice * them here and get rid of the unnecessary final write. */ int swap_writepage(struct page *page, struct writeback_control *wbc) { struct folio *folio = page_folio(page); int ret; if (folio_free_swap(folio)) { folio_unlock(folio); return 0; } /* * Arch code may have to preserve more data than just the page * contents, e.g. memory tags. */ ret = arch_prepare_to_swap(&folio->page); if (ret) { folio_mark_dirty(folio); folio_unlock(folio); return ret; } if (zswap_store(folio)) { folio_start_writeback(folio); folio_unlock(folio); folio_end_writeback(folio); return 0; } if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) { folio_mark_dirty(folio); return AOP_WRITEPAGE_ACTIVATE; } __swap_writepage(folio, wbc); return 0; } static inline void count_swpout_vm_event(struct folio *folio) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (unlikely(folio_test_pmd_mappable(folio))) { count_memcg_folio_events(folio, THP_SWPOUT, 1); count_vm_event(THP_SWPOUT); } #endif count_vm_events(PSWPOUT, folio_nr_pages(folio)); } #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio) { struct cgroup_subsys_state *css; struct mem_cgroup *memcg; memcg = folio_memcg(folio); 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, folio) do { } while (0) #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ struct swap_iocb { struct kiocb iocb; struct bio_vec bvec[SWAP_CLUSTER_MAX]; int pages; int len; }; static mempool_t *sio_pool; int sio_pool_init(void) { if (!sio_pool) { mempool_t *pool = mempool_create_kmalloc_pool( SWAP_CLUSTER_MAX, sizeof(struct swap_iocb)); if (cmpxchg(&sio_pool, NULL, pool)) mempool_destroy(pool); } if (!sio_pool) return -ENOMEM; return 0; } static void sio_write_complete(struct kiocb *iocb, long ret) { struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); struct page *page = sio->bvec[0].bv_page; int p; if (ret != sio->len) { /* * In the case of swap-over-nfs, this can be a * temporary failure if the system has limited * memory for allocating transmit buffers. * Mark the page dirty and avoid * folio_rotate_reclaimable but rate-limit the * messages but do not flag PageError like * the normal direct-to-bio case as it could * be temporary. */ pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n", ret, page_file_offset(page)); for (p = 0; p < sio->pages; p++) { page = sio->bvec[p].bv_page; set_page_dirty(page); ClearPageReclaim(page); } } for (p = 0; p < sio->pages; p++) end_page_writeback(sio->bvec[p].bv_page); mempool_free(sio, sio_pool); } static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc) { struct swap_iocb *sio = NULL; struct swap_info_struct *sis = swp_swap_info(folio->swap); struct file *swap_file = sis->swap_file; loff_t pos = folio_file_pos(folio); count_swpout_vm_event(folio); folio_start_writeback(folio); folio_unlock(folio); if (wbc->swap_plug) sio = *wbc->swap_plug; if (sio) { if (sio->iocb.ki_filp != swap_file || sio->iocb.ki_pos + sio->len != pos) { swap_write_unplug(sio); sio = NULL; } } if (!sio) { sio = mempool_alloc(sio_pool, GFP_NOIO); init_sync_kiocb(&sio->iocb, swap_file); sio->iocb.ki_complete = sio_write_complete; sio->iocb.ki_pos = pos; sio->pages = 0; sio->len = 0; } bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0); sio->len += folio_size(folio); sio->pages += 1; if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) { swap_write_unplug(sio); sio = NULL; } if (wbc->swap_plug) *wbc->swap_plug = sio; } static void swap_writepage_bdev_sync(struct folio *folio, struct writeback_control *wbc, struct swap_info_struct *sis) { struct bio_vec bv; struct bio bio; bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc)); bio.bi_iter.bi_sector = swap_folio_sector(folio); bio_add_folio_nofail(&bio, folio, folio_size(folio), 0); bio_associate_blkg_from_page(&bio, folio); count_swpout_vm_event(folio); folio_start_writeback(folio); folio_unlock(folio); submit_bio_wait(&bio); __end_swap_bio_write(&bio); } static void swap_writepage_bdev_async(struct folio *folio, struct writeback_control *wbc, struct swap_info_struct *sis) { struct bio *bio; bio = bio_alloc(sis->bdev, 1, REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc), GFP_NOIO); bio->bi_iter.bi_sector = swap_folio_sector(folio); bio->bi_end_io = end_swap_bio_write; bio_add_folio_nofail(bio, folio, folio_size(folio), 0); bio_associate_blkg_from_page(bio, folio); count_swpout_vm_event(folio); folio_start_writeback(folio); folio_unlock(folio); submit_bio(bio); } void __swap_writepage(struct folio *folio, struct writeback_control *wbc) { struct swap_info_struct *sis = swp_swap_info(folio->swap); VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); /* * ->flags can be updated non-atomicially (scan_swap_map_slots), * but that will never affect SWP_FS_OPS, so the data_race * is safe. */ if (data_race(sis->flags & SWP_FS_OPS)) swap_writepage_fs(folio, wbc); else if (sis->flags & SWP_SYNCHRONOUS_IO) swap_writepage_bdev_sync(folio, wbc, sis); else swap_writepage_bdev_async(folio, wbc, sis); } void swap_write_unplug(struct swap_iocb *sio) { struct iov_iter from; struct address_space *mapping = sio->iocb.ki_filp->f_mapping; int ret; iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len); ret = mapping->a_ops->swap_rw(&sio->iocb, &from); if (ret != -EIOCBQUEUED) sio_write_complete(&sio->iocb, ret); } static void sio_read_complete(struct kiocb *iocb, long ret) { struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); int p; if (ret == sio->len) { for (p = 0; p < sio->pages; p++) { struct folio *folio = page_folio(sio->bvec[p].bv_page); folio_mark_uptodate(folio); folio_unlock(folio); } count_vm_events(PSWPIN, sio->pages); } else { for (p = 0; p < sio->pages; p++) { struct folio *folio = page_folio(sio->bvec[p].bv_page); folio_unlock(folio); } pr_alert_ratelimited("Read-error on swap-device\n"); } mempool_free(sio, sio_pool); } static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) { struct swap_info_struct *sis = swp_swap_info(folio->swap); struct swap_iocb *sio = NULL; loff_t pos = folio_file_pos(folio); if (plug) sio = *plug; if (sio) { if (sio->iocb.ki_filp != sis->swap_file || sio->iocb.ki_pos + sio->len != pos) { swap_read_unplug(sio); sio = NULL; } } if (!sio) { sio = mempool_alloc(sio_pool, GFP_KERNEL); init_sync_kiocb(&sio->iocb, sis->swap_file); sio->iocb.ki_pos = pos; sio->iocb.ki_complete = sio_read_complete; sio->pages = 0; sio->len = 0; } bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0); sio->len += folio_size(folio); sio->pages += 1; if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) { swap_read_unplug(sio); sio = NULL; } if (plug) *plug = sio; } static void swap_read_folio_bdev_sync(struct folio *folio, struct swap_info_struct *sis) { struct bio_vec bv; struct bio bio; bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ); bio.bi_iter.bi_sector = swap_folio_sector(folio); bio_add_folio_nofail(&bio, folio, folio_size(folio), 0); /* * Keep this task valid during swap readpage because the oom killer may * attempt to access it in the page fault retry time check. */ get_task_struct(current); count_vm_event(PSWPIN); submit_bio_wait(&bio); __end_swap_bio_read(&bio); put_task_struct(current); } static void swap_read_folio_bdev_async(struct folio *folio, struct swap_info_struct *sis) { struct bio *bio; bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL); bio->bi_iter.bi_sector = swap_folio_sector(folio); bio->bi_end_io = end_swap_bio_read; bio_add_folio_nofail(bio, folio, folio_size(folio), 0); count_vm_event(PSWPIN); submit_bio(bio); } void swap_read_folio(struct folio *folio, bool synchronous, struct swap_iocb **plug) { struct swap_info_struct *sis = swp_swap_info(folio->swap); bool workingset = folio_test_workingset(folio); unsigned long pflags; bool in_thrashing; VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio); VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio); /* * Count submission time as memory stall and delay. When the device * is congested, or the submitting cgroup IO-throttled, submission * can be a significant part of overall IO time. */ if (workingset) { delayacct_thrashing_start(&in_thrashing); psi_memstall_enter(&pflags); } delayacct_swapin_start(); if (zswap_load(folio)) { folio_mark_uptodate(folio); folio_unlock(folio); } else if (data_race(sis->flags & SWP_FS_OPS)) { swap_read_folio_fs(folio, plug); } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) { swap_read_folio_bdev_sync(folio, sis); } else { swap_read_folio_bdev_async(folio, sis); } if (workingset) { delayacct_thrashing_end(&in_thrashing); psi_memstall_leave(&pflags); } delayacct_swapin_end(); } void __swap_read_unplug(struct swap_iocb *sio) { struct iov_iter from; struct address_space *mapping = sio->iocb.ki_filp->f_mapping; int ret; iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len); ret = mapping->a_ops->swap_rw(&sio->iocb, &from); if (ret != -EIOCBQUEUED) sio_read_complete(&sio->iocb, ret); }