// 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/buffer_head.h> #include <linux/writeback.h> #include <linux/frontswap.h> #include <linux/blkdev.h> #include <linux/psi.h> #include <linux/uio.h> #include <linux/sched/task.h> #include <asm/pgtable.h> static struct bio *get_swap_bio(gfp_t gfp_flags, struct page *page, bio_end_io_t end_io) { struct bio *bio; bio = bio_alloc(gfp_flags, 1); if (bio) { struct block_device *bdev; bio->bi_iter.bi_sector = map_swap_page(page, &bdev); bio_set_dev(bio, bdev); bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; bio->bi_end_io = end_io; bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0); } return bio; } 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("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; struct gendisk *disk; swp_entry_t entry; /* * There is no guarantee that the page is in swap cache - the software * suspend code (at least) uses end_swap_bio_read() against a non- * swapcache page. So we must check PG_swapcache before proceeding with * this optimization. */ if (unlikely(!PageSwapCache(page))) return; sis = page_swap_info(page); if (!(sis->flags & SWP_BLKDEV)) return; /* * The swap subsystem performs lazy swap slot freeing, * expecting that the page will be swapped out again. * So we can avoid an unnecessary write if the page * isn't redirtied. * This is good for real swap storage because we can * reduce unnecessary I/O and enhance wear-leveling * if an SSD is used as the as swap device. * But if in-memory swap device (eg zram) is used, * this causes a duplicated copy between uncompressed * data in VM-owned memory and compressed data in * zram-owned memory. So let's free zram-owned memory * and make the VM-owned decompressed page *dirty*, * so the page should be swapped out somewhere again if * we again wish to reclaim it. */ disk = sis->bdev->bd_disk; entry.val = page_private(page); if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) { unsigned long offset; offset = swp_offset(entry); SetPageDirty(page); disk->fops->swap_slot_free_notify(sis->bdev, offset); } } 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("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) { 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 = bmap(inode, probe_block); if (first_block == 0) 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 = bmap(inode, probe_block + block_in_page); if (block == 0) 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) { int ret = 0; if (try_to_free_swap(page)) { unlock_page(page); goto out; } if (frontswap_store(page) == 0) { set_page_writeback(page); unlock_page(page); end_page_writeback(page); goto out; } ret = __swap_writepage(page, wbc, end_swap_bio_write); out: return ret; } static sector_t swap_page_sector(struct page *page) { return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); } static inline void count_swpout_vm_event(struct page *page) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (unlikely(PageTransHuge(page))) count_vm_event(THP_SWPOUT); #endif count_vm_events(PSWPOUT, hpage_nr_pages(page)); } int __swap_writepage(struct page *page, struct writeback_control *wbc, bio_end_io_t end_write_func) { struct bio *bio; int ret; struct swap_info_struct *sis = page_swap_info(page); VM_BUG_ON_PAGE(!PageSwapCache(page), page); if (sis->flags & SWP_FS) { struct kiocb kiocb; struct file *swap_file = sis->swap_file; struct address_space *mapping = swap_file->f_mapping; struct bio_vec bv = { .bv_page = page, .bv_len = PAGE_SIZE, .bv_offset = 0 }; struct iov_iter from; iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); init_sync_kiocb(&kiocb, swap_file); kiocb.ki_pos = page_file_offset(page); set_page_writeback(page); unlock_page(page); ret = mapping->a_ops->direct_IO(&kiocb, &from); if (ret == PAGE_SIZE) { count_vm_event(PSWPOUT); ret = 0; } else { /* * 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 * rotate_reclaimable_page but rate-limit the * messages but do not flag PageError like * the normal direct-to-bio case as it could * be temporary. */ set_page_dirty(page); ClearPageReclaim(page); pr_err_ratelimited("Write error on dio swapfile (%llu)\n", page_file_offset(page)); } end_page_writeback(page); return ret; } ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); if (!ret) { count_swpout_vm_event(page); return 0; } ret = 0; bio = get_swap_bio(GFP_NOIO, page, end_write_func); if (bio == NULL) { set_page_dirty(page); unlock_page(page); ret = -ENOMEM; goto out; } bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); bio_associate_blkg_from_page(bio, page); count_swpout_vm_event(page); set_page_writeback(page); unlock_page(page); submit_bio(bio); out: return ret; } 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; VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(PageUptodate(page), page); /* * Count submission time as memory stall. When the device is congested, * or the submitting cgroup IO-throttled, submission can be a * significant part of overall IO time. */ psi_memstall_enter(&pflags); if (frontswap_load(page) == 0) { SetPageUptodate(page); unlock_page(page); goto out; } if (sis->flags & SWP_FS) { struct file *swap_file = sis->swap_file; struct address_space *mapping = swap_file->f_mapping; ret = mapping->a_ops->readpage(swap_file, page); if (!ret) count_vm_event(PSWPIN); goto out; } 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 = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); if (bio == NULL) { unlock_page(page); ret = -ENOMEM; goto out; } disk = bio->bi_disk; /* * Keep this task valid during swap readpage because the oom killer may * attempt to access it in the page fault retry time check. */ bio_set_op_attrs(bio, REQ_OP_READ, 0); 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)) io_schedule(); } __set_current_state(TASK_RUNNING); bio_put(bio); out: psi_memstall_leave(&pflags); return ret; } int swap_set_page_dirty(struct page *page) { struct swap_info_struct *sis = page_swap_info(page); if (sis->flags & SWP_FS) { struct address_space *mapping = sis->swap_file->f_mapping; VM_BUG_ON_PAGE(!PageSwapCache(page), page); return mapping->a_ops->set_page_dirty(page); } else { return __set_page_dirty_no_writeback(page); } }