diff options
Diffstat (limited to 'mm/page_io.c')
| -rw-r--r-- | mm/page_io.c | 381 |
1 files changed, 381 insertions, 0 deletions
diff --git a/mm/page_io.c b/mm/page_io.c new file mode 100644 index 000000000..6424869e2 --- /dev/null +++ b/mm/page_io.c @@ -0,0 +1,381 @@ +/* + * 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/uio.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) { + bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev); + bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; + bio->bi_io_vec[0].bv_page = page; + bio->bi_io_vec[0].bv_len = PAGE_SIZE; + bio->bi_io_vec[0].bv_offset = 0; + bio->bi_vcnt = 1; + bio->bi_iter.bi_size = PAGE_SIZE; + bio->bi_end_io = end_io; + } + return bio; +} + +void end_swap_bio_write(struct bio *bio, int err) +{ + const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); + struct page *page = bio->bi_io_vec[0].bv_page; + + if (!uptodate) { + 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); + printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", + imajor(bio->bi_bdev->bd_inode), + iminor(bio->bi_bdev->bd_inode), + (unsigned long long)bio->bi_iter.bi_sector); + ClearPageReclaim(page); + } + end_page_writeback(page); + bio_put(bio); +} + +void end_swap_bio_read(struct bio *bio, int err) +{ + const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); + struct page *page = bio->bi_io_vec[0].bv_page; + + if (!uptodate) { + SetPageError(page); + ClearPageUptodate(page); + printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", + imajor(bio->bi_bdev->bd_inode), + iminor(bio->bi_bdev->bd_inode), + (unsigned long long)bio->bi_iter.bi_sector); + goto out; + } + + SetPageUptodate(page); + + /* + * 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 (likely(PageSwapCache(page))) { + struct swap_info_struct *sis; + + sis = page_swap_info(page); + if (sis->flags & SWP_BLKDEV) { + /* + * 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. + */ + struct gendisk *disk = sis->bdev->bd_disk; + if (disk->fops->swap_slot_free_notify) { + swp_entry_t entry; + unsigned long offset; + + entry.val = page_private(page); + offset = swp_offset(entry); + + SetPageDirty(page); + disk->fops->swap_slot_free_notify(sis->bdev, + offset); + } + } + } + +out: + unlock_page(page); + 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 list. 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; + + 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: + printk(KERN_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_CACHE_SHIFT - 9); +} + +int __swap_writepage(struct page *page, struct writeback_control *wbc, + void (*end_write_func)(struct bio *, int)) +{ + struct bio *bio; + int ret, rw = WRITE; + struct swap_info_struct *sis = page_swap_info(page); + + if (sis->flags & SWP_FILE) { + 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, ITER_BVEC | 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, kiocb.ki_pos); + 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 (%Lu)\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_vm_event(PSWPOUT); + 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; + } + if (wbc->sync_mode == WB_SYNC_ALL) + rw |= REQ_SYNC; + count_vm_event(PSWPOUT); + set_page_writeback(page); + unlock_page(page); + submit_bio(rw, bio); +out: + return ret; +} + +int swap_readpage(struct page *page) +{ + struct bio *bio; + int ret = 0; + struct swap_info_struct *sis = page_swap_info(page); + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageUptodate(page), page); + if (frontswap_load(page) == 0) { + SetPageUptodate(page); + unlock_page(page); + goto out; + } + + if (sis->flags & SWP_FILE) { + 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); + return ret; + } + + ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); + if (!ret) { + count_vm_event(PSWPIN); + return 0; + } + + ret = 0; + bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); + if (bio == NULL) { + unlock_page(page); + ret = -ENOMEM; + goto out; + } + count_vm_event(PSWPIN); + submit_bio(READ, bio); +out: + return ret; +} + +int swap_set_page_dirty(struct page *page) +{ + struct swap_info_struct *sis = page_swap_info(page); + + if (sis->flags & SWP_FILE) { + struct address_space *mapping = sis->swap_file->f_mapping; + return mapping->a_ops->set_page_dirty(page); + } else { + return __set_page_dirty_no_writeback(page); + } +} |