linux/mm/page_io.c
Jens Axboe caf6912f3f swap: fix swapfile read/write offset
We're not factoring in the start of the file for where to write and
read the swapfile, which leads to very unfortunate side effects of
writing where we should not be...

Fixes: 48d15436fd ("mm: remove get_swap_bio")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-02 17:25:46 -07:00

455 lines
11 KiB
C

// 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>
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;
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 (data_race(!(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_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)
{
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)
{
int ret = 0;
if (try_to_free_swap(page)) {
unlock_page(page);
goto out;
}
/*
* Arch code may have to preserve more data than just the page
* contents, e.g. memory tags.
*/
ret = arch_prepare_to_swap(page);
if (ret) {
set_page_dirty(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 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, 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 */
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 (data_race(sis->flags & SWP_FS_OPS)) {
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;
}
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_write_func;
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;
}
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 (data_race(sis->flags & SWP_FS_OPS)) {
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;
}
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;
}
int swap_set_page_dirty(struct page *page)
{
struct swap_info_struct *sis = page_swap_info(page);
if (data_race(sis->flags & SWP_FS_OPS)) {
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);
}
}