cregit-Linux how code gets into the kernel

Release 4.11 mm/page_io.c

Directory: mm
/*
 *  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_end_io = end_io;

		bio_add_page(bio, page, PAGE_SIZE, 0);
		BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE);
	}
	return bio;
}


Contributors
PersonTokensPropCommitsCommitProp
Andrew Morton4546.88%215.38%


Kent Overstreet1919.79%215.38%


Linus Torvalds (pre-git)1919.79%538.46%


Hugh Dickins1010.42%17.69%


Lee Schermerhorn11.04%17.69%


Linus Torvalds11.04%17.69%


Al Viro11.04%17.69%


Total96100.00%13100.00%






void end_swap_bio_write(struct bio *bio)
{
	struct page *page = bio->bi_io_vec[0].bv_page;

	if (bio->bi_error) {
		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",
			 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);
}


Contributors
PersonTokensPropCommitsCommitProp
Peter Zijlstra4346.74%112.50%


Andrew Morton3639.13%112.50%


Linus Torvalds (pre-git)55.43%225.00%


Christoph Hellwig33.26%112.50%


Kent Overstreet22.17%112.50%


Joe Perches22.17%112.50%


Neil Brown11.09%112.50%


Total92100.00%8100.00%






static void swap_slot_free_notify(struct page *page)
{
	struct swap_info_struct *sis;
	struct gendisk *disk;

	/*
         * 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;
	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);
	}
}


Contributors
PersonTokensPropCommitsCommitProp
MinChan Kim10391.15%240.00%


Andrew Morton87.08%120.00%


Christoph Hellwig10.88%120.00%


Neil Brown10.88%120.00%


Total113100.00%5100.00%






static void end_swap_bio_read(struct bio *bio)
{
	struct page *page = bio->bi_io_vec[0].bv_page;

	if (bio->bi_error) {
		SetPageError(page);
		ClearPageUptodate(page);
		pr_alert("Read-error on swap-device (%u:%u:%llu)\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);
	swap_slot_free_notify(page);
out:
	unlock_page(page);
	bio_put(bio);
}


Contributors
PersonTokensPropCommitsCommitProp
MinChan Kim9088.24%240.00%


Andrew Morton65.88%120.00%


Linus Torvalds (pre-git)65.88%240.00%


Total102100.00%5100.00%






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;

		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;
}


Contributors
PersonTokensPropCommitsCommitProp
Mel Gorman35598.89%133.33%


Mikulas Patocka30.84%133.33%


Joe Perches10.28%133.33%


Total359100.00%3100.00%



/*
 * 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;
}


Contributors
PersonTokensPropCommitsCommitProp
Dan Magenheimer2834.15%19.09%


Seth Jennings1720.73%218.18%


Andrew Morton1720.73%218.18%


Linus Torvalds (pre-git)1720.73%327.27%


Hugh Dickins11.22%19.09%


Mel Gorman11.22%19.09%


Konrad Rzeszutek Wilk11.22%19.09%


Total82100.00%11100.00%






static sector_t swap_page_sector(struct page *page)
{
	return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
}


Contributors
PersonTokensPropCommitsCommitProp
Matthew Wilcox2596.15%150.00%


Kirill A. Shutemov13.85%150.00%


Total26100.00%2100.00%






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_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);
		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_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;
	}
	bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
	count_vm_event(PSWPOUT);
	set_page_writeback(page);
	unlock_page(page);
	submit_bio(bio);
out:
	return ret;
}


Contributors
PersonTokensPropCommitsCommitProp
Mel Gorman12438.51%310.71%


Andrew Morton5416.77%828.57%


Matthew Wilcox3711.49%13.57%


Seth Jennings3510.87%27.14%


Al Viro329.94%414.29%


Linus Torvalds (pre-git)103.11%27.14%


Jens Axboe92.80%27.14%


Jerome Marchand82.48%13.57%


Santosh Shilimkar82.48%13.57%


Christoph Lameter20.62%13.57%


Joe Perches10.31%13.57%


Michael Christie10.31%13.57%


Christoph Hellwig10.31%13.57%


Total322100.00%28100.00%






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(!PageSwapCache(page), 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) {
		if (trylock_page(page)) {
			swap_slot_free_notify(page);
			unlock_page(page);
		}

		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;
	}
	bio_set_op_attrs(bio, REQ_OP_READ, 0);
	count_vm_event(PSWPIN);
	submit_bio(bio);
out:
	return ret;
}


Contributors
PersonTokensPropCommitsCommitProp
Andrew Morton7730.80%630.00%


Mel Gorman6425.60%15.00%


Matthew Wilcox3514.00%15.00%


Dan Magenheimer239.20%15.00%


MinChan Kim197.60%210.00%


Michael Christie93.60%210.00%


Santosh Shilimkar83.20%15.00%


Sasha Levin62.40%15.00%


Linus Torvalds (pre-git)31.20%210.00%


Nicholas Piggin31.20%15.00%


Christoph Lameter20.80%15.00%


Konrad Rzeszutek Wilk10.40%15.00%


Total250100.00%20100.00%






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;

		VM_BUG_ON_PAGE(!PageSwapCache(page), page);
		return mapping->a_ops->set_page_dirty(page);
	} else {
		return __set_page_dirty_no_writeback(page);
	}
}

Contributors
PersonTokensPropCommitsCommitProp
Mel Gorman6084.51%133.33%


Santosh Shilimkar811.27%133.33%


Andrew Morton34.23%133.33%


Total71100.00%3100.00%




Overall Contributors
PersonTokensPropCommitsCommitProp
Mel Gorman60739.06%46.35%


Andrew Morton25316.28%1117.46%


MinChan Kim21413.77%34.76%


Matthew Wilcox976.24%11.59%


Linus Torvalds (pre-git)754.83%812.70%


Dan Magenheimer543.47%11.59%


Seth Jennings523.35%23.17%


Peter Zijlstra432.77%11.59%


Al Viro332.12%57.94%


Santosh Shilimkar241.54%11.59%


Kent Overstreet231.48%34.76%


Christoph Hellwig110.71%57.94%


Hugh Dickins110.71%23.17%


Michael Christie100.64%23.17%


Jens Axboe90.58%23.17%


Jerome Marchand80.51%11.59%


Sasha Levin60.39%11.59%


Christoph Lameter40.26%11.59%


Joe Perches40.26%11.59%


Mikulas Patocka30.19%11.59%


Tejun Heo30.19%11.59%


Nicholas Piggin30.19%11.59%


Neil Brown20.13%11.59%


Konrad Rzeszutek Wilk20.13%11.59%


Kirill A. Shutemov10.06%11.59%


Linus Torvalds10.06%11.59%


Lee Schermerhorn10.06%11.59%


Total1554100.00%63100.00%


Directory: mm



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