1 files changed, 160 insertions, 0 deletions

diff --git a/mm/page_io.c b/mm/page_io.c
new file mode 100644
index 000000000000..667c76df1ec2
--- /dev/null
+++ b/mm/page_io.c
@@ -0,0 +1,160 @@
+/*
+ *  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/pagemap.h>
+#include <linux/swap.h>
+#include <linux/bio.h>
+#include <linux/swapops.h>
+#include <linux/writeback.h>
+#include <asm/pgtable.h>
+
+static struct bio *get_swap_bio(unsigned int __nocast gfp_flags, pgoff_t index,
+				struct page *page, bio_end_io_t end_io)
+{
+	struct bio *bio;
+
+	bio = bio_alloc(gfp_flags, 1);
+	if (bio) {
+		struct swap_info_struct *sis;
+		swp_entry_t entry = { .val = index, };
+
+		sis = get_swap_info_struct(swp_type(entry));
+		bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
+					(PAGE_SIZE >> 9);
+		bio->bi_bdev = sis->bdev;
+		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_idx = 0;
+		bio->bi_size = PAGE_SIZE;
+		bio->bi_end_io = end_io;
+	}
+	return bio;
+}
+
+static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct page *page = bio->bi_io_vec[0].bv_page;
+
+	if (bio->bi_size)
+		return 1;
+
+	if (!uptodate)
+		SetPageError(page);
+	end_page_writeback(page);
+	bio_put(bio);
+	return 0;
+}
+
+static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct page *page = bio->bi_io_vec[0].bv_page;
+
+	if (bio->bi_size)
+		return 1;
+
+	if (!uptodate) {
+		SetPageError(page);
+		ClearPageUptodate(page);
+	} else {
+		SetPageUptodate(page);
+	}
+	unlock_page(page);
+	bio_put(bio);
+	return 0;
+}
+
+/*
+ * 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 bio *bio;
+	int ret = 0, rw = WRITE;
+
+	if (remove_exclusive_swap_page(page)) {
+		unlock_page(page);
+		goto out;
+	}
+	bio = get_swap_bio(GFP_NOIO, page->private, page, end_swap_bio_write);
+	if (bio == NULL) {
+		set_page_dirty(page);
+		unlock_page(page);
+		ret = -ENOMEM;
+		goto out;
+	}
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		rw |= (1 << BIO_RW_SYNC);
+	inc_page_state(pswpout);
+	set_page_writeback(page);
+	unlock_page(page);
+	submit_bio(rw, bio);
+out:
+	return ret;
+}
+
+int swap_readpage(struct file *file, struct page *page)
+{
+	struct bio *bio;
+	int ret = 0;
+
+	BUG_ON(!PageLocked(page));
+	ClearPageUptodate(page);
+	bio = get_swap_bio(GFP_KERNEL, page->private, page, end_swap_bio_read);
+	if (bio == NULL) {
+		unlock_page(page);
+		ret = -ENOMEM;
+		goto out;
+	}
+	inc_page_state(pswpin);
+	submit_bio(READ, bio);
+out:
+	return ret;
+}
+
+#if defined(CONFIG_SOFTWARE_SUSPEND) || defined(CONFIG_PM_DISK)
+/*
+ * A scruffy utility function to read or write an arbitrary swap page
+ * and wait on the I/O.  The caller must have a ref on the page.
+ *
+ * We use end_swap_bio_read() even for writes, because it happens to do what
+ * we want.
+ */
+int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page)
+{
+	struct bio *bio;
+	int ret = 0;
+
+	lock_page(page);
+
+	bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read);
+	if (bio == NULL) {
+		unlock_page(page);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	submit_bio(rw | (1 << BIO_RW_SYNC), bio);
+	wait_on_page_locked(page);
+
+	if (!PageUptodate(page) || PageError(page))
+		ret = -EIO;
+out:
+	return ret;
+}
+#endif