v4.19.13 snapshot.
diff --git a/fs/btrfs/tests/extent-io-tests.c b/fs/btrfs/tests/extent-io-tests.c
new file mode 100644
index 0000000..d9269a5
--- /dev/null
+++ b/fs/btrfs/tests/extent-io-tests.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2013 Fusion IO.  All rights reserved.
+ */
+
+#include <linux/pagemap.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/sizes.h>
+#include "btrfs-tests.h"
+#include "../ctree.h"
+#include "../extent_io.h"
+
+#define PROCESS_UNLOCK		(1 << 0)
+#define PROCESS_RELEASE		(1 << 1)
+#define PROCESS_TEST_LOCKED	(1 << 2)
+
+static noinline int process_page_range(struct inode *inode, u64 start, u64 end,
+				       unsigned long flags)
+{
+	int ret;
+	struct page *pages[16];
+	unsigned long index = start >> PAGE_SHIFT;
+	unsigned long end_index = end >> PAGE_SHIFT;
+	unsigned long nr_pages = end_index - index + 1;
+	int i;
+	int count = 0;
+	int loops = 0;
+
+	while (nr_pages > 0) {
+		ret = find_get_pages_contig(inode->i_mapping, index,
+				     min_t(unsigned long, nr_pages,
+				     ARRAY_SIZE(pages)), pages);
+		for (i = 0; i < ret; i++) {
+			if (flags & PROCESS_TEST_LOCKED &&
+			    !PageLocked(pages[i]))
+				count++;
+			if (flags & PROCESS_UNLOCK && PageLocked(pages[i]))
+				unlock_page(pages[i]);
+			put_page(pages[i]);
+			if (flags & PROCESS_RELEASE)
+				put_page(pages[i]);
+		}
+		nr_pages -= ret;
+		index += ret;
+		cond_resched();
+		loops++;
+		if (loops > 100000) {
+			printk(KERN_ERR
+		"stuck in a loop, start %llu, end %llu, nr_pages %lu, ret %d\n",
+				start, end, nr_pages, ret);
+			break;
+		}
+	}
+	return count;
+}
+
+static int test_find_delalloc(u32 sectorsize)
+{
+	struct inode *inode;
+	struct extent_io_tree tmp;
+	struct page *page;
+	struct page *locked_page = NULL;
+	unsigned long index = 0;
+	u64 total_dirty = SZ_256M;
+	u64 max_bytes = SZ_128M;
+	u64 start, end, test_start;
+	u64 found;
+	int ret = -EINVAL;
+
+	test_msg("running find delalloc tests");
+
+	inode = btrfs_new_test_inode();
+	if (!inode) {
+		test_err("failed to allocate test inode");
+		return -ENOMEM;
+	}
+
+	extent_io_tree_init(&tmp, inode);
+
+	/*
+	 * First go through and create and mark all of our pages dirty, we pin
+	 * everything to make sure our pages don't get evicted and screw up our
+	 * test.
+	 */
+	for (index = 0; index < (total_dirty >> PAGE_SHIFT); index++) {
+		page = find_or_create_page(inode->i_mapping, index, GFP_KERNEL);
+		if (!page) {
+			test_err("failed to allocate test page");
+			ret = -ENOMEM;
+			goto out;
+		}
+		SetPageDirty(page);
+		if (index) {
+			unlock_page(page);
+		} else {
+			get_page(page);
+			locked_page = page;
+		}
+	}
+
+	/* Test this scenario
+	 * |--- delalloc ---|
+	 * |---  search  ---|
+	 */
+	set_extent_delalloc(&tmp, 0, sectorsize - 1, 0, NULL);
+	start = 0;
+	end = 0;
+	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
+					 &end, max_bytes);
+	if (!found) {
+		test_err("should have found at least one delalloc");
+		goto out_bits;
+	}
+	if (start != 0 || end != (sectorsize - 1)) {
+		test_err("expected start 0 end %u, got start %llu end %llu",
+			sectorsize - 1, start, end);
+		goto out_bits;
+	}
+	unlock_extent(&tmp, start, end);
+	unlock_page(locked_page);
+	put_page(locked_page);
+
+	/*
+	 * Test this scenario
+	 *
+	 * |--- delalloc ---|
+	 *           |--- search ---|
+	 */
+	test_start = SZ_64M;
+	locked_page = find_lock_page(inode->i_mapping,
+				     test_start >> PAGE_SHIFT);
+	if (!locked_page) {
+		test_err("couldn't find the locked page");
+		goto out_bits;
+	}
+	set_extent_delalloc(&tmp, sectorsize, max_bytes - 1, 0, NULL);
+	start = test_start;
+	end = 0;
+	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
+					 &end, max_bytes);
+	if (!found) {
+		test_err("couldn't find delalloc in our range");
+		goto out_bits;
+	}
+	if (start != test_start || end != max_bytes - 1) {
+		test_err("expected start %llu end %llu, got start %llu, end %llu",
+				test_start, max_bytes - 1, start, end);
+		goto out_bits;
+	}
+	if (process_page_range(inode, start, end,
+			       PROCESS_TEST_LOCKED | PROCESS_UNLOCK)) {
+		test_err("there were unlocked pages in the range");
+		goto out_bits;
+	}
+	unlock_extent(&tmp, start, end);
+	/* locked_page was unlocked above */
+	put_page(locked_page);
+
+	/*
+	 * Test this scenario
+	 * |--- delalloc ---|
+	 *                    |--- search ---|
+	 */
+	test_start = max_bytes + sectorsize;
+	locked_page = find_lock_page(inode->i_mapping, test_start >>
+				     PAGE_SHIFT);
+	if (!locked_page) {
+		test_err("couldn't find the locked page");
+		goto out_bits;
+	}
+	start = test_start;
+	end = 0;
+	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
+					 &end, max_bytes);
+	if (found) {
+		test_err("found range when we shouldn't have");
+		goto out_bits;
+	}
+	if (end != (u64)-1) {
+		test_err("did not return the proper end offset");
+		goto out_bits;
+	}
+
+	/*
+	 * Test this scenario
+	 * [------- delalloc -------|
+	 * [max_bytes]|-- search--|
+	 *
+	 * We are re-using our test_start from above since it works out well.
+	 */
+	set_extent_delalloc(&tmp, max_bytes, total_dirty - 1, 0, NULL);
+	start = test_start;
+	end = 0;
+	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
+					 &end, max_bytes);
+	if (!found) {
+		test_err("didn't find our range");
+		goto out_bits;
+	}
+	if (start != test_start || end != total_dirty - 1) {
+		test_err("expected start %llu end %llu, got start %llu end %llu",
+			 test_start, total_dirty - 1, start, end);
+		goto out_bits;
+	}
+	if (process_page_range(inode, start, end,
+			       PROCESS_TEST_LOCKED | PROCESS_UNLOCK)) {
+		test_err("pages in range were not all locked");
+		goto out_bits;
+	}
+	unlock_extent(&tmp, start, end);
+
+	/*
+	 * Now to test where we run into a page that is no longer dirty in the
+	 * range we want to find.
+	 */
+	page = find_get_page(inode->i_mapping,
+			     (max_bytes + SZ_1M) >> PAGE_SHIFT);
+	if (!page) {
+		test_err("couldn't find our page");
+		goto out_bits;
+	}
+	ClearPageDirty(page);
+	put_page(page);
+
+	/* We unlocked it in the previous test */
+	lock_page(locked_page);
+	start = test_start;
+	end = 0;
+	/*
+	 * Currently if we fail to find dirty pages in the delalloc range we
+	 * will adjust max_bytes down to PAGE_SIZE and then re-search.  If
+	 * this changes at any point in the future we will need to fix this
+	 * tests expected behavior.
+	 */
+	found = find_lock_delalloc_range(inode, &tmp, locked_page, &start,
+					 &end, max_bytes);
+	if (!found) {
+		test_err("didn't find our range");
+		goto out_bits;
+	}
+	if (start != test_start && end != test_start + PAGE_SIZE - 1) {
+		test_err("expected start %llu end %llu, got start %llu end %llu",
+			 test_start, test_start + PAGE_SIZE - 1, start, end);
+		goto out_bits;
+	}
+	if (process_page_range(inode, start, end, PROCESS_TEST_LOCKED |
+			       PROCESS_UNLOCK)) {
+		test_err("pages in range were not all locked");
+		goto out_bits;
+	}
+	ret = 0;
+out_bits:
+	clear_extent_bits(&tmp, 0, total_dirty - 1, (unsigned)-1);
+out:
+	if (locked_page)
+		put_page(locked_page);
+	process_page_range(inode, 0, total_dirty - 1,
+			   PROCESS_UNLOCK | PROCESS_RELEASE);
+	iput(inode);
+	return ret;
+}
+
+static int check_eb_bitmap(unsigned long *bitmap, struct extent_buffer *eb,
+			   unsigned long len)
+{
+	unsigned long i;
+
+	for (i = 0; i < len * BITS_PER_BYTE; i++) {
+		int bit, bit1;
+
+		bit = !!test_bit(i, bitmap);
+		bit1 = !!extent_buffer_test_bit(eb, 0, i);
+		if (bit1 != bit) {
+			test_err("bits do not match");
+			return -EINVAL;
+		}
+
+		bit1 = !!extent_buffer_test_bit(eb, i / BITS_PER_BYTE,
+						i % BITS_PER_BYTE);
+		if (bit1 != bit) {
+			test_err("offset bits do not match");
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+static int __test_eb_bitmaps(unsigned long *bitmap, struct extent_buffer *eb,
+			     unsigned long len)
+{
+	unsigned long i, j;
+	u32 x;
+	int ret;
+
+	memset(bitmap, 0, len);
+	memzero_extent_buffer(eb, 0, len);
+	if (memcmp_extent_buffer(eb, bitmap, 0, len) != 0) {
+		test_err("bitmap was not zeroed");
+		return -EINVAL;
+	}
+
+	bitmap_set(bitmap, 0, len * BITS_PER_BYTE);
+	extent_buffer_bitmap_set(eb, 0, 0, len * BITS_PER_BYTE);
+	ret = check_eb_bitmap(bitmap, eb, len);
+	if (ret) {
+		test_err("setting all bits failed");
+		return ret;
+	}
+
+	bitmap_clear(bitmap, 0, len * BITS_PER_BYTE);
+	extent_buffer_bitmap_clear(eb, 0, 0, len * BITS_PER_BYTE);
+	ret = check_eb_bitmap(bitmap, eb, len);
+	if (ret) {
+		test_err("clearing all bits failed");
+		return ret;
+	}
+
+	/* Straddling pages test */
+	if (len > PAGE_SIZE) {
+		bitmap_set(bitmap,
+			(PAGE_SIZE - sizeof(long) / 2) * BITS_PER_BYTE,
+			sizeof(long) * BITS_PER_BYTE);
+		extent_buffer_bitmap_set(eb, PAGE_SIZE - sizeof(long) / 2, 0,
+					sizeof(long) * BITS_PER_BYTE);
+		ret = check_eb_bitmap(bitmap, eb, len);
+		if (ret) {
+			test_err("setting straddling pages failed");
+			return ret;
+		}
+
+		bitmap_set(bitmap, 0, len * BITS_PER_BYTE);
+		bitmap_clear(bitmap,
+			(PAGE_SIZE - sizeof(long) / 2) * BITS_PER_BYTE,
+			sizeof(long) * BITS_PER_BYTE);
+		extent_buffer_bitmap_set(eb, 0, 0, len * BITS_PER_BYTE);
+		extent_buffer_bitmap_clear(eb, PAGE_SIZE - sizeof(long) / 2, 0,
+					sizeof(long) * BITS_PER_BYTE);
+		ret = check_eb_bitmap(bitmap, eb, len);
+		if (ret) {
+			test_err("clearing straddling pages failed");
+			return ret;
+		}
+	}
+
+	/*
+	 * Generate a wonky pseudo-random bit pattern for the sake of not using
+	 * something repetitive that could miss some hypothetical off-by-n bug.
+	 */
+	x = 0;
+	bitmap_clear(bitmap, 0, len * BITS_PER_BYTE);
+	extent_buffer_bitmap_clear(eb, 0, 0, len * BITS_PER_BYTE);
+	for (i = 0; i < len * BITS_PER_BYTE / 32; i++) {
+		x = (0x19660dULL * (u64)x + 0x3c6ef35fULL) & 0xffffffffU;
+		for (j = 0; j < 32; j++) {
+			if (x & (1U << j)) {
+				bitmap_set(bitmap, i * 32 + j, 1);
+				extent_buffer_bitmap_set(eb, 0, i * 32 + j, 1);
+			}
+		}
+	}
+
+	ret = check_eb_bitmap(bitmap, eb, len);
+	if (ret) {
+		test_err("random bit pattern failed");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int test_eb_bitmaps(u32 sectorsize, u32 nodesize)
+{
+	struct btrfs_fs_info *fs_info;
+	unsigned long len;
+	unsigned long *bitmap;
+	struct extent_buffer *eb;
+	int ret;
+
+	test_msg("running extent buffer bitmap tests");
+
+	/*
+	 * In ppc64, sectorsize can be 64K, thus 4 * 64K will be larger than
+	 * BTRFS_MAX_METADATA_BLOCKSIZE.
+	 */
+	len = (sectorsize < BTRFS_MAX_METADATA_BLOCKSIZE)
+		? sectorsize * 4 : sectorsize;
+
+	fs_info = btrfs_alloc_dummy_fs_info(len, len);
+
+	bitmap = kmalloc(len, GFP_KERNEL);
+	if (!bitmap) {
+		test_err("couldn't allocate test bitmap");
+		return -ENOMEM;
+	}
+
+	eb = __alloc_dummy_extent_buffer(fs_info, 0, len);
+	if (!eb) {
+		test_err("couldn't allocate test extent buffer");
+		kfree(bitmap);
+		return -ENOMEM;
+	}
+
+	ret = __test_eb_bitmaps(bitmap, eb, len);
+	if (ret)
+		goto out;
+
+	/* Do it over again with an extent buffer which isn't page-aligned. */
+	free_extent_buffer(eb);
+	eb = __alloc_dummy_extent_buffer(NULL, nodesize / 2, len);
+	if (!eb) {
+		test_err("couldn't allocate test extent buffer");
+		kfree(bitmap);
+		return -ENOMEM;
+	}
+
+	ret = __test_eb_bitmaps(bitmap, eb, len);
+out:
+	free_extent_buffer(eb);
+	kfree(bitmap);
+	return ret;
+}
+
+int btrfs_test_extent_io(u32 sectorsize, u32 nodesize)
+{
+	int ret;
+
+	test_msg("running extent I/O tests");
+
+	ret = test_find_delalloc(sectorsize);
+	if (ret)
+		goto out;
+
+	ret = test_eb_bitmaps(sectorsize, nodesize);
+out:
+	test_msg("extent I/O tests finished");
+	return ret;
+}