Btrfs: add tests for btrfs_get_extent

I'm going to be removing hole extents in the near future so I wanted to make a
sanity test for btrfs_get_extent to make sure I don't break anything in the
meantime.  This patch just puts btrfs_get_extent through its paces by giving it
a completely unreasonable mapping to look at and make sure it is giving us back
maps that make sense.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

7 files changed, 861 insertions, 2 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index cac4f2d001a3..1a44e42d602a 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -15,4 +15,5 @@ btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
 
 btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \
-	tests/extent-buffer-tests.o tests/btrfs-tests.o tests/extent-io-tests.o
+	tests/extent-buffer-tests.o tests/btrfs-tests.o \
+	tests/extent-io-tests.o tests/inode-tests.o
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 2f398062b942..9f5e1cfb0209 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -4034,5 +4034,9 @@ static inline int btrfs_defrag_cancelled(struct btrfs_fs_info *fs_info)
 	return signal_pending(current);
 }
 
+/* Sanity test specific functions */
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+void btrfs_test_destroy_inode(struct inode *inode);
+#endif
 
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index bba7f1a5e9f3..b5c2ad8fe2ca 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7795,6 +7795,14 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
 	return inode;
 }
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+void btrfs_test_destroy_inode(struct inode *inode)
+{
+	btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
+	kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
+}
+#endif
+
 static void btrfs_i_callback(struct rcu_head *head)
 {
 	struct inode *inode = container_of(head, struct inode, i_rcu);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 78041e34d15a..1f62c1ccab1f 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1802,6 +1802,9 @@ static int btrfs_run_sanity_tests(void)
 	if (ret)
 		goto out;
 	ret = btrfs_test_extent_io();
+	if (ret)
+		goto out;
+	ret = btrfs_test_inodes();
 out:
 	btrfs_destroy_test_fs();
 	return ret;
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index 697d527377c1..757ef00a75a4 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -24,11 +24,17 @@
 
 static struct vfsmount *test_mnt = NULL;
 
+static const struct super_operations btrfs_test_super_ops = {
+	.alloc_inode	= btrfs_alloc_inode,
+	.destroy_inode	= btrfs_test_destroy_inode,
+};
+
 static struct dentry *btrfs_test_mount(struct file_system_type *fs_type,
 				       int flags, const char *dev_name,
 				       void *data)
 {
-	return mount_pseudo(fs_type, "btrfs_test:", NULL, NULL, BTRFS_TEST_MAGIC);
+	return mount_pseudo(fs_type, "btrfs_test:", &btrfs_test_super_ops,
+			    NULL, BTRFS_TEST_MAGIC);
 }
 
 static struct file_system_type test_type = {
diff --git a/fs/btrfs/tests/btrfs-tests.h b/fs/btrfs/tests/btrfs-tests.h
index e935fe5291e7..b353bc806ca0 100644
--- a/fs/btrfs/tests/btrfs-tests.h
+++ b/fs/btrfs/tests/btrfs-tests.h
@@ -26,6 +26,7 @@
 int btrfs_test_free_space_cache(void);
 int btrfs_test_extent_buffer_operations(void);
 int btrfs_test_extent_io(void);
+int btrfs_test_inodes(void);
 int btrfs_init_test_fs(void);
 void btrfs_destroy_test_fs(void);
 struct inode *btrfs_new_test_inode(void);
@@ -49,6 +50,10 @@ static inline int btrfs_test_extent_io(void)
 {
 	return 0;
 }
+static inline int btrfs_test_inodes(void)
+{
+	return 0;
+}
 #endif
 
 #endif
diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c
new file mode 100644
index 000000000000..b0fc3bab2a96
--- /dev/null
+++ b/fs/btrfs/tests/inode-tests.c
@@ -0,0 +1,832 @@
+/*
+ * Copyright (C) 2013 Fusion IO.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include "btrfs-tests.h"
+#include "../ctree.h"
+#include "../btrfs_inode.h"
+#include "../disk-io.h"
+#include "../extent_io.h"
+#include "../volumes.h"
+
+static struct btrfs_fs_info *alloc_dummy_fs_info(void)
+{
+	struct btrfs_fs_info *fs_info = kzalloc(sizeof(struct btrfs_fs_info),
+						GFP_NOFS);
+	if (!fs_info)
+		return fs_info;
+	fs_info->fs_devices = kzalloc(sizeof(struct btrfs_fs_devices),
+				      GFP_NOFS);
+	if (!fs_info->fs_devices) {
+		kfree(fs_info);
+		return NULL;
+	}
+	return fs_info;
+}
+static void free_dummy_root(struct btrfs_root *root)
+{
+	if (!root)
+		return;
+	if (root->fs_info) {
+		kfree(root->fs_info->fs_devices);
+		kfree(root->fs_info);
+	}
+	if (root->node)
+		free_extent_buffer(root->node);
+	kfree(root);
+}
+
+static void insert_extent(struct btrfs_root *root, u64 start, u64 len,
+			  u64 ram_bytes, u64 offset, u64 disk_bytenr,
+			  u64 disk_len, u32 type, u8 compression, int slot)
+{
+	struct btrfs_path path;
+	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *leaf = root->node;
+	struct btrfs_key key;
+	u32 value_len = sizeof(struct btrfs_file_extent_item);
+
+	if (type == BTRFS_FILE_EXTENT_INLINE)
+		value_len += len;
+	memset(&path, 0, sizeof(path));
+
+	path.nodes[0] = leaf;
+	path.slots[0] = slot;
+
+	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = start;
+
+	setup_items_for_insert(root, &path, &key, &value_len, value_len,
+			       value_len + sizeof(struct btrfs_item), 1);
+	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+	btrfs_set_file_extent_generation(leaf, fi, 1);
+	btrfs_set_file_extent_type(leaf, fi, type);
+	btrfs_set_file_extent_disk_bytenr(leaf, fi, disk_bytenr);
+	btrfs_set_file_extent_disk_num_bytes(leaf, fi, disk_len);
+	btrfs_set_file_extent_offset(leaf, fi, offset);
+	btrfs_set_file_extent_num_bytes(leaf, fi, len);
+	btrfs_set_file_extent_ram_bytes(leaf, fi, ram_bytes);
+	btrfs_set_file_extent_compression(leaf, fi, compression);
+	btrfs_set_file_extent_encryption(leaf, fi, 0);
+	btrfs_set_file_extent_other_encoding(leaf, fi, 0);
+}
+
+/*
+ * Build the most complicated map of extents the earth has ever seen.  We want
+ * this so we can test all of the corner cases of btrfs_get_extent.  Here is a
+ * diagram of how the extents will look though this may not be possible we still
+ * want to make sure everything acts normally (the last number is not inclusive)
+ *
+ * [0 - 5][5 -  6][6 - 10][10 - 4096][  4096 - 8192 ][8192 - 12288]
+ * [hole ][inline][ hole ][ regular ][regular1 split][    hole    ]
+ *
+ * [ 12288 - 20480][20480 - 24576][  24576 - 28672  ][28672 - 36864][36864 - 45056]
+ * [regular1 split][   prealloc1 ][prealloc1 written][   prealloc1 ][ compressed  ]
+ *
+ * [45056 - 49152][49152-53248][53248-61440][61440-65536][     65536+81920   ]
+ * [ compressed1 ][  regular  ][compressed1][  regular  ][ hole but no extent]
+ *
+ * [81920-86016]
+ * [  regular  ]
+ */
+static void setup_file_extents(struct btrfs_root *root)
+{
+	int slot = 0;
+	u64 disk_bytenr = 1 * 1024 * 1024;
+	u64 offset = 0;
+
+	/* First we want a hole */
+	insert_extent(root, offset, 5, 5, 0, 0, 0, BTRFS_FILE_EXTENT_REG, 0,
+		      slot);
+	slot++;
+	offset += 5;
+
+	/*
+	 * Now we want an inline extent, I don't think this is possible but hey
+	 * why not?  Also keep in mind if we have an inline extent it counts as
+	 * the whole first page.  If we were to expand it we would have to cow
+	 * and we wouldn't have an inline extent anymore.
+	 */
+	insert_extent(root, offset, 1, 1, 0, 0, 0, BTRFS_FILE_EXTENT_INLINE, 0,
+		      slot);
+	slot++;
+	offset = 4096;
+
+	/* Now another hole */
+	insert_extent(root, offset, 4, 4, 0, 0, 0, BTRFS_FILE_EXTENT_REG, 0,
+		      slot);
+	slot++;
+	offset += 4;
+
+	/* Now for a regular extent */
+	insert_extent(root, offset, 4095, 4095, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	disk_bytenr += 4096;
+	offset += 4095;
+
+	/*
+	 * Now for 3 extents that were split from a hole punch so we test
+	 * offsets properly.
+	 */
+	insert_extent(root, offset, 4096, 16384, 0, disk_bytenr, 16384,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 4096, 4096, 0, 0, 0, BTRFS_FILE_EXTENT_REG,
+		      0, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 8192, 16384, 8192, disk_bytenr, 16384,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	offset += 8192;
+	disk_bytenr += 16384;
+
+	/* Now for a unwritten prealloc extent */
+	insert_extent(root, offset, 4096, 4096, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_PREALLOC, 0, slot);
+	slot++;
+	offset += 4096;
+
+	/*
+	 * We want to jack up disk_bytenr a little more so the em stuff doesn't
+	 * merge our records.
+	 */
+	disk_bytenr += 8192;
+
+	/*
+	 * Now for a partially written prealloc extent, basically the same as
+	 * the hole punch example above.  Ram_bytes never changes when you mark
+	 * extents written btw.
+	 */
+	insert_extent(root, offset, 4096, 16384, 0, disk_bytenr, 16384,
+		      BTRFS_FILE_EXTENT_PREALLOC, 0, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 4096, 16384, 4096, disk_bytenr, 16384,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 8192, 16384, 8192, disk_bytenr, 16384,
+		      BTRFS_FILE_EXTENT_PREALLOC, 0, slot);
+	slot++;
+	offset += 8192;
+	disk_bytenr += 16384;
+
+	/* Now a normal compressed extent */
+	insert_extent(root, offset, 8192, 8192, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, BTRFS_COMPRESS_ZLIB, slot);
+	slot++;
+	offset += 8192;
+	/* No merges */
+	disk_bytenr += 8192;
+
+	/* Now a split compressed extent */
+	insert_extent(root, offset, 4096, 16384, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, BTRFS_COMPRESS_ZLIB, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 4096, 4096, 0, disk_bytenr + 4096, 4096,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	offset += 4096;
+	insert_extent(root, offset, 8192, 16384, 8192, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, BTRFS_COMPRESS_ZLIB, slot);
+	slot++;
+	offset += 8192;
+	disk_bytenr += 8192;
+
+	/* Now extents that have a hole but no hole extent */
+	insert_extent(root, offset, 4096, 4096, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+	slot++;
+	offset += 16384;
+	disk_bytenr += 4096;
+	insert_extent(root, offset, 4096, 4096, 0, disk_bytenr, 4096,
+		      BTRFS_FILE_EXTENT_REG, 0, slot);
+}
+
+static unsigned long prealloc_only = 0;
+static unsigned long compressed_only = 0;
+static unsigned long vacancy_only = 0;
+
+static noinline int test_btrfs_get_extent(void)
+{
+	struct inode *inode = NULL;
+	struct btrfs_root *root = NULL;
+	struct extent_map *em = NULL;
+	u64 orig_start;
+	u64 disk_bytenr;
+	u64 offset;
+	int ret = -ENOMEM;
+
+	set_bit(EXTENT_FLAG_COMPRESSED, &compressed_only);
+	set_bit(EXTENT_FLAG_VACANCY, &vacancy_only);
+	set_bit(EXTENT_FLAG_PREALLOC, &prealloc_only);
+
+	inode = btrfs_new_test_inode();
+	if (!inode) {
+		test_msg("Couldn't allocate inode\n");
+		return ret;
+	}
+
+	BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
+	BTRFS_I(inode)->location.objectid = BTRFS_FIRST_FREE_OBJECTID;
+	BTRFS_I(inode)->location.offset = 0;
+
+	root = btrfs_alloc_dummy_root();
+	if (IS_ERR(root)) {
+		test_msg("Couldn't allocate root\n");
+		goto out;
+	}
+
+	/*
+	 * We do this since btrfs_get_extent wants to assign em->bdev to
+	 * root->fs_info->fs_devices->latest_bdev.
+	 */
+	root->fs_info = alloc_dummy_fs_info();
+	if (!root->fs_info) {
+		test_msg("Couldn't allocate dummy fs info\n");
+		goto out;
+	}
+
+	root->node = alloc_dummy_extent_buffer(0, 4096);
+	if (!root->node) {
+		test_msg("Couldn't allocate dummy buffer\n");
+		goto out;
+	}
+
+	/*
+	 * We will just free a dummy node if it's ref count is 2 so we need an
+	 * extra ref so our searches don't accidently release our page.
+	 */
+	extent_buffer_get(root->node);
+	btrfs_set_header_nritems(root->node, 0);
+	btrfs_set_header_level(root->node, 0);
+	ret = -EINVAL;
+
+	/* First with no extents */
+	BTRFS_I(inode)->root = root;
+	em = btrfs_get_extent(inode, NULL, 0, 0, 4096, 0);
+	if (IS_ERR(em)) {
+		em = NULL;
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_HOLE) {
+		test_msg("Expected a hole, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
+		test_msg("Vacancy flag wasn't set properly\n");
+		goto out;
+	}
+	free_extent_map(em);
+	btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
+
+	/*
+	 * All of the magic numbers are based on the mapping setup in
+	 * setup_file_extents, so if you change anything there you need to
+	 * update the comment and update the expected values below.
+	 */
+	setup_file_extents(root);
+
+	em = btrfs_get_extent(inode, NULL, 0, 0, (u64)-1, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_HOLE) {
+		test_msg("Expected a hole, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != 0 || em->len != 5) {
+		test_msg("Unexpected extent wanted start 0 len 5, got start "
+			 "%llu len %llu\n", em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_INLINE) {
+		test_msg("Expected an inline, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4091) {
+		test_msg("Unexpected extent wanted start %llu len 1, got start "
+			 "%llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	/*
+	 * We don't test anything else for inline since it doesn't get set
+	 * unless we have a page for it to write into.  Maybe we should change
+	 * this?
+	 */
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_HOLE) {
+		test_msg("Expected a hole, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4) {
+		test_msg("Unexpected extent wanted start %llu len 4, got start "
+			 "%llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* Regular extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4095) {
+		test_msg("Unexpected extent wanted start %llu len 4095, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* The next 3 are split extents */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	disk_bytenr = em->block_start;
+	orig_start = em->start;
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_HOLE) {
+		test_msg("Expected a hole, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 8192) {
+		test_msg("Unexpected extent wanted start %llu len 8192, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != orig_start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n",
+			 orig_start, em->orig_start);
+		goto out;
+	}
+	disk_bytenr += (em->start - orig_start);
+	if (em->block_start != disk_bytenr) {
+		test_msg("Wrong block start, want %llu, have %llu\n",
+			 disk_bytenr, em->block_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* Prealloc extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != prealloc_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 prealloc_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* The next 3 are a half written prealloc extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != prealloc_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 prealloc_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	disk_bytenr = em->block_start;
+	orig_start = em->start;
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_HOLE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != orig_start) {
+		test_msg("Unexpected orig offset, wanted %llu, have %llu\n",
+			 orig_start, em->orig_start);
+		goto out;
+	}
+	if (em->block_start != (disk_bytenr + (em->start - em->orig_start))) {
+		test_msg("Unexpected block start, wanted %llu, have %llu\n",
+			 disk_bytenr + (em->start - em->orig_start),
+			 em->block_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 8192) {
+		test_msg("Unexpected extent wanted start %llu len 8192, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != prealloc_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 prealloc_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != orig_start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", orig_start,
+			 em->orig_start);
+		goto out;
+	}
+	if (em->block_start != (disk_bytenr + (em->start - em->orig_start))) {
+		test_msg("Unexpected block start, wanted %llu, have %llu\n",
+			 disk_bytenr + (em->start - em->orig_start),
+			 em->block_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* Now for the compressed extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 8192) {
+		test_msg("Unexpected extent wanted start %llu len 8192, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != compressed_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 compressed_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n",
+			 em->start, em->orig_start);
+		goto out;
+	}
+	if (em->compress_type != BTRFS_COMPRESS_ZLIB) {
+		test_msg("Unexpected compress type, wanted %d, got %d\n",
+			 BTRFS_COMPRESS_ZLIB, em->compress_type);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* Split compressed extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != compressed_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 compressed_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n",
+			 em->start, em->orig_start);
+		goto out;
+	}
+	if (em->compress_type != BTRFS_COMPRESS_ZLIB) {
+		test_msg("Unexpected compress type, wanted %d, got %d\n",
+			 BTRFS_COMPRESS_ZLIB, em->compress_type);
+		goto out;
+	}
+	disk_bytenr = em->block_start;
+	orig_start = em->start;
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != disk_bytenr) {
+		test_msg("Block start does not match, want %llu got %llu\n",
+			 disk_bytenr, em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 8192) {
+		test_msg("Unexpected extent wanted start %llu len 8192, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != compressed_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 compressed_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != orig_start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n",
+			 em->start, orig_start);
+		goto out;
+	}
+	if (em->compress_type != BTRFS_COMPRESS_ZLIB) {
+		test_msg("Unexpected compress type, wanted %d, got %d\n",
+			 BTRFS_COMPRESS_ZLIB, em->compress_type);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	/* A hole between regular extents but no hole extent */
+	em = btrfs_get_extent(inode, NULL, 0, offset + 6, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096 * 1024, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start != EXTENT_MAP_HOLE) {
+		test_msg("Expected a hole extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	/*
+	 * Currently we just return a length that we requested rather than the
+	 * length of the actual hole, if this changes we'll have to change this
+	 * test.
+	 */
+	if (em->start != offset || em->len != 12288) {
+		test_msg("Unexpected extent wanted start %llu len 12288, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != vacancy_only) {
+		test_msg("Unexpected flags set, want %lu have %lu\n",
+			 vacancy_only, em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	offset = em->start + em->len;
+	free_extent_map(em);
+
+	em = btrfs_get_extent(inode, NULL, 0, offset, 4096, 0);
+	if (IS_ERR(em)) {
+		test_msg("Got an error when we shouldn't have\n");
+		goto out;
+	}
+	if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+		test_msg("Expected a real extent, got %llu\n", em->block_start);
+		goto out;
+	}
+	if (em->start != offset || em->len != 4096) {
+		test_msg("Unexpected extent wanted start %llu len 4096, got "
+			 "start %llu len %llu\n", offset, em->start, em->len);
+		goto out;
+	}
+	if (em->flags != 0) {
+		test_msg("Unexpected flags set, want 0 have %lu\n", em->flags);
+		goto out;
+	}
+	if (em->orig_start != em->start) {
+		test_msg("Wrong orig offset, want %llu, have %llu\n", em->start,
+			 em->orig_start);
+		goto out;
+	}
+	ret = 0;
+out:
+	if (!IS_ERR(em))
+		free_extent_map(em);
+	iput(inode);
+	free_dummy_root(root);
+	return ret;
+}
+
+int btrfs_test_inodes(void)
+{
+	test_msg("Running btrfs_get_extent tests\n");
+	return test_btrfs_get_extent();
+}