dm提交失败后readonly模式读取到陈旧的元数据

【标题描述】dm提交失败后readonly模式读取到陈旧的元数据
【环境信息】
硬件信息：
NA
软件信息：
OLK-5.10
【问题复现步骤】
qemu config:
sda 20G
sdb 5G

1. Apply diff
2. ./test.sh
出现概率(是否必现，概率性错误)必现
【预期结果】
dm commit失败后仍使用最新的root，访问broken btree读取到陈旧的节点
【实际结果】
```
[   32.447722] [NEW TRANS] pwd root 261
[   32.448756] update root 266
[   32.542533] current
[   32.543073] flags 2 blocknr 272 nr_entries 206
[   32.543838] 0 key 556 value 1922
[   32.544362] 1 key 557 value 1934
[   32.544901] 2 key 559 value 2406
[   32.545414] 3 key 560 value 2407
[   32.545946] 4 key 561 value 2821
[   32.546461] 5 key 569 value 2491
[   32.546991] 6 key 570 value 2492
[   32.547505] 7 key 573 value 1980
[   32.548036] 8 key 574 value 1981
[   32.548578] 9 key 586 value 1643
[   32.549098] 10 key 587 value 1960
[   32.549665] 11 key 588 value 2813
[   32.550204] 12 key 589 value 2814
[   32.550757] 13 key 598 value 1936
[   32.551292] 14 key 599 value 1937
[   32.551845] 15 key 600 value 1939
[   32.552379] 16 key 601 value 1961
[   32.552927] 17 key 608 value 2313
[   32.553457] 18 key 609 value 2314
[   32.554009] 19 key 620 value 2063
[   32.554549] 20 key 621 value 2064
[   32.555102] 21 key 631 value 2054
[   32.555656] 22 key 632 value 2055
[   32.556181] 23 key 645 value 1682
[   32.556739] 24 key 646 value 2073
[   32.557272] 25 key 647 value 2074
[   32.557820] 26 key 655 value 2480
[   32.558361] 27 key 656 value 2481
[   32.558912] 28 key 663 value 2087
[   32.559436] 29 key 677 value 2219
[   32.559995] 30 key 678 value 2220
[   32.560528] 31 key 683 value 2208
[   32.561105] 32 key 684 value 2209
[   32.561663] 33 key 685 value 2161
[   32.562195] 34 key 692 value 2605
[   32.562744] 35 key 693 value 2206
[   32.563291] 36 key 694 value 2207
[   32.563849] 37 key 705 value 2071
[   32.564384] 38 key 707 value 2315
[   32.564946] 39 key 708 value 2602
[   32.565475] 40 key 709 value 2603
[   32.566032] 41 key 730 value 2316
[   32.566585] 42 key 731 value 2317
[   32.567125] 43 key 734 value 2322
[   32.567681] 44 key 735 value 2353
[   32.568225] 45 key 737 value 2610
[   32.568776] 46 key 738 value 2611
[   32.569329] 47 key 742 value 2691
[   32.569900] 48 key 743 value 2692
[   32.570434] 49 key 744 value 2693
[   32.570992] 50 key 753 value 2376
[   32.571532] 51 key 754 value 2377
[   32.572098] 52 key 765 value 2354
[   32.572657] 53 key 769 value 2358
[   32.573200] 54 key 770 value 2359
[   32.573756] 55 key 778 value 2360
[   32.574292] 56 key 779 value 2361
[   32.574851] 57 key 783 value 2400
[   32.575386] 58 key 785 value 2402
[   32.575942] 59 key 797 value 2463
[   32.576476] 60 key 798 value 2464
[   32.577030] 61 key 807 value 2669
[   32.577591] 62 key 808 value 2670
[   32.578130] 63 key 822 value 2362
[   32.578690] 64 key 823 value 2363
[   32.579236] 65 key 826 value 2810
[   32.579790] 66 key 840 value 2489
[   32.580322] 67 key 852 value 2184
[   32.580878] 68 key 853 value 2466
[   32.581408] 69 key 861 value 2467
[   32.581960] 70 key 862 value 2468
[   32.582498] 71 key 863 value 2469
[   32.583054] 72 key 875 value 2720
[   32.583604] 73 key 876 value 2721
[   32.584130] 74 key 878 value 2676
[   32.584684] 75 key 879 value 2677
[   32.585214] 76 key 886 value 2671
[   32.585775] 77 key 887 value 2672
[   32.586313] 78 key 896 value 2695
[   32.586868] 79 key 897 value 2696
[   32.587404] 80 key 898 value 2697
[   32.587961] 81 key 910 value 1501
[   32.588494] 82 key 912 value 2816
[   32.589046] 83 key 916 value 2817
[   32.589596] 84 key 917 value 2818
[   32.590126] 85 key 932 value 2694
[   32.590680] 86 key 947 value 2699
[   32.591205] 87 key 948 value 2700
[   32.591755] 88 key 957 value 1921
[   32.592283] 89 key 958 value 2231
[   32.592832] 90 key 967 value 2174
[   32.593367] 91 key 968 value 2585
[   32.593933] 92 key 2048 value 11
[   32.594449] 93 key 2056 value 808
[   32.595006] 94 key 2057 value 809
[   32.595560] 95 key 2058 value 1068
[   32.596105] 96 key 2059 value 2512
[   32.596677] 97 key 2060 value 937
[   32.597213] 98 key 2062 value 938
[   32.597787] 99 key 2063 value 853
[   32.598321] 100 key 2064 value 1633
[   32.598900] 101 key 2065 value 855
[   32.599446] 102 key 2066 value 1659
[   32.600023] 103 key 2068 value 863
[   32.600591] 104 key 2069 value 904
[   32.601141] 105 key 2070 value 856
[   32.601713] 106 key 2071 value 857
[   32.602261] 107 key 2072 value 905
[   32.602830] 108 key 2073 value 906
[   32.603381] 109 key 2074 value 864
[   32.603952] 110 key 2075 value 865
[   32.604504] 111 key 2076 value 1224
[   32.605090] 112 key 2077 value 1299
[   32.605681] 113 key 2078 value 781
[   32.606255] 114 key 2089 value 996
[   32.606823] 115 key 2090 value 1266
[   32.607375] 116 key 2091 value 1277
[   32.607961] 117 key 2092 value 889
[   32.608508] 118 key 2093 value 549
[   32.609075] 119 key 2094 value 550
[   32.609647] 120 key 2095 value 555
[   32.610190] 121 key 2096 value 1036
[   32.610768] 122 key 2097 value 1018
[   32.611334] 123 key 2098 value 1100
[   32.611918] 124 key 2099 value 1101
[   32.612476] 125 key 2100 value 1896
[   32.613058] 126 key 2101 value 954
[   32.613639] 127 key 2102 value 907
[   32.614194] 128 key 2103 value 925
[   32.614772] 129 key 2104 value 858
[   32.615324] 130 key 2105 value 859
[   32.615900] 131 key 2107 value 1026
[   32.616454] 132 key 2108 value 1001
[   32.617040] 133 key 2109 value 1002
[   32.617628] 134 key 2110 value 1007
[   32.618198] 135 key 2111 value 908
[   32.618769] 136 key 2112 value 1102
[   32.619333] 137 key 2113 value 2689
[   32.619919] 138 key 2114 value 593
[   32.620472] 139 key 2115 value 1097
[   32.621059] 140 key 2116 value 1225
[   32.621646] 141 key 2117 value 1226
[   32.622263] 142 key 2118 value 1236
[   32.622855] 143 key 2119 value 1012
[   32.623427] 144 key 2120 value 1013
[   32.624015] 145 key 2121 value 1278
[   32.624603] 146 key 2122 value 1275
[   32.625169] 147 key 2123 value 1276
[   32.625774] 148 key 2124 value 1308
[   32.626340] 149 key 2125 value 1532
[   32.626946] 150 key 2126 value 1309
[   32.627510] 151 key 2127 value 1242
[   32.628097] 152 key 2128 value 1243
[   32.628683] 153 key 2129 value 1244
[   32.629251] 154 key 2130 value 1332
[   32.629842] 155 key 2131 value 1333
[   32.630412] 156 key 2132 value 995
[   32.630997] 157 key 2133 value 1335
[   32.631594] 158 key 2134 value 721
[   32.632154] 159 key 2135 value 1475
[   32.632749] 160 key 2136 value 1014
[   32.633323] 161 key 2137 value 1015
[   32.633920] 162 key 2138 value 2279
[   32.634501] 163 key 2139 value 1355
[   32.635092] 164 key 2140 value 806
[   32.635668] 165 key 2141 value 1369
[   32.636240] 166 key 2142 value 683
[   32.636826] 167 key 2143 value 1317
[   32.637394] 168 key 2144 value 1374
[   32.637982] 169 key 2145 value 1422
[   32.638570] 170 key 2146 value 1423
[   32.639139] 171 key 2147 value 680
[   32.639723] 172 key 2148 value 710
[   32.640280] 173 key 2149 value 1502
[   32.640897] 174 key 2150 value 1027
[   32.641471] 175 key 2151 value 1216
[   32.642068] 176 key 2152 value 1295
[   32.642652] 177 key 2153 value 1661
[   32.643206] 178 key 2154 value 1662
[   32.643781] 179 key 2155 value 1663
[   32.644340] 180 key 2156 value 1505
[   32.644916] 181 key 2157 value 536
[   32.645456] 182 key 2158 value 537
[   32.646019] 183 key 2160 value 1511
[   32.646599] 184 key 2161 value 1456
[   32.647151] 185 key 2162 value 1457
[   32.647732] 186 key 2166 value 685
[   32.648275] 187 key 2167 value 686
[   32.648846] 188 key 2168 value 1542
[   32.649397] 189 key 2169 value 1056
[   32.649972] 190 key 2170 value 1955
[   32.650525] 191 key 2171 value 1366
[   32.651096] 192 key 2175 value 1545
[   32.651669] 193 key 2176 value 2160
[   32.652216] 194 key 2177 value 1547
[   32.652778] 195 key 2178 value 1367
[   32.653325] 196 key 2179 value 1368
[   32.653906] 197 key 2180 value 2355
[   32.654479] 198 key 2182 value 1490
[   32.655053] 199 key 2183 value 1491
[   32.655635] 200 key 2188 value 2223
[   32.656202] 201 key 2189 value 1370
[   32.656793] 202 key 2190 value 1371
[   32.657363] 203 key 2193 value 1815
[   32.660922] 204 key 2196 value 910
[   32.661474] 205 key 2197 value 1800
[   32.662062] 
[   32.662062] 
[   32.662062] origin
[   32.662872] flags 1 blocknr 272 nr_entries 14
[   32.663608] 0 key 0 value 292
[   32.664078] 1 key 210 value 273
[   32.664603] 2 key 556 value 279
[   32.665107] 3 key 2198 value 283
[   32.665661] 4 key 2552 value 274
[   32.666183] 5 key 4202 value 270
[   32.666726] 6 key 4729 value 287
[   32.667240] 7 key 6425 value 275
[   32.667790] 8 key 8257 value 290
[   32.668323] 9 key 8431 value 271
[   32.668884] 10 key 8638 value 269
[   32.669488] 11 key 10492 value 268
[   32.670119] 12 key 12422 value 276
[   32.670733] 13 key 14427 value 289
[   32.671423] found block 272
[   32.673171] fail io
[   32.702095] device-mapper: thin: 252:0: metadata operation 'dm_pool_commit_metadata' failed: error = -5
[   32.703848] device-mapper: thin: 252:0: aborting current metadata transaction
[   32.707844] __find_block: root 266
[   32.709653] 
[   32.709653] 
[   32.709653] dump origin(pmd root 266):
[   32.710882] flags 1 blocknr 272 nr_entries 14
[   32.711680] 0 key 0 value 292
[   32.712213] 1 key 210 value 273
[   32.712791] 2 key 556 value 279
[   32.713362] 3 key 2198 value 283
[   32.713960] 4 key 2552 value 274
[   32.714531] 5 key 4202 value 270
[   32.715212] 6 key 4729 value 287
[   32.715826] 7 key 6425 value 275
[   32.716413] 8 key 8257 value 290
[   32.717027] 9 key 8431 value 271
[   32.717644] 10 key 8638 value 269
[   32.718233] 11 key 10492 value 268
[   32.718863] 12 key 12422 value 276
[   32.719459] 13 key 14427 value 289
[   32.720113] Kernel panic - not syncing: DONE
[   32.720880] CPU: 0 PID: 127 Comm: kworker/u4:6 Not tainted 5.10.0-02750-g63e393693738-dirty #443
[   32.722388] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc314
[   32.724702] Workqueue: dm-thin do_worker
[   32.725396] Call Trace:
[   32.725860]  dump_stack+0xa6/0xd5
[   32.726480]  panic+0x164/0x491
[   32.727039]  btree_lookup_raw.constprop.0.cold+0x3b/0x3b
[   32.727999]  dm_btree_lookup+0xc5/0x160
[   32.728711]  __find_block+0x84/0x100
[   32.729348]  ? queue_io+0x77/0xa0
[   32.729988]  dm_thin_find_block+0x58/0xb0
[   32.730713]  __process_bio_read_only+0x60/0x2e0
[   32.731513]  process_cell_read_only+0x19/0x30
[   32.732289]  do_worker+0x338/0xe80
[   32.732897]  ? pwq_activate_delayed_work+0x53/0x130
[   32.733757]  process_one_work+0x27c/0x5f0
[   32.734475]  worker_thread+0x28b/0x6b0
[   32.735143]  ? rescuer_thread+0x590/0x590
[   32.735851]  kthread+0x153/0x1b0
[   32.736426]  ? kthread_flush_work+0x170/0x170
[   32.737246]  ret_from_fork+0x1f/0x30
[   32.737972] Kernel Offset: disabled
[   32.738622] ---[ end Kernel panic - not syncing: DONE ]---
```

【附件信息】
diff
```
diff --git a/block/blk-core.c b/block/blk-core.c
index d0dbb67fe46d..389e75d47209 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -739,10 +739,14 @@ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part)
 	return false;
 }
 
+struct bio *g_bio;
 static noinline int should_fail_bio(struct bio *bio)
 {
-	if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size))
+	if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size) || bio == g_bio) {
+		pr_err("fail io\n");
+		g_bio = (void *)-1;
 		return -EIO;
+	}
 	return 0;
 }
 ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 50f3e673729c..d938e19f85c2 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/rbtree.h>
 #include <linux/stacktrace.h>
+#include "persistent-data/dm-btree-internal.h"
 
 #define DM_MSG_PREFIX "bufio"
 
@@ -165,6 +166,8 @@ struct dm_buffer {
 
 #define dm_bufio_in_request()	(!!current->bio_list)
 
+static void read_endio(struct dm_buffer *b, blk_status_t status);
+
 static void dm_bufio_lock(struct dm_bufio_client *c)
 {
 	mutex_lock_nested(&c->lock, dm_bufio_in_request());
@@ -615,6 +618,9 @@ static void bio_complete(struct bio *bio)
 	b->end_io(b, status);
 }
 
+int g_found = 0;
+extern struct bio *g_bio;
+
 static void use_bio(struct dm_buffer *b, int rw, sector_t sector,
 		    unsigned n_sectors, unsigned offset)
 {
@@ -633,6 +639,11 @@ static void use_bio(struct dm_buffer *b, int rw, sector_t sector,
 		return;
 	}
 
+	if (!g_bio && g_found && g_found == b->block) {
+		pr_err("found block %llu\n", b->block);
+		g_bio = bio;
+	}
+
 	bio->bi_iter.bi_sector = sector;
 	bio_set_dev(bio, b->c->bdev);
 	bio_set_op_attrs(bio, rw, 0);
@@ -742,6 +753,8 @@ static void write_endio(struct dm_buffer *b, blk_status_t status)
  * - Submit our write and don't wait on it. We set B_WRITING indicating
  *   that there is a write in progress.
  */
+extern int g_blocks[100000];
+
 static void __write_dirty_buffer(struct dm_buffer *b,
 				 struct list_head *write_list)
 {
@@ -754,6 +767,35 @@ static void __write_dirty_buffer(struct dm_buffer *b,
 	b->write_start = b->dirty_start;
 	b->write_end = b->dirty_end;
 
+	if (!g_found && g_blocks[b->block] >= 2) {
+		struct btree_node *node = b->data;
+		struct dm_buffer bu;
+		memcpy(&bu, b, sizeof(bu));
+		char data[4096];
+		bu.data = (void *)data;
+
+		bu.state = 1 << B_READING;
+		submit_io(&bu, REQ_OP_READ, read_endio);
+		wait_on_bit_io(&bu.state, B_READING, TASK_UNINTERRUPTIBLE);
+		if (bu.read_error)
+			panic("WRONG\n");
+
+		if (le32_to_cpu(node->header.flags) == 2 && le32_to_cpu(((struct btree_node *)bu.data)->header.flags) == 1 && le32_to_cpu(node->header.nr_entries) != le32_to_cpu(((struct btree_node *)bu.data)->header.nr_entries)) {
+			int i;
+
+			g_found = b->block;
+			pr_err("current\n");
+			pr_err("flags %u blocknr %llu nr_entries %u\n", le32_to_cpu(node->header.flags), b->block, le32_to_cpu(node->header.nr_entries));
+			for (i = 0; i < le32_to_cpu(node->header.nr_entries); ++i)
+				pr_err("%d key %llu value %llu\n", i, le64_to_cpu(node->keys[i]), value64(node, i) >> 24);
+			pr_err("\n\norigin\n");
+			node = (struct btree_node *)bu.data;
+			pr_err("flags %u blocknr %u nr_entries %u\n", le32_to_cpu(node->header.flags), le32_to_cpu(node->header.blocknr), le32_to_cpu(node->header.nr_entries));
+			for (i = 0; i < le32_to_cpu(node->header.nr_entries); ++i)
+				pr_err("%d key %llu value %llu\n", i, le64_to_cpu(node->keys[i]), value64(node, i));
+		}
+	}
+
 	if (!write_list)
 		submit_io(b, REQ_OP_WRITE, write_endio);
 	else
diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 5961caf17c71..3b1ad2497c8f 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1487,6 +1487,7 @@ static void unpack_lookup_result(struct dm_thin_device *td, __le64 value,
 	result->shared = __snapshotted_since(td, exception_time);
 }
 
+extern int g_read_only, g_root;
 static int __find_block(struct dm_thin_device *td, dm_block_t block,
 			int can_issue_io, struct dm_thin_lookup_result *result)
 {
@@ -1495,12 +1496,19 @@ static int __find_block(struct dm_thin_device *td, dm_block_t block,
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[2] = { td->id, block };
 	struct dm_btree_info *info;
+	static int pr = 0;
 
 	if (can_issue_io) {
 		info = &pmd->info;
 	} else
 		info = &pmd->nb_info;
 
+	if (!pr && g_read_only) {
+		pr = 1;
+		pr_err("%s: root %llu\n", __func__, pmd->root);
+		g_root = pmd->root;
+	}
+
 	r = dm_btree_lookup(info, pmd->root, keys, &value);
 	if (!r)
 		unpack_lookup_result(td, value, result);
@@ -1613,14 +1621,18 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
 	__le64 value;
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[2] = { td->id, block };
+	dm_block_t old;
 
 	value = cpu_to_le64(pack_block_time(data_block, pmd->time));
 	__dm_bless_for_disk(&value);
 
+	old = pmd->root;
 	r = dm_btree_insert_notify(&pmd->info, pmd->root, keys, &value,
 				   &pmd->root, &inserted);
 	if (r)
 		return r;
+	if (old != pmd->root)
+		pr_err("update root %llu\n", pmd->root);
 
 	td->changed = true;
 	if (inserted)
@@ -1665,7 +1677,7 @@ static int __remove_range(struct dm_thin_device *td, dm_block_t begin, dm_block_
 	struct dm_pool_metadata *pmd = td->pmd;
 	dm_block_t keys[1] = { td->id };
 	__le64 value;
-	dm_block_t mapping_root;
+	dm_block_t mapping_root, old;
 
 	/*
 	 * Find the mapping tree
@@ -1680,10 +1692,13 @@ static int __remove_range(struct dm_thin_device *td, dm_block_t begin, dm_block_
 	 */
 	mapping_root = le64_to_cpu(value);
 	dm_tm_inc(pmd->tm, mapping_root);
+	old = pmd->root;
 	r = dm_btree_remove(&pmd->tl_info, pmd->root, keys, &pmd->root);
 	if (r)
 		return r;
 
+	if (old != pmd->root)
+		pr_err("update root %llu\n", pmd->root);
 	/*
 	 * Remove leaves stops at the first unmapped entry, so we have to
 	 * loop round finding mapped ranges.
@@ -1857,6 +1872,7 @@ int dm_pool_commit_metadata(struct dm_pool_metadata *pmd)
 	 * Open the next transaction.
 	 */
 	r = __begin_transaction(pmd);
+	pr_err("[NEW TRANS] pwd root %llu\n", pmd->root);
 out:
 	pmd_write_unlock(pmd);
 	return r;
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index e837839e4def..2965f63ffccd 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2524,6 +2524,7 @@ static void set_discard_callbacks(struct pool *pool)
 	}
 }
 
+int g_read_only;
 static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 {
 	struct pool_c *pt = pool->ti->private;
@@ -2567,6 +2568,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 	case PM_OUT_OF_METADATA_SPACE:
 	case PM_READ_ONLY:
 		dm_pool_metadata_read_only(pool->pmd);
+		g_read_only = 1;
 		pool->process_bio = process_bio_read_only;
 		pool->process_discard = process_bio_success;
 		pool->process_cell = process_cell_read_only;
diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index ee3e63aa864b..10ae54d50f23 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -343,6 +343,9 @@ EXPORT_SYMBOL_GPL(dm_btree_del);
 
 /*----------------------------------------------------------------*/
 
+#include <linux/delay.h>
+int g_root;
+extern int g_found, g_read_only;
 static int btree_lookup_raw(struct ro_spine *s, dm_block_t block, uint64_t key,
 			    int (*search_fn)(struct btree_node *, uint64_t),
 			    uint64_t *result_key, void *v, size_t value_size)
@@ -355,6 +358,14 @@ static int btree_lookup_raw(struct ro_spine *s, dm_block_t block, uint64_t key,
 		if (r < 0)
 			return r;
 
+		if (g_found && g_found == block && g_read_only) {
+			printk_ratelimited("\n\ndump origin(pmd root %d):\n", g_root);
+			pr_err("flags %u blocknr %u nr_entries %u\n", le32_to_cpu(ro_node(s)->header.flags), le32_to_cpu(ro_node(s)->header.blocknr), le32_to_cpu(ro_node(s)->header.nr_entries));
+			for (i = 0; i < le32_to_cpu(ro_node(s)->header.nr_entries); ++i)
+				pr_err("%d key %llu value %llu\n", i, le64_to_cpu(ro_node(s)->keys[i]), value64(ro_node(s), i));
+			panic("DONE");
+		}
+
 		i = search_fn(ro_node(s), key);
 
 		flags = le32_to_cpu(ro_node(s)->header.flags);
@@ -532,6 +543,7 @@ EXPORT_SYMBOL_GPL(dm_btree_lookup_next);
  *
  * Where A* is a shadow of A.
  */
+int g_blocks[100000];
 static int btree_split_sibling(struct shadow_spine *s, unsigned parent_index,
 			       uint64_t key)
 {
@@ -588,6 +600,9 @@ static int btree_split_sibling(struct shadow_spine *s, unsigned parent_index,
 		return r;
 	}
 
+	pr_err("ALLOC2 new block %llu\n", dm_block_location(right));
+	g_blocks[dm_block_location(right)]++;
+
 	if (key < le64_to_cpu(rn->keys[0])) {
 		unlock_block(s->info, right);
 		s->nodes[1] = left;
@@ -687,6 +702,10 @@ static int btree_split_beneath(struct shadow_spine *s, uint64_t key)
 	pn->keys[1] = rn->keys[0];
 	memcpy_disk(value_ptr(pn, 1), &val, sizeof(__le64));
 
+	pr_err("ALLOC new block %llu %llu\n", dm_block_location(left), dm_block_location(right));
+	g_blocks[dm_block_location(right)]++;
+	g_blocks[dm_block_location(left)]++;
+
 	unlock_block(s->info, left);
 	unlock_block(s->info, right);
 	return 0;
```
test.sh
```
#!/bin/bash

dmesg -c
umount temp
dmsetup remove_all

dd if=/dev/zero of=/dev/sda bs=1M count=100
dmsetup create pool --table "0 2097152 thin-pool /dev/sda /dev/sdb 128 0"
dmsetup message /dev/mapper/pool 0 "create_thin 0"
dmsetup create thin --table "0 2097152 thin /dev/mapper/pool 0"

mkfs.ext4 -F /dev/dm-1
mount -odiscard /dev/dm-1 /root/temp
./xfstests-dev/ltp/fsstress -d temp -l0 -n 1000 -p 4
#while true; do dd if=/dev/zero of=/root/temp/file bs=1M && sync; rm -f file; sync; done
```

GVP openEuler/kernel

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