[BUG]
If the first copy of a tree block has a bad key order, but the second
copy is completely good, then "btrfs ins dump-tree -b <bytenr>" fails to
print anything past the bad key:
leaf 29786112 items 47 free space 983 generation 20 owner EXTENT_TREE
leaf 29786112 flags 0x1(WRITTEN) backref revision 1
fs uuid 3381d111-94a3-4ac7-8f39-611bbbdab7e6
chunk uuid 9af1c3c7-2af5-488b-8553-530bd515f14c
[snip]
item 9 key (20975616 METADATA_ITEM 0) itemoff 3543 itemsize 33
refs 1 gen 16 flags TREE_BLOCK
tree block skinny level 0
tree block backref root CHUNK_TREE
item 10 key (29360128 BLOCK_GROUP_ITEM 33554432) itemoff 3519 itemsize
24
block group used 94208 chunk_objectid 256 flags METADATA|DUP
ERROR: leaf 29786112 slot 11 pointer invalid, offset 1245184 size 0 leaf data
limit 3995
ERROR: skip remaining slots
While kernel can locate the good copy and acts just like nothing
happened.
[CAUSE]
btrfs-progs uses read_tree_block() to try each copy. But it only uses
less strict check_tree_block(), which has less sanity check than
btrfs_check_node/leaf().
Some error like bad key order is ignored to allow btrfs check to fix it.
This leads to above problem.
[FIX]
Introduce a new member, @candidate_mirror in read_tree_block(), which
records the copy passes check_tree_block() but fails
btrfs_check_leaf/node() as last chance.
Only if no better copy found, then use @candidate_mirror.
So btrfs-progs can act just like kernel to use best copy.
Reported-by: Yoon Jungyeon <jungy...@gatech.edu>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202691
[Inspired by that image, not to fix any bug of that bugzilla]
Signed-off-by: Qu Wenruo <w...@suse.com>
---
disk-io.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/disk-io.c b/disk-io.c
index 1736d4a1f94b..737f1cdf6f4c 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -327,6 +327,7 @@ struct extent_buffer* read_tree_block(struct btrfs_fs_info
*fs_info, u64 bytenr,
u32 sectorsize = fs_info->sectorsize;
int mirror_num = 1;
int good_mirror = 0;
+ int candidate_mirror = 0;
int num_copies;
int ignore = 0;
@@ -362,10 +363,30 @@ struct extent_buffer* read_tree_block(struct
btrfs_fs_info *fs_info, u64 bytenr,
&fs_info->recow_ebs);
eb->refs++;
}
- btrfs_set_buffer_uptodate(eb);
- return eb;
+
+ /*
+ * check_tree_block() is less strict to allow btrfs
+ * check to get raw eb with bad key order and fix it.
+ * But we still need to try to get a good copy if
+ * possible, or bad key order can go into tools like
+ * btrfs ins dump-tree.
+ */
+ if (btrfs_header_level(eb))
+ ret = btrfs_check_node(fs_info, NULL, eb);
+ else
+ ret = btrfs_check_leaf(fs_info, NULL, eb);
+ if (!ret || candidate_mirror == mirror_num) {
+ btrfs_set_buffer_uptodate(eb);
+ return eb;
+ }
+ if (candidate_mirror <= 0)
+ candidate_mirror = mirror_num;
}
if (ignore) {
+ if (candidate_mirror > 0) {
+ mirror_num = candidate_mirror;
+ continue;
+ }
if (check_tree_block(fs_info, eb)) {
if (!fs_info->suppress_check_block_errors)
print_tree_block_error(fs_info, eb,
@@ -387,7 +408,10 @@ struct extent_buffer* read_tree_block(struct btrfs_fs_info
*fs_info, u64 bytenr,
}
mirror_num++;
if (mirror_num > num_copies) {
- mirror_num = good_mirror;
+ if (candidate_mirror > 0)
+ mirror_num = candidate_mirror;
+ else
+ mirror_num = good_mirror;
ignore = 1;
continue;
}
--
2.21.0
