-------- Original Message --------
Subject: Re: [PATCH] btrfs-progs: rebuild missing block group during
chunk recovery if possible
From: Alex Lyakas <alex.bt...@zadarastorage.com>
To: Qu Wenruo <quwen...@cn.fujitsu.com>
Date: 2014年12月24日 16:49
Hi Qu,
On Wed, Dec 24, 2014 at 3:09 AM, Qu Wenruo <quwen...@cn.fujitsu.com> wrote:
-------- Original Message --------
Subject: Re: [PATCH] btrfs-progs: rebuild missing block group during chunk
recovery if possible
From: Alex Lyakas <alex.bt...@zadarastorage.com>
To: Qu Wenruo <quwen...@cn.fujitsu.com>
Date: 2014年12月24日 00:49
Hi Qu,
On Thu, Oct 30, 2014 at 4:54 AM, Qu Wenruo <quwen...@cn.fujitsu.com>
wrote:
[snipped]
+
+static int __insert_block_group(struct btrfs_trans_handle *trans,
+ struct chunk_record *chunk_rec,
+ struct btrfs_root *extent_root,
+ u64 used)
+{
+ struct btrfs_block_group_item bg_item;
+ struct btrfs_key key;
+ int ret = 0;
+
+ btrfs_set_block_group_used(&bg_item, used);
+ btrfs_set_block_group_chunk_objectid(&bg_item, used);
This looks like a bug. Instead of "used", I think it should be
"BTRFS_FIRST_CHUNK_TREE_OBJECTID".
Oh, my mistake, BTRFS_FIRST_CHUNK_TREE_OBJECTID is right.
Thanks for pointing out this.
[snipped]
--
2.1.2
Couple of questions:
# In remove_chunk_extent_item, should we also consider "rebuild"
chunks now? It can happen that a "rebuild" chunks is a SYSTEM chunk.
Should we try to handle it as well?
Not quite sure about the meaning of "rebuild" here.
The chunk-recovery has the rebuild_chunk_tree() function to rebuild the
whole chunk tree with
the good/repaired chunks we found.
# Same question for "rebuild_sys_array". Should we also consider
"rebuild" chunks?
The chunk-recovery has rebuild_sys_array() to handle SYSTEM chunk too.
I meant that with this patch you have added "rebuild_chunks" list:
struct list_head good_chunks;
struct list_head bad_chunks;
struct list_head rebuild_chunks; <--- you added this
struct list_head unrepaired_chunks;
Oh, now I understand it.
These are chunks that have no block-group record, but we are confident
that we can rebuild the block-group records for these chunks by
scanning all EXTENT_ITEMs in the block-group range and calculating the
"used" value for the block-group. If we fail, we just set
used==block-group size. My question is: should we now consider those
"rebuild_chunks" same as "good_chunks"? I.e., should we also consider
those chunks in the following functions:
- remove_chunk_extent_item: probably no, because we need the
EXTENT_ITEMs to recalculate the "used" value
Yep, no need to remove extents.
- rebuild_sys_array: if it happens that a "rebuild_chunk" is also a
SYSTEM chunk, should we add it to the sys_chunk_array too? (In
addition to good_chunks).
That's right, it should be added to SYSTEM chunks.
Great thanks for reviewing and pointing out this!
Thanks,
Qu
Thanks,
Alex.
Thanks,
Qu
Thanks,
Alex.
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