-------- Original Message --------
Subject: Re: [PATCH 1/2] btrfs-progs: Fix a bug in __btrfs_map_block()
always maps wrong stripe for DUP/RAID1
From: David Sterba <dste...@suse.cz>
To: Qu Wenruo <quwen...@cn.fujitsu.com>
Date: 2015年05月22日 00:06
On Mon, May 11, 2015 at 08:45:47AM +0800, Qu Wenruo wrote:
In __btrfs_map_block(), stripe_index is always wrong if mirror_num is
given.
For DUP/RAID1 case, if mirror_num is given, e.g. 1, it should return the
second stripe.
But codes consider the mirror_num is start from 1 and always minus 1,
causing even mirror number is given as 1, __btrfs_map_block() will still
map the first stripe not the second.
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
volumes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/volumes.c b/volumes.c
index 16dbf64..c66c02a 100644
--- a/volumes.c
+++ b/volumes.c
@@ -1397,7 +1397,7 @@ again:
- stripe_index = mirror_num - 1;
+ stripe_index = mirror_num;
@@ -1416,7 +1416,7 @@ again:
- stripe_index = mirror_num - 1;
+ stripe_index = mirror_num;
The original code is same in kernel, is the logic different in the
userspace code? If yes I don't see it.
It seems that I was confused about mirror_num of btrfs_map_block function.
When mirror mirror_num 0, it will map all stripes and if larger than 0,
it will map the <mirror_num>th stripe.
So when mirror_num is given 1, it should return the first stripe.
And it's the correct behavior.
If I am wrong again, please correct me.
Please ignore the patch.
Thanks,
Qu
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