On 07/20/2016 09:49 PM, Wang Xiaoguang wrote:
hello,
On 07/20/2016 09:18 PM, Josef Bacik wrote:
On 07/20/2016 01:56 AM, Wang Xiaoguang wrote:
In prealloc_file_extent_cluster(), btrfs_check_data_free_space() uses
wrong file offset for reloc_inode, it uses cluster->start and cluster->end,
which indeed are extent's bytenr. The correct value should be
cluster->[start|end] minus block group's start bytenr.
start bytenr cluster->start
| | extent | extent | ...| extent |
|----------------------------------------------------------------|
| block group reloc_inode |
Signed-off-by: Wang Xiaoguang <wangxg.f...@cn.fujitsu.com>
---
fs/btrfs/relocation.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 0477dca..a0de885 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3030,12 +3030,14 @@ int prealloc_file_extent_cluster(struct inode *inode,
u64 num_bytes;
int nr = 0;
int ret = 0;
+ u64 prealloc_start = cluster->start - offset;
+ u64 prealloc_end = cluster->end - offset;
BUG_ON(cluster->start != cluster->boundary[0]);
inode_lock(inode);
- ret = btrfs_check_data_free_space(inode, cluster->start,
- cluster->end + 1 - cluster->start);
+ ret = btrfs_check_data_free_space(inode, prealloc_start,
+ prealloc_end + 1 - prealloc_start);
if (ret)
goto out;
@@ -3056,8 +3058,8 @@ int prealloc_file_extent_cluster(struct inode *inode,
break;
nr++;
}
- btrfs_free_reserved_data_space(inode, cluster->start,
- cluster->end + 1 - cluster->start);
+ btrfs_free_reserved_data_space(inode, prealloc_start,
+ prealloc_end + 1 - prealloc_start);
out:
inode_unlock(inode);
return ret;
This ends up being the same amount. Consider this scenario
bg bytenr = 4096
cluster->start = 8192
cluster->end = 12287
cluster->end + 1 - cluster->start = 4096
prealloc_start = cluster->start - offset = 0
prealloc_end = cluster->end - offset = 8191
prealloc_end + 1 - prealloc_start = 4096
You shift both by the same amount, which gives you the same answer. Thanks,
Thanks for reviewing.
Yes, I know the amount of preallocated data space is the same, this patch
does not fix any bugs :)
For every block group to be balanced, we create a corresponding inode.
For this inode, the initial offset should be 0. In your above example,
before this patch, it's btrfs_free_reserved_data_space(inode, 8192, 4096);
with this patch, it's btrfs_free_reserved_data_space(inode, 4096, 4096).
I just want to make btrfs_free_reserved_data_space()'s 'start' argument
be offset inside block group, not offset inside whole fs byternr space. I'm not
a English native, hope that I have expressed what I want to :)
But yes, I'm also OK with removing this patch.
Oh I see, ok that's fine if we're just trying to make it look sane then go for
it.
Signed-off-by: Josef Bacik <jba...@fb.com>
Thanks,
Josef
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