On 3/11/20 9:01 PM, Qu Wenruo wrote:
On 2020/3/11 下午7:33, Anand Jain wrote:
For chunk type Single, %metadata_profile and %data_profile in
create_raid_groups() is NULL, so we continue to use the initially
created 8MB chunks for both metadata and data.
8MB is too small. Kernel default chunk size for type Single is 256MB.
Further the mkfs.btrfs created chunk will stay unless relocated or
cleanup during balance. Consider an ENOSPC case due to 8MB metadata
full.
I don't see any reason that mkfs.btrfs should create 8MB chunks for
chunk type Single instead it could match it with the kernel allocation
size of 256MB for the chunk type Single.
For other chunk-types the create_one_raid_group() is called and creates
the required bigger chunks and there is no change with this patch. Also
for fs sizes (-b option) smaller than 256MB there is no issue as the
chunks sizes are 10% of the requested fs-size until the maximum of
256MB.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
The fio in generic/299 is failing to create the files which shall be
deleted in the later part of the test case and the failure happens
only with the MKFS_OPTIONS="-n64K -msingle" only and not with other types
of chunks. This is bit inconsistent. And it appears that in case of
Single chunk type it fails to create (or touch) the necessary file
as the metadata is full, so increasing the metadata chunk size to the
sizes as kernel would create will add consistency.
Have you tried all existing btrfs-progs test cases?
IIRC there are some minimal device related corner cases preventing us
from using larger default chunk size.
I forgot btrfs-progs tests. Will run them.
Despite that, for generic/299 error, I believe it should be more
appropriate to address the problem in ticket space system
Agreed.
other than
initial metadata chunk size.
As btrfs can do metadata overcommit as long as we have enough
unallocated space, thus the initial chunk size should make minimal impact.
IMO problem is if all the unallocated space has been occupied by
the data chunks leading to enospc for the metadata then we have an
imbalance which we didn't design in the kernel.
To further debug enospc issues, the approach should be an ability to
tune chunk sizes on demand. Generally inconsistency makes debugging
more difficult. IMO it ok to fix the inconsistency in the chunk sizes.
Thanks, Anand
But don't get me wrong, I'm pretty fine with the unified minimal chunk size.
Just don't believe it's the proper fix for your problem, and want to be
extra safe before we hit some strange problems.
Thanks,
Qu
volumes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/volumes.c b/volumes.c
index b46bf5988a95..d56f2fc897e3 100644
--- a/volumes.c
+++ b/volumes.c
@@ -1004,7 +1004,7 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
struct list_head *cur;
struct map_lookup *map;
int min_stripe_size = SZ_1M;
- u64 calc_size = SZ_8M;
+ u64 calc_size = SZ_256M;
u64 min_free;
u64 max_chunk_size = 4 * calc_size;
u64 avail = 0;
