For the following disk layout, can_overcommit() can cause false
confidence in available space:
devid 1 unallocated: 1T
devid 2 unallocated: 10T
metadata type: RAID1
As can_overcommit() simply uses unallocated space with factor to
calculate the allocatable metadata chunk size.
can_overcommit() believes we still have 5.5T for metadata chunks, while
the truth is, we only have 1T available for metadata chunks.
This can lead to ENOSPC at run_delalloc_range() and cause transaction
abort.
Since factor based calculation can't distinguish RAID1/RAID10 and DUP at
all, we need proper chunk-allocator level awareness to do such estimation.
Thankfully, we have per-profile available space already calculated, just
use that facility to avoid such false confidence.
Reported-by: Marc Lehmann <schmorp@xxxxxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
fs/btrfs/space-info.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 41ee88633769..f3b4e14f3727 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -310,25 +310,21 @@ static u64 calc_available_free_space(struct btrfs_fs_info *fs_info,
struct btrfs_space_info *space_info,
enum btrfs_reserve_flush_enum flush)
{
+ enum btrfs_raid_types index;
u64 profile;
u64 avail;
- int factor;
if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
profile = btrfs_system_alloc_profile(fs_info);
else
profile = btrfs_metadata_alloc_profile(fs_info);
- avail = atomic64_read(&fs_info->free_chunk_space);
-
/*
- * If we have dup, raid1 or raid10 then only half of the free
- * space is actually usable. For raid56, the space info used
- * doesn't include the parity drive, so we don't have to
- * change the math
+ * Grab avail space from per-profile array which should be as accurate
+ * as chunk allocator.
*/
- factor = btrfs_bg_type_to_factor(profile);
- avail = div_u64(avail, factor);
+ index = btrfs_bg_flags_to_raid_index(profile);
+ avail = atomic64_read(&fs_info->fs_devices->per_profile_avail[index]);
/*
* If we aren't flushing all things, let us overcommit up to
--
2.26.2
