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.

CC: stable@vger.kernel.org # 5.4+ Reported-by: Marc Lehmann schmorp@schmorp.de Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: Josef Bacik josef@toxicpanda.com --- 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 64b6e1d44f47..4bb4e3c3531f 100644 --- a/fs/btrfs/space-info.c +++ b/fs/btrfs/space-info.c @@ -336,25 +336,21 @@ 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