@@ -3884,7 +3884,14 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
}
}
- num_devices = btrfs_num_devices(fs_info);
+ /*
+ * Balance is an exculsive operation, so no operation that's going to
+ * affect rw_devices can run concurrent with it, thus it is safe to
+ * simply grab the value. We want rw_devices because we do not want to
+ * allow restriping if we don't have enough devices we can actually
+ * allocate from.
+ */
+ num_devices = fs_info->fs_devices->rw_devices;
/*
* SINGLE profile on-disk has no profile bit, but in-memory we have a
While running xfstests with compression on I noticed I was panicing on btrfs/154. I bisected this down to my inc_block_group_ro patches, which was strange. What was happening is with my patches we now use btrfs_can_overcommit() to see if we can flip a block group read only. Before this would fail because we weren't taking into account the usable un-allocated space for allocating chunks. With my patches we were allowed to do the balance, which is technically correct. However this test is testing restriping with a degraded mount, something that isn't working right because Anand's fix for the test was never actually merged. So now we're trying to allocate a chunk and cannot because we want to allocate a RAID1 chunk, but there's only 1 device that's available for usage. This results in an ENOSPC in one of the BUG_ON(ret) paths in relocation (and a tricky path that is going to take many more patches to fix.) But we shouldn't even be making it this far, we don't have enough devices to restripe. The problem is we're using btrfs_num_devices(), which for some reason includes missing devices. That's not actually what we want, we want the rw_devices. Fix this by getting the rw_devices. With this patch we're no longer panicing with my other patches applied, and we're in fact erroring out at the correct spot instead of at inc_block_group_ro. The fact that this was working before was just sheer dumb luck. Fixes: e4d8ec0f65b9 ("Btrfs: implement online profile changing") Signed-off-by: Josef Bacik <josef@toxicpanda.com> --- fs/btrfs/volumes.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)