Re: [PATCH 5/5] btrfs: zoned: make auto-reclaim less aggressive

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 23/03/2022 10:14, Pankaj Raghav wrote:
> 
> 
> On 2022-03-23 10:11, Johannes Thumshirn wrote:
>> On 23/03/2022 10:09, Pankaj Raghav wrote:
>>> I am also noticing the same behaviour for ZNS drive with size 1280M:
>>>
>>> [   86.276409] btrfs: factor: 350 used: 1409286144, total: 402653184
>>>
>>> Is something going wrong with the calculation? Or am I missing something
>>> here?
>>>
>>
>> Apparently I'm either too dumb for basic maths, or 
>> btrfs_calc_available_free_space() doesn't give us the values we're expecting.
>>
> I would say the latter :)
>> I'll recheck.
> Let me know if you can also reproduce the results.
> 

It looks like we can't use btrfs_calc_available_free_space(), can
you try this one on top:

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index f2a412427921..4a6c1f1a7223 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2082,23 +2082,27 @@ void btrfs_free_zone_cache(struct btrfs_fs_info *fs_info)
 
 bool btrfs_zoned_should_reclaim(struct btrfs_fs_info *fs_info)
 {
-       struct btrfs_space_info *sinfo;
+       struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+       struct btrfs_device *device;
        u64 used = 0;
        u64 total = 0;
        u64 factor;
 
-       if (!btrfs_is_zoned(fs_info))
-               return false;
-
        if (!fs_info->bg_reclaim_threshold)
                return false;
 
-       list_for_each_entry(sinfo, &fs_info->space_info, list) {
-               total += sinfo->total_bytes;
-               used += btrfs_calc_available_free_space(fs_info, sinfo,
-                                                       BTRFS_RESERVE_NO_FLUSH);
+
+       mutex_lock(&fs_devices->device_list_mutex);
+       list_for_each_entry(device, &fs_devices->devices, dev_list) {
+               if (!device->bdev)
+                       continue;
+
+               total += device->disk_total_bytes;
+               used += device->bytes_used;
+
        }
+       mutex_unlock(&fs_devices->device_list_mutex);
 
-       factor = div_u64(used * 100, total);
+       factor = div64_u64(used * 100, total);
        return factor >= fs_info->bg_reclaim_threshold;
 }