Re: [PATCH 2/2] btrfs: drop optimal argument from find_live_mirror()

[Anand Jain <anand.jain@oracle.com>]

On 01/30/2018 05:12 PM, Nikolay Borisov wrote:
> 
> 
> On 30.01.2018 08:28, Anand Jain wrote:
>> Drop optimal argument from the function find_live_mirror()
>> as we can deduce it in the function itself.
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>>   fs/btrfs/volumes.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index 9c9d987838c2..a61715677b67 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -5253,10 +5253,11 @@ int btrfs_is_parity_mirror(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
>>   
>>   static int find_live_mirror(struct btrfs_fs_info *fs_info,
>>   			    struct map_lookup *map, int first,
>> -			    int optimal, int dev_replace_is_ongoing)
>> +			    int dev_replace_is_ongoing)
>>   {
>>   	int i;
>>   	int num;
>> +	int optimal;
>>   	int tolerance;
>>   	struct btrfs_device *srcdev;
>>   
>> @@ -5268,6 +5269,8 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
>>   	else
>>   		num = map->num_stripes;
>>   
>> +	optimal = first + current->pid % num;
>> +
>>   	if (dev_replace_is_ongoing &&
>>   	    fs_info->dev_replace.cont_reading_from_srcdev_mode ==
>>   	     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID)
>> @@ -5821,7 +5824,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>>   			stripe_index = mirror_num - 1;
>>   		else {
>>   			stripe_index = find_live_mirror(fs_info, map, 0,
>> -					    current->pid % map->num_stripes,
>>   					    dev_replace_is_ongoing);
>>   			mirror_num = stripe_index + 1;
>>   		}
>> @@ -5849,8 +5851,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>>   			int old_stripe_index = stripe_index;
>>   			stripe_index = find_live_mirror(fs_info, map,
>>   					      stripe_index,
>> -					      stripe_index +
>> -					      current->pid % map->sub_stripes,
> 
> The value of optimal here (BTRFS_BLOCK_GROUP_RAID10) is different than
> the value of optimal in BTRFS_BLOCK_GROUP_RAID1 case. So you need to put
> optimal in the conditional branch you added in the previous patch. In
> raid 1 case:
> 
> optimal = current->pid % num;
> 
> In raid 10:
> 
> optimal = first + current->pid % num;
> 
> to current semantics

  First/stripe_index is 0 for RAID1. So I purposely kept it like this 
for easy code flow.

Thanks, Anand

>>   					      dev_replace_is_ongoing);
>>   			mirror_num = stripe_index - old_stripe_index + 1;
>>   		}
>>