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

Anand Jain <anand.jain@xxxxxxxxxx> · Tue, 30 Jan 2018 18:04:40 +0800

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@xxxxxxxxxx>
---
  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;
  		}

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