[PATCH] btrfs: Always initialize btrfs_bio::tgtdev_map/raid_map pointers

[PATCH] btrfs: Always initialize btrfs_bio::tgtdev_map/raid_map pointers

[Nikolay Borisov]

Since btrfs_bio always contains the extra space for the tgtdev_map and
raid_maps it's pointless to make the assignment iff specific conditions
are met. Instead, always assign the pointers to their correct value at
allocation time.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/volumes.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index cb9883c7f8b7..1b1fc1485a41 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5522,6 +5522,9 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
 	atomic_set(&bbio->error, 0);
 	refcount_set(&bbio->refs, 1);
 
+	bbio->tgtdev_map = (int *)(bbio->stripes + total_stripes);
+	bbio->raid_map = (u64 *)(bbio->tgtdev_map + real_stripes);
+
 	return bbio;
 }
 
@@ -6144,8 +6147,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 		ret = -ENOMEM;
 		goto out;
 	}
-	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL)
-		bbio->tgtdev_map = (int *)(bbio->stripes + num_alloc_stripes);
 
 	/* build raid_map */
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
@@ -6153,10 +6154,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 		u64 tmp;
 		unsigned rot;
 
-		bbio->raid_map = (u64 *)((void *)bbio->stripes +
-				 sizeof(struct btrfs_bio_stripe) *
-				 num_alloc_stripes +
-				 sizeof(int) * tgtdev_indexes);
 
 		/* Work out the disk rotation on this stripe-set */
 		div_u64_rem(stripe_nr, num_stripes, &rot);
-- 
2.17.1

Re: [PATCH] btrfs: Always initialize btrfs_bio::tgtdev_map/raid_map pointers

[Nikolay Borisov]

On 29.06.20 г. 17:16 ч., Nikolay Borisov wrote:
> Since btrfs_bio always contains the extra space for the tgtdev_map and
> raid_maps it's pointless to make the assignment iff specific conditions
> are met. Instead, always assign the pointers to their correct value at
> allocation time.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/volumes.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index cb9883c7f8b7..1b1fc1485a41 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5522,6 +5522,9 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
>  	atomic_set(&bbio->error, 0);
>  	refcount_set(&bbio->refs, 1);
>  
> +	bbio->tgtdev_map = (int *)(bbio->stripes + total_stripes);
> +	bbio->raid_map = (u64 *)(bbio->tgtdev_map + real_stripes);
> +
>  	return bbio;
>  }
>  
> @@ -6144,8 +6147,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>  		ret = -ENOMEM;
>  		goto out;
>  	}
> -	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL)
> -		bbio->tgtdev_map = (int *)(bbio->stripes + num_alloc_stripes);
>  
>  	/* build raid_map */
>  	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
> @@ -6153,10 +6154,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
>  		u64 tmp;
>  		unsigned rot;
>  
> -		bbio->raid_map = (u64 *)((void *)bbio->stripes +
> -				 sizeof(struct btrfs_bio_stripe) *
> -				 num_alloc_stripes +
> -				 sizeof(int) * tgtdev_indexes);
>  
>  		/* Work out the disk rotation on this stripe-set */
>  		div_u64_rem(stripe_nr, num_stripes, &rot);
> 

This patch is not complete since the presence of raid_map now means that
the sort parityu function in __btrfs_map_block will always be invoked,
which is not what we want. I'll send a fixed v2 later.