Re: [PATCH] Btrfs: set the free space control unit properly

[Miao Xie <miaox@cn.fujitsu.com>]

On 	tue, 28 May 2013 14:50:25 -0400, Josef Bacik wrote:
> Stefan pointed out that xfstests generic/013 was failing because the free space
> cache checker was complaining with leafsize of 16k.  Turns out this is because
> we were unconditionally using root->sectorsize as the free space ctl unit in the
> kernel, which doesn't work out if leafsize != sectorsize.  This caused the in
> memory free space cache to get screwed up which translated to a wrong space
> cache on disk.  This patch fixes the problem by not carrying the sectorsize in
> the block group since we have the ctl->unit, and we set the ctl->unit according
> to the type of block group we are.  This made generic/013 pass with 16k
> leafsize, whereas before it failed every single time.  Thanks,

But this patch will make the old filesystem be corrupted because one bit in it
equals one sector(4K), not 16K.

Thanks
Miao

> 
> Cc: stable@vger.kernel.org
> Reported-by: Stefan Behrens <sbehrens@giantdisaster.de>
> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
> ---
>  fs/btrfs/ctree.h            |    1 -
>  fs/btrfs/extent-tree.c      |    7 ++-----
>  fs/btrfs/free-space-cache.c |   32 +++++++++++++++++++++++++-------
>  fs/btrfs/free-space-cache.h |    3 ++-
>  4 files changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index fd62aa8..3442976 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1206,7 +1206,6 @@ struct btrfs_block_group_cache {
>  	u64 reserved;
>  	u64 bytes_super;
>  	u64 flags;
> -	u64 sectorsize;
>  	u64 cache_generation;
>  
>  	/* for raid56, this is a full stripe, without parity */
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4ec8305..f7af6a0 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -8128,11 +8128,10 @@ int btrfs_read_block_groups(struct btrfs_root *root)
>  		key.objectid = found_key.objectid + found_key.offset;
>  		btrfs_release_path(path);
>  		cache->flags = btrfs_block_group_flags(&cache->item);
> -		cache->sectorsize = root->sectorsize;
>  		cache->full_stripe_len = btrfs_full_stripe_len(root,
>  					       &root->fs_info->mapping_tree,
>  					       found_key.objectid);
> -		btrfs_init_free_space_ctl(cache);
> +		btrfs_init_free_space_ctl(cache, root);
>  
>  		/*
>  		 * We need to exclude the super stripes now so that the space
> @@ -8283,7 +8282,6 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
>  	cache->key.objectid = chunk_offset;
>  	cache->key.offset = size;
>  	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
> -	cache->sectorsize = root->sectorsize;
>  	cache->fs_info = root->fs_info;
>  	cache->full_stripe_len = btrfs_full_stripe_len(root,
>  					       &root->fs_info->mapping_tree,
> @@ -8295,12 +8293,11 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
>  	INIT_LIST_HEAD(&cache->cluster_list);
>  	INIT_LIST_HEAD(&cache->new_bg_list);
>  
> -	btrfs_init_free_space_ctl(cache);
> -
>  	btrfs_set_block_group_used(&cache->item, bytes_used);
>  	btrfs_set_block_group_chunk_objectid(&cache->item, chunk_objectid);
>  	cache->flags = type;
>  	btrfs_set_block_group_flags(&cache->item, type);
> +	btrfs_init_free_space_ctl(cache, root);
>  
>  	cache->last_byte_to_unpin = (u64)-1;
>  	cache->cached = BTRFS_CACHE_FINISHED;
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index 7517285..ec43e422 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -1654,7 +1654,7 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
>  		 * of cache left then go ahead an dadd them, no sense in adding
>  		 * the overhead of a bitmap if we don't have to.
>  		 */
> -		if (info->bytes <= block_group->sectorsize * 4) {
> +		if (info->bytes <= ctl->unit * 4) {
>  			if (ctl->free_extents * 2 <= ctl->extents_thresh)
>  				return false;
>  		} else {
> @@ -2001,12 +2001,19 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
>  	       "\n", count);
>  }
>  
> -void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group)
> +void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group,
> +			       struct btrfs_root *root)
>  {
>  	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
>  
>  	spin_lock_init(&ctl->tree_lock);
> -	ctl->unit = block_group->sectorsize;
> +
> +	/* This works for mixed block groups too since sectorsize == leafsize */
> +	if (block_group->flags & (BTRFS_BLOCK_GROUP_METADATA |
> +				  BTRFS_BLOCK_GROUP_SYSTEM))
> +		ctl->unit = root->leafsize;
> +	else
> +		ctl->unit = root->sectorsize;
>  	ctl->start = block_group->key.objectid;
>  	ctl->private = block_group;
>  	ctl->op = &free_space_op;
> @@ -2548,10 +2555,10 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
>  		cont1_bytes = min_bytes = bytes + empty_size;
>  	} else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
>  		cont1_bytes = bytes;
> -		min_bytes = block_group->sectorsize;
> +		min_bytes = ctl->unit;
>  	} else {
>  		cont1_bytes = max(bytes, (bytes + empty_size) >> 2);
> -		min_bytes = block_group->sectorsize;
> +		min_bytes = ctl->unit;
>  	}
>  
>  	spin_lock(&ctl->tree_lock);
> @@ -2976,6 +2983,7 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
>  static struct btrfs_block_group_cache *init_test_block_group(void)
>  {
>  	struct btrfs_block_group_cache *cache;
> +	struct btrfs_free_space_ctl *ctl;
>  
>  	cache = kzalloc(sizeof(*cache), GFP_NOFS);
>  	if (!cache)
> @@ -2987,17 +2995,27 @@ static struct btrfs_block_group_cache *init_test_block_group(void)
>  		return NULL;
>  	}
>  
> +	ctl = cache->free_space_ctl;
>  	cache->key.objectid = 0;
>  	cache->key.offset = 1024 * 1024 * 1024;
>  	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
> -	cache->sectorsize = 4096;
>  
>  	spin_lock_init(&cache->lock);
>  	INIT_LIST_HEAD(&cache->list);
>  	INIT_LIST_HEAD(&cache->cluster_list);
>  	INIT_LIST_HEAD(&cache->new_bg_list);
>  
> -	btrfs_init_free_space_ctl(cache);
> +	/*
> +	 * Have to do btrfs_init_free_space_ctl open coded here since we don't
> +	 * have a root to pass in for ctl->unit.
> +	 */
> +	spin_lock_init(&ctl->tree_lock);
> +	ctl->unit = 4096;
> +	ctl->start = block_group->key.objectid;
> +	ctl->private = block_group;
> +	ctl->op = &free_space_op;
> +	ctl->extents_thresh = ((1024 * 32) / 2) /
> +				sizeof(struct btrfs_free_space);
>  
>  	return cache;
>  }
> diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
> index 894116b..482fbd6 100644
> --- a/fs/btrfs/free-space-cache.h
> +++ b/fs/btrfs/free-space-cache.h
> @@ -78,7 +78,8 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
>  			      struct btrfs_trans_handle *trans,
>  			      struct btrfs_path *path);
>  
> -void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group);
> +void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group,
> +			       struct btrfs_root *root);
>  int __btrfs_add_free_space(struct btrfs_free_space_ctl *ctl,
>  			   u64 bytenr, u64 size);
>  static inline int
>