linux-kernel - Re: [PATCH V2] f2fs: introduce free nid bitmap

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Date:   Mon, 27 Feb 2017 11:11:21 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH V2] f2fs: introduce free nid bitmap

On 2017/2/26 3:02, Jaegeuk Kim wrote:
> On 02/25, Chao Yu wrote:
>> Hi Jaegeuk,
>>
>> I added below diff code into this patch in order to fix incorrectly nid status
>> updating to reduce large latency of generic/251 in fstest, could you help to
>> review code below?
> 
> Understand the problem, and how about this?
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 52db02396878..83b305689913 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1765,7 +1765,7 @@ static void __remove_nid_from_list(struct f2fs_sb_info *sbi,
>  		radix_tree_delete(&nm_i->free_nid_root, i->nid);
>  }
>  
> -static int add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
> +static bool add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
>  {
>  	struct f2fs_nm_info *nm_i = NM_I(sbi);
>  	struct free_nid *i;
> @@ -1774,14 +1774,14 @@ static int add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
>  
>  	/* 0 nid should not be used */
>  	if (unlikely(nid == 0))
> -		return 0;
> +		return false;
>  
>  	if (build) {
>  		/* do not add allocated nids */
>  		ne = __lookup_nat_cache(nm_i, nid);
>  		if (ne && (!get_nat_flag(ne, IS_CHECKPOINTED) ||
>  				nat_get_blkaddr(ne) != NULL_ADDR))
> -			return 0;
> +			return false;
>  	}
>  
>  	i = f2fs_kmem_cache_alloc(free_nid_slab, GFP_NOFS);
> @@ -1790,7 +1790,7 @@ static int add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
>  
>  	if (radix_tree_preload(GFP_NOFS)) {
>  		kmem_cache_free(free_nid_slab, i);
> -		return 0;
> +		return false;

If there is no memory, actually current free nid is still available, we need to
return true (or other value -1?), then caller can set free_nid_bitmap correctly.

>  	}
>  
>  	spin_lock(&nm_i->nid_list_lock);
> @@ -1799,9 +1799,9 @@ static int add_free_nid(struct f2fs_sb_info *sbi, nid_t nid, bool build)
>  	radix_tree_preload_end();
>  	if (err) {
>  		kmem_cache_free(free_nid_slab, i);
> -		return 0;
> +		return false;

ditto.

Thanks,

>  	}
> -	return 1;
> +	return true;
>  }
>  
>  static void remove_free_nid(struct f2fs_sb_info *sbi, nid_t nid)
> @@ -1851,6 +1851,7 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
>  	i = start_nid % NAT_ENTRY_PER_BLOCK;
>  
>  	for (; i < NAT_ENTRY_PER_BLOCK; i++, start_nid++) {
> +		bool freed = false;
>  
>  		if (unlikely(start_nid >= nm_i->max_nid))
>  			break;
> @@ -1858,8 +1859,8 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
>  		blk_addr = le32_to_cpu(nat_blk->entries[i].block_addr);
>  		f2fs_bug_on(sbi, blk_addr == NEW_ADDR);
>  		if (blk_addr == NULL_ADDR)
> -			add_free_nid(sbi, start_nid, true);
> -		update_free_nid_bitmap(sbi, start_nid, blk_addr == NULL_ADDR);
> +			freed = add_free_nid(sbi, start_nid, true);
> +		update_free_nid_bitmap(sbi, start_nid, freed);
>  	}
>  }
>  
>