linux-ext4 - Re: [PATCH 2/4] ext4: speed up group trim with the right free block count.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.2.00.1107011146350.4168@dhcp-27-109.brq.redhat.com>
Date:	Fri, 1 Jul 2011 11:48:24 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Tao Ma <tm@....ma>
cc:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH 2/4] ext4: speed up group trim with the right free block
 count.

On Thu, 30 Jun 2011, Tao Ma wrote:

> From: Tao Ma <boyu.mt@...bao.com>
> 
> When we trim some free blocks in a group of ext4, we should
> calculate the free blocks properly and check whether there are
> enough freed blocks left for us to trim. Current solution will
> only calculate free spaces if they are large for a trim which
> isn't appropriate.
> 
> Let us see a small example:
> a group has 1.5M free which are 300k, 300k, 300k, 300k, 300k.
> And minblocks is 1M. With current solution, we have to iterate
> the whole group since these 300k will never be subtracted from
> 1.5M. But actually we should exit after we find the first 2
> free spaces since the left 3 chunks only sum up to 900K if we
> subtract the first 600K although they can't be trimed.

Looks good, thanks!

-Lukas

> 
> Signed-off-by: Tao Ma <boyu.mt@...bao.com>
> ---
>  fs/ext4/mballoc.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 2336424..83fb04b 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4823,7 +4823,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
>  		   ext4_grpblk_t minblocks)
>  {
>  	void *bitmap;
> -	ext4_grpblk_t next, count = 0;
> +	ext4_grpblk_t next, count = 0, free_count = 0;
>  	struct ext4_buddy e4b;
>  	int ret;
>  
> @@ -4850,6 +4850,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
>  					 next - start, group, &e4b);
>  			count += next - start;
>  		}
> +		free_count += next - start;
>  		start = next + 1;
>  
>  		if (fatal_signal_pending(current)) {
> @@ -4863,7 +4864,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
>  			ext4_lock_group(sb, group);
>  		}
>  
> -		if ((e4b.bd_info->bb_free - count) < minblocks)
> +		if ((e4b.bd_info->bb_free - free_count) < minblocks)
>  			break;
>  	}
>  	ext4_unlock_group(sb, group);
> 

-- 
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html