From mboxrd@z Thu Jan  1 00:00:00 1970
From: lutz.euler@freenet.de (Lutz Euler)
Subject: Re: Bulk discard doesn't work after add/delete of devices
Date: Thu, 9 Feb 2012 16:50:48 +0100
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References: <20270.59513.240729.662692@localhost.localdomain>
	<4F3386D8.6010108@cn.fujitsu.com>
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Cc: linux-btrfs@vger.kernel.org
To: Liu Bo <liubo2009@cn.fujitsu.com>
Return-path: <linux-btrfs-owner@vger.kernel.org>
In-Reply-To: <4F3386D8.6010108@cn.fujitsu.com>
List-ID: <linux-btrfs.vger.kernel.org>

Hi Liu,

thanks for looking into this!

You wrote:

> Would you please test the following patch on your box?
> 
> thanks,
> liubo
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 77ea23c..b6e2c92 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -7653,9 +7653,16 @@ int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
>  	u64 start;
>  	u64 end;
>  	u64 trimmed = 0;
> +	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
>  	int ret = 0;
>  
> -	cache = btrfs_lookup_block_group(fs_info, range->start);
> +	/*
> +	 * try to trim all FS space, our block group may start from non-zero.
> +	 */
> +	if (range->len == total_bytes)
> +		cache = btrfs_lookup_first_block_group(fs_info, range->start);
> +	else
> +		cache = btrfs_lookup_block_group(fs_info, range->start);
>  
>  	while (cache) {
>  		if (cache->key.objectid >= (range->start + range->len)) {
> -- 
> 1.6.5.2

I'm sorry but that didn't help.
I applied the patch on top of v3.3-rc2-172-g23783f8 and still fstrim
says: "0 bytes were trimmed".

I left the printk's I mentioned in place. They show that now "cache"
is not 0 so the "while (cache)" loop is entered but nevertheless
"btrfs_trim_block_group" is never called. So I put in more printk's
and found that the objectid is so large that the loop is immediately
terminated (output of printk's in "//" comments below):

int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct btrfs_block_group_cache *cache = NULL;
	u64 group_trimmed;
	u64 start;
	u64 end;
	u64 trimmed = 0;
	u64 total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
	int ret = 0;

// range.start = 0, .len = 160815300608, .minlen = 512

	/*
	 * try to trim all FS space, our block group may start from non-zero.
	 */
	if (range->len == total_bytes)
		cache = btrfs_lookup_first_block_group(fs_info, range->start);
	else
		cache = btrfs_lookup_block_group(fs_info, range->start);

// cache != 0

	while (cache) {

// cache->key.objectid = 213702934528

		if (cache->key.objectid >= (range->start + range->len)) {
			btrfs_put_block_group(cache);
			break;
		}

// This line is not reached.

Here's the output of "btrfs fi show /dev/sda3" again:

failed to read /dev/sr0
Label: none  uuid: 88af7576-3027-4a3b-a5ae-34bfd167982f
	Total devices 2 FS bytes used 29.05GB
	devid    4 size 74.53GB used 40.06GB path /dev/sdb1
	devid    3 size 75.24GB used 40.06GB path /dev/sda3

Kind regards,

Lutz