linux-kernel - Re: [PATCH v2] btrfs: qgroup: Fix wrong parameter order for trace events

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Message-ID: <20d8b346-3db6-d207-00ea-8776a3f43097@suse.com>
Date:   Thu, 17 Oct 2019 02:40:17 +0000
From:   Qu WenRuo <wqu@...e.com>
To:     "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-trace-devel@...r.kernel.org" 
        <linux-trace-devel@...r.kernel.org>
Subject: Re: [PATCH v2] btrfs: qgroup: Fix wrong parameter order for trace
 events

Please discard this patch.
It's sent out by accident.

The correct one is only sent to btrfs mail list.

Thanks,
Qu

On 2019/10/17 上午10:23, Qu Wenruo wrote:
> [BUG]
> For btrfs:qgroup_meta_reserve event, the trace event can output garbage:
> qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=DATA diff=2
> qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=0x258792 diff=2
> 
> Since we're in qgroup_meta_reserve() trace event, the @type should never
> be DATA, while diff must be aligned to sectorsize (4K in this case).
> 
> Only UUID and refroot is correct.
> 
> [CAUSE]
> There are two causes for this bug:
> 
> - Bad parameter order
>   For trace event btrfs:qgroup_meta_reserve, we're passing wrong
>   parameters.
> 
>   The correct parameters are:
>   struct btrfs_root, s64 diff, int type.
> 
>   However the used order is:
>   struct btrfs_root, int type, s64 diff.
> 
> - @type is not even assigned
>   What I was doing !? /facepalm
> 
> [FIX]
> Fix the super stupid bug.
> 
> Now everything works fine:
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PERTRANS diff=81920
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=0
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=-16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=-16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=16384
> qgroup_meta_reserve: 0477ad60-9aeb-4040-8a03-1900844d46ba: refroot=5(FS_TREE) type=META_PREALLOC diff=-16384
> 
> Fixes: 4ee0d8832c2e ("btrfs: qgroup: Update trace events for metadata reservation")
> Signed-off-by: Qu Wenruo <wqu@...e.com>
> ---
> Changelog:
> v2:
> - Use more accurate comment about the fintuning options
> - Use more elegant method to output uuid
> ---
>  fs/btrfs/qgroup.c            | 4 ++--
>  include/trace/events/btrfs.h | 1 +
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index c4bb69941c77..3ad151655eb8 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -3629,7 +3629,7 @@ int __btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
>  		return 0;
>  
>  	BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
> -	trace_qgroup_meta_reserve(root, type, (s64)num_bytes);
> +	trace_qgroup_meta_reserve(root, (s64)num_bytes, type);
>  	ret = qgroup_reserve(root, num_bytes, enforce, type);
>  	if (ret < 0)
>  		return ret;
> @@ -3676,7 +3676,7 @@ void __btrfs_qgroup_free_meta(struct btrfs_root *root, int num_bytes,
>  	 */
>  	num_bytes = sub_root_meta_rsv(root, num_bytes, type);
>  	BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
> -	trace_qgroup_meta_reserve(root, type, -(s64)num_bytes);
> +	trace_qgroup_meta_reserve(root, -(s64)num_bytes, type);
>  	btrfs_qgroup_free_refroot(fs_info, root->root_key.objectid,
>  				  num_bytes, type);
>  }
> diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
> index 5df604de4f11..0ebcaa153f93 100644
> --- a/include/trace/events/btrfs.h
> +++ b/include/trace/events/btrfs.h
> @@ -1710,6 +1710,7 @@ TRACE_EVENT(qgroup_meta_reserve,
>  	TP_fast_assign_btrfs(root->fs_info,
>  		__entry->refroot	= root->root_key.objectid;
>  		__entry->diff		= diff;
> +		__entry->type		= type;
>  	),
>  
>  	TP_printk_btrfs("refroot=%llu(%s) type=%s diff=%lld",
> 



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