Re: [PATCH] ceph: fix duplicate increment of opened_inodes metric

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2021-11-22 at 22:22 +0800, Hu Weiwen wrote:
> opened_inodes is incremented twice when the same inode is opened twice
> with O_RDONLY and O_WRONLY respectively.
> 
> To reproduce, run this python script, then check the metrics:
> 
> import os
> for _ in range(10000):
>     fd_r = os.open('a', os.O_RDONLY)
>     fd_w = os.open('a', os.O_WRONLY)
>     os.close(fd_r)
>     os.close(fd_w)
> 
> Fixes: 1dd8d4708136 ("ceph: metrics for opened files, pinned caps and opened inodes")
> Signed-off-by: Hu Weiwen <sehuww@mail.scut.edu.cn>
> ---
>  fs/ceph/caps.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index b9460b6fb76f..c447fa2e2d1f 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -4350,7 +4350,7 @@ void ceph_get_fmode(struct ceph_inode_info *ci, int fmode, int count)
>  {
>  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(ci->vfs_inode.i_sb);
>  	int bits = (fmode << 1) | 1;
> -	bool is_opened = false;
> +	bool already_opened = false;
>  	int i;
>  
>  	if (count == 1)
> @@ -4358,19 +4358,19 @@ void ceph_get_fmode(struct ceph_inode_info *ci, int fmode, int count)
>  
>  	spin_lock(&ci->i_ceph_lock);
>  	for (i = 0; i < CEPH_FILE_MODE_BITS; i++) {
> -		if (bits & (1 << i))
> -			ci->i_nr_by_mode[i] += count;
> -
>  		/*
> -		 * If any of the mode ref is larger than 1,
> +		 * If any of the mode ref is larger than 0,
>  		 * that means it has been already opened by
>  		 * others. Just skip checking the PIN ref.
>  		 */
> -		if (i && ci->i_nr_by_mode[i] > 1)
> -			is_opened = true;
> +		if (i && ci->i_nr_by_mode[i])
> +			already_opened = true;
> +
> +		if (bits & (1 << i))
> +			ci->i_nr_by_mode[i] += count;
>  	}
>  
> -	if (!is_opened)
> +	if (!already_opened)
>  		percpu_counter_inc(&mdsc->metric.opened_inodes);
>  	spin_unlock(&ci->i_ceph_lock);
>  }

Merged into the ceph-client testing branch. Thanks for the patch!
-- 
Jeff Layton <jlayton@kernel.org>