Re: [PATCH] ceph: allow `ceph.dir.rctime' xattr to be updatable

From: Jeff Layton <jlayton@kernel.org>
To: Venky Shankar <vshankar@redhat.com>, idryomov@gmail.com
Cc: xiubli@redhat.com, ceph-devel@vger.kernel.org
Subject: Re: [PATCH] ceph: allow `ceph.dir.rctime' xattr to be updatable
Date: Fri, 11 Mar 2022 10:16:17 -0500	[thread overview]
Message-ID: <12877268cdbd9fabfec0ee40e8684467984e15f5.camel@kernel.org> (raw)
In-Reply-To: <20220310143419.14284-1-vshankar@redhat.com>

On Thu, 2022-03-10 at 09:34 -0500, Venky Shankar wrote:
> `rctime' has been a pain point in cephfs due to its buggy
> nature - inconsistent values reported and those sorts.
> Fixing rctime is non-trivial needing an overall redesign
> of the entire nested statistics infrastructure.
> 
> As a workaround, PR
> 
>      http://github.com/ceph/ceph/pull/37938
> 
> allows this extended attribute to be manually set. This allows
> users to "fixup" inconsistency rctime values. While this sounds
> messy, its probably the wisest approach allowing users/scripts
> to workaround buggy rctime values.
> 
> The above PR enables Ceph MDS to allow manually setting
> rctime extended attribute with the corresponding user-land
> changes. We may as well allow the same to be done via kclient
> for parity.
> 
> Signed-off-by: Venky Shankar <vshankar@redhat.com>
> ---
>  fs/ceph/xattr.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
> index afec84088471..8c2dc2c762a4 100644
> --- a/fs/ceph/xattr.c
> +++ b/fs/ceph/xattr.c
> @@ -366,6 +366,14 @@ static ssize_t ceph_vxattrcb_auth_mds(struct ceph_inode_info *ci,
>  	}
>  #define XATTR_RSTAT_FIELD(_type, _name)			\
>  	XATTR_NAME_CEPH(_type, _name, VXATTR_FLAG_RSTAT)
> +#define XATTR_RSTAT_FIELD_UPDATABLE(_type, _name)			\
> +	{								\
> +		.name = CEPH_XATTR_NAME(_type, _name),			\
> +		.name_size = sizeof (CEPH_XATTR_NAME(_type, _name)),	\
> +		.getxattr_cb = ceph_vxattrcb_ ## _type ## _ ## _name,	\
> +		.exists_cb = NULL,					\
> +		.flags = VXATTR_FLAG_RSTAT,				\
> +	}
>  #define XATTR_LAYOUT_FIELD(_type, _name, _field)			\
>  	{								\
>  		.name = CEPH_XATTR_NAME2(_type, _name, _field),	\
> @@ -404,7 +412,7 @@ static struct ceph_vxattr ceph_dir_vxattrs[] = {
>  	XATTR_RSTAT_FIELD(dir, rsubdirs),
>  	XATTR_RSTAT_FIELD(dir, rsnaps),
>  	XATTR_RSTAT_FIELD(dir, rbytes),
> -	XATTR_RSTAT_FIELD(dir, rctime),
> +	XATTR_RSTAT_FIELD_UPDATABLE(dir, rctime),
>  	{
>  		.name = "ceph.dir.pin",
>  		.name_size = sizeof("ceph.dir.pin"),

Thanks Venky, looks good. Merged into testing branch.
-- 
Jeff Layton <jlayton@kernel.org>