Re: [PATCH] ceph: add 'noshare' mount option support

From: Jeff Layton <jlayton@kernel.org>
To: xiubli@redhat.com
Cc: idryomov@gmail.com, zyan@redhat.com, pdonnell@redhat.com,
	ceph-devel@vger.kernel.org
Subject: Re: [PATCH] ceph: add 'noshare' mount option support
Date: Tue, 13 Oct 2020 08:31:45 -0400	[thread overview]
Message-ID: <6240402b3e530f3ffa8fba3cedd0113325c821fa.camel@kernel.org> (raw)
In-Reply-To: <20201013103112.12132-1-xiubli@redhat.com>

On Tue, 2020-10-13 at 18:31 +0800, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> This will disable different mount points to share superblocks.
> 

Why? What problem does this solve? Don't make us dig through random
tracker bugs to determine this, please. :)

Also, the subject mentions a "noshare" mount option, but the code below
will be expecting sharesb/nosharesb.

> URL: https://tracker.ceph.com/issues/46883
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  fs/ceph/super.c | 12 ++++++++++++
>  fs/ceph/super.h |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 2f530a111b3a..6f283e4d62ee 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -159,6 +159,7 @@ enum {
>  	Opt_quotadf,
>  	Opt_copyfrom,
>  	Opt_wsync,
> +	Opt_sharesb,
>  };
>  
>  enum ceph_recover_session_mode {
> @@ -199,6 +200,7 @@ static const struct fs_parameter_spec ceph_mount_parameters[] = {
>  	fsparam_string	("source",			Opt_source),
>  	fsparam_u32	("wsize",			Opt_wsize),
>  	fsparam_flag_no	("wsync",			Opt_wsync),
> +	fsparam_flag_no	("sharesb",			Opt_sharesb),
>  	{}
>  };
>  
> @@ -455,6 +457,12 @@ static int ceph_parse_mount_param(struct fs_context *fc,
>  		else
>  			fsopt->flags |= CEPH_MOUNT_OPT_ASYNC_DIROPS;
>  		break;
> +	case Opt_sharesb:
> +		if (!result.negated)
> +			fsopt->flags &= ~CEPH_MOUNT_OPT_NO_SHARE_SB;
> +		else
> +			fsopt->flags |= CEPH_MOUNT_OPT_NO_SHARE_SB;
> +		break;
>  	default:
>  		BUG();
>  	}
> @@ -1007,6 +1015,10 @@ static int ceph_compare_super(struct super_block *sb, struct fs_context *fc)
>  
>  	dout("ceph_compare_super %p\n", sb);
>  
> +	if (fsopt->flags & CEPH_MOUNT_OPT_NO_SHARE_SB ||
> +	    other->mount_options->flags & CEPH_MOUNT_OPT_NO_SHARE_SB)
> +		return 0;
> +
>  	if (compare_mount_options(fsopt, opt, other)) {
>  		dout("monitor(s)/mount options don't match\n");
>  		return 0;
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index f097237a5ad3..e877c21196e5 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -44,6 +44,7 @@
>  #define CEPH_MOUNT_OPT_NOQUOTADF       (1<<13) /* no root dir quota in statfs */
>  #define CEPH_MOUNT_OPT_NOCOPYFROM      (1<<14) /* don't use RADOS 'copy-from' op */
>  #define CEPH_MOUNT_OPT_ASYNC_DIROPS    (1<<15) /* allow async directory ops */
> +#define CEPH_MOUNT_OPT_NO_SHARE_SB     (1<<16) /* disable sharing the same superblock */
>  
>  #define CEPH_MOUNT_OPT_DEFAULT			\
>  	(CEPH_MOUNT_OPT_DCACHE |		\

-- 
Jeff Layton <jlayton@kernel.org>