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

Xiubo Li <xiubli@xxxxxxxxxx> · Tue, 13 Oct 2020 20:44:11 +0800

On 2020/10/13 20:31, Jeff Layton wrote:
On Tue, 2020-10-13 at 18:31 +0800, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

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. :)

So, should we just mannully trigger to crash the kernel to get the 
coredump ?


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@xxxxxxxxxx>
---
  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 |		\








