zero_info_block: skip seed devices

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commit fb13dfb8d84c4f0a749665c8f07179450b199f3e
Author: Jeff Moyer <jmoyer@redhat.com>
Date:   Tue Feb 9 16:51:53 2021 -0500

    zero_info_block: skip seed devices
    
    Currently, ndctl destroy-namespace -f all will output errors of the
    form:
    
      Error: destroy namespace: namespace0.0 failed to enable for zeroing, continuing
    
    for any zero-sized namespace.  That particular namespace looks like this:
    
      {
        "dev":"namespace0.0",
        "mode":"raw",
        "size":0,
        "uuid":"00000000-0000-0000-0000-000000000000",
        "sector_size":512,
        "state":"disabled"
      }
    
    This patch skips over namespaces with size=0 when zeroing out info
    blocks.
    
    Fixes: 46654c2d60b70 ("ndctl/namespace: Always zero info-blocks")
    Reported-by: Zhang Yi <yizhan@redhat.com>
    Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
    Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
    Link: https://lore.kernel.org/r/x49r1lohpty.fsf@segfault.boston.devel.redhat.com

diff --git a/ndctl/namespace.c b/ndctl/namespace.c
index 1feb74d..1e8a2cd 100644
--- a/ndctl/namespace.c
+++ b/ndctl/namespace.c
@@ -1052,6 +1052,9 @@ static int zero_info_block(struct ndctl_namespace *ndns)
 	void *buf = NULL, *read_buf = NULL;
 	char path[50];
 
+	if (ndctl_namespace_get_size(ndns) == 0)
+		return 1;
+
 	ndctl_namespace_set_raw_mode(ndns, 1);
 	rc = ndctl_namespace_enable(ndns);
 	if (rc < 0) {