Fix 'zpool import' detection issue

Before adding the entry to the configuration verify that the
device can be opened exclusively.  This ensures that as long
as multipathd is running the underlying multipath devices, which
otherwise appear identical to their /dev/mapper counterpart,
are pruned from the configuration.

Failure to do so can result in a result in the vdev appearing
as UNAVAIL when the vdev path provided to the kernel can't be
opened exclusively.

This check would normally be performed in zpool_open_func()
but placing it there would result in false positives because
it is called concurrently for many devices.


Reviewed-by: Olaf Faaland <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #5387 

1 files changed, 16 insertions, 3 deletions

diff --git a/lib/libzfs/libzfs_import.c b/lib/libzfs/libzfs_import.c
index e23232792..fe783a3a3 100644
--- a/lib/libzfs/libzfs_import.c
+++ b/lib/libzfs/libzfs_import.c
@@ -1912,6 +1912,7 @@ zpool_find_import_impl(libzfs_handle_t *hdl, importargs_t *iarg)
 		if (slice->rn_config != NULL) {
 			nvlist_t *config = slice->rn_config;
 			boolean_t matched = B_TRUE;
+			int fd;
 
 			if (iarg->poolname != NULL) {
 				char *pname;
@@ -1929,9 +1930,21 @@ zpool_find_import_impl(libzfs_handle_t *hdl, importargs_t *iarg)
 			if (!matched) {
 				nvlist_free(config);
 			} else {
-				add_config(hdl, &pools,
-				    slice->rn_name, slice->rn_order,
-				    slice->rn_num_labels, config);
+				/*
+				 * Verify all remaining entries can be opened
+				 * exclusively. This will prune all underlying
+				 * multipath devices which otherwise could
+				 * result in the vdev appearing as UNAVAIL.
+				 */
+				fd = open(slice->rn_name, O_RDONLY | O_EXCL);
+				if (fd >= 0) {
+					close(fd);
+					add_config(hdl, &pools,
+					    slice->rn_name, slice->rn_order,
+					    slice->rn_num_labels, config);
+				} else {
+					nvlist_free(config);
+				}
 			}
 		}
 		free(slice->rn_name);