NFS: Fix comparison between DS address lists

data_server_cache entries should only be treated as the same if the address
list hasn't changed.

A new entry will be made when an MDS changes an address list (as seen by
GETDEVINFO). The old entry will be freed once all references are gone.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 24 insertions, 47 deletions

diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index 80fce8dade2e..41677f0bf792 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -108,58 +108,40 @@ same_sockaddr(struct sockaddr *addr1, struct sockaddr *addr2)
         return false;
 }
 
-/*
- * Lookup DS by addresses.  The first matching address returns true.
- * nfs4_ds_cache_lock is held
- */
-static struct nfs4_pnfs_ds *
-_data_server_lookup_locked(struct list_head *dsaddrs)
+bool
+_same_data_server_addrs_locked(const struct list_head *dsaddrs1,
+                               const struct list_head *dsaddrs2)
 {
-        struct nfs4_pnfs_ds *ds;
         struct nfs4_pnfs_ds_addr *da1, *da2;
 
-        list_for_each_entry(da1, dsaddrs, da_node) {
-                list_for_each_entry(ds, &nfs4_data_server_cache, ds_node) {
-                        list_for_each_entry(da2, &ds->ds_addrs, da_node) {
-                                if (same_sockaddr(
-                                        (struct sockaddr *)&da1->da_addr,
-                                        (struct sockaddr *)&da2->da_addr))
-                                        return ds;
-                        }
-                }
+        /* step through both lists, comparing as we go */
+        for (da1 = list_first_entry(dsaddrs1, typeof(*da1), da_node),
+             da2 = list_first_entry(dsaddrs2, typeof(*da2), da_node);
+             da1 != NULL && da2 != NULL;
+             da1 = list_entry(da1->da_node.next, typeof(*da1), da_node),
+             da2 = list_entry(da2->da_node.next, typeof(*da2), da_node)) {
+                if (!same_sockaddr((struct sockaddr *)&da1->da_addr,
+                                   (struct sockaddr *)&da2->da_addr))
+                        return false;
         }
-        return NULL;
+        if (da1 == NULL && da2 == NULL)
+                return true;
+
+        return false;
 }
 
 /*
- * Compare two lists of addresses.
+ * Lookup DS by addresses.  nfs4_ds_cache_lock is held
  */
-static bool
-_data_server_match_all_addrs_locked(struct list_head *dsaddrs1,
-                                    struct list_head *dsaddrs2)
+static struct nfs4_pnfs_ds *
+_data_server_lookup_locked(const struct list_head *dsaddrs)
 {
-        struct nfs4_pnfs_ds_addr *da1, *da2;
-        size_t count1 = 0,
-               count2 = 0;
-
-        list_for_each_entry(da1, dsaddrs1, da_node)
-                count1++;
-
-        list_for_each_entry(da2, dsaddrs2, da_node) {
-                bool found = false;
-                count2++;
-                list_for_each_entry(da1, dsaddrs1, da_node) {
-                        if (same_sockaddr((struct sockaddr *)&da1->da_addr,
-                                (struct sockaddr *)&da2->da_addr)) {
-                                found = true;
-                                break;
-                        }
-                }
-                if (!found)
-                        return false;
-        }
+        struct nfs4_pnfs_ds *ds;
 
-        return (count1 == count2);
+        list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
+                if (_same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
+                        return ds;
+        return NULL;
 }
 
 /*
@@ -356,11 +338,6 @@ nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
                 dprintk("%s add new data server %s\n", __func__,
                         ds->ds_remotestr);
         } else {
-                if (!_data_server_match_all_addrs_locked(&tmp_ds->ds_addrs,
-                                                         dsaddrs)) {
-                        dprintk("%s:  multipath address mismatch: %s != %s",
-                                __func__, tmp_ds->ds_remotestr, remotestr);
-                }
                 kfree(remotestr);
                 kfree(ds);
                 atomic_inc(&tmp_ds->ds_count);