NFSd: fix locking in nfsd_forget_delegations()

This patch adds recall_lock hold to nfsd_forget_delegations() to protect
nfsd_process_n_delegations() call.
Also, looks like it would be better to collect delegations to some local
on-stack list, and then unhash collected list. This split allows to
simplify locking, because delegation traversing is protected by recall_lock,
when delegation unhash is protected by client_mutex.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index fe96015fbfc..d10ad8bc47a 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4575,7 +4575,7 @@ void nfsd_forget_openowners(u64 num)
         printk(KERN_INFO "NFSD: Forgot %d open owners", count);
 }
 
-int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegation *))
+int nfsd_process_n_delegations(u64 num, struct list_head *list)
 {
         int i, count = 0;
         struct nfs4_file *fp, *fnext;
@@ -4584,7 +4584,7 @@ int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegatio
         for (i = 0; i < FILE_HASH_SIZE; i++) {
                 list_for_each_entry_safe(fp, fnext, &file_hashtbl[i], fi_hash) {
                         list_for_each_entry_safe(dp, dnext, &fp->fi_delegations, dl_perfile) {
-                                deleg_func(dp);
+                                list_move(&dp->dl_recall_lru, list);
                                 if (++count == num)
                                         return count;
                         }
@@ -4597,9 +4597,16 @@ int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegatio
 void nfsd_forget_delegations(u64 num)
 {
         unsigned int count;
+        LIST_HEAD(victims);
+        struct nfs4_delegation *dp, *dnext;
+
+        spin_lock(&recall_lock);
+        count = nfsd_process_n_delegations(num, &victims);
+        spin_unlock(&recall_lock);
 
         nfs4_lock_state();
-        count = nfsd_process_n_delegations(num, unhash_delegation);
+        list_for_each_entry_safe(dp, dnext, &victims, dl_recall_lru)
+                unhash_delegation(dp);
         nfs4_unlock_state();
 
         printk(KERN_INFO "NFSD: Forgot %d delegations", count);
@@ -4608,12 +4615,16 @@ void nfsd_forget_delegations(u64 num)
 void nfsd_recall_delegations(u64 num)
 {
         unsigned int count;
+        LIST_HEAD(victims);
+        struct nfs4_delegation *dp, *dnext;
 
-        nfs4_lock_state();
         spin_lock(&recall_lock);
-        count = nfsd_process_n_delegations(num, nfsd_break_one_deleg);
+        count = nfsd_process_n_delegations(num, &victims);
+        list_for_each_entry_safe(dp, dnext, &victims, dl_recall_lru) {
+                list_del(&dp->dl_recall_lru);
+                nfsd_break_one_deleg(dp);
+        }
         spin_unlock(&recall_lock);
-        nfs4_unlock_state();
 
         printk(KERN_INFO "NFSD: Recalled %d delegations", count);
 }