lockd: Add refcounting to struct nlm_block

Otherwise, the block may disappear from underneath us when in
nlmsvc_retry_blocked.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 47 insertions, 50 deletions

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 1d3a74df93f3..20caeceffb14 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -39,6 +39,7 @@
 #define nlm_deadlock    nlm_lck_denied
 #endif
 
+static void nlmsvc_release_block(struct nlm_block *block);
 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
 static int      nlmsvc_remove_block(struct nlm_block *block);
 
@@ -58,6 +59,7 @@ nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
         struct nlm_block **bp, *b;
 
         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
+        kref_get(&block->b_count);
         if (block->b_queued)
                 nlmsvc_remove_block(block);
         bp = &nlm_blocked;
@@ -90,6 +92,7 @@ nlmsvc_remove_block(struct nlm_block *block)
                 if (b == block) {
                         *bp = block->b_next;
                         block->b_queued = 0;
+                        nlmsvc_release_block(block);
                         return 1;
                 }
         }
@@ -123,6 +126,7 @@ nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove)
                                 *head = block->b_next;
                                 block->b_queued = 0;
                         }
+                        kref_get(&block->b_count);
                         return block;
                 }
         }
@@ -155,6 +159,8 @@ nlmsvc_find_block(struct nlm_cookie *cookie,  struct sockaddr_in *sin)
                         break;
         }
 
+        if (block != NULL)
+                kref_get(&block->b_count);
         return block;
 }
 
@@ -188,6 +194,7 @@ nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
         memset(block, 0, sizeof(*block));
         locks_init_lock(&block->b_call.a_args.lock.fl);
         locks_init_lock(&block->b_call.a_res.lock.fl);
+        kref_init(&block->b_count);
 
         if (!nlmclnt_setgrantargs(&block->b_call, lock))
                 goto failed_free;
@@ -228,27 +235,24 @@ failed:
  * It is the caller's responsibility to check whether the file
  * can be closed hereafter.
  */
-static int
-nlmsvc_delete_block(struct nlm_block *block)
+static int nlmsvc_unlink_block(struct nlm_block *block)
 {
-        struct file_lock        *fl = &block->b_call.a_args.lock.fl;
-        struct nlm_file         *file = block->b_file;
-        struct nlm_block        **bp;
         int status;
-
-        dprintk("lockd: deleting block %p...\n", block);
+        dprintk("lockd: unlinking block %p...\n", block);
 
         /* Remove block from list */
+        status = posix_unblock_lock(block->b_file->f_file, &block->b_call.a_args.lock.fl);
         nlmsvc_remove_block(block);
-        status = posix_unblock_lock(file->f_file, fl);
+        return status;
+}
 
-        /* If the block is in the middle of a GRANT callback,
-         * don't kill it yet. */
-        if (block->b_incall) {
-                nlmsvc_insert_block(block, NLM_NEVER);
-                block->b_done = 1;
-                return status;
-        }
+static void nlmsvc_free_block(struct kref *kref)
+{
+        struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
+        struct nlm_file         *file = block->b_file;
+        struct nlm_block        **bp;
+
+        dprintk("lockd: freeing block %p...\n", block);
 
         /* Remove block from file's list of blocks */
         for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
@@ -262,7 +266,12 @@ nlmsvc_delete_block(struct nlm_block *block)
                 nlm_release_host(block->b_host);
         nlmclnt_freegrantargs(&block->b_call);
         kfree(block);
-        return status;
+}
+
+static void nlmsvc_release_block(struct nlm_block *block)
+{
+        if (block != NULL)
+                kref_put(&block->b_count, nlmsvc_free_block);
 }
 
 /*
@@ -282,7 +291,7 @@ nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
                         block->b_host->h_inuse = 1;
                 else if (action == NLM_ACT_UNLOCK) {
                         if (host == NULL || host == block->b_host)
-                                nlmsvc_delete_block(block);
+                                nlmsvc_unlink_block(block);
                 }
         }
         up(&file->f_sema);
@@ -318,9 +327,9 @@ again:
         block = nlmsvc_lookup_block(file, lock, 0);
         if (block == NULL) {
                 if (newblock != NULL)
-                        lock = &newblock->b_call.a_args.lock.fl;
+                        lock = &newblock->b_call.a_args.lock;
         } else
-                lock = &block->b_call.a_args.lock.fl;
+                lock = &block->b_call.a_args.lock;
 
         error = posix_lock_file(file->f_file, &lock->fl);
         lock->fl.fl_flags &= ~FL_SLEEP;
@@ -363,12 +372,10 @@ again:
 
         /* Append to list of blocked */
         nlmsvc_insert_block(newblock, NLM_NEVER);
-        newblock = NULL;
-
 out:
         up(&file->f_sema);
-        if (newblock != NULL)
-                nlmsvc_delete_block(newblock);
+        nlmsvc_release_block(newblock);
+        nlmsvc_release_block(block);
         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
         return ret;
 }
@@ -450,8 +457,10 @@ nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
                                 (long long)lock->fl.fl_end);
 
         down(&file->f_sema);
-        if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL)
-                status = nlmsvc_delete_block(block);
+        if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL) {
+                status = nlmsvc_unlink_block(block);
+                nlmsvc_release_block(block);
+        }
         up(&file->f_sema);
         return status ? nlm_lck_denied : nlm_granted;
 }
@@ -514,7 +523,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
         down(&file->f_sema);
 
         /* Unlink block request from list */
-        nlmsvc_remove_block(block);
+        nlmsvc_unlink_block(block);
 
         /* If b_granted is true this means we've been here before.
          * Just retry the grant callback, possibly refreshing the RPC
@@ -525,7 +534,6 @@ nlmsvc_grant_blocked(struct nlm_block *block)
         }
 
         /* Try the lock operation again */
-        posix_unblock_lock(file->f_file, &lock->fl);
         lock->fl.fl_flags |= FL_SLEEP;
         error = posix_lock_file(file->f_file, &lock->fl);
         lock->fl.fl_flags &= ~FL_SLEEP;
@@ -548,16 +556,15 @@ callback:
         /* Lock was granted by VFS. */