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. */
         dprintk("lockd: GRANTing blocked lock.\n");
         block->b_granted = 1;
-        block->b_incall  = 1;
 
         /* Schedule next grant callback in 30 seconds */
         nlmsvc_insert_block(block, 30 * HZ);
 
         /* Call the client */
-        nlm_get_host(block->b_call.a_host);
+        kref_get(&block->b_count);
         if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
                                                 &nlmsvc_grant_ops) < 0)
-                nlm_release_host(block->b_call.a_host);
+                nlmsvc_release_block(block);
 out_unlock:
         up(&file->f_sema);
 }
@@ -573,20 +580,10 @@ out_unlock:
 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 {
         struct nlm_rqst         *call = data;
-        struct nlm_block        *block;
+        struct nlm_block        *block = container_of(call, struct nlm_block, b_call);
         unsigned long           timeout;
-        struct sockaddr_in      *peer_addr = RPC_PEERADDR(task->tk_client);
 
         dprintk("lockd: GRANT_MSG RPC callback\n");
-        dprintk("callback: looking for cookie %s, host (%u.%u.%u.%u)\n",
-                nlmdbg_cookie2a(&call->a_args.cookie),
-                NIPQUAD(peer_addr->sin_addr.s_addr));
-        if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) {
-                dprintk("lockd: no block for cookie %s, host (%u.%u.%u.%u)\n",
-                        nlmdbg_cookie2a(&call->a_args.cookie),
-                        NIPQUAD(peer_addr->sin_addr.s_addr));
-                return;
-        }
 
         /* Technically, we should down the file semaphore here. Since we
          * move the block towards the head of the queue only, no harm
@@ -603,9 +600,7 @@ static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
         }
         nlmsvc_insert_block(block, timeout);
         svc_wake_up(block->b_daemon);
-        block->b_incall = 0;
-
-        nlm_release_host(call->a_host);
+        nlmsvc_release_block(block);
 }
 
 static const struct rpc_call_ops nlmsvc_grant_ops = {
@@ -631,20 +626,19 @@ nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status
 
         file->f_count++;
         down(&file->f_sema);
-        block = nlmsvc_find_block(cookie, &rqstp->rq_addr);
         if (block) {
                 if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
                         /* Try again in a couple of seconds */
                         nlmsvc_insert_block(block, 10 * HZ);
-                        up(&file->f_sema);
                 } else {
                         /* Lock is now held by client, or has been rejected.
                          * In both cases, the block should be removed. */
-                        nlmsvc_delete_block(block);
-                        up(&file->f_sema);
+                        nlmsvc_unlink_block(block);
                 }
         }
+        up(&file->f_sema);
         nlm_release_file(file);
+        nlmsvc_release_block(block);
 }
 
 /*
@@ -667,10 +661,12 @@ nlmsvc_retry_blocked(void)
                         break;
                 dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
                         block, block->b_when, block->b_done);
+                kref_get(&block->b_count);
                 if (block->b_done)
-                        nlmsvc_delete_block(block);
+                        nlmsvc_unlink_block(block);
                 else
                         nlmsvc_grant_blocked(block);
+                nlmsvc_release_block(block);
         }
 
         if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index ef21ed296039..08ab9773f762 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -14,6 +14,7 @@
 #include <linux/config.h>
 #include <linux/in.h>
 #include <linux/fs.h>
+#include <linux/kref.h>
 #include <linux/utsname.h>
 #include <linux/nfsd/nfsfh.h>
 #include <linux/lockd/bind.h>
@@ -110,6 +111,7 @@ struct nlm_file {
  */
 #define NLM_NEVER               (~(unsigned long) 0)
 struct nlm_block {
+        struct kref             b_count;        /* Reference count */
         struct nlm_block *      b_next;         /* linked list (all blocks) */
         struct nlm_block *      b_fnext;        /* linked list (per file) */
         struct nlm_rqst         b_call;         /* RPC args & callback info */
@@ -119,7 +121,6 @@ struct nlm_block {
         unsigned int            b_id;           /* block id */
         unsigned char           b_queued;       /* re-queued */
         unsigned char           b_granted;      /* VFS granted lock */
-        unsigned char           b_incall;       /* doing callback */
         unsigned char           b_done;         /* callback complete */
         struct nlm_file *       b_file;         /* file in question */
 };