nfs: use blocking page_group_lock in add_request

[linux-2.6-block.git] / fs / nfs / pagelist.c

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index ba491926df5f7df2db1e224c96e7e070bd36dcec..30c9626f96b071bd6b7a1fe2de8588d844469528 100644 (file)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -139,26 +139,32 @@ nfs_iocounter_wait(struct nfs_io_counter *c)
 /*
  * nfs_page_group_lock - lock the head of the page group
  * @req - request in group that is to be locked
+ * @nonblock - if true don't block waiting for lock
  *
  * this lock must be held if modifying the page group list
  *
- * returns result from wait_on_bit_lock: 0 on success, < 0 on error
+ * return 0 on success, < 0 on error: -EDELAY if nonblocking or the
+ * result from wait_on_bit_lock
+ *
+ * NOTE: calling with nonblock=false should always have set the
+ *       lock bit (see fs/buffer.c and other uses of wait_on_bit_lock
+ *       with TASK_UNINTERRUPTIBLE), so there is no need to check the result.
  */
 int
-nfs_page_group_lock(struct nfs_page *req, bool wait)
+nfs_page_group_lock(struct nfs_page *req, bool nonblock)
 {
        struct nfs_page *head = req->wb_head;
-       int ret;
 
        WARN_ON_ONCE(head != head->wb_head);
 
-       do {
-               ret = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
-                       TASK_UNINTERRUPTIBLE);
-       } while (wait && ret != 0);
+       if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
+               return 0;
 
-       WARN_ON_ONCE(ret > 0);
-       return ret;
+       if (!nonblock)
+               return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
+                               TASK_UNINTERRUPTIBLE);
+
+       return -EAGAIN;
 }
 
 /*
@@ -219,7 +225,7 @@ bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
 {
        bool ret;
 
-       nfs_page_group_lock(req, true);
+       nfs_page_group_lock(req, false);
        ret = nfs_page_group_sync_on_bit_locked(req, bit);
        nfs_page_group_unlock(req);
 
@@ -858,13 +864,8 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
        struct nfs_page *subreq;
        unsigned int bytes_left = 0;
        unsigned int offset, pgbase;
-       int ret;
 
-       ret = nfs_page_group_lock(req, false);
-       if (ret < 0) {
-               desc->pg_error = ret;
-               return 0;
-       }
+       nfs_page_group_lock(req, false);
 
        subreq = req;
        bytes_left = subreq->wb_bytes;
@@ -886,11 +887,7 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                        if (desc->pg_recoalesce)
                                return 0;
                        /* retry add_request for this subreq */
-                       ret = nfs_page_group_lock(req, false);
-                       if (ret < 0) {
-                               desc->pg_error = ret;
-                               return 0;
-                       }
+                       nfs_page_group_lock(req, false);
                        continue;
                }