3 files changed, 77 insertions, 29 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index ba491926df5f..be7cbce6e4c7 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -116,7 +116,7 @@ __nfs_iocounter_wait(struct nfs_io_counter *c)
                 if (atomic_read(&c->io_count) == 0)
                         break;
                 ret = nfs_wait_bit_killable(&q.key);
-        } while (atomic_read(&c->io_count) != 0);
+        } while (atomic_read(&c->io_count) != 0 && !ret);
         finish_wait(wq, &q.wait);
         return ret;
 }
@@ -139,26 +139,49 @@ 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;
+}
+
+/*
+ * nfs_page_group_lock_wait - wait for the lock to clear, but don't grab it
+ * @req - a request in the group
+ *
+ * This is a blocking call to wait for the group lock to be cleared.
+ */
+void
+nfs_page_group_lock_wait(struct nfs_page *req)
+{
+        struct nfs_page *head = req->wb_head;
+
+        WARN_ON_ONCE(head != head->wb_head);
+
+        wait_on_bit(&head->wb_flags, PG_HEADLOCK,
+                TASK_UNINTERRUPTIBLE);
 }
 
 /*
@@ -219,7 +242,7 @@ 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);
 
@@ -701,10 +724,11 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
                      struct nfs_pgio_header *hdr)
 {
         struct nfs_page         *req;
-        struct page             **pages;
+        struct page             **pages,
+                                *last_page;
         struct list_head *head = &desc->pg_list;
         struct nfs_commit_info cinfo;
-        unsigned int pagecount;
+        unsigned int pagecount, pageused;
 
         pagecount = nfs_page_array_len(desc->pg_base, desc->pg_count);
         if (!nfs_pgarray_set(&hdr->page_array, pagecount))
@@ -712,12 +736,23 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
 
         nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
         pages = hdr->page_array.pagevec;
+        last_page = NULL;
+        pageused = 0;
         while (!list_empty(head)) {
                 req = nfs_list_entry(head->next);
                 nfs_list_remove_request(req);
                 nfs_list_add_request(req, &hdr->pages);
-                *pages++ = req->wb_page;
+
+                if (WARN_ON_ONCE(pageused >= pagecount))
+                        return nfs_pgio_error(desc, hdr);
+
+                if (!last_page || last_page != req->wb_page) {
+                        *pages++ = last_page = req->wb_page;
+                        pageused++;
+                }
         }
+        if (WARN_ON_ONCE(pageused != pagecount))
+                return nfs_pgio_error(desc, hdr);
 
         if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
             (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))
@@ -788,6 +823,14 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
                         return false;
                 if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
                         return false;
+                if (req->wb_page == prev->wb_page) {
+                        if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
+                                return false;
+                } else {
+                        if (req->wb_pgbase != 0 ||
+                            prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
+                                return false;
+                }
         }
         size = pgio->pg_ops->pg_test(pgio, prev, req);
         WARN_ON_ONCE(size > req->wb_bytes);
@@ -858,13 +901,8 @@ 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 +924,7 @@ 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;
                 }
 
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index e3b5cf28bdc5..175d5d073ccf 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -241,7 +241,7 @@ static bool nfs_page_group_covers_page(struct nfs_page *req)
         unsigned int pos = 0;
         unsigned int len = nfs_page_length(req->wb_page);
 
-        nfs_page_group_lock(req, true);
+        nfs_page_group_lock(req, false);
 
         do {
                 tmp = nfs_page_group_search_locked(req->wb_head, pos);
@@ -478,10 +478,23 @@ try_again:
                 return NULL;
         }
 
-        /* lock each request in the page group */
-        ret = nfs_page_group_lock(head, false);
-        if (ret < 0)
+        /* holding inode lock, so always make a non-blocking call to try the
+         * page group lock */
+        ret = nfs_page_group_lock(head, true);
+        if (ret < 0) {
+                spin_unlock(&inode->i_lock);
+
+                if (!nonblock && ret == -EAGAIN) {
+                        nfs_page_group_lock_wait(head);
+                        nfs_release_request(head);
+                        goto try_again;
+                }
+
+                nfs_release_request(head);
                 return ERR_PTR(ret);
+        }
+
+        /* lock each request in the page group */
         subreq = head;
         do {
                 /*
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index 6ad2bbcad405..6c3e06ee2fb7 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -123,6 +123,7 @@ extern  int nfs_wait_on_request(struct nfs_page *);
 extern  void nfs_unlock_request(struct nfs_page *req);
 extern  void nfs_unlock_and_release_request(struct nfs_page *);
 extern int nfs_page_group_lock(struct nfs_page *, bool);
+extern void nfs_page_group_lock_wait(struct nfs_page *);
 extern void nfs_page_group_unlock(struct nfs_page *);
 extern bool nfs_page_group_sync_on_bit(struct nfs_page *, unsigned int);