NFS: Simplify page writeback

We don't expect the page header lock to ever be held across I/O, so
it should always be safe to wait for it, even if we're doing nonblocking
writebacks.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index b1af5de..1d447e3 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -366,7 +366,6 @@ nfs_page_group_clear_bits(struct nfs_page *req)
  * @inode - inode associated with request page group, must be holding inode lock
  * @head  - head request of page group, must be holding head lock
  * @req   - request that couldn't lock and needs to wait on the req bit lock
- * @nonblock - if true, don't actually wait
  *
  * NOTE: this must be called holding page_group bit lock and inode spin lock
  *       and BOTH will be released before returning.
@@ -375,7 +374,7 @@ nfs_page_group_clear_bits(struct nfs_page *req)
  */
 static int
 nfs_unroll_locks_and_wait(struct inode *inode, struct nfs_page *head,
-                         struct nfs_page *req, bool nonblock)
+                         struct nfs_page *req)
        __releases(&inode->i_lock)
 {
        struct nfs_page *tmp;
@@ -396,10 +395,7 @@ nfs_unroll_locks_and_wait(struct inode *inode, struct nfs_page *head,
        /* release ref from nfs_page_find_head_request_locked */
        nfs_release_request(head);
 
-       if (!nonblock)
-               ret = nfs_wait_on_request(req);
-       else
-               ret = -EAGAIN;
+       ret = nfs_wait_on_request(req);
        nfs_release_request(req);
 
        return ret;
@@ -464,7 +460,6 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
  *                              operations for this page.
  *
  * @page - the page used to lookup the "page group" of nfs_page structures
- * @nonblock - if true, don't block waiting for request locks
  *
  * This function joins all sub requests to the head request by first
  * locking all requests in the group, cancelling any pending operations
@@ -478,7 +473,7 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
  * error was encountered.
  */
 static struct nfs_page *
-nfs_lock_and_join_requests(struct page *page, bool nonblock)
+nfs_lock_and_join_requests(struct page *page)
 {
        struct inode *inode = page_file_mapping(page)->host;
        struct nfs_page *head, *subreq;
@@ -511,14 +506,9 @@ try_again:
        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_page_group_lock_wait(head);
                nfs_release_request(head);
-               return ERR_PTR(ret);
+               goto try_again;
        }
 
        /* lock each request in the page group */
@@ -543,7 +533,7 @@ try_again:
                        /* releases page group bit lock and
                         * inode spin lock and all references */
                        ret = nfs_unroll_locks_and_wait(inode, head,
-                               subreq, nonblock);
+                               subreq);
 
                        if (ret == 0)
                                goto try_again;
@@ -624,12 +614,12 @@ nfs_error_is_fatal_on_server(int err)
  * May return an error if the user signalled nfs_wait_on_request().
  */
 static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
-                               struct page *page, bool nonblock)
+                               struct page *page)
 {
        struct nfs_page *req;
        int ret = 0;
 
-       req = nfs_lock_and_join_requests(page, nonblock);
+       req = nfs_lock_and_join_requests(page);
        if (!req)
                goto out;
        ret = PTR_ERR(req);
@@ -672,7 +662,7 @@ static int nfs_do_writepage(struct page *page, struct writeback_control *wbc,
        int ret;
 
        nfs_pageio_cond_complete(pgio, page_index(page));
-       ret = nfs_page_async_flush(pgio, page, wbc->sync_mode == WB_SYNC_NONE);
+       ret = nfs_page_async_flush(pgio, page);
        if (ret == -EAGAIN) {
                redirty_page_for_writepage(wbc, page);
                ret = 0;
@@ -2015,7 +2005,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page)
 
        /* blocking call to cancel all requests and join to a single (head)
         * request */
-       req = nfs_lock_and_join_requests(page, false);
+       req = nfs_lock_and_join_requests(page);
 
        if (IS_ERR(req)) {
                ret = PTR_ERR(req);