Merge tag 'nfs-for-3.16-3' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client fixes from Trond Myklebust:
 "Apologies for the relative lateness of this pull request, however the
  commits fix some issues with the NFS read/write code updates in
  3.16-rc1 that can cause serious Oopsing when using small r/wsize.  The
  delay was mainly due to extra testing to make sure that the fixes
  behave correctly.

  Highlights include;
   - Stable fix for an NFSv3 posix ACL regression
   - Multiple fixes for regressions to the NFS generic read/write code:
     - Fix page splitting bugs that come into play when a small
       rsize/wsize read/write needs to be sent again (due to error
       conditions or page redirty)
     - Fix nfs_wb_page_cancel, which is called by the "invalidatepage"
       method
   - Fix 2 compile warnings about unused variables
   - Fix a performance issue affecting unstable writes"

* tag 'nfs-for-3.16-3' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFS: Don't reset pg_moreio in __nfs_pageio_add_request
  NFS: Remove 2 unused variables
  nfs: handle multiple reqs in nfs_wb_page_cancel
  nfs: handle multiple reqs in nfs_page_async_flush
  nfs: change find_request to find_head_request
  nfs: nfs_page should take a ref on the head req
  nfs: mark nfs_page reqs with flag for extra ref
  nfs: only show Posix ACLs in listxattr if actually present

1 files changed, 15 insertions, 5 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index b6ee3a6ee96d..17fab89f6358 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -29,8 +29,6 @@
 static struct kmem_cache *nfs_page_cachep;
 static const struct rpc_call_ops nfs_pgio_common_ops;
 
-static void nfs_free_request(struct nfs_page *);
-
 static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
 {
         p->npages = pagecount;
@@ -239,20 +237,28 @@ nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
         WARN_ON_ONCE(prev == req);
 
         if (!prev) {
+                /* a head request */
                 req->wb_head = req;
                 req->wb_this_page = req;
         } else {
+                /* a subrequest */
                 WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
                 WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
                 req->wb_head = prev->wb_head;
                 req->wb_this_page = prev->wb_this_page;
                 prev->wb_this_page = req;
 
+                /* All subrequests take a ref on the head request until
+                 * nfs_page_group_destroy is called */
+                kref_get(&req->wb_head->wb_kref);
+
                 /* grab extra ref if head request has extra ref from
                  * the write/commit path to handle handoff between write
                  * and commit lists */
-                if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags))
+                if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
+                        set_bit(PG_INODE_REF, &req->wb_flags);
                         kref_get(&req->wb_kref);
+                }
         }
 }
 
@@ -269,6 +275,10 @@ nfs_page_group_destroy(struct kref *kref)
         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
         struct nfs_page *tmp, *next;
 
+        /* subrequests must release the ref on the head request */
+        if (req->wb_head != req)
+                nfs_release_request(req->wb_head);
+
         if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
                 return;
 
@@ -394,7 +404,7 @@ static void nfs_clear_request(struct nfs_page *req)
  *
  * Note: Should never be called with the spinlock held!
  */
-static void nfs_free_request(struct nfs_page *req)
+void nfs_free_request(struct nfs_page *req)
 {
         WARN_ON_ONCE(req->wb_this_page != req);
 
@@ -925,7 +935,6 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
                         nfs_pageio_doio(desc);
                         if (desc->pg_error < 0)
                                 return 0;
-                        desc->pg_moreio = 0;
                         if (desc->pg_recoalesce)
                                 return 0;
                         /* retry add_request for this subreq */
@@ -972,6 +981,7 @@ static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
                 desc->pg_count = 0;
                 desc->pg_base = 0;
                 desc->pg_recoalesce = 0;
+                desc->pg_moreio = 0;
 
                 while (!list_empty(&head)) {
                         struct nfs_page *req;