NFS: Fix up nfs_page_group_covers_page()

Fix up the test in nfs_page_group_covers_page(). The simplest implementation
is to check that we have a set of intersecting or contiguous subrequests
that connect page offset 0 to nfs_page_length(req->wb_page).

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

1 files changed, 6 insertions, 12 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 0f418d825185..759e37d26acf 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -243,9 +243,6 @@ nfs_page_group_search_locked(struct nfs_page *head, unsigned int page_offset)
 {
         struct nfs_page *req;
 
-        WARN_ON_ONCE(head != head->wb_head);
-        WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &head->wb_head->wb_flags));
-
         req = head;
         do {
                 if (page_offset >= req->wb_pgbase &&
@@ -273,18 +270,15 @@ static bool nfs_page_group_covers_page(struct nfs_page *req)
 
         nfs_page_group_lock(req);
 
-        do {
+        for (;;) {
                 tmp = nfs_page_group_search_locked(req->wb_head, pos);
-                if (tmp) {
-                        /* no way this should happen */
-                        WARN_ON_ONCE(tmp->wb_pgbase != pos);
-                        pos += tmp->wb_bytes - (pos - tmp->wb_pgbase);
-                }
-        } while (tmp && pos < len);
+                if (!tmp)
+                        break;
+                pos = tmp->wb_pgbase + tmp->wb_bytes;
+        }
 
         nfs_page_group_unlock(req);
-        WARN_ON_ONCE(pos > len);
-        return pos == len;
+        return pos >= len;
 }
 
 /* We can set the PG_uptodate flag if we see that a write request