nfs: handle overlapping reqs in lock_and_join

This is needed for mirrored DS support, where multuple requests
cover the same range.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 8800bd3b235d..e9974574b19a 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -473,13 +473,18 @@ try_again:
         do {
                 /*
                  * Subrequests are always contiguous, non overlapping
-                 * and in order. If not, it's a programming error.
+                 * and in order - but may be repeated (mirrored writes).
                  */
-                WARN_ON_ONCE(subreq->wb_offset !=
-                     (head->wb_offset + total_bytes));
-
-                /* keep track of how many bytes this group covers */
-                total_bytes += subreq->wb_bytes;
+                if (subreq->wb_offset == (head->wb_offset + total_bytes)) {
+                        /* keep track of how many bytes this group covers */
+                        total_bytes += subreq->wb_bytes;
+                } else if (WARN_ON_ONCE(subreq->wb_offset < head->wb_offset ||
+                            ((subreq->wb_offset + subreq->wb_bytes) >
+                             (head->wb_offset + total_bytes)))) {
+                        nfs_page_group_unlock(head);
+                        spin_unlock(&inode->i_lock);
+                        return ERR_PTR(-EIO);
+                }
 
                 if (!nfs_lock_request(subreq)) {
                         /* releases page group bit lock and