1 files changed, 20 insertions, 0 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index cbdd1c6aaa94..c5bb51a29e80 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -355,6 +355,26 @@ void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
         nfs_pageio_doio(desc);
 }
 
+/**
+ * nfs_pageio_cond_complete - Conditional I/O completion
+ * @desc: pointer to io descriptor
+ * @index: page index
+ *
+ * It is important to ensure that processes don't try to take locks
+ * on non-contiguous ranges of pages as that might deadlock. This
+ * function should be called before attempting to wait on a locked
+ * nfs_page. It will complete the I/O if the page index 'index'
+ * is not contiguous with the existing list of pages in 'desc'.
+ */
+void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
+{
+        if (!list_empty(&desc->pg_list)) {
+                struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
+                if (index != prev->wb_index + 1)
+                        nfs_pageio_doio(desc);
+        }
+}
+
 #define NFS_SCAN_MAXENTRIES 16
 /**
  * nfs_scan_list - Scan a list for matching requests