nfs/localio: Ensure DIO WRITE's IO on stable storage upon completion

LOCALIO's misaligned DIO WRITE support requires synchronous IO for any
misaligned head and/or tail that are issued using buffered IO.  In
addition, it is important that the O_DIRECT middle be on stable
storage upon its completion via AIO.

Otherwise, a misaligned DIO WRITE could mix buffered IO for the
head/tail and direct IO for the DIO-aligned middle -- which could lead
to problems associated with deferred writes to stable storage (such as
out of order partial completions causing incorrect advancement of the
file's offset, etc).

Fixes: c817248fc831 ("nfs/localio: add proper O_DIRECT support for READ and WRITE")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 9c205f8b5e59c4aa9e369e6d1b9733c58ade1fbe..839dbda0b37040be728691c77bce55a54a30dbdc 100644 (file)
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -485,8 +485,12 @@ nfs_local_iters_init(struct nfs_local_kiocb *iocb, int rw)
                struct nfs_local_dio local_dio;
 
                if (nfs_is_local_dio_possible(iocb, rw, len, &local_dio) &&
-                   nfs_local_iters_setup_dio(iocb, rw, v, len, &local_dio) != 0)
+                   nfs_local_iters_setup_dio(iocb, rw, v, len, &local_dio) != 0) {
+                       /* Ensure DIO WRITE's IO on stable storage upon completion */
+                       if (rw == ITER_SOURCE)
+                               iocb->kiocb.ki_flags |= IOCB_DSYNC|IOCB_SYNC;
                        return; /* is DIO-aligned */
+               }
        }
 
        /* Use buffered IO */