LU-14805 llite: No locked parallel DIO

If we are doing locked DIO, the OSC & LDLM locks are
released at the end of cl_io_loop, ie, before we wait for
parallel DIO at the llite layer.

This is problematic because the locks are released before
i/o done using them is complete; this can lead to data
inconsistencies.  (And at least one LBUG, see LU-14805.)

The easiest solution for now is only do parallel DIO when
working lockless (which is the default; DIO only switches
to locked to manage conflicts with buffered i/o).

This problem & fix apply to AIO as well as parallel DIO.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: If98a0551d6dde54220b406b26e978e284a6b1ebf
Reviewed-on: https://review.whamcloud.com/44131
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/llite/rw26.c b/lustre/llite/rw26.c
index 36d9c56..d412261 100644 (file)
--- a/lustre/llite/rw26.c
+++ b/lustre/llite/rw26.c
@@ -518,10 +518,19 @@ out:
        else
                vio->u.readwrite.vui_read += tot_bytes;
 
        else
                vio->u.readwrite.vui_read += tot_bytes;
 

-       /* If async dio submission is not allowed, we must wait here. */
-       if (is_sync_kiocb(iocb) && !io->ci_parallel_dio) {
+       /* We cannot do async submission - for AIO or regular DIO - unless
+        * lockless because it causes us to release the lock early.
+        *
+        * There are also several circumstances in which we must disable
+        * parallel DIO, so we check if it is enabled.
+        *
+        * The check for "is_sync_kiocb" excludes AIO, which does not need to
+        * be disabled in these situations.
+        */
+       if (io->ci_dio_lock || (is_sync_kiocb(iocb) && !io->ci_parallel_dio)) {

                ssize_t rc2;
 
                ssize_t rc2;
 

+               /* Wait here rather than doing async submission */

                rc2 = cl_sync_io_wait_recycle(env, &aio->cda_sync, 0, 0);
                if (result == 0 && rc2)
                        result = rc2;
                rc2 = cl_sync_io_wait_recycle(env, &aio->cda_sync, 0, 0);
                if (result == 0 && rc2)
                        result = rc2;