block: set REQ_SYNC if we clear REQ_FUA|REQ_PREFLUSH

If we insert a flush request, we clear REQ_PREFLUSH and/or REQ_FUA,
depending on flush settings. Since op_is_sync() factors those flags
in for deciding whether this request is sync or not, we should
set REQ_SYNC to avoid screwing up this accounting.

This should be less fragile.

Reported-by: Logan Gunthorpe <logang@deltatee.com>
Fixes: b685d3d65ac ("block: treat REQ_FUA and REQ_PREFLUSH as synchronous")
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-flush.c b/block/blk-flush.c
index c486b7a..1bdbb3d 100644 (file)
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -396,6 +396,13 @@ void blk_insert_flush(struct request *rq)
                rq->cmd_flags &= ~REQ_FUA;
 
        /*
+        * REQ_PREFLUSH|REQ_FUA implies REQ_SYNC, so if we clear any
+        * of those flags, we have to set REQ_SYNC to avoid skewing
+        * the request accounting.
+        */
+       rq->cmd_flags |= REQ_SYNC;
+
+       /*
         * An empty flush handed down from a stacking driver may
         * translate into nothing if the underlying device does not
         * advertise a write-back cache.  In this case, simply