Add warning about potentially missing O_DIRECT support or bad alignment

If the first O_DIRECT fails, then it's likely because:

1) The file system does not support O_DIRECT, or
2) The user set iomem_align to an unsupported value.

Let the user know, otherwise they only see EINVAL and may not realize
why things aren't working.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/ioengines.c b/ioengines.c
index 4c97d038630e05c8767907fbd09db1ac862f21f4..7f0a5c4520bab954d1e8eaa4df04ee115f8290e1 100644 (file)
--- a/ioengines.c
+++ b/ioengines.c
@@ -245,6 +245,18 @@ int td_io_queue(struct thread_data *td, struct io_u *io_u)
 
        unlock_file(td, io_u->file);
 
+       /*
+        * Add warning for O_DIRECT so that users have an easier time
+        * spotting potentially bad alignment. If this triggers for the first
+        * IO, then it's likely an alignment problem or because the host fs
+        * does not support O_DIRECT
+        */
+       if (io_u->error == EINVAL && td->io_issues[io_u->ddir] == 1 &&
+           td->o.odirect) {
+               log_info("fio: first direct IO errored. File system may not "
+                        "support direct IO, or iomem_align= is bad.\n");
+       }
+
        if (!td->io_ops->commit) {
                io_u_mark_submit(td, 1);
                io_u_mark_complete(td, 1);