Re: [PATCH 4/5] block: add trace point when fdatasync fails

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> A flush failure is a critical failure scenario for some operations.
> For example, it will prevent migration from completing, as it will
> make vm_stop() report an error. Thus it is important to have a
> trace point present for debugging.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

I'd have had to admit to not having thought that would fail; the fact
we're debugging something where it does, suggests it's a good idea!


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  block/file-posix.c | 2 ++
>  block/trace-events | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 99cf452f84..6aafeda44f 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1362,6 +1362,8 @@ static int handle_aiocb_flush(void *opaque)
>  
>      ret = qemu_fdatasync(aiocb->aio_fildes);
>      if (ret == -1) {
> +        trace_file_flush_fdatasync_failed(errno);
> +
>          /* There is no clear definition of the semantics of a failing fsync(),
>           * so we may have to assume the worst. The sad truth is that this
>           * assumption is correct for Linux. Some pages are now probably marked
> diff --git a/block/trace-events b/block/trace-events
> index 1a12d634e2..c8a943e992 100644
> --- a/block/trace-events
> +++ b/block/trace-events
> @@ -206,6 +206,7 @@ file_copy_file_range(void *bs, int src, int64_t src_off, int dst, int64_t dst_of
>  file_FindEjectableOpticalMedia(const char *media) "Matching using %s"
>  file_setup_cdrom(const char *partition) "Using %s as optical disc"
>  file_hdev_is_sg(int type, int version) "SG device found: type=%d, version=%d"
> +file_flush_fdatasync_failed(int err) "errno %d"
>  
>  # sheepdog.c
>  sheepdog_reconnect_to_sdog(void) "Wait for connection to be established"
> -- 
> 2.30.2
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK