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Date: Tue, 01 Nov 2011 13:03:14 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH v2] migration: flush migration data to disk.
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiri Denemark <jdenemar@redhat.com>, qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>

On 10/27/2011 02:12 AM, Gerd Hoffmann wrote:
> This patch increases robustness when migrating to a file with
> two little changes:
>
>   (1) Before closing the migration file handle checks if it happens to be
>       a regular file and if so it issues a fsync.  This way the data is
>       flushed to disk before qemu sends the migration completed event.
>   (2) It adds error checking.  In case either fsync or close syscall
>       fails pass up the error (and fail migration).
>
> [ v2: return -errno instead of -1 ]
>
> Cc: Juan Quintela<quintela@redhat.com>
> Cc: Jiri Denemark<jdenemar@redhat.com>
> Signed-off-by: Gerd Hoffmann<kraxel@redhat.com>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>   migration-fd.c |   23 ++++++++++++++++++++++-
>   1 files changed, 22 insertions(+), 1 deletions(-)
>
> diff --git a/migration-fd.c b/migration-fd.c
> index d0aec89..6211124 100644
> --- a/migration-fd.c
> +++ b/migration-fd.c
> @@ -42,10 +42,31 @@ static int fd_write(MigrationState *s, const void * buf, size_t size)
>
>   static int fd_close(MigrationState *s)
>   {
> +    struct stat st;
> +    int ret;
> +
>       DPRINTF("fd_close\n");
>       if (s->fd != -1) {
> -        close(s->fd);
> +        ret = fstat(s->fd,&st);
> +        if (ret == 0&&  S_ISREG(st.st_mode)) {
> +            /*
> +             * If the file handle is a regular file make sure the
> +             * data is flushed to disk before signaling success.
> +             */
> +            ret = fsync(s->fd);
> +            if (ret != 0) {
> +                ret = -errno;
> +                perror("migration-fd: fsync");
> +                return ret;
> +            }
> +        }
> +        ret = close(s->fd);
>           s->fd = -1;
> +        if (ret != 0) {
> +            ret = -errno;
> +            perror("migration-fd: close");
> +            return ret;
> +        }
>       }
>       return 0;
>   }