Hello Christoph,
On 8 April 2016 at 01:52, Christoph Hellwig <hch@xxxxxx> wrote:
> This is the per-I/O equivalent of O_DSYNC and O_SYNC, and very useful for
> all kinds of file servers and storage targets.
I've added some documentation for these flags to the man page, but in
the process I realized that have a question. Do these flags provide
equivalents of O_DSYNC and O_SYNC for the I/O operation, or for the
file? What I mean is this: with, say, RWF_DSYNC, is it just the data
written by this pwritev2() call that is synced to the underlying file,
or is all dirty data for the file synced at that point?
Thanks,
Michael
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/read_write.c | 6 +++++-
> include/uapi/linux/fs.h | 2 ++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index cf377cf..3729d8d 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -698,12 +698,16 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
> struct kiocb kiocb;
> ssize_t ret;
>
> - if (flags & ~RWF_HIPRI)
> + if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))
> return -EOPNOTSUPP;
>
> init_sync_kiocb(&kiocb, filp);
> if (flags & RWF_HIPRI)
> kiocb.ki_flags |= IOCB_HIPRI;
> + if (flags & RWF_DSYNC)
> + kiocb.ki_flags |= IOCB_DSYNC;
> + if (flags & RWF_SYNC)
> + kiocb.ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
> kiocb.ki_pos = *ppos;
>
> ret = fn(&kiocb, iter);
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index a079d50..e21fe04 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -324,5 +324,7 @@ struct fscrypt_policy {
>
> /* flags for preadv2/pwritev2: */
> #define RWF_HIPRI 0x00000001 /* high priority request, poll if possible */
> +#define RWF_DSYNC 0x00000002 /* per-IO O_DSYNC */
> +#define RWF_SYNC 0x00000004 /* per-IO O_SYNC */
>
> #endif /* _UAPI_LINUX_FS_H */
> --
> 2.1.4
>
> --
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--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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