Hi Christoph,
Sorry -- somehow I missed that you replied to my message...
On 08/09/2016 08:15 PM, Christoph Hellwig wrote:
> Hi Michael,
>
> On Sun, Aug 07, 2016 at 07:45:03AM +1000, Michael Kerrisk (man-pages) wrote:
>> 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?
>
> You beat me to it - I'm overdue sending you updates for these flags.
>
> The flags only affect the actual pwritev2 operation they are applied
> to. That is only the range just written is guaranteed to be on
> stable storage.
Thanks. I added some words to make that clear:
RWF_DSYNC (since Linux 4.7)
Provide a per-write equivalent of the O_DSYNC open(2) flag.
# This flag is meaningful only for pwritev2(), and its effect
# applies only to the data range written by the system call.
RWF_SYNC (since Linux 4.7)
Provide a per-write equivalent of the O_SYNC open(2) flag.
# This flag is meaningful only for pwritev2(), and its effect
# applies only to the data range written by the system call.
> Btw, I was going to just send you a patch, but it seems your update
> isn't out in the git tree yet, is it?
They were sitting in a private branch while I waited for (and missed)
your reply. The changes are now pushed in master. Thanks for your help.
Cheers,
Michael
--
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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