Re: [PATCH 09/10] fs: add RWF_DSYNC aand RWF_SYNC

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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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