linux-kernel - sync_file_range(SYNC_FILE_RANGE

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Message-ID: <20080530102619.GA2468@elf.ucw.cz>
Date:	Fri, 30 May 2008 12:26:19 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	kernel list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: sync_file_range(SYNC_FILE_RANGE_WRITE) blocks?

Hi!

sync_file_range(SYNC_FILE_RANGE_WRITE) blocks ... which makes problem
for s2disk: there we want to start writeout as early as possible
(system is going to shut down after write, and we need the data on
disk).

Unfortuantely, sync_file_range(SYNC_FILE_RANGE_WRITE) blocks, which
does not work for us. Is there non-blocking variant? "Start writeout
on this fd, but don't block me"?

For now I'm doing:

static inline int start_writeout(int fd)
{
#ifdef SYS_sync_file_range
        if (fork())
                return 0;
        else {
                syscall(SYS_sync_file_range, fd,
                        (loff_t)0, (loff_t)0, SYNC_FILE_RANGE_WRITE);
                exit(0);
        }
#else
        errno = ENOSYS;
        return -1;
#endif
}

...but I'd prefer something more elegant...
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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