Steven Scholz wrote:
Hi there,
According to an (old) man page of sync(2)
According to the standard specification (e.g., SVID),
sync() schedules the writes, but may return before the
actual writing is done. However, since version 1.3.20
Linux does actually wait. (This still does not guarantee
data integrity: modern disks have large caches.)
How about recent kernels? Does sync() block until buffers are flushed?
How can I find out if the disk caches are actually flushed?
I want to make sure that all data is flushed to my disk drive before
powering down the system.
Thanks.
All disk caches are flushed before shutdown via the following path.
kernel/sys.c::sys_reboot()
kernel/drivers/base/power/shutdown.c::device_shutdown()
driver specific ->shutdown callback, for ide disks, the path is
drivers/ide/ide-disk.c::ide_device_shutdown()
drivers/ide/ide-disk.c::ide_cacheflush_p()
drivers/ide/ide-disk.c::do_idedisk_flushcache()
And, AFAIK, sync() doesn't flush disk caches.
--
tejun
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