On 1/24/24 21:13, Anthony Iliopoulos wrote:
On Wed, Jan 24, 2024 at 01:35:49PM +0100, Zdenek Kabelac wrote:
I guess our dev_flush() function is mostly handling all those cases properly
with the use of ioctl(BLKFLSBUF).
This ioctl by itself will only flush the page cache and not device
caches, but it is indeed followed by a fsync on the blockdev which is
basically the only way for userspace to trigger a device cache flush
when operating directly on a block device.
The only problem is - it's usage somehow vanished - and even in the past
it's been basically used only for non-direct usage so likely still not
correct.
Indeed, the device cache flushing is required for data integrity
irrespective of the io mode (unless O_DSYNC/RWF_DSYNC), direct-io only
obviates the need for flushing the page cache.
In my view, vg_commit() is a good place to call dev_flush(). This could
only affect (important) metadata IOs, make all write IOs to persistent
storage ASAP.
Thanks,
Heming
