On Thu, Nov 3, 2011 at 14:45, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> Using sync_file_range means that neither any required metadata gets commited,
> nor the disk cache gets flushed. Stop using it for the journal, and add
> a comment on why a fsync_range system call would be helpful here.
One clarification here that came up in a conversation: the code quoted
was explicitly inside if (is_bdev), that is, it is only used when the
journal was on a raw block device. That should make a lot of the
metadata & block allocation irrelevant.
We're still very interested in hearing what are the real world barrier
/ write cache flush guarantees from all the syscalls; the
documentation doesn't guarantee much, even for fsync.. from fsync(2):
If the underlying hard disk has write caching enabled, then the
data may not really be on
permanent storage when fsync() / fdatasync() return.
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