Synchronization in UBIFS (zero length files)

[Tanya Brokhman <tlinder@codeaurora.org>]

Hi Artem/Richard

I've been looking into the "zero length files" issue in UBIFS and came 
across "Synchronization exceptions for buggy applications" @ 
http://www.linux-mtd.infradead.org/doc/ubifs.html#L_sync_semantics. This 
section concludes with:

"We have plans to implement these features in UBIFS, but this has not 
been done yet. The problem is that UBI/MTD are fully synchronous and we 
cannot initiate asynchronous write-out, so we'd have to synchronously 
write files on close/rename, which is slow. So implementing these 
features would require implementing asynchronous I/O in UBI, which is a 
big job. But feel free to do this :-)."

So two questions:
1. was anything done in ubifs to handle file truncation and rename 
similar to ext4? Didn't find anything but afraid I might be missing 
something
2. Not sure I understand why "implementing these features would require 
implementing asynchronous I/O in UBI". Could you please elaborate on this?

Thanks,
Tanya Brokhman
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