On 12/14/2017 11:38 AM, Avi Kivity wrote:
I'm looking to add support for RWF_NOWAIT within a linux-aio iocb.Here is the return codes for RWF_NOWAIT
Naturally, I need to detect at runtime whether the kernel support
RWF_NOWAIT or not.
The only method I could find was to issue an I/O with RWF_NOWAIT set,
and look for errors. This is somewhat less than perfect:
Â- from the error, I can't tell whether RWF_NOWAIT was the problem, or
something else. If I enable a number of new features, I have to run
through all combinations to figure out which ones are supported and
which are not.
EINVAL - not supported (older kernel)
EOPNOTSUPP - not supported
EAGAIN - supported but could not complete because I/O will be delayed
0 - supported and I/O completed (success).
Â- RWF_NOWAIT support is per-filesystem, so I can't just remember not toYes, the support is per filesystem. So, the application must know if the
enable RWF_NOWAIT globally, I have to track it per file.
filesystem supports it, possibly by performing a small I/O.