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I'm trying to access a block device (say /dev/sdb) using libaio. I works correctly, but I was wondering how to perform FUA (Force Unit Access) using the API of libaio.

I must say the documentation I found on the subject is quite poor, hope one of you will be able to help me with this.

OznOg
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1 Answers1

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You can't, unfortunately. The interface is too limited. But what you should be able to do is use the SG_IO ioctl() for SYNCHRONIZE CACHE (10) or (16). That is, if your device supports the command. SYNCHRONIZE CACHE lets you instruct the device to commit a range of logical blocks to the medium.

See the manpage for the sg_sync command: http://manpages.ubuntu.com/manpages/trusty/man8/sg_sync.8.html

And download the latest sg3_utils source here: http://sg.danny.cz/sg/sg3_utils.html (as of now, version 1.41 http://sg.danny.cz/sg/p/sg3_utils-1.41.tar.xz). Look at the sg_sync command source to see how the ioctl is invoked.

ioctl(SG_IO) blocks, but there is a way to transact these commands with non-blocking I/O. Refer to the SCSI Generic HOWTO: http://sg.danny.cz/sg/p/sg_v3_ho.html

Mike Andrews
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