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Date:      Wed, 11 Nov 1998 20:57:37 -0700 (MST)
From:      "Justin T. Gibbs" <gibbs@narnia.plutotech.com>
To:        Greg Lehey <grog@lemis.com>
Cc:        hackers@FreeBSD.ORG
Subject:   Re: SCSI tagged queueing and softupdates
Message-ID:  <199811120357.UAA06570@narnia.plutotech.com>
In-Reply-To: <199811110257.TAA28938@narnia.plutotech.com> <199811110854.BAA07678@usr02.primenet.com> <19981112120754.E463@freebie.lemis.com>

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> Bowrite guarantees that buffers queued after a call to bowrite will
> be written after the specified buffer (to a particular device).
> Bowrite does this either by taking advantage of hardware ordering support
> (e.g. tagged queueing on SCSI devices) or by resorting to a synchronous write.

bowrite never does a synchronous write.  Both the kernel elevator sort
and the SCSI tagged queuing code honor the B_ORDERED flag, so even
devices that cannot perform concurrent I/O can safely handled an ordered
write in a non-blocking fashion.

--
Justin

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