Messages in this thread | | | Subject | Re: [PATCH 2/3] target: Add max_write_same_len device attribute | From | "Nicholas A. Bellinger" <> | Date | Thu, 15 Nov 2012 11:23:12 -0800 |
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On Thu, 2012-11-15 at 05:53 -0500, Christoph Hellwig wrote: > On Thu, Nov 08, 2012 at 08:07:17PM +0000, Nicholas A. Bellinger wrote: > > From: Nicholas Bellinger <nab@linux-iscsi.org> > > > > This patch adds a new max_write_same_len device attribute for use with > > WRITE_SAME w/ UNMAP=0 backend emulation. > > > > Also, update block limits VPD emulation code in spc_emulate_evpd_b0() to > > set the default MAXIMUM WRITE SAME LENGTH value of zero. > > why do we need an exposed attribute for this? >
This is useful for userspace to reduce the allowed maximum from the default 0xFFFF set by IBLOCK. Allowing huge WRITE_SAMEs can very much effect performance (esp. with spinning media), so being able to reduce the max we accept via a userspace tunable is helpful.
--nab
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