Messages in this thread | | | Date | Wed, 30 Oct 2002 10:05:34 -0800 | From | Patrick Mansfield <> | Subject | Re: [PATCH] 2.5 current bk fix setting scsi queue depths |
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On Wed, Oct 30, 2002 at 11:17:52AM -0600, James Bottomley wrote: > patmans@us.ibm.com said: > > This patch fixes a problem with the current linus bk tree setting scsi > > queue depths to 1. Please apply. > > This patch causes the depth specification to be retained when we release > commandblocks. Since releasing command blocks is supposed only to be done > when we give up the device (and therefore, is supposed to clear everything), > your fix looks like it's merely masking a problem, not fixing it. > > Is the real problem that this controller is getting a release command blocks > and then a reallocate of them after slave_attach is called? If so, that's > probably what needs to be fixed. > > James
Yes, the problem is that in scsi_register_host() if there are no upper level drivers - the standard case if building no modules - we call scsi_release_commandblocks even though we are NOT getting rid of the scsi_device. So, with current code, new_queue_depth and current_queue_depth are zero.
When we register upper level drivers in scsi_register_device(), we call scsi_build_commandblocks (again), and get a queue depth of 1, since we've cleared new_queue_depth.
(In many cases, for one device we call build command blocks twice, call release command blocks, and then build command blocks again. Yuck)
Removing the scsi_release_commandblocks() in scsi_register_host() would also fix the problem, and in most cases, would not waste any space. In the worst case AFAICT it would waste one scsi_cmnd (about 300 or so bytes?).
I see no good reason to zero new_queue_depth in scsi_release_commandblocks, as new_queue_depth is the desired queue depth, and should remain so until scsi_adjust_queue_depth is called. Setting new_queue_depth to zero means we have to call slave_attach again to set it right, and depending on what else an adapter slave_attach does could be very wrong.
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