[dm-devel] Re: [PATCH RFC 0/4] use scatter lists for all block pc requests and simplify hw handlers
James Bottomley
James.Bottomley at SteelEye.com
Sun Jun 5 14:40:08 UTC 2005
On Sun, 2005-06-05 at 00:15 -0700, Mike Christie wrote:
> +int scsi_execute_req(struct scsi_device *sdev, unsigned char *cmd,
> + int data_direction, void *buffer, unsigned
> bufflen,
> + unsigned char *sense, int timeout, int retries)
Actually, not quite; there are two problems with this
1. We may not be able to compute the command length for vendor specific
commands and the group 3 (variable length command 0x7f).
2. some requests want to set other flags (REQ_FAILFAST mostly).
However, extra arguments should accommodate these.
This:
> + if (!req)
Should be if (IS_ERR(req))
Also, you can't do this (use after free):
> + blk_put_request(req);
> + return req->errors;
Finally, there's coming up with a replacement API for scsi_do_req that
returns via the end_io callback ... since that doesn't do a wait/wake,
perhaps this should be the core API upon which the others are built?
James
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