Messages in this thread Patch in this message | | | Date | Fri, 22 Feb 2008 16:25:20 -0600 | From | Mike Christie <> | Subject | Re: New 2.6.24.2 SG_IO SCSI problems |
| |
Mark Hounschell wrote: > Mark Hounschell wrote: >> Mike Christie wrote: >>> Mike Christie wrote: >>>> Mark Hounschell wrote: >>>>> I seem to have run into some sort of regression in the SG_IO >>>>> interface of 2.6.24.2. I have an application that up until 2.6.24 >>>>> worked fine. The 2.6.23.16 kernel works fine. >>>>> >>>>> During reads I get these kernel messages. Writes and other functions >>>>> _seem_ OK. Actually basic >>>>> reads are working. Its with large BC reads using an io_vec list that >>>>> the problem shows up. >>>>> >>>> Are you doing SG_IO to the sg device (/dev/sg*) or to the block device >>>> (/dev/sdX)? >>> If you are doing SG_IO to the sg device, then I know of one regression >>> (well not regression exactly, but I fixed a bug but the patch got >>> partially overwritten by another patch and that caused a new bug). Both >>> bugs are fixed in 2.6.25-rc2. Could you try that out if you are doing >>> SG_IO to the sg device. >>> >> Yes, I'm using /dev/sg*. And yes again I'll checkout 2.6.25-rc2 ASIC. >> >> Thanks >> Mark >> - > > 2.6.25-rc2 does fix the problem I'm having. I don't suppose there is a patch > lying around for 2.6.24.2?? >
I attached a backport of the patch from Tony (added as cc) that is in 2.6.25-rc2. Could you try it out against 2.6.24.2 just to make sure it was this patch, then we can send it to stable. Backport 76d78300a6eb8b7f08e47703b7e68a659ffc2053 to 2.6.24
From Tony Battersby:
When sending a SCSI command to a tape drive via the SCSI Generic (sg) driver, if the command has a data transfer length more than scatter_elem_sz (32 KB default) and not a multiple of 512, then I either hit BUG_ON(!valid_dma_direction(direction)) in dma_unmap_sg() or else the command never completes (depending on the LLDD).
When constructing scatterlists, the sg driver rounds up the scatterlist element sizes to be a multiple of 512. This can result in sum(scatterlist lengths) > bufflen. In this case, scsi_req_map_sg() incorrectly sets bio->bi_size to sum(scatterlist lengths) rather than to bufflen. When the command completes, req_bio_endio() detects that bio->bi_size != 0, and so it doesn't call bio_endio(). This causes the command to be resubmitted, resulting in BUG_ON or the command never completing.
This patch makes scsi_req_map_sg() set bio->bi_size to bufflen rather than to sum(scatterlist lengths), which fixes the problem.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
--- linux-2.6.24.2/drivers/scsi/scsi_lib.c 2008-02-10 23:51:11.000000000 -0600 +++ linux-2.6.24.2.work/drivers/scsi/scsi_lib.c 2008-02-22 16:20:09.000000000 -0600 @@ -298,7 +298,6 @@ static int scsi_req_map_sg(struct reques page = sg_page(sg); off = sg->offset; len = sg->length; - data_len += len; while (len > 0 && data_len > 0) { /* | |