On 2016-02-21, at 7:53 PM, John David Anglin wrote:
> Backtrace:
> [<000000004046f4b0>] scsi_init_sgtable+0x70/0xb8
> [<000000004046f564>] scsi_init_io+0x6c/0x220
> [<000000000811c5c0>] sd_setup_read_write_cmnd+0x58/0x968 [sd_mod]
> [<000000000811cf14>] sd_init_command+0x44/0x130 [sd_mod]
> [<000000004046f81c>] scsi_setup_cmnd+0x104/0x1b0
> [<000000004046fab8>] scsi_prep_fn+0x100/0x1a0
> [<000000004035b9b0>] blk_peek_request+0x1b8/0x298
> [<0000000040471028>] scsi_request_fn+0xf8/0xa90
> [<0000000040357244>] __blk_run_queue+0x4c/0x70
> [<00000000403802c4>] cfq_insert_request+0x2dc/0x580
> [<0000000040356404>] __elv_add_request+0x1b4/0x300
>
> We have in blk-merge.c:
>
> else {
> /*
> * If the driver previously mapped a shorter
> * list, we could see a termination bit
> * prematurely unless it fully inits the sg
> * table on each mapping. We KNOW that there
> * must be more entries here or the driver
> * would be buggy, so force clear the
> * termination bit to avoid doing a full
> * sg_init_table() in drivers for each command.
> */
> if (sg_is_last (*sg))
> printk ("__blk_segment_map_sg: clearing termination bi
> t\n");
> sg_unmark_end(*sg);
> *sg = sg_next(*sg);
> BUG_ON (!*sg);
> }
>
> The comment suggests there must be more entries...
I'm thinking with the split the scsi driver needs to provide one or two extra entires in the sg list.
Dave
--
John David Anglin dave.anglin@xxxxxxxx
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