[PATCH] Initialise scatter/gather list in sg driver

[PATCH] Initialise scatter/gather list in sg driver

[Anton Blanchard]

After turning on DEBUG_SG I hit a fail:

kernel BUG at include/linux/scatterlist.h:50!

	ata_qc_issue
	ata_scsi_translate
	ipr_queuecommand
	scsi_dispatch_cmd
	scsi_request_fn
	elv_insert
	blk_execute_rq_nowait
	blk_execute_rq
	sg_io
	scsi_cmd_ioctl
	cdrom_ioctl
	sr_block_ioctl
	blkdev_driver_ioctl
	blkdev_ioctl
	block_ioctl
	do_ioctl
	vfs_ioctl
	sys_ioctl
	sg_ioctl_trans

It looks like ata_sg_setup is working on an uninitialised sg table. Call
sg_init_table to initialise it before use.

Signed-off-by: Anton Blanchard <anton@samba.org>
---

Jens this is against your sg branch. This fixes the fail but Id
appreciate a confirmation that it's the right fix :)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index b5f7c59..4de41bb 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4689,6 +4689,7 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
 		 * data in this function or read data in ata_sg_clean.
 		 */
 		offset = lsg->offset + lsg->length - qc->pad_len;
+		sg_init_table(psg, 1);
 		sg_set_page(psg, nth_page(sg_page(lsg), offset >> PAGE_SHIFT),
 				qc->pad_len, offset_in_page(offset));
 

[PATCH] Initialise scatter/gather list in sg driver

[Anton Blanchard]

After turning on DEBUG_SG I hit a fail:

kernel BUG at include/linux/scatterlist.h:50!

	sg_build_indirect
	sg_build_reserve
	sg_open
	chrdev_open
	__dentry_open
	do_filp_open
	do_sys_open

We should initialise the sg list when we allocate it in sg_build_sgat.

Signed-off-by: Anton Blanchard <anton@samba.org>
---

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index b5fa4f0..f1871ea 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1652,6 +1652,7 @@ sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
 	schp->buffer = kzalloc(sg_bufflen, gfp_flags);
 	if (!schp->buffer)
 		return -ENOMEM;
+	sg_init_table(schp->buffer, tablesize);
 	schp->sglist_len = sg_bufflen;
 	return tablesize;	/* number of scat_gath elements allocated */
 }

Re: [PATCH] Initialise scatter/gather list in sg driver

[Jens Axboe]

On Thu, Oct 25 2007, Anton Blanchard wrote:
> 
> After turning on DEBUG_SG I hit a fail:
> 
> kernel BUG at include/linux/scatterlist.h:50!
> 
> 	sg_build_indirect
> 	sg_build_reserve
> 	sg_open
> 	chrdev_open
> 	__dentry_open
> 	do_filp_open
> 	do_sys_open
> 
> We should initialise the sg list when we allocate it in sg_build_sgat.
> 
> Signed-off-by: Anton Blanchard <anton@samba.org>
> ---
> 
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index b5fa4f0..f1871ea 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -1652,6 +1652,7 @@ sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
>  	schp->buffer = kzalloc(sg_bufflen, gfp_flags);
>  	if (!schp->buffer)
>  		return -ENOMEM;
> +	sg_init_table(schp->buffer, tablesize);
>  	schp->sglist_len = sg_bufflen;
>  	return tablesize;	/* number of scat_gath elements allocated */
>  }

Thanks, applied!

-- 
Jens Axboe