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[SCSI] sg: cap reserved_size values at max_sectors

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This patch (as857) modifies the SG_GET_RESERVED_SIZE and
SG_SET_RESERVED_SIZE ioctls in the sg driver, capping the values at
the device's request_queue's max_sectors value.  This will permit
cdrecord to obtain a legal value for the maximum transfer length,
fixing Bugzilla #7026.

The patch also caps the initial reserved_size value.  There's no
reason to have a reserved buffer larger than max_sectors, since it
would be impossible to use the extra space.

The corresponding ioctls in the block layer are modified similarly,
and the initial value for the reserved_size is set as large as
possible.  This will effectively make it default to max_sectors.
Note that the actual value is meaningless anyway, since block devices
don't have a reserved buffer.

Finally, the BLKSECTGET ioctl is added to sg, so that there will be a
uniform way for users to determine the actual max_sectors value for
any raw SCSI transport.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Acked-by: Douglas Gilbert <dougg@torque.net>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
This commit is contained in:
Alan Stern 2007-02-20 11:01:57 -05:00 committed by James Bottomley
parent 1079a2d251
commit 44ec95425c
3 changed files with 16 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
block/ll_rw_blk.c
View File

@ -1925,6 +1925,8 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
q->sg_reserved_size = INT_MAX;
/*
* all done
*/

4
block/scsi_ioctl.c
View File

@ -78,7 +78,9 @@ static int sg_set_timeout(request_queue_t *q, int __user *p)
static int sg_get_reserved_size(request_queue_t *q, int __user *p)
{
return put_user(q->sg_reserved_size, p);
unsigned val = min(q->sg_reserved_size, q->max_sectors << 9);
return put_user(val, p);
}
static int sg_set_reserved_size(request_queue_t *q, int __user *p)

13
drivers/scsi/sg.c
View File

@ -917,6 +917,8 @@ sg_ioctl(struct inode *inode, struct file *filp,
return result;
if (val < 0)
return -EINVAL;
val = min_t(int, val,
sdp->device->request_queue->max_sectors * 512);
if (val != sfp->reserve.bufflen) {
if (sg_res_in_use(sfp) || sfp->mmap_called)
return -EBUSY;
@ -925,7 +927,8 @@ sg_ioctl(struct inode *inode, struct file *filp,
}
return 0;
case SG_GET_RESERVED_SIZE:
val = (int) sfp->reserve.bufflen;
val = min_t(int, sfp->reserve.bufflen,
sdp->device->request_queue->max_sectors * 512);
return put_user(val, ip);
case SG_SET_COMMAND_Q:
result = get_user(val, ip);
@ -1061,6 +1064,9 @@ sg_ioctl(struct inode *inode, struct file *filp,
if (sdp->detached)
return -ENODEV;
return scsi_ioctl(sdp->device, cmd_in, p);
case BLKSECTGET:
return put_user(sdp->device->request_queue->max_sectors * 512,
ip);
default:
if (read_only)
return -EPERM; /* don't know so take safe approach */
@ -2339,6 +2345,7 @@ sg_add_sfp(Sg_device * sdp, int dev)
{
Sg_fd *sfp;
unsigned long iflags;
int bufflen;
sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
if (!sfp)
@ -2369,7 +2376,9 @@ sg_add_sfp(Sg_device * sdp, int dev)
if (unlikely(sg_big_buff != def_reserved_size))
sg_big_buff = def_reserved_size;
sg_build_reserve(sfp, sg_big_buff);
bufflen = min_t(int, sg_big_buff,
sdp->device->request_queue->max_sectors * 512);
sg_build_reserve(sfp, bufflen);
SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: bufflen=%d, k_use_sg=%d\n",
sfp->reserve.bufflen, sfp->reserve.k_use_sg));
return sfp;