[PATCH] Reduce stack usage in sg.c

Yum Rayan
2005-03-22T08:03:42Z

Attempt to reduce stack usage in sg.c.

Used checkstack.pl script to measure stack usage and noted follows:

Before patch:
sg_ioctl - 412
sg_read - 200

After patch:
sg_ioctl - 92
sg_read - 96

Thanks,
Rayan

Signed-off-by: Yum Rayan <yum.rayan@gmail.com>

diff -Nur linux-2.6.11.5.orig/drivers/scsi/sg.c linux-2.6.11.5/drivers/scsi/sg.c
--- linux-2.6.11.5.orig/drivers/scsi/sg.c 2005-03-18 22:34:56.000000000 -0800
+++ linux-2.6.11.5/drivers/scsi/sg.c 2005-03-21 23:48:52.000000000 -0800
@@ -335,109 +335,143 @@
Sg_fd *sfp;
Sg_request *srp;
int req_pack_id = -1;
- struct sg_header old_hdr;
- sg_io_hdr_t new_hdr;
+ struct sg_header *old_hdr;
sg_io_hdr_t *hp;
+ int retval = 0;
+

if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
SCSI_LOG_TIMEOUT(3, printk("sg_read: %s, count=%d\n",
sdp->disk->disk_name, (int) count));
- if ((k = verify_area(VERIFY_WRITE, buf, count)))
- return k;
+ old_hdr = kmalloc(SZ_SG_HEADER, GFP_KERNEL);
+ if (!old_hdr)
+ return -ENOMEM;
+ if ((k = verify_area(VERIFY_WRITE, buf, count))) {
+ retval = k;
+ goto free_old_hdr;
+ }
if (sfp->force_packid && (count >= SZ_SG_HEADER)) {
- if (__copy_from_user(&old_hdr, buf, SZ_SG_HEADER))
- return -EFAULT;
- if (old_hdr.reply_len < 0) {
+ if (__copy_from_user(old_hdr, buf, SZ_SG_HEADER)){
+ retval = -EFAULT;
+ goto free_old_hdr;
+ }
+ if (old_hdr->reply_len < 0) {
if (count >= SZ_SG_IO_HDR) {
- if (__copy_from_user
- (&new_hdr, buf, SZ_SG_IO_HDR))
- return -EFAULT;
- req_pack_id = new_hdr.pack_id;
+ sg_io_hdr_t *new_hdr;
+ new_hdr = kmalloc(SZ_SG_IO_HDR, GFP_KERNEL);
+ if (!new_hdr) {
+ retval = -ENOMEM;
+ goto free_old_hdr;
+ }
+ retval = __copy_from_user(new_hdr, buf,
+ SZ_SG_IO_HDR);
+ req_pack_id = new_hdr->pack_id;
+ kfree(new_hdr);
+ if (retval) {
+ retval = -EFAULT;
+ goto free_old_hdr;
+ }
}
} else
- req_pack_id = old_hdr.pack_id;
+ req_pack_id = old_hdr->pack_id;
}
srp = sg_get_rq_mark(sfp, req_pack_id);
if (!srp) { /* now wait on packet to arrive */
- if (sdp->detached)
- return -ENODEV;
- if (filp->f_flags & O_NONBLOCK)
- return -EAGAIN;
+ if (sdp->detached) {
+ retval = -ENODEV;
+ goto free_old_hdr;
+ }
+ if (filp->f_flags & O_NONBLOCK) {
+ retval = -EAGAIN;
+ goto free_old_hdr;
+ }
while (1) {
- res = 0; /* following is a macro that beats race condition */
+ res = 0; /* following macro beats race condition */
__wait_event_interruptible(sfp->read_wait,
- (sdp->detached || (srp = sg_get_rq_mark(sfp, req_pack_id))),
- res);
- if (sdp->detached)
- return -ENODEV;
+ (sdp->detached ||
+ (srp = sg_get_rq_mark(sfp, req_pack_id))),
+ res);
+ if (sdp->detached) {
+ retval = -ENODEV;
+ goto free_old_hdr;
+ }
if (0 == res)
break;
- return res; /* -ERESTARTSYS because signal hit process */
+ retval = res; /* -ERESTARTSYS as signal hit process */
+ goto free_old_hdr;
}
}
- if (srp->header.interface_id != '\0')
- return sg_new_read(sfp, buf, count, srp);
+ if (srp->header.interface_id != '\0') {
+ retval = sg_new_read(sfp, buf, count, srp);
+ goto free_old_hdr;
+ }

hp = &srp->header;
- memset(&old_hdr, 0, SZ_SG_HEADER);
- old_hdr.reply_len = (int) hp->timeout;
- old_hdr.pack_len = old_hdr.reply_len; /* very old, strange behaviour */
- old_hdr.pack_id = hp->pack_id;
- old_hdr.twelve_byte =
+ memset(old_hdr, 0, SZ_SG_HEADER);
+ old_hdr->reply_len = (int) hp->timeout;
+ old_hdr->pack_len = old_hdr->reply_len; /* old, strange behaviour */
+ old_hdr->pack_id = hp->pack_id;
+ old_hdr->twelve_byte =
((srp->data.cmd_opcode >= 0xc0) && (12 == hp->cmd_len)) ? 1 : 0;
- old_hdr.target_status = hp->masked_status;
- old_hdr.host_status = hp->host_status;
- old_hdr.driver_status = hp->driver_status;
+ old_hdr->target_status = hp->masked_status;
+ old_hdr->host_status = hp->host_status;
+ old_hdr->driver_status = hp->driver_status;
if ((CHECK_CONDITION & hp->masked_status) ||
(DRIVER_SENSE & hp->driver_status))
- memcpy(old_hdr.sense_buffer, srp->sense_b,
- sizeof (old_hdr.sense_buffer));
+ memcpy(old_hdr->sense_buffer, srp->sense_b,
+ sizeof (old_hdr->sense_buffer));
switch (hp->host_status) {
/* This setup of 'result' is for backward compatibility and is best
ignored by the user who should use target, host + driver status */
case DID_OK:
case DID_PASSTHROUGH:
case DID_SOFT_ERROR:
- old_hdr.result = 0;
+ old_hdr->result = 0;
break;
case DID_NO_CONNECT:
case DID_BUS_BUSY:
case DID_TIME_OUT:
- old_hdr.result = EBUSY;
+ old_hdr->result = EBUSY;
break;
case DID_BAD_TARGET:
case DID_ABORT:
case DID_PARITY:
case DID_RESET:
case DID_BAD_INTR:
- old_hdr.result = EIO;
+ old_hdr->result = EIO;
break;
case DID_ERROR:
- old_hdr.result = (srp->sense_b[0] == 0 &&
+ old_hdr->result = (srp->sense_b[0] == 0 &&
hp->masked_status == GOOD) ? 0 : EIO;
break;
default:
- old_hdr.result = EIO;
+ old_hdr->result = EIO;
break;
}

/* Now copy the result back to the user buffer. */
if (count >= SZ_SG_HEADER) {
- if (__copy_to_user(buf, &old_hdr, SZ_SG_HEADER))
- return -EFAULT;
+ if (__copy_to_user(buf, old_hdr, SZ_SG_HEADER)) {
+ retval = -EFAULT;
+ goto free_old_hdr;
+ }
buf += SZ_SG_HEADER;
- if (count > old_hdr.reply_len)
- count = old_hdr.reply_len;
+ if (count > old_hdr->reply_len)
+ count = old_hdr->reply_len;
if (count > SZ_SG_HEADER) {
if ((res =
sg_read_oxfer(srp, buf, count - SZ_SG_HEADER)))
- return -EFAULT;
+ retval = -EFAULT;
+ goto free_old_hdr;
}
} else
- count = (old_hdr.result == 0) ? 0 : -EIO;
+ count = (old_hdr->result == 0) ? 0 : -EIO;
sg_finish_rem_req(srp);
- return count;
+ retval = count;
+free_old_hdr:
+ kfree(old_hdr);
+ return retval;
}

static ssize_t
@@ -943,8 +977,11 @@
if (result)
return result;
else {
- sg_req_info_t rinfo[SG_MAX_QUEUE];
- Sg_request *srp;
+ sg_req_info_t *rinfo;
+ rinfo = kmalloc(SG_MAX_QUEUE * SZ_SG_REQ_INFO,
+ GFP_KERNEL);
+ if (!rinfo)
+ return -ENOMEM;
read_lock_irqsave(&sfp->rq_list_lock, iflags);
for (srp = sfp->headrp, val = 0; val < SG_MAX_QUEUE;
++val, srp = srp ? srp->nextrp : srp) {
@@ -966,8 +1003,11 @@
}
}
read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
- return (__copy_to_user(p, rinfo,
- SZ_SG_REQ_INFO * SG_MAX_QUEUE) ? -EFAULT : 0);
+ result = __copy_to_user(p, rinfo, SZ_SG_REQ_INFO *
+ SG_MAX_QUEUE);
+ result = result ? -EFAULT : 0;
+ kfree(rinfo);
+ return result;
}
case SG_EMULATED_HOST:
if (sdp->detached)