cdrom: reduce stack usage of mmc_ioctl_dvd_read_struct

1. kmalloc 192 bytes in dvd_read_bca (which is inlined into dvd_read_struct)
2. Pass struct packet_command to all dvd_read_* functions.

Checkstack output:
Before: mmc_ioctl_dvd_read_struct:         280
After:  mmc_ioctl_dvd_read_struct:         56

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 77 insertions, 62 deletions

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index b927aa244247..cceace61ef28 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -1712,29 +1712,30 @@ static int dvd_do_auth(struct cdrom_device_info *cdi, dvd_authinfo *ai)
         return 0;
 }
 
-static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s,
+                                struct packet_command *cgc)
 {
         unsigned char buf[21], *base;
         struct dvd_layer *layer;
-        struct packet_command cgc;
         struct cdrom_device_ops *cdo = cdi->ops;
         int ret, layer_num = s->physical.layer_num;
 
         if (layer_num >= DVD_LAYERS)
                 return -EINVAL;
 
-        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
-        cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
-        cgc.cmd[6] = layer_num;
-        cgc.cmd[7] = s->type;
-        cgc.cmd[9] = cgc.buflen & 0xff;
+        init_cdrom_command(cgc, buf, sizeof(buf), CGC_DATA_READ);
+        cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+        cgc->cmd[6] = layer_num;
+        cgc->cmd[7] = s->type;
+        cgc->cmd[9] = cgc->buflen & 0xff;
 
         /*
          * refrain from reporting errors on non-existing layers (mainly)
          */
-        cgc.quiet = 1;
+        cgc->quiet = 1;
 
-        if ((ret = cdo->generic_packet(cdi, &cgc)))
+        ret = cdo->generic_packet(cdi, cgc);
+        if (ret)
                 return ret;
 
         base = &buf[4];
@@ -1762,21 +1763,22 @@ static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s)
         return 0;
 }
 
-static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s,
+                                struct packet_command *cgc)
 {
         int ret;
         u_char buf[8];
-        struct packet_command cgc;
         struct cdrom_device_ops *cdo = cdi->ops;
 
-        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
-        cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
-        cgc.cmd[6] = s->copyright.layer_num;
-        cgc.cmd[7] = s->type;
-        cgc.cmd[8] = cgc.buflen >> 8;
-        cgc.cmd[9] = cgc.buflen & 0xff;
+        init_cdrom_command(cgc, buf, sizeof(buf), CGC_DATA_READ);
+        cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+        cgc->cmd[6] = s->copyright.layer_num;
+        cgc->cmd[7] = s->type;
+        cgc->cmd[8] = cgc->buflen >> 8;
+        cgc->cmd[9] = cgc->buflen & 0xff;
 
-        if ((ret = cdo->generic_packet(cdi, &cgc)))
+        ret = cdo->generic_packet(cdi, cgc);
+        if (ret)
                 return ret;
 
         s->copyright.cpst = buf[4];
@@ -1785,79 +1787,89 @@ static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s)
         return 0;
 }
 
-static int dvd_read_disckey(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_disckey(struct cdrom_device_info *cdi, dvd_struct *s,
+                                struct packet_command *cgc)
 {
         int ret, size;
         u_char *buf;
-        struct packet_command cgc;
         struct cdrom_device_ops *cdo = cdi->ops;
 
         size = sizeof(s->disckey.value) + 4;
 
-        if ((buf = kmalloc(size, GFP_KERNEL)) == NULL)
+        buf = kmalloc(size, GFP_KERNEL);
+        if (!buf)
                 return -ENOMEM;
 
-        init_cdrom_command(&cgc, buf, size, CGC_DATA_READ);
-        cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
-        cgc.cmd[7] = s->type;
-        cgc.cmd[8] = size >> 8;
-        cgc.cmd[9] = size & 0xff;
-        cgc.cmd[10] = s->disckey.agid << 6;
+        init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+        cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+        cgc->cmd[7] = s->type;
+        cgc->cmd[8] = size >> 8;
+        cgc->cmd[9] = size & 0xff;
+        cgc->cmd[10] = s->disckey.agid << 6;
 
-        if (!(ret = cdo->generic_packet(cdi, &cgc)))
+        ret = cdo->generic_packet(cdi, cgc);
+        if (!ret)
                 memcpy(s->disckey.value, &buf[4], sizeof(s->disckey.value));
 
         kfree(buf);
         return ret;
 }
 
-static int dvd_read_bca(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_bca(struct cdrom_device_info *cdi, dvd_struct *s,
+                        struct packet_command *cgc)
 {
-        int ret;
-        u_char buf[4 + 188];
-        struct packet_command cgc;
+        int ret, size = 4 + 188;
+        u_char *buf;
         struct cdrom_device_ops *cdo = cdi->ops;
 
-        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
-        cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
-        cgc.cmd[7] = s->type;
-        cgc.cmd[9] = cgc.buflen & 0xff;
+        buf = kmalloc(size, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
 
-        if ((ret = cdo->generic_packet(cdi, &cgc)))
-                return ret;
+        init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+        cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+        cgc->cmd[7] = s->type;
+        cgc->cmd[9] = cgc->buflen & 0xff;
+
+        ret = cdo->generic_packet(cdi, cgc);
+        if (ret)
+                goto out;
 
         s->bca.len = buf[0] << 8 | buf[1];
         if (s->bca.len < 12 || s->bca.len > 188) {
                 cdinfo(CD_WARNING, "Received invalid BCA length (%d)\n", s->bca.len);
-                return -EIO;
+                ret = -EIO;
+                goto out;
         }
         memcpy(s->bca.value, &buf[4], s->bca.len);
-
-        return 0;
+        ret = 0;
+out:
+        kfree(buf);
+        return ret;
 }
 
-static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s,
+                                struct packet_command *cgc)
 {
         int ret = 0, size;
         u_char *buf;
-        struct packet_command cgc;
         struct cdrom_device_ops *cdo = cdi->ops;
 
         size = sizeof(s->manufact.value) + 4;
 
-        if ((buf = kmalloc(size, GFP_KERNEL)) == NULL)
+        buf = kmalloc(size, GFP_KERNEL);
+        if (!buf)
                 return -ENOMEM;
 
-        init_cdrom_command(&cgc, buf, size, CGC_DATA_READ);
-        cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
-        cgc.cmd[7] = s->type;
-        cgc.cmd[8] = size >> 8;
-        cgc.cmd[9] = size & 0xff;
+        init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+        cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+        cgc->cmd[7] = s->type;
+        cgc->cmd[8] = size >> 8;
+        cgc->cmd[9] = size & 0xff;
 
-        if ((ret = cdo->generic_packet(cdi, &cgc))) {
-                kfree(buf);
-                return ret;
-        }
+        ret = cdo->generic_packet(cdi, cgc);
+        if (ret)
+                goto out;
 
         s->manufact.len = buf[0] << 8 | buf[1];
         if (s->manufact.len < 0 || s->manufact.len > 2048) {
@@ -1868,27 +1880,29 @@ static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s)
                 memcpy(s->manufact.value, &buf[4], s->manufact.len);
         }
 
+out:
         kfree(buf);
         return ret;
 }
 
-static int dvd_read_struct(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_struct(struct cdrom_device_info *cdi, dvd_struct *s,
+                                struct packet_command *cgc)
 {
         switch (s->type) {
         case DVD_STRUCT_PHYSICAL:
-                return dvd_read_physical(cdi, s);
+                return dvd_read_physical(cdi, s, cgc);
 
         case DVD_STRUCT_COPYRIGHT:
-                return dvd_read_copyright(cdi, s);
+                return dvd_read_copyright(cdi, s, cgc);
 
         case DVD_STRUCT_DISCKEY:
-                return dvd_read_disckey(cdi, s);
+                return dvd_read_disckey(cdi, s, cgc);
 
         case DVD_STRUCT_BCA:
-                return dvd_read_bca(cdi, s);
+                return dvd_read_bca(cdi, s, cgc);
 
         case DVD_STRUCT_MANUFACT:
-                return dvd_read_manufact(cdi, s);
+                return dvd_read_manufact(cdi, s, cgc);
                 
         default:
                 cdinfo(CD_WARNING, ": Invalid DVD structure read requested (%d)\n",
@@ -3027,7 +3041,8 @@ static noinline int mmc_ioctl_cdrom_pause_resume(struct cdrom_device_info *cdi,
 }
 
 static noinline int mmc_ioctl_dvd_read_struct(struct cdrom_device_info *cdi,
-                                                void __user *arg)
+                                                void __user *arg,
+                                                struct packet_command *cgc)
 {
         int ret;
         dvd_struct *s;
@@ -3046,7 +3061,7 @@ static noinline int mmc_ioctl_dvd_read_struct(struct cdrom_device_info *cdi,
                 return -EFAULT;
         }
 
-        ret = dvd_read_struct(cdi, s);
+        ret = dvd_read_struct(cdi, s, cgc);
         if (ret)
                 goto out;
 
@@ -3132,7 +3147,7 @@ static int mmc_ioctl(struct cdrom_device_info *cdi, unsigned int cmd,
         case CDROMRESUME:
                 return mmc_ioctl_cdrom_pause_resume(cdi, &cgc, cmd);
         case DVD_READ_STRUCT:
-                return mmc_ioctl_dvd_read_struct(cdi, userptr);
+                return mmc_ioctl_dvd_read_struct(cdi, userptr, &cgc);
         case DVD_AUTH:
                 return mmc_ioctl_dvd_auth(cdi, userptr);
         case CDROM_NEXT_WRITABLE: