Re: lots and lots of disks again

Kurt Garloff
2004-02-10T11:32:31Z

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Hi,

On Tue, Feb 10, 2004 at 12:04:17PM +0100, Kurt Garloff wrote:
> Hi Andrew,
>
> On Wed, Feb 04, 2004 at 02:45:12AM -0800, Andrew Morton wrote:
> > What to do about this?
>
> Apply my patch ;-)
>
> Find attached a patch that combines Badari's and Matthew's ideas.
> It corrects the typos in Matthew's code snippets.

Only that the patch was not attached.

Regadrs,
--
Kurt Garloff <garloff@suse.de> Cologne, DE
SUSE LINUX AG, Nuernberg, DE SUSE Labs (Head)

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--- drivers/scsi/sd.c.orig 2004-01-09 07:59:49.000000000 +0100
+++ drivers/scsi/sd.c 2004-02-10 09:44:24.913264768 +0100
@@ -19,6 +19,9 @@
* not being read in sd_open. Fix problem where removable media
* could be ejected after sd_open.
* - Douglas Gilbert <dgilbert@interlog.com> cleanup for lk 2.5.x
+ * - Badari Pulavarty <pbadari@us.ibm.com>, Matthew Wilcox
+ * <willy@debian.org>, Kurt Garloff <garloff@suse.de>:
+ * Support 256k disks (with potentially 64 partitions, TBD).
*
* Logging policy (needs CONFIG_SCSI_LOGGING defined):
* - setting up transfer: SCSI_LOG_HLQUEUE levels 1 and 2
@@ -61,7 +64,16 @@
* Remaining dev_t-handling stuff
*/
#define SD_MAJORS 16
-#define SD_DISKS (SD_MAJORS << 4)
+/* sd_index_bits array size / disks
+ * 32 / 256
+ * 4096 / 32768
+ * 32768 / 262144
+ */
+#ifdef CONFIG_EMBEDDED
+# define SD_DISKS 256
+#else
+# define SD_DISKS 32768 // we can raise this to 262144 if needed
+#endif

/*
* Time out in seconds for disks and Magneto-opticals (which are slower).
@@ -121,6 +132,22 @@
.init_command = sd_init_command,
};

+/* Major / minor to disk mapping, from Matthew Wilcox, corrected
+ * (mail to linux-scsi@vger.kernel.org from 2003-10-16)
+ *
+ * major p2 disc2 disc p1
+ * |............|..|..........|....|....| <- dev_t
+ * 31 20 17 8 7 4 3 0
+ *
+ * We allow 64 partitions per disk, by adding two more bits.
+ * Inside a major, we have 16k disks, however mapped non-
+ * contiguously. The first 16 disks are for major0, the next
+ * ones with major1, ... Disk 256 is for major0 again, disk 272
+ * for major1, ...
+ * We can't currently use the partitions beyond 16, as the
+ * genhd infrastructure expects contiguous minors.
+ */
+
static int sd_major(int major_idx)
{
switch (major_idx) {
@@ -136,6 +163,35 @@
}
}

+static int inv_sd_major(int major)
+{
+ switch (major) {
+ case SCSI_DISK0_MAJOR:
+ return 0;
+ case SCSI_DISK1_MAJOR ... SCSI_DISK7_MAJOR:
+ return major + 1 - SCSI_DISK1_MAJOR;
+ case SCSI_DISK8_MAJOR ... SCSI_DISK15_MAJOR:
+ return major + 8 - SCSI_DISK8_MAJOR;
+ default:
+ BUG();
+ return 0; /* shut up gcc */
+ }
+}
+
+unsigned int dev_to_sd_nr(unsigned int dev) {
+ return ((dev >> 4) & 15) | (inv_sd_major(dev >> 20) << 4) |
+ (dev & 0x3ff00);
+}
+
+unsigned int dev_to_sd_part(unsigned int dev) {
+ return (dev & 15) | ((dev >> 14) & 0x30);
+}
+
+unsigned int make_sd_dev(unsigned int sd_nr, unsigned int part) {
+ return (part & 0xf) | ((part & 0x30) << 14) | ((sd_nr & 0xf) << 4) |
+ (sd_major((sd_nr & 0xf0) >> 4) << 20) | (sd_nr & 0x3ff00);
+}
+
#define to_scsi_disk(obj) container_of(obj,struct scsi_disk,kobj);

static inline struct scsi_disk *scsi_disk(struct gendisk *disk)
@@ -1297,7 +1353,7 @@
struct scsi_disk *sdkp;
struct gendisk *gd;
u32 index;
- int error;
+ int error, devno;

error = -ENODEV;
if ((sdp->type != TYPE_DISK) && (sdp->type != TYPE_MOD))
@@ -1315,6 +1371,12 @@
kobject_init(&sdkp->kobj);
sdkp->kobj.ktype = &scsi_disk_kobj_type;

+ /* Note: We can accomodate 64 partitions, but the genhd code
+ * assumes partitions allocate consecutive minors, which they don't.
+ * So for now stay with max 16 partitions and leave two spare bits.
+ * Later, we may change the genhd code and the alloc_disk() call
+ * and the ->minors assignment here. KG, 2004-02-10
+ */
gd = alloc_disk(16);
if (!gd)
goto out_free;
@@ -1335,16 +1397,23 @@
sdkp->index = index;
sdkp->openers = 0;

- gd->major = sd_major(index >> 4);
- gd->first_minor = (index & 15) << 4;
+ devno = make_sd_dev(index, 0);
+ gd->major = MAJOR(devno);
+ gd->first_minor = MINOR(devno);
gd->minors = 16;
gd->fops = &sd_fops;

- if (index >= 26) {
+ if (index < 26) {
+ sprintf(gd->disk_name, "sd%c", 'a' + index % 26);
+ } else if (index < (26*27)) {
sprintf(gd->disk_name, "sd%c%c",
- 'a' + index/26-1,'a' + index % 26);
+ 'a' + index / 26 - 1,'a' + index % 26);
} else {
- sprintf(gd->disk_name, "sd%c", 'a' + index % 26);
+ const unsigned int m1 = (index / 26 - 1) / 26 - 1;
+ const unsigned int m2 = (index / 26 - 1) % 26;
+ const unsigned int m3 = index % 26;
+ sprintf(gd->disk_name, "sd%c%c%c",
+ 'a' + m1, 'a' + m2, 'a' + m3);
}

strcpy(gd->devfs_name, sdp->devfs_name);

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