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Date: Mon, 25 Aug 2008 19:56:17 +0900
From: Tejun Heo <tj@...nel.org>
To: Jens Axboe <jens.axboe@...cle.com>
Cc: James.Bottomley@...senPartnership.com, bzolnier@...il.com,
bharrosh@...asas.com, greg.freemyer@...il.com,
linux-scsi@...r.kernel.org, brking@...ux.vnet.ibm.com, liml@....ca,
viro@....linux.org.uk, linux-ide@...r.kernel.org, neilb@...e.de,
linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: [PATCH 13/13] block: allow disk to have extended device number
Now that disk and partition handlings are mostly unified, it's easy to
allow disk to have extended device number. This patch makes
add_disk() use extended device number if disk->minors is zero. Both
sd and ide-disk are updated to use this.
* sd_format_disk_name() is implemented which can generically determine
the drive name. This removes disk number restriction stemming from
limited device names.
* If sd index goes over SD_MAX_DISKS (which can be increased now BTW),
sd simply doesn't initialize minors letting block layer choose
extended device number.
* If CONFIG_DEBUG_EXT_DEVT is set, both sd and ide-disk always set
minors to 0 and use extended device numbers.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
block/genhd.c | 25 +++++++++++++++-
drivers/ide/ide-disk.c | 2 +-
drivers/scsi/sd.c | 74 +++++++++++++++++++++++++++++++++++-------------
fs/partitions/check.c | 1 +
include/linux/genhd.h | 3 +-
5 files changed, 82 insertions(+), 23 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 2bf0e67..90a986f 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -478,14 +478,37 @@ static int exact_lock(dev_t devt, void *data)
*
* This function registers the partitioning information in @disk
* with the kernel.
+ *
+ * FIXME: error handling
*/
void add_disk(struct gendisk *disk)
{
struct backing_dev_info *bdi;
+ dev_t devt;
int retval;
+ /* minors == 0 indicates to use ext devt from part0 and should
+ * be accompanied with EXT_DEVT flag. Make sure all
+ * parameters make sense.
+ */
+ WARN_ON(disk->minors && !(disk->major || disk->first_minor));
+ WARN_ON(!disk->minors && !(disk->flags & GENHD_FL_EXT_DEVT));
+
disk->flags |= GENHD_FL_UP;
- disk_to_dev(disk)->devt = MKDEV(disk->major, disk->first_minor);
+
+ retval = blk_alloc_devt(&disk->part0, &devt);
+ if (retval) {
+ WARN_ON(1);
+ return;
+ }
+ disk_to_dev(disk)->devt = devt;
+
+ /* ->major and ->first_minor aren't supposed to be
+ * dereferenced from here on, but set them just in case.
+ */
+ disk->major = MAJOR(devt);
+ disk->first_minor = MINOR(devt);
+
blk_register_region(disk_devt(disk), disk->minors, NULL,
exact_match, exact_lock, disk);
register_disk(disk);
diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index f584ef8..e6776c4 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -44,7 +44,7 @@
#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
#define IDE_DISK_MINORS (1 << PARTN_BITS)
#else
-#define IDE_DISK_MINORS 1
+#define IDE_DISK_MINORS 0
#endif
struct ide_disk_obj {
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 6598024..bcb04b2 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -89,7 +89,7 @@ MODULE_ALIAS_SCSI_DEVICE(TYPE_RBC);
#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
#define SD_MINORS 16
#else
-#define SD_MINORS 1
+#define SD_MINORS 0
#endif
static int sd_revalidate_disk(struct gendisk *);
@@ -1770,6 +1770,52 @@ static int sd_revalidate_disk(struct gendisk *disk)
}
/**
+ * sd_format_disk_name - format disk name
+ * @prefix: name prefix - ie. "sd" for SCSI disks
+ * @index: index of the disk to format name for
+ * @buf: output buffer
+ * @buflen: length of the output buffer
+ *
+ * SCSI disk names starts at sda. The 26th device is sdz and the
+ * 27th is sdaa. The last one for two lettered suffix is sdzz
+ * which is followed by sdaaa.
+ *
+ * This is basically 26 base counting with one extra 'nil' entry
+ * at the beggining from the second digit on and can be
+ * determined using similar method as 26 base conversion with the
+ * index shifted -1 after each digit is computed.
+ *
+ * CONTEXT:
+ * Don't care.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int sd_format_disk_name(char *prefix, int index, char *buf, int buflen)
+{
+ const int base = 'z' - 'a' + 1;
+ char *begin = buf + strlen(prefix);
+ char *end = buf + buflen;
+ char *p;
+ int unit;
+
+ p = end - 1;
+ *p = '\0';
+ unit = base;
+ do {
+ if (p == begin)
+ return -EINVAL;
+ *--p = 'a' + (index % unit);
+ index = (index / unit) - 1;
+ } while (index >= 0);
+
+ memmove(begin, p, end - p);
+ memcpy(buf, prefix, strlen(prefix));
+
+ return 0;
+}
+
+/**
* sd_probe - called during driver initialization and whenever a
* new scsi device is attached to the system. It is called once
* for each scsi device (not just disks) present.
@@ -1821,8 +1867,8 @@ static int sd_probe(struct device *dev)
if (error)
goto out_put;
- error = -EBUSY;
- if (index >= SD_MAX_DISKS)
+ error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
+ if (error)
goto out_free_index;
sdkp->device = sdp;
@@ -1849,24 +1895,12 @@ static int sd_probe(struct device *dev)
get_device(&sdp->sdev_gendev);
- gd->major = sd_major((index & 0xf0) >> 4);
- gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
- gd->minors = SD_MINORS;
- gd->fops = &sd_fops;
-
- if (index < 26) {
- sprintf(gd->disk_name, "sd%c", 'a' + index % 26);
- } else if (index < (26 + 1) * 26) {
- sprintf(gd->disk_name, "sd%c%c",
- 'a' + index / 26 - 1,'a' + index % 26);
- } else {
- 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);
+ if (index < SD_MAX_DISKS) {
+ gd->major = sd_major((index & 0xf0) >> 4);
+ gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
+ gd->minors = SD_MINORS;
}
-
+ gd->fops = &sd_fops;
gd->private_data = &sdkp->driver;
gd->queue = sdkp->device->request_queue;
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 6b7ac10..e6f378f 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -593,6 +593,7 @@ void del_gendisk(struct gendisk *disk)
disk_part_iter_exit(&piter);
invalidate_partition(disk, 0);
+ blk_free_devt(disk_to_dev(disk)->devt);
set_capacity(disk, 0);
disk->flags &= ~GENHD_FL_UP;
unlink_gendisk(disk);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 4b5d762..26868ca 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -59,6 +59,7 @@ enum {
};
#define DISK_MAX_PARTS 256
+#define DISK_NAME_LEN 32
#include <linux/major.h>
#include <linux/device.h>
@@ -140,7 +141,7 @@ struct gendisk {
int minors; /* maximum number of minors, =1 for
* disks that can't be partitioned. */
- char disk_name[32]; /* name of major driver */
+ char disk_name[DISK_NAME_LEN]; /* name of major driver */
/* Array of pointers to partitions indexed by partno.
* Protected with matching bdev lock but stat and other
--
1.5.4.5
--
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