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@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/genhd.c b/block/genhd.c
index eedab5b..d9de3e4 100644 (file)
--- 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 29c8ae7..33ea8c0 100644 (file)
--- 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 (file)
--- 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 *);
@@ -1769,6 +1769,52 @@ static int sd_revalidate_disk(struct gendisk *disk)
        return 0;
 }
 
+/**
+ *     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
@@ -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 772b2ed..0e41160 100644 (file)
--- 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 04524c2..206cdf9 100644 (file)
--- 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