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>

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>
Tejun Heo · Jens Axboe
1 parent 689d6fac40
Showing 5 changed files with 82 additions and 23 deletions Side-by-side Diff
block/genhd.c
drivers/ide/ide-disk.c
drivers/scsi/sd.c
fs/partitions/check.c
include/linux/genhd.h
@@ -478,14 +478,37 @@
  *
  * 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);
@@ -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 {
@@ -89,7 +89,7 @@
 #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 @@
 }
  
 /**
+ *	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 @@
 	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 @@
  
 	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;
  
@@ -593,6 +593,7 @@
 	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);
@@ -59,6 +59,7 @@
 };
  
 #define DISK_MAX_PARTS			256
+#define DISK_NAME_LEN			32
  
 #include <linux/major.h>
 #include <linux/device.h>
@@ -140,7 +141,7 @@
 	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
...	...	@@ -478,14 +478,37 @@
478	478	*
479	479	* This function registers the partitioning information in @disk
480	480	* with the kernel.
	481	+ *
	482	+ * FIXME: error handling
481	483	*/
482	484	void add_disk(struct gendisk *disk)
483	485	{
484	486	struct backing_dev_info *bdi;
	487	+ dev_t devt;
485	488	int retval;
486	489
	490	+ /* minors == 0 indicates to use ext devt from part0 and should
	491	+ * be accompanied with EXT_DEVT flag. Make sure all
	492	+ * parameters make sense.
	493	+ */
	494	+ WARN_ON(disk->minors && !(disk->major \|\| disk->first_minor));
	495	+ WARN_ON(!disk->minors && !(disk->flags & GENHD_FL_EXT_DEVT));
	496	+
487	497	disk->flags \|= GENHD_FL_UP;
488		- disk_to_dev(disk)->devt = MKDEV(disk->major, disk->first_minor);
	498	+
	499	+ retval = blk_alloc_devt(&disk->part0, &devt);
	500	+ if (retval) {
	501	+ WARN_ON(1);
	502	+ return;
	503	+ }
	504	+ disk_to_dev(disk)->devt = devt;
	505	+
	506	+ /* ->major and ->first_minor aren't supposed to be
	507	+ * dereferenced from here on, but set them just in case.
	508	+ */
	509	+ disk->major = MAJOR(devt);
	510	+ disk->first_minor = MINOR(devt);
	511	+
489	512	blk_register_region(disk_devt(disk), disk->minors, NULL,
490	513	exact_match, exact_lock, disk);
491	514	register_disk(disk);
...	...	@@ -44,7 +44,7 @@
44	44	#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
45	45	#define IDE_DISK_MINORS (1 << PARTN_BITS)
46	46	#else
47		-#define IDE_DISK_MINORS 1
	47	+#define IDE_DISK_MINORS 0
48	48	#endif
49	49
50	50	struct ide_disk_obj {
...	...	@@ -89,7 +89,7 @@
89	89	#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
90	90	#define SD_MINORS 16
91	91	#else
92		-#define SD_MINORS 1
	92	+#define SD_MINORS 0
93	93	#endif
94	94
95	95	static int sd_revalidate_disk(struct gendisk *);
...	...	@@ -1770,6 +1770,52 @@
1770	1770	}
1771	1771
1772	1772	/**
	1773	+ * sd_format_disk_name - format disk name
	1774	+ * @prefix: name prefix - ie. "sd" for SCSI disks
	1775	+ * @index: index of the disk to format name for
	1776	+ * @buf: output buffer
	1777	+ * @buflen: length of the output buffer
	1778	+ *
	1779	+ * SCSI disk names starts at sda. The 26th device is sdz and the
	1780	+ * 27th is sdaa. The last one for two lettered suffix is sdzz
	1781	+ * which is followed by sdaaa.
	1782	+ *
	1783	+ * This is basically 26 base counting with one extra 'nil' entry
	1784	+ * at the beggining from the second digit on and can be
	1785	+ * determined using similar method as 26 base conversion with the
	1786	+ * index shifted -1 after each digit is computed.
	1787	+ *
	1788	+ * CONTEXT:
	1789	+ * Don't care.
	1790	+ *
	1791	+ * RETURNS:
	1792	+ * 0 on success, -errno on failure.
	1793	+ */
	1794	+static int sd_format_disk_name(char prefix, int index, char buf, int buflen)
	1795	+{
	1796	+ const int base = 'z' - 'a' + 1;
	1797	+ char *begin = buf + strlen(prefix);
	1798	+ char *end = buf + buflen;
	1799	+ char *p;
	1800	+ int unit;
	1801	+
	1802	+ p = end - 1;
	1803	+ *p = '\0';
	1804	+ unit = base;
	1805	+ do {
	1806	+ if (p == begin)
	1807	+ return -EINVAL;
	1808	+ *--p = 'a' + (index % unit);
	1809	+ index = (index / unit) - 1;
	1810	+ } while (index >= 0);
	1811	+
	1812	+ memmove(begin, p, end - p);
	1813	+ memcpy(buf, prefix, strlen(prefix));
	1814	+
	1815	+ return 0;
	1816	+}
	1817	+
	1818	+/**
1773	1819	* sd_probe - called during driver initialization and whenever a
1774	1820	* new scsi device is attached to the system. It is called once
1775	1821	* for each scsi device (not just disks) present.
...	...	@@ -1821,8 +1867,8 @@
1821	1867	if (error)
1822	1868	goto out_put;
1823	1869
1824		- error = -EBUSY;
1825		- if (index >= SD_MAX_DISKS)
	1870	+ error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
	1871	+ if (error)
1826	1872	goto out_free_index;
1827	1873
1828	1874	sdkp->device = sdp;
1829	1875
...	...	@@ -1849,24 +1895,12 @@
1849	1895
1850	1896	get_device(&sdp->sdev_gendev);
1851	1897
1852		- gd->major = sd_major((index & 0xf0) >> 4);
1853		- gd->first_minor = ((index & 0xf) << 4) \| (index & 0xfff00);
1854		- gd->minors = SD_MINORS;
1855		- gd->fops = &sd_fops;
1856		-
1857		- if (index < 26) {
1858		- sprintf(gd->disk_name, "sd%c", 'a' + index % 26);
1859		- } else if (index < (26 + 1) * 26) {
1860		- sprintf(gd->disk_name, "sd%c%c",
1861		- 'a' + index / 26 - 1,'a' + index % 26);
1862		- } else {
1863		- const unsigned int m1 = (index / 26 - 1) / 26 - 1;
1864		- const unsigned int m2 = (index / 26 - 1) % 26;
1865		- const unsigned int m3 = index % 26;
1866		- sprintf(gd->disk_name, "sd%c%c%c",
1867		- 'a' + m1, 'a' + m2, 'a' + m3);
	1898	+ if (index < SD_MAX_DISKS) {
	1899	+ gd->major = sd_major((index & 0xf0) >> 4);
	1900	+ gd->first_minor = ((index & 0xf) << 4) \| (index & 0xfff00);
	1901	+ gd->minors = SD_MINORS;
1868	1902	}
1869		-
	1903	+ gd->fops = &sd_fops;
1870	1904	gd->private_data = &sdkp->driver;
1871	1905	gd->queue = sdkp->device->request_queue;
1872	1906
...	...	@@ -593,6 +593,7 @@
593	593	disk_part_iter_exit(&piter);
594	594
595	595	invalidate_partition(disk, 0);
	596	+ blk_free_devt(disk_to_dev(disk)->devt);
596	597	set_capacity(disk, 0);
597	598	disk->flags &= ~GENHD_FL_UP;
598	599	unlink_gendisk(disk);
...	...	@@ -59,6 +59,7 @@
59	59	};
60	60
61	61	#define DISK_MAX_PARTS 256
	62	+#define DISK_NAME_LEN 32
62	63
63	64	#include <linux/major.h>
64	65	#include <linux/device.h>
...	...	@@ -140,7 +141,7 @@
140	141	int minors; /* maximum number of minors, =1 for
141	142	* disks that can't be partitioned. */
142	143
143		- char disk_name[32]; /* name of major driver */
	144	+ char disk_name[DISK_NAME_LEN]; /* name of major driver */
144	145
145	146	/* Array of pointers to partitions indexed by partno.
146	147	* Protected with matching bdev lock but stat and other