Implement extended minors. A block driver can tell block layer that
it wants to use extended minors. After the usual minor space is used
up, block layer automatically allocates devt from EXT_BLOCK_MAJOR.
Currently only one major number is allocated for this but as the
allocation is on-demand so ~1mil minor space under it should suffice
for most cases.
For internal implementation simplicity, the first partition can't be
allocated on the extended area. In other words, genhd->minors should
at least be 1. Lifting this restriction shouldn't be too difficult.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
block/genhd.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++--
fs/partitions/check.c | 11 +++++
include/linux/genhd.h | 8 +++-
include/linux/major.h | 2 +
4 files changed, 134 insertions(+), 5 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index e7310ba..97cc5e4 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -16,6 +16,7 @@
#include <linux/kobj_map.h>
#include <linux/buffer_head.h>
#include <linux/mutex.h>
+#include <linux/idr.h>
#include "blk.h"
@@ -24,6 +25,10 @@ static DEFINE_MUTEX(block_class_lock);
struct kobject *block_depr;
#endif
+/* for extended dynamic devt allocation, currently only one major is used */
+#define MAX_EXT_DEVT (1 << MINORBITS)
+static DEFINE_IDR(ext_devt_idr);
+
static struct device_type disk_type;
/*
@@ -136,6 +141,65 @@ EXPORT_SYMBOL(unregister_blkdev);
static struct kobj_map *bdev_map;
+/**
+ * blk_alloc_devt - allocate a dev_t for a partition
+ * @part: partition to allocate dev_t for
+ * @gfp_mask: memory allocation flag
+ * @devt: out parameter for resulting dev_t
+ *
+ * Allocate a dev_t for block device.
+ *
+ * RETURNS:
+ * 0 on success, allocated dev_t is returned in *@devt. -errno on
+ * failure.
+ *
+ * CONTEXT:
+ * Determined by @gfp_mask.
+ */
+int blk_alloc_devt(struct hd_struct *part, gfp_t gfp_mask, dev_t *devt)
+{
+ int idx, rc;
+
+ if (part->partno < part->disk->minors) {
+ *devt = MKDEV(part->disk->major, part->partno);
+ return 0;
+ }
+
+ while (true) {
+ if (!idr_pre_get(&ext_devt_idr, gfp_mask))
+ return -ENOMEM;
+
+ rc = idr_get_new(&ext_devt_idr, part, &idx);
+ if (rc == 0)
+ break;
+ if (rc && rc != -EAGAIN)
+ return rc;
+ }
+
+ if (idx > MAX_EXT_DEVT) {
+ idr_remove(&ext_devt_idr, idx);
+ return -EBUSY;
+ }
+
+ *devt = MKDEV(EXT_BLOCK_MAJOR, idx);
+ return 0;
+}
+
+/**
+ * blk_free_devt - free a dev_t
+ * @devt: dev_t to free
+ *
+ * Free @devt which was allocated using blk_alloc_devt().
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+void blk_free_devt(dev_t devt)
+{
+ if (MAJOR(devt) == EXT_BLOCK_MAJOR)
+ idr_remove(&ext_devt_idr, MINOR(devt));
+}
+
/*
* Register device numbers dev..(dev+range-1)
* range must be nonzero
@@ -368,12 +432,43 @@ static struct kobject *base_probe(dev_t devt, int *part, void *data)
return NULL;
}
+static struct kobject *ext_probe(dev_t devt, int *idx, void *data)
+{
+ struct hd_struct *part;
+
+ part = idr_find(&ext_devt_idr, MINOR(devt));
+ if (unlikely(!part))
+ return NULL;
+
+ *idx = part->partno;
+ return &part->disk->dev.kobj;
+}
+
+static int ext_lock(dev_t devt, void *data)
+{
+ struct hd_struct *part;
+
+ part = idr_find(&ext_devt_idr, MINOR(devt));
+ if (likely(part && get_disk(part->disk)))
+ return 0;
+ return -1;
+}
+
static int __init genhd_device_init(void)
{
- int error = class_register(&block_class);
+ int error;
+
+ error = class_register(&block_class);
if (unlikely(error))
return error;
+
bdev_map = kobj_map_init(base_probe, &block_class_lock);
+ if (!bdev_map)
+ return -ENOMEM;
+
+ blk_register_region(MKDEV(EXT_BLOCK_MAJOR, 0), 1 << MINORBITS, NULL,
+ ext_probe, ext_lock, NULL);
+
blk_dev_init();
#ifndef CONFIG_SYSFS_DEPRECATED
@@ -691,22 +786,34 @@ EXPORT_SYMBOL(blk_lookup_devt);
struct gendisk *alloc_disk(int minors)
{
- return alloc_disk_node(minors, -1);
+ return alloc_disk_ext(minors, 0);
}
struct gendisk *alloc_disk_node(int minors, int node_id)
{
+ return alloc_disk_ext_node(minors, 0, node_id);
+}
+
+struct gendisk *alloc_disk_ext(int minors, int ext_minors)
+{
+ return alloc_disk_ext_node(minors, ext_minors, -1);
+}
+
+struct gendisk *alloc_disk_ext_node(int minors, int ext_minors, int node_id)
+{
struct gendisk *disk;
disk = kmalloc_node(sizeof(struct gendisk),
GFP_KERNEL | __GFP_ZERO, node_id);
if (disk) {
+ int tot_minors = minors + ext_minors;
+
if (!init_disk_stats(disk)) {
kfree(disk);
return NULL;
}
- if (minors > 1) {
- int size = (minors - 1) * sizeof(struct hd_struct *);
+ if (tot_minors > 1) {
+ int size = (tot_minors - 1) * sizeof(struct hd_struct *);
disk->part = kmalloc_node(size,
GFP_KERNEL | __GFP_ZERO, node_id);
if (!disk->part) {
@@ -716,6 +823,7 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
}
}
disk->minors = minors;
+ disk->ext_minors = ext_minors;
rand_initialize_disk(disk);
disk->dev.class = &block_class;
disk->dev.type = &disk_type;
@@ -728,6 +836,8 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
EXPORT_SYMBOL(alloc_disk);
EXPORT_SYMBOL(alloc_disk_node);
+EXPORT_SYMBOL(alloc_disk_ext);
+EXPORT_SYMBOL(alloc_disk_ext_node);
struct kobject *get_disk(struct gendisk *disk)
{
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 994a621..15d231f 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -331,6 +331,7 @@ void delete_partition(struct gendisk *disk, int part)
return;
if (!p->nr_sects)
return;
+ blk_free_devt(p->dev.devt);
disk->part[part-1] = NULL;
p->start_sect = 0;
p->nr_sects = 0;
@@ -386,6 +387,16 @@ void add_partition(struct gendisk *disk, int part, sector_t start, sector_t len,
p->dev.class = &block_class;
p->dev.type = &part_type;
p->dev.parent = &disk->dev;
+
+ err = blk_alloc_devt(p, GFP_KERNEL, &p->dev.devt);
+ if (err) {
+ printk(KERN_WARNING "%s: failed to to allocate MAJOR:MINOR "
+ "(part=%d, err=%d)\n", name, part, err);
+ free_part_stats(p);
+ kfree(p);
+ return;
+ }
+
disk->part[part-1] = p;
/* delay uevent until 'holders' subdir is created */
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 1db5740..a1843e6 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -117,6 +117,7 @@ struct gendisk {
int first_minor;
int minors; /* maximum number of minors, =1 for
* disks that can't be partitioned. */
+ int ext_minors; /* number of extended dynamic minors */
char disk_name[32]; /* name of major driver */
struct hd_struct **part; /* [indexed by minor - 1] */
struct block_device_operations *fops;
@@ -146,7 +147,7 @@ struct gendisk {
static inline int disk_max_parts(struct gendisk *disk)
{
- return disk->minors - 1;
+ return disk->minors + disk->ext_minors - 1;
}
static inline int disk_major(struct gendisk *disk)
@@ -551,6 +552,8 @@ struct unixware_disklabel {
#define ADDPART_FLAG_RAID 1
#define ADDPART_FLAG_WHOLEDISK 2
+extern int blk_alloc_devt(struct hd_struct *part, gfp_t gfp_mask, dev_t *devt);
+extern void blk_free_devt(dev_t devt);
extern dev_t blk_lookup_devt(const char *name, int part);
extern char *disk_name (struct gendisk *hd, int part, char *buf);
@@ -561,6 +564,9 @@ extern void printk_all_partitions(void);
extern struct gendisk *alloc_disk_node(int minors, int node_id);
extern struct gendisk *alloc_disk(int minors);
+extern struct gendisk *alloc_disk_ext_node(int minors, int ext_minrs,
+ int node_id);
+extern struct gendisk *alloc_disk_ext(int minors, int ext_minors);
extern struct kobject *get_disk(struct gendisk *disk);
extern void put_disk(struct gendisk *disk);
extern void blk_register_region(dev_t devt, unsigned long range,
diff --git a/include/linux/major.h b/include/linux/major.h
index 0cb9805..e7fa573 100644
--- a/include/linux/major.h
+++ b/include/linux/major.h
@@ -170,4 +170,6 @@
#define VIOTAPE_MAJOR 230
+#define EXT_BLOCK_MAJOR 259
+
#endif
--
1.5.4.5
--
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