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Subject[PATCH] remove MAX_BLKDEV from genhd.c
A patch for genhd.c:

- removed outdated comments
- removed MAX_BLKDEV

In genhd.c the variable MAX_BLKDEV was only the size of a hash
table, so I made it MAX_PROBE_HASH. It can be 1, or 23, or 256, or
whatever one wants.

Note that the current setup requires that every device number
in a given range is mapped by dev_to_index() to the same index
in the hash table, so this routine will have to be adapted in
case one wants to register multimajor ranges.

Discussion is possible about whether struct blk_probe needs
a dev_t or a kdev_t, but I left things this time.

If a range can end at precisely the end of [k]dev_t space,
the old code was wrong since (p->dev + p->range) would be 0.
That is why "p->dev + p->range <= dev" was replaced by
"p->dev + p->range - 1 < dev".

Andries


diff -u --recursive --new-file -X /linux/dontdiff a/drivers/block/genhd.c b/drivers/block/genhd.c
--- a/drivers/block/genhd.c Sat Feb 15 20:41:56 2003
+++ b/drivers/block/genhd.c Mon Feb 24 00:50:41 2003
@@ -1,17 +1,5 @@
/*
- * Code extracted from
- * linux/kernel/hd.c
- *
- * Copyright (C) 1991-1998 Linus Torvalds
- *
- * devfs support - jj, rgooch, 980122
- *
- * Moved partition checking code to fs/partitions* - Russell King
- * (linux@arm.uk.linux.org)
- */
-
-/*
- * TODO: rip out the remaining init crap from this file --hch
+ * gendisk handling
*/

#include <linux/config.h>
@@ -29,8 +17,9 @@

static struct subsystem block_subsys;

+#define MAX_PROBE_HASH 23 /* random */

-struct blk_probe {
+static struct blk_probe {
struct blk_probe *next;
dev_t dev;
unsigned long range;
@@ -38,21 +27,27 @@
struct gendisk *(*get)(dev_t dev, int *part, void *data);
int (*lock)(dev_t, void *);
void *data;
-} *probes[MAX_BLKDEV];
+} *probes[MAX_PROBE_HASH];

-/* index in the above */
+/* index in the above - for now: assume no multimajor ranges */
static inline int dev_to_index(dev_t dev)
{
- return MAJOR(dev);
+ return MAJOR(dev) % MAX_PROBE_HASH;
}

+/*
+ * Register device numbers dev..(dev+range-1)
+ * range must be nonzero
+ * The hash chain is sorted on range, so that subranges can override.
+ */
void blk_register_region(dev_t dev, unsigned long range, struct module *module,
- struct gendisk *(*probe)(dev_t, int *, void *),
- int (*lock)(dev_t, void *), void *data)
+ struct gendisk *(*probe)(dev_t, int *, void *),
+ int (*lock)(dev_t, void *), void *data)
{
int index = dev_to_index(dev);
struct blk_probe *p = kmalloc(sizeof(struct blk_probe), GFP_KERNEL);
struct blk_probe **s;
+
p->owner = module;
p->get = probe;
p->lock = lock;
@@ -71,6 +66,7 @@
{
int index = dev_to_index(dev);
struct blk_probe **s;
+
down_write(&block_subsys.rwsem);
for (s = &probes[index]; *s; s = &(*s)->next) {
struct blk_probe *p = *s;
@@ -94,6 +90,7 @@
static int exact_lock(dev_t dev, void *data)
{
struct gendisk *p = data;
+
if (!get_disk(p))
return -1;
return 0;
@@ -109,14 +106,14 @@
void add_disk(struct gendisk *disk)
{
disk->flags |= GENHD_FL_UP;
- blk_register_region(MKDEV(disk->major, disk->first_minor), disk->minors,
- NULL, exact_match, exact_lock, disk);
+ blk_register_region(MKDEV(disk->major, disk->first_minor),
+ disk->minors, NULL, exact_match, exact_lock, disk);
register_disk(disk);
elv_register_queue(disk);
}

EXPORT_SYMBOL(add_disk);
-EXPORT_SYMBOL(del_gendisk);
+EXPORT_SYMBOL(del_gendisk); /* in partitions/check.c */

void unlink_gendisk(struct gendisk *disk)
{
@@ -146,18 +143,17 @@
struct gendisk *(*probe)(dev_t, int *, void *);
struct module *owner;
void *data;
- if (p->dev > dev || p->dev + p->range <= dev)
+
+ if (p->dev > dev || p->dev + p->range - 1 < dev)
continue;
- if (p->range >= best) {
- up_read(&block_subsys.rwsem);
- return NULL;
- }
+ if (p->range - 1 >= best)
+ break;
if (!try_module_get(p->owner))
continue;
owner = p->owner;
data = p->data;
probe = p->get;
- best = p->range;
+ best = p->range - 1;
*part = dev - p->dev;
if (p->lock && p->lock(dev, data) < 0) {
module_put(owner);
@@ -169,7 +165,7 @@
module_put(owner);
if (disk)
return disk;
- goto retry;
+ goto retry; /* this terminates: best decreases */
}
up_read(&block_subsys.rwsem);
return NULL;
@@ -245,7 +241,7 @@

static struct gendisk *base_probe(dev_t dev, int *part, void *data)
{
- char name[20];
+ char name[30];
sprintf(name, "block-major-%d", MAJOR(dev));
request_module(name);
return NULL;
@@ -256,11 +252,11 @@
struct blk_probe *base = kmalloc(sizeof(struct blk_probe), GFP_KERNEL);
int i;
memset(base, 0, sizeof(struct blk_probe));
- base->dev = MKDEV(1,0);
- base->range = MKDEV(MAX_BLKDEV-1, 255) - base->dev + 1;
+ base->dev = 1;
+ base->range = ~0; /* range 1 .. ~0 */
base->get = base_probe;
- for (i = 1; i < MAX_BLKDEV; i++)
- probes[i] = base;
+ for (i = 0; i < MAX_PROBE_HASH; i++)
+ probes[i] = base; /* must remain last in chain */
blk_dev_init();
subsystem_register(&block_subsys);
return 0;
@@ -281,12 +277,14 @@
ssize_t (*show)(struct gendisk *, char *);
};

-static ssize_t disk_attr_show(struct kobject * kobj, struct attribute * attr,
- char * page)
+static ssize_t disk_attr_show(struct kobject *kobj, struct attribute *attr,
+ char *page)
{
- struct gendisk * disk = to_disk(kobj);
- struct disk_attribute * disk_attr = container_of(attr,struct disk_attribute,attr);
+ struct gendisk *disk = to_disk(kobj);
+ struct disk_attribute *disk_attr =
+ container_of(attr,struct disk_attribute,attr);
ssize_t ret = 0;
+
if (disk_attr->show)
ret = disk_attr->show(disk,page);
return ret;
@@ -303,11 +301,11 @@
}
static ssize_t disk_range_read(struct gendisk * disk, char *page)
{
- return sprintf(page, "%d\n",disk->minors);
+ return sprintf(page, "%d\n", disk->minors);
}
static ssize_t disk_size_read(struct gendisk * disk, char *page)
{
- return sprintf(page, "%llu\n",(unsigned long long)get_capacity(disk));
+ return sprintf(page, "%llu\n", (unsigned long long)get_capacity(disk));
}

static inline unsigned jiffies_to_msec(unsigned jif)
-
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