[PATCH 02/18] block: open code kobj_map into in block/genhd.c

Christoph Hellwig
2020-10-29T15:05:39Z

Copy and paste the kobj_map functionality in the block code in preparation
for completely rewriting it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/genhd.c | 130 +++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 117 insertions(+), 13 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 3ed591970ea640..0e22ca64aca09e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -17,7 +17,6 @@
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/kmod.h>
-#include <linux/kobj_map.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/log2.h>
@@ -29,6 +28,16 @@
static DEFINE_MUTEX(block_class_lock);
static struct kobject *block_depr;

+struct bdev_map {
+ struct bdev_map *next;
+ dev_t dev;
+ unsigned long range;
+ struct module *owner;
+ struct kobject *(*probe)(dev_t, int *, void *);
+ int (*lock)(dev_t, void *);
+ void *data;
+} *bdev_map[255];
+
/* for extended dynamic devt allocation, currently only one major is used */
#define NR_EXT_DEVT (1 << MINORBITS)

@@ -517,8 +526,6 @@ void unregister_blkdev(unsigned int major, const char *name)

EXPORT_SYMBOL(unregister_blkdev);

-static struct kobj_map *bdev_map;
-
/**
* blk_mangle_minor - scatter minor numbers apart
* @minor: minor number to mangle
@@ -645,16 +652,60 @@ void blk_register_region(dev_t devt, unsigned long range, struct module *module,
struct kobject *(*probe)(dev_t, int *, void *),
int (*lock)(dev_t, void *), void *data)
{
- kobj_map(bdev_map, devt, range, module, probe, lock, data);
-}
+ unsigned n = MAJOR(devt + range - 1) - MAJOR(devt) + 1;
+ unsigned index = MAJOR(devt);
+ unsigned i;
+ struct bdev_map *p;
+
+ n = min(n, 255u);
+ p = kmalloc_array(n, sizeof(struct bdev_map), GFP_KERNEL);
+ if (p == NULL)
+ return;

+ for (i = 0; i < n; i++, p++) {
+ p->owner = module;
+ p->probe = probe;
+ p->lock = lock;
+ p->dev = devt;
+ p->range = range;
+ p->data = data;
+ }
+
+ mutex_lock(&block_class_lock);
+ for (i = 0, p -= n; i < n; i++, p++, index++) {
+ struct bdev_map **s = &bdev_map[index % 255];
+ while (*s && (*s)->range < range)
+ s = &(*s)->next;
+ p->next = *s;
+ *s = p;
+ }
+ mutex_unlock(&block_class_lock);
+}
EXPORT_SYMBOL(blk_register_region);

void blk_unregister_region(dev_t devt, unsigned long range)
{
- kobj_unmap(bdev_map, devt, range);
-}
+ unsigned n = MAJOR(devt + range - 1) - MAJOR(devt) + 1;
+ unsigned index = MAJOR(devt);
+ unsigned i;
+ struct bdev_map *found = NULL;

+ mutex_lock(&block_class_lock);
+ for (i = 0; i < min(n, 255u); i++, index++) {
+ struct bdev_map **s;
+ for (s = &bdev_map[index % 255]; *s; s = &(*s)->next) {
+ struct bdev_map *p = *s;
+ if (p->dev == devt && p->range == range) {
+ *s = p->next;
+ if (!found)
+ found = p;
+ break;
+ }
+ }
+ }
+ mutex_unlock(&block_class_lock);
+ kfree(found);
+}
EXPORT_SYMBOL(blk_unregister_region);

static struct kobject *exact_match(dev_t devt, int *partno, void *data)
@@ -976,6 +1027,47 @@ static ssize_t disk_badblocks_store(struct device *dev,
return badblocks_store(disk->bb, page, len, 0);
}

+static struct gendisk *lookup_gendisk(dev_t dev, int *partno)
+{
+ struct kobject *kobj;
+ struct bdev_map *p;
+ unsigned long best = ~0UL;
+
+retry:
+ mutex_lock(&block_class_lock);
+ for (p = bdev_map[MAJOR(dev) % 255]; p; p = p->next) {
+ struct kobject *(*probe)(dev_t, int *, void *);
+ struct module *owner;
+ void *data;
+
+ if (p->dev > dev || p->dev + p->range - 1 < dev)
+ continue;
+ if (p->range - 1 >= best)
+ break;
+ if (!try_module_get(p->owner))
+ continue;
+ owner = p->owner;
+ data = p->data;
+ probe = p->probe;
+ best = p->range - 1;
+ *partno = dev - p->dev;
+ if (p->lock && p->lock(dev, data) < 0) {
+ module_put(owner);
+ continue;
+ }
+ mutex_unlock(&block_class_lock);
+ kobj = probe(dev, partno, data);
+ /* Currently ->owner protects _only_ ->probe() itself. */
+ module_put(owner);
+ if (kobj)
+ return dev_to_disk(kobj_to_dev(kobj));
+ goto retry;
+ }
+ mutex_unlock(&block_class_lock);
+ return NULL;
+}
+
+
/**
* get_gendisk - get partitioning information for a given device
* @devt: device to get partitioning information for
@@ -993,11 +1085,7 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
might_sleep();

if (MAJOR(devt) != BLOCK_EXT_MAJOR) {
- struct kobject *kobj;
-
- kobj = kobj_lookup(bdev_map, devt, partno);
- if (kobj)
- disk = dev_to_disk(kobj_to_dev(kobj));
+ disk = lookup_gendisk(devt, partno);
} else {
struct hd_struct *part;

@@ -1210,6 +1298,22 @@ static struct kobject *base_probe(dev_t devt, int *partno, void *data)
return NULL;
}

+static void bdev_map_init(void)
+{
+ struct bdev_map *base;
+ int i;
+
+ base = kzalloc(sizeof(*base), GFP_KERNEL);
+ if (!base)
+ panic("cannot allocate bdev_map");
+
+ base->dev = 1;
+ base->range = ~0 ;
+ base->probe = base_probe;
+ for (i = 0; i < 255; i++)
+ bdev_map[i] = base;
+}
+
static int __init genhd_device_init(void)
{
int error;
@@ -1218,7 +1322,7 @@ static int __init genhd_device_init(void)
error = class_register(&block_class);
if (unlikely(error))
return error;
- bdev_map = kobj_map_init(base_probe, &block_class_lock);
+ bdev_map_init();
blk_dev_init();

register_blkdev(BLOCK_EXT_MAJOR, "blkext");
--
2.28.0