Mailing List Archive

15 partitions (at least for sd_mod devices) are too few.

So I tried the following: after scanning the disk (sda), when we know
the number of partitions P on a disk, create a new block device
/dev/gd0 that is a copy of sda (in terms of disk->queue, etc.). This
is done using alloc_disk(P).

However, read() on gd0 will just return 0. It takes a `blockdev --rereadpt
/dev/gd0` before the disk is accessible. And if I add a call to
rescan inside gpdisk_new() it oopses (probably rightfully so). I do not
know all the block layer magic, so expect some horrible code.

Ideas, hints, anything is welcome.

---
block/Makefile | 1
block/genhd.c | 5 +
block/gpdisk.c | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++
drivers/scsi/sd.c | 1
fs/partitions/check.c | 19 ++++++
include/linux/genhd.h | 16 +++++
include/scsi/sd.h | 3 +
7 files changed, 182 insertions(+), 2 deletions(-)

Index: linux-2.6.23/block/Makefile
===================================================================
--- linux-2.6.23.orig/block/Makefile
+++ linux-2.6.23/block/Makefile
@@ -3,6 +3,7 @@
#

obj-$(CONFIG_BLOCK) := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
+obj-${CONFIG_BLOCK} += gpdisk.o

obj-$(CONFIG_BLK_DEV_BSG) += bsg.o
obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
Index: linux-2.6.23/block/genhd.c
===================================================================
--- linux-2.6.23.orig/block/genhd.c
+++ linux-2.6.23/block/genhd.c
@@ -744,6 +744,9 @@ struct gendisk *alloc_disk_node(int mino
rand_initialize_disk(disk);
INIT_WORK(&disk->async_notify,
media_change_notify_thread);
+ atomic_set(&disk->gpdisk_enabled, false);
+ disk->gpdisk = NULL;
+ disk->gpdisk_parent = NULL;
}
return disk;
}
@@ -793,6 +796,8 @@ EXPORT_SYMBOL(set_device_ro);
void set_disk_ro(struct gendisk *disk, int flag)
{
int i;
+ if (gpdisk_online(disk))
+ set_disk_ro(disk->gpdisk, flag);
disk->policy = flag;
for (i = 0; i < disk->minors - 1; i++)
if (disk->part[i]) disk->part[i]->policy = flag;
Index: linux-2.6.23/block/gpdisk.c
===================================================================
--- /dev/null
+++ linux-2.6.23/block/gpdisk.c
@@ -0,0 +1,139 @@
+#include <linux/genhd.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#define MINOR_IS_ALLOCATED ((void *)0xB4C4)
+
+static unsigned int gpdisk_major = 0;
+module_param(gpdisk_major, uint, S_IRUGO);
+
+static LIST_HEAD(gpdisk_regions);
+static DEFINE_SPINLOCK(gpdisk_region_lock);
+static DEFINE_SPINLOCK(gpdisk_id_lock);
+static DEFINE_IDR(gpdisk_id_idr);
+
+static unsigned int gpdisk_first_minor = 0;
+
+static int gpdisk_get_region(unsigned int size)
+{
+ /* still to be done */
+ unsigned int old;
+
+ old = gpdisk_first_minor;
+ gpdisk_first_minor += size;
+ return old;
+}
+
+static void gpdisk_put_region(unsigned int start, unsigned int n)
+{
+ /* same */
+}
+
+static int gpdisk_get_diskid(void)
+{
+ int new_id, ret;
+
+ again:
+ ret = idr_pre_get(&gpdisk_id_idr, GFP_KERNEL);
+ if (ret == 0)
+ return -ENOMEM;
+
+ spin_lock(&gpdisk_id_lock);
+ ret = idr_get_new(&gpdisk_id_idr, MINOR_IS_ALLOCATED, &new_id);
+ if (ret == -EAGAIN) {
+ spin_unlock(&gpdisk_id_lock);
+ cond_resched();
+ goto again;
+ }
+ if (ret != 0)
+ goto out;
+
+ ret = new_id;
+ out:
+ spin_unlock(&gpdisk_id_lock);
+ return ret;
+}
+
+static void gpdisk_put_diskid(unsigned int id)
+{
+ idr_remove(&gpdisk_id_idr, id);
+}
+
+void gpdisk_new(struct gendisk *disk, unsigned int minors)
+{
+ struct block_device *bdev;
+ struct gendisk *gpdisk;
+ int disk_id, minor_start;
+
+ gpdisk = alloc_disk(minors);
+ if (gpdisk == NULL)
+ return;
+
+ disk_id = gpdisk_get_diskid();
+ if (disk_id < 0)
+ goto out;
+
+ minor_start = gpdisk_get_region(minors);
+ if (minor_start < 0)
+ goto out2;
+
+ disk->gpdisk = gpdisk;
+ disk->gpdisk_id = disk_id;
+
+ sprintf(gpdisk->disk_name, "gd%u", disk_id);
+ gpdisk->gpdisk_parent = disk;
+ gpdisk->major = gpdisk_major;
+ gpdisk->first_minor = minor_start;
+ gpdisk->minors = minors;
+ gpdisk->fops = disk->fops;
+
+ /* safe? */
+ gpdisk->private_data = disk->private_data;
+ gpdisk->queue = disk->queue;
+ gpdisk->driverfs_dev = disk->driverfs_dev;
+ gpdisk->flags = disk->flags;
+
+ add_disk(gpdisk);
+ return;
+
+ out2:
+ gpdisk_put_diskid(disk_id);
+ out:
+ put_disk(gpdisk);
+ return;
+}
+
+void gpdisk_release(struct gendisk *disk)
+{
+ gpdisk_put_region(disk->gpdisk->first_minor, disk->gpdisk->minors);
+ gpdisk_put_diskid(disk->gpdisk_id);
+}
+
+static int __init gpdisk_init(void)
+{
+ int i;
+
+ i = register_blkdev(gpdisk_major, "gpdisk");
+ if (gpdisk_major == 0) {
+ /* dynamic major */
+ if (i == 0)
+ return -ENODEV;
+ gpdisk_major = i;
+ } else {
+ /* fixed major */
+ if (i != 0)
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+static void __exit gpdisk_exit(void)
+{
+ unregister_blkdev(gpdisk_major, "gpdisk");
+}
+
+module_init(gpdisk_init);
+module_exit(gpdisk_exit);
Index: linux-2.6.23/drivers/scsi/sd.c
===================================================================
--- linux-2.6.23.orig/drivers/scsi/sd.c
+++ linux-2.6.23/drivers/scsi/sd.c
@@ -1610,6 +1610,7 @@ static int sd_probe(struct device *dev)
gd = alloc_disk(16);
if (!gd)
goto out_free;
+ atomic_set(&gd->gpdisk_enabled, true);

if (!idr_pre_get(&sd_index_idr, GFP_KERNEL))
goto out_put;
Index: linux-2.6.23/fs/partitions/check.c
===================================================================
--- linux-2.6.23.orig/fs/partitions/check.c
+++ linux-2.6.23/fs/partitions/check.c
@@ -168,7 +168,7 @@ check_partition(struct gendisk *hd, stru
if (isdigit(state->name[strlen(state->name)-1]))
sprintf(state->name, "p");

- state->limit = hd->minors;
+ state->limit = MAX_PART;
i = res = err = 0;
while (!res && check_part[i]) {
memset(&state->parts, 0, sizeof(state->parts));
@@ -528,6 +528,7 @@ exit:
int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
{
struct parsed_partitions *state;
+ unsigned int max;
int p, res;

if (bdev->bd_part_count)
@@ -536,6 +537,11 @@ int rescan_partitions(struct gendisk *di
if (res)
return res;
bdev->bd_invalidated = 0;
+ if (gpdisk_online(disk)) {
+ gpdisk_release(disk);
+ del_gendisk(disk->gpdisk);
+ disk->gpdisk = NULL;
+ }
for (p = 1; p < disk->minors; p++)
delete_partition(disk, p);
if (disk->fops->revalidate_disk)
@@ -544,7 +550,8 @@ int rescan_partitions(struct gendisk *di
return 0;
if (IS_ERR(state)) /* I/O error reading the partition table */
return -EIO;
- for (p = 1; p < state->limit; p++) {
+ max = min(disk->minors, state->next);
+ for (p = 1; p < max; p++) {
sector_t size = state->parts[p].size;
sector_t from = state->parts[p].from;
if (!size)
@@ -560,6 +567,8 @@ int rescan_partitions(struct gendisk *di
#endif
}
kfree(state);
+ if (atomic_read(&disk->gpdisk_enabled) > 0)
+ gpdisk_new(disk, state->next);
return 0;
}

@@ -588,6 +597,12 @@ void del_gendisk(struct gendisk *disk)
{
int p;

+ if (gpdisk_online(disk)) {
+ gpdisk_release(disk);
+ del_gendisk(disk->gpdisk);
+ disk->gpdisk = NULL;
+ }
+
/* invalidate stuff */
for (p = disk->minors - 1; p > 0; p--) {
invalidate_partition(disk, p);
Index: linux-2.6.23/include/linux/genhd.h
===================================================================
--- linux-2.6.23.orig/include/linux/genhd.h
+++ linux-2.6.23/include/linux/genhd.h
@@ -67,6 +67,7 @@ struct partition {
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/workqueue.h>
+#include <asm/atomic.h>

struct partition {
unsigned char boot_ind; /* 0x80 - active */
@@ -141,6 +142,10 @@ struct gendisk {
struct disk_stats dkstats;
#endif
struct work_struct async_notify;
+
+ struct gendisk *gpdisk, *gpdisk_parent;
+ unsigned int gpdisk_id;
+ atomic_t gpdisk_enabled;
};

/* Structure for sysfs attributes on block devices */
@@ -255,11 +260,22 @@ static inline sector_t get_capacity(stru
{
return disk->capacity;
}
+
+static inline bool gpdisk_online(const struct gendisk *disk)
+{
+ return atomic_read(&disk->gpdisk_enabled) > 0 && disk->gpdisk != NULL;
+}
+
static inline void set_capacity(struct gendisk *disk, sector_t size)
{
disk->capacity = size;
+ if (gpdisk_online(disk))
+ disk->gpdisk->capacity = size;
}

+extern void gpdisk_new(struct gendisk *, unsigned int);
+extern void gpdisk_release(struct gendisk *);
+
#endif /* __KERNEL__ */

#ifdef CONFIG_SOLARIS_X86_PARTITION
Index: linux-2.6.23/include/scsi/sd.h
===================================================================
--- linux-2.6.23.orig/include/scsi/sd.h
+++ linux-2.6.23/include/scsi/sd.h
@@ -62,6 +62,9 @@ static void sd_print_sense_hdr(struct sc
static void sd_print_result(struct scsi_disk *, int);

#define sd_printk(prefix, sdsk, fmt, a...) \
+ gpdisk_online((sdsk)->disk) ? \
+ sdev_printk(prefix, (sdsk)->device, "[%s] " fmt, \
+ (sdsk)->disk->gpdisk->disk_name, ##a) : \
(sdsk)->disk ? \
sdev_printk(prefix, (sdsk)->device, "[%s] " fmt, \
(sdsk)->disk->disk_name, ##a) : \
-
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