[PATCHv2 03/10] zram: use idr instead of `zram_devices' array

Sergey Senozhatsky
2015-04-16T11:58:30Z

This patch makes some preparations for on-demand device add/remove
functionality.

Remove `zram_devices' array and switch to id-to-pointer translation (idr).
idr doesn't bloat zram struct with additional members, f.e. list_head,
yet still provides ability to match the device_id with the device pointer.

No user-space visible changes.

[do not lose -ENOMEM return code when `queue' allocation has failed]
Reported-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
drivers/block/zram/zram_drv.c | 86 ++++++++++++++++++++++++-------------------
1 file changed, 49 insertions(+), 37 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 14043b2..4511830 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -32,12 +32,12 @@
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <linux/err.h>
+#include <linux/idr.h>

#include "zram_drv.h"

-/* Globals */
+static DEFINE_IDR(zram_index_idr);
static int zram_major;
-static struct zram *zram_devices;
static const char *default_compressor = "lzo";

/* Module params (documentation at end) */
@@ -1156,10 +1156,20 @@ static struct attribute_group zram_disk_attr_group = {
.attrs = zram_disk_attrs,
};

-static int create_device(struct zram *zram, int device_id)
+static int zram_add(int device_id)
{
+ struct zram *zram;
struct request_queue *queue;
- int ret = -ENOMEM;
+ int ret;
+
+ zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
+ if (!zram)
+ return -ENOMEM;
+
+ ret = idr_alloc(&zram_index_idr, zram, device_id,
+ device_id + 1, GFP_KERNEL);
+ if (ret < 0)
+ goto out_free_dev;

init_rwsem(&zram->init_lock);

@@ -1167,12 +1177,13 @@ static int create_device(struct zram *zram, int device_id)
if (!queue) {
pr_err("Error allocating disk queue for device %d\n",
device_id);
- goto out;
+ ret = -ENOMEM;
+ goto out_free_idr;
}

blk_queue_make_request(queue, zram_make_request);

- /* gendisk structure */
+ /* gendisk structure */
zram->disk = alloc_disk(1);
if (!zram->disk) {
pr_warn("Error allocating disk structure for device %d\n",
@@ -1237,34 +1248,42 @@ out_free_disk:
put_disk(zram->disk);
out_free_queue:
blk_cleanup_queue(queue);
-out:
+out_free_idr:
+ idr_remove(&zram_index_idr, device_id);
+out_free_dev:
+ kfree(zram);
return ret;
}

-static void destroy_devices(unsigned int nr)
+static void zram_remove(struct zram *zram)
{
- struct zram *zram;
- unsigned int i;
-
- for (i = 0; i < nr; i++) {
- zram = &zram_devices[i];
- /*
- * Remove sysfs first, so no one will perform a disksize
- * store while we destroy the devices
- */
- sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
- &zram_disk_attr_group);
+ /*
+ * Remove sysfs first, so no one will perform a disksize
+ * store while we destroy the devices
+ */
+ sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
+ &zram_disk_attr_group);

- zram_reset_device(zram);
+ zram_reset_device(zram);
+ idr_remove(&zram_index_idr, zram->disk->first_minor);
+ blk_cleanup_queue(zram->disk->queue);
+ del_gendisk(zram->disk);
+ put_disk(zram->disk);
+ kfree(zram);
+}

- blk_cleanup_queue(zram->disk->queue);
- del_gendisk(zram->disk);
- put_disk(zram->disk);
- }
+static int zram_exit_cb(int id, void *ptr, void *data)
+{
+ zram_remove(ptr);
+ return 0;
+}

- kfree(zram_devices);
+static void destroy_devices(void)
+{
+ idr_for_each(&zram_index_idr, &zram_exit_cb, NULL);
+ idr_destroy(&zram_index_idr);
unregister_blkdev(zram_major, "zram");
- pr_info("Destroyed %u device(s)\n", nr);
+ pr_info("Destroyed device(s)\n");
}

static int __init zram_init(void)
@@ -1283,16 +1302,9 @@ static int __init zram_init(void)
return -EBUSY;
}

- /* Allocate the device array and initialize each one */
- zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
- if (!zram_devices) {
- unregister_blkdev(zram_major, "zram");
- return -ENOMEM;
- }
-
for (dev_id = 0; dev_id < num_devices; dev_id++) {
- ret = create_device(&zram_devices[dev_id], dev_id);
- if (ret)
+ ret = zram_add(dev_id);
+ if (ret != 0)
goto out_error;
}

@@ -1300,13 +1312,13 @@ static int __init zram_init(void)
return 0;

out_error:
- destroy_devices(dev_id);
+ destroy_devices();
return ret;
}

static void __exit zram_exit(void)
{
- destroy_devices(num_devices);
+ destroy_devices();
}

module_init(zram_init);
--
2.4.0.rc2