zram: use idr instead of `zram_devices' array

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.

[Julia.Lawall@lip6.fr: return -ENOMEM when `queue' alloc fails]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 49 insertions, 37 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 7814e686e23c..addb18d1b8d7 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -28,12 +28,12 @@
 #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) */
@@ -1154,10 +1154,20 @@ 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);
 
@@ -1165,12 +1175,13 @@ 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",
@@ -1235,34 +1246,42 @@ 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_remove_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_remove_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)
@@ -1281,16 +1300,9 @@ 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;
         }
 
@@ -1298,13 +1310,13 @@ 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);