zram: remove max_num_devices limitation

Limiting the number of zram devices to 32 (default max_num_devices value)
is confusing, let's drop it.  A user with 2TB or 4TB of RAM, for example,
can request as many devices as he can handle.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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>

Documentation/blockdev/zram.txt

@@ -19,7 +19,9 @@ Following shows a typical sequence of steps for using zram.
 1) Load Module:
 	modprobe zram num_devices=4
 	This creates 4 devices: /dev/zram{0,1,2,3}
-	(num_devices parameter is optional. Default: 1)
+
+num_devices parameter is optional and tells zram how many devices should be
+pre-created. Default: 1.
 
 2) Set max number of compression streams
 	Compression backend may use up to max_comp_streams compression streams,

drivers/block/zram/zram_drv.c

@@ -1287,12 +1287,6 @@ static int __init zram_init(void)
 {
 	int ret, dev_id;
 
-	if (num_devices > max_num_devices) {
-		pr_warn("Invalid value for num_devices: %u\n",
-				num_devices);
-		return -EINVAL;
-	}
-
 	zram_major = register_blkdev(0, "zram");
 	if (zram_major <= 0) {
 		pr_warn("Unable to get major number\n");
@@ -1322,7 +1316,7 @@ module_init(zram_init);
 module_exit(zram_exit);
 
 module_param(num_devices, uint, 0);
-MODULE_PARM_DESC(num_devices, "Number of zram devices");
+MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
 
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");

drivers/block/zram/zram_drv.h

@@ -20,12 +20,6 @@
 
 #include "zcomp.h"
 
-/*
- * Some arbitrary value. This is just to catch
- * invalid value for num_devices module parameter.
- */
-static const unsigned max_num_devices = 32;
-
 /*-- Configurable parameters */
 
 /*