zram: unify error reporting

Make zram syslog error reporting more consistent. We have random
error levels in some places. For example, critical errors like
  "Error allocating memory for compressed page"
and
  "Unable to allocate temp memory"
are reported as KERN_INFO messages.

a) Reassign error levels

Error messages that directly affect zram
functionality -- pr_err():

 Error allocating zram address table
 Error creating memory pool
 Decompression failed! err=%d, page=%u
 Unable to allocate temp memory
 Compression failed! err=%d
 Error allocating memory for compressed page: %u, size=%zu
 Cannot initialise %s compressing backend
 Error allocating disk queue for device %d
 Error allocating disk structure for device %d
 Error creating sysfs group for device %d
 Unable to register zram-control class
 Unable to get major number

Messages that do not affect functionality, but user
must be warned (because sysfs attrs will be removed in
this particular case) -- pr_warn():

 %d (%s) Attribute %s (and others) will be removed. %s

Messages that do not affect functionality and mostly are
informative -- pr_info():

 Cannot change max compression streams
 Can't change algorithm for initialized device
 Cannot change disksize for initialized device
 Added device: %s
 Removed device: %s

b) Update sysfs_create_group() error message

First, it lacks a trailing new line; add it.  Second, every error message
in zram_add() has a "for device %d" part, which makes errors more
informative.  Add missing part to "Error creating sysfs group" message.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -622,7 +622,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 		uncmem = user_mem;
 
 	if (!uncmem) {
-		pr_info("Unable to allocate temp memory\n");
+		pr_err("Unable to allocate temp memory\n");
 		ret = -ENOMEM;
 		goto out_cleanup;
 	}
@@ -719,7 +719,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	handle = zs_malloc(meta->mem_pool, clen);
 	if (!handle) {
-		pr_info("Error allocating memory for compressed page: %u, size=%zu\n",
+		pr_err("Error allocating memory for compressed page: %u, size=%zu\n",
 			index, clen);
 		ret = -ENOMEM;
 		goto out;
@@ -1039,7 +1039,7 @@ static ssize_t disksize_store(struct device *dev,
 
 	comp = zcomp_create(zram->compressor, zram->max_comp_streams);
 	if (IS_ERR(comp)) {
-		pr_info("Cannot initialise %s compressing backend\n",
+		pr_err("Cannot initialise %s compressing backend\n",
 				zram->compressor);
 		err = PTR_ERR(comp);
 		goto out_free_meta;
@@ -1217,7 +1217,7 @@ static int zram_add(void)
 	/* gendisk structure */
 	zram->disk = alloc_disk(1);
 	if (!zram->disk) {
-		pr_warn("Error allocating disk structure for device %d\n",
+		pr_err("Error allocating disk structure for device %d\n",
 			device_id);
 		ret = -ENOMEM;
 		goto out_free_queue;
@@ -1266,7 +1266,8 @@ static int zram_add(void)
 	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 				&zram_disk_attr_group);
 	if (ret < 0) {
-		pr_warn("Error creating sysfs group");
+		pr_err("Error creating sysfs group for device %d\n",
+				device_id);
 		goto out_free_disk;
 	}
 	strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
@@ -1406,13 +1407,13 @@ static int __init zram_init(void)
 
 	ret = class_register(&zram_control_class);
 	if (ret) {
-		pr_warn("Unable to register zram-control class\n");
+		pr_err("Unable to register zram-control class\n");
 		return ret;
 	}
 
 	zram_major = register_blkdev(0, "zram");
 	if (zram_major <= 0) {
-		pr_warn("Unable to get major number\n");
+		pr_err("Unable to get major number\n");
 		class_unregister(&zram_control_class);
 		return -EBUSY;
 	}