Btrfs: fix output of compression message in btrfs_parse_options()

The compression message might not be correctly output.
Fix it.

[[before fix]]

# mount -o compress /dev/sdb3 /test3
[  996.874264] BTRFS info (device sdb3): disk space caching is enabled
[  996.874268] BTRFS: has skinny extents
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/)

# mount -o remount,compress-force /dev/sdb3 /test3
[ 1035.075017] BTRFS info (device sdb3): force zlib compression
[ 1035.075021] BTRFS info (device sdb3): disk space caching is enabled
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress-force=zlib,space_cache,subvolid=5,subvol=/)

# mount -o remount,compress /dev/sdb3 /test3
[ 1053.679092] BTRFS info (device sdb3): disk space caching is enabled
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/)

[[after fix]]

# mount -o compress /dev/sdb3 /test3
[  401.021753] BTRFS info (device sdb3): use zlib compression
[  401.021758] BTRFS info (device sdb3): disk space caching is enabled
[  401.021760] BTRFS: has skinny extents
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/)

# mount -o remount,compress-force /dev/sdb3 /test3
[  439.824624] BTRFS info (device sdb3): force zlib compression
[  439.824629] BTRFS info (device sdb3): disk space caching is enabled
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress-force=zlib,space_cache,subvolid=5,subvol=/)

# mount -o remount,compress /dev/sdb3 /test3
[  459.918430] BTRFS info (device sdb3): use zlib compression
[  459.918434] BTRFS info (device sdb3): disk space caching is enabled
# mount | grep /test3
/dev/sdb3 on /test3 type btrfs (rw,relatime,compress=zlib,space_cache,subvolid=5,subvol=/)
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/super.c

@@ -381,6 +381,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 	int ret = 0;
 	char *compress_type;
 	bool compress_force = false;
+	enum btrfs_compression_type saved_compress_type;
+	bool saved_compress_force;
+	int no_compress = 0;
 
 	cache_gen = btrfs_super_cache_generation(root->fs_info->super_copy);
 	if (cache_gen)
@@ -458,6 +461,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 			/* Fallthrough */
 		case Opt_compress:
 		case Opt_compress_type:
+			saved_compress_type = btrfs_test_opt(root, COMPRESS) ?
+				info->compress_type : BTRFS_COMPRESS_NONE;
+			saved_compress_force =
+				btrfs_test_opt(root, FORCE_COMPRESS);
 			if (token == Opt_compress ||
 			    token == Opt_compress_force ||
 			    strcmp(args[0].from, "zlib") == 0) {
@@ -466,6 +473,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				btrfs_set_opt(info->mount_opt, COMPRESS);
 				btrfs_clear_opt(info->mount_opt, NODATACOW);
 				btrfs_clear_opt(info->mount_opt, NODATASUM);
+				no_compress = 0;
 			} else if (strcmp(args[0].from, "lzo") == 0) {
 				compress_type = "lzo";
 				info->compress_type = BTRFS_COMPRESS_LZO;
@@ -473,25 +481,21 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				btrfs_clear_opt(info->mount_opt, NODATACOW);
 				btrfs_clear_opt(info->mount_opt, NODATASUM);
 				btrfs_set_fs_incompat(info, COMPRESS_LZO);
+				no_compress = 0;
 			} else if (strncmp(args[0].from, "no", 2) == 0) {
 				compress_type = "no";
 				btrfs_clear_opt(info->mount_opt, COMPRESS);
 				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
 				compress_force = false;
+				no_compress++;
 			} else {
 				ret = -EINVAL;
 				goto out;
 			}
 
 			if (compress_force) {
-				btrfs_set_and_info(root, FORCE_COMPRESS,
-						   "force %s compression",
-						   compress_type);
+				btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
 			} else {
-				if (!btrfs_test_opt(root, COMPRESS))
-					btrfs_info(root->fs_info,
-						   "btrfs: use %s compression",
-						   compress_type);
 				/*
 				 * If we remount from compress-force=xxx to
 				 * compress=xxx, we need clear FORCE_COMPRESS
@@ -500,6 +504,17 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				 */
 				btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
 			}
+			if ((btrfs_test_opt(root, COMPRESS) &&
+			     (info->compress_type != saved_compress_type ||
+			      compress_force != saved_compress_force)) ||
+			    (!btrfs_test_opt(root, COMPRESS) &&
+			     no_compress == 1)) {
+				btrfs_info(root->fs_info,
+					   "%s %s compression",
+					   (compress_force) ? "force" : "use",
+					   compress_type);
+			}
+			compress_force = false;
 			break;
 		case Opt_ssd:
 			btrfs_set_and_info(root, SSD,