btrfs: sysfs: convert scnprintf and snprintf to sysfs_emit

Commit 2efc459 ("sysfs: Add sysfs_emit and sysfs_emit_at to format
sysfs out") merged in 5.10 introduced two new functions sysfs_emit() and
sysfs_emit_at() which are aware of the PAGE_SIZE limit of the output
buffer.

Use the above two new functions instead of scnprintf() and snprintf()
in various sysfs show().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/sysfs.c

@@ -177,7 +177,7 @@ static ssize_t btrfs_feature_attr_show(struct kobject *kobj,
 	} else
 		val = can_modify_feature(fa);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+	return sysfs_emit(buf, "%d\n", val);
 }
 
 static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
@@ -330,7 +330,7 @@ static const struct attribute_group btrfs_feature_attr_group = {
 static ssize_t rmdir_subvol_show(struct kobject *kobj,
 				 struct kobj_attribute *ka, char *buf)
 {
-	return scnprintf(buf, PAGE_SIZE, "0\n");
+	return sysfs_emit(buf, "0\n");
 }
 BTRFS_ATTR(static_feature, rmdir_subvol, rmdir_subvol_show);
 
@@ -345,20 +345,20 @@ static ssize_t supported_checksums_show(struct kobject *kobj,
 		 * This "trick" only works as long as 'enum btrfs_csum_type' has
 		 * no holes in it
 		 */
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
-				(i == 0 ? "" : " "), btrfs_super_csum_name(i));
+		ret += sysfs_emit_at(buf, ret, "%s%s", (i == 0 ? "" : " "),
+				     btrfs_super_csum_name(i));
 
 	}
 
-	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+	ret += sysfs_emit_at(buf, ret, "\n");
 	return ret;
 }
 BTRFS_ATTR(static_feature, supported_checksums, supported_checksums_show);
 
 static ssize_t send_stream_version_show(struct kobject *kobj,
 					struct kobj_attribute *ka, char *buf)
 {
-	return snprintf(buf, PAGE_SIZE, "%d\n", BTRFS_SEND_STREAM_VERSION);
+	return sysfs_emit(buf, "%d\n", BTRFS_SEND_STREAM_VERSION);
 }
 BTRFS_ATTR(static_feature, send_stream_version, send_stream_version_show);
 
@@ -378,9 +378,8 @@ static ssize_t supported_rescue_options_show(struct kobject *kobj,
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(rescue_opts); i++)
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
-				 (i ? " " : ""), rescue_opts[i]);
-	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+		ret += sysfs_emit_at(buf, ret, "%s%s", (i ? " " : ""), rescue_opts[i]);
+	ret += sysfs_emit_at(buf, ret, "\n");
 	return ret;
 }
 BTRFS_ATTR(static_feature, supported_rescue_options,
@@ -394,10 +393,10 @@ static ssize_t supported_sectorsizes_show(struct kobject *kobj,
 
 	/* 4K sector size is also supported with 64K page size */
 	if (PAGE_SIZE == SZ_64K)
-		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%u ", SZ_4K);
+		ret += sysfs_emit_at(buf, ret, "%u ", SZ_4K);
 
 	/* Only sectorsize == PAGE_SIZE is now supported */
-	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%lu\n", PAGE_SIZE);
+	ret += sysfs_emit_at(buf, ret, "%lu\n", PAGE_SIZE);
 
 	return ret;
 }
@@ -437,7 +436,7 @@ static ssize_t btrfs_discardable_bytes_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%lld\n",
+	return sysfs_emit(buf, "%lld\n",
 			atomic64_read(&fs_info->discard_ctl.discardable_bytes));
 }
 BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
@@ -448,7 +447,7 @@ static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n",
+	return sysfs_emit(buf, "%d\n",
 			atomic_read(&fs_info->discard_ctl.discardable_extents));
 }
 BTRFS_ATTR(discard, discardable_extents, btrfs_discardable_extents_show);
@@ -459,8 +458,8 @@ static ssize_t btrfs_discard_bitmap_bytes_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%llu\n",
-			fs_info->discard_ctl.discard_bitmap_bytes);
+	return sysfs_emit(buf, "%llu\n",
+			  fs_info->discard_ctl.discard_bitmap_bytes);
 }
 BTRFS_ATTR(discard, discard_bitmap_bytes, btrfs_discard_bitmap_bytes_show);
 
@@ -470,7 +469,7 @@ static ssize_t btrfs_discard_bytes_saved_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%lld\n",
+	return sysfs_emit(buf, "%lld\n",
 		atomic64_read(&fs_info->discard_ctl.discard_bytes_saved));
 }
 BTRFS_ATTR(discard, discard_bytes_saved, btrfs_discard_bytes_saved_show);
@@ -481,8 +480,8 @@ static ssize_t btrfs_discard_extent_bytes_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%llu\n",
-			fs_info->discard_ctl.discard_extent_bytes);
+	return sysfs_emit(buf, "%llu\n",
+			  fs_info->discard_ctl.discard_extent_bytes);
 }
 BTRFS_ATTR(discard, discard_extent_bytes, btrfs_discard_extent_bytes_show);
 
@@ -492,8 +491,8 @@ static ssize_t btrfs_discard_iops_limit_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%u\n",
-			READ_ONCE(fs_info->discard_ctl.iops_limit));
+	return sysfs_emit(buf, "%u\n",
+			  READ_ONCE(fs_info->discard_ctl.iops_limit));
 }
 
 static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
@@ -523,8 +522,8 @@ static ssize_t btrfs_discard_kbps_limit_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%u\n",
-			READ_ONCE(fs_info->discard_ctl.kbps_limit));
+	return sysfs_emit(buf, "%u\n",
+			  READ_ONCE(fs_info->discard_ctl.kbps_limit));
 }
 
 static ssize_t btrfs_discard_kbps_limit_store(struct kobject *kobj,
@@ -553,8 +552,8 @@ static ssize_t btrfs_discard_max_discard_size_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%llu\n",
-			READ_ONCE(fs_info->discard_ctl.max_discard_size));
+	return sysfs_emit(buf, "%llu\n",
+			  READ_ONCE(fs_info->discard_ctl.max_discard_size));
 }
 
 static ssize_t btrfs_discard_max_discard_size_store(struct kobject *kobj,
@@ -627,7 +626,7 @@ static ssize_t btrfs_show_u64(u64 *value_ptr, spinlock_t *lock, char *buf)
 	val = *value_ptr;
 	if (lock)
 		spin_unlock(lock);
-	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
+	return sysfs_emit(buf, "%llu\n", val);
 }
 
 static ssize_t global_rsv_size_show(struct kobject *kobj,
@@ -673,7 +672,7 @@ static ssize_t raid_bytes_show(struct kobject *kobj,
 			val += block_group->used;
 	}
 	up_read(&sinfo->groups_sem);
-	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
+	return sysfs_emit(buf, "%llu\n", val);
 }
 
 /*
@@ -771,7 +770,7 @@ static ssize_t btrfs_label_show(struct kobject *kobj,
 	ssize_t ret;
 
 	spin_lock(&fs_info->super_lock);
-	ret = scnprintf(buf, PAGE_SIZE, label[0] ? "%s\n" : "%s", label);
+	ret = sysfs_emit(buf, label[0] ? "%s\n" : "%s", label);
 	spin_unlock(&fs_info->super_lock);
 
 	return ret;
@@ -819,7 +818,7 @@ static ssize_t btrfs_nodesize_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->nodesize);
+	return sysfs_emit(buf, "%u\n", fs_info->super_copy->nodesize);
 }
 
 BTRFS_ATTR(, nodesize, btrfs_nodesize_show);
@@ -829,8 +828,7 @@ static ssize_t btrfs_sectorsize_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%u\n",
-			 fs_info->super_copy->sectorsize);
+	return sysfs_emit(buf, "%u\n", fs_info->super_copy->sectorsize);
 }
 
 BTRFS_ATTR(, sectorsize, btrfs_sectorsize_show);
@@ -840,7 +838,7 @@ static ssize_t btrfs_clone_alignment_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->sectorsize);
+	return sysfs_emit(buf, "%u\n", fs_info->super_copy->sectorsize);
 }
 
 BTRFS_ATTR(, clone_alignment, btrfs_clone_alignment_show);
@@ -852,7 +850,7 @@ static ssize_t quota_override_show(struct kobject *kobj,
 	int quota_override;
 
 	quota_override = test_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags);
-	return scnprintf(buf, PAGE_SIZE, "%d\n", quota_override);
+	return sysfs_emit(buf, "%d\n", quota_override);
 }
 
 static ssize_t quota_override_store(struct kobject *kobj,
@@ -890,8 +888,7 @@ static ssize_t btrfs_metadata_uuid_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%pU\n",
-			fs_info->fs_devices->metadata_uuid);
+	return sysfs_emit(buf, "%pU\n", fs_info->fs_devices->metadata_uuid);
 }
 
 BTRFS_ATTR(, metadata_uuid, btrfs_metadata_uuid_show);
@@ -902,9 +899,9 @@ static ssize_t btrfs_checksum_show(struct kobject *kobj,
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 	u16 csum_type = btrfs_super_csum_type(fs_info->super_copy);
 
-	return scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
-			btrfs_super_csum_name(csum_type),
-			crypto_shash_driver_name(fs_info->csum_shash));
+	return sysfs_emit(buf, "%s (%s)\n",
+			  btrfs_super_csum_name(csum_type),
+			  crypto_shash_driver_name(fs_info->csum_shash));
 }
 
 BTRFS_ATTR(, checksum, btrfs_checksum_show);
@@ -941,7 +938,7 @@ static ssize_t btrfs_exclusive_operation_show(struct kobject *kobj,
 			str = "UNKNOWN\n";
 			break;
 	}
-	return scnprintf(buf, PAGE_SIZE, "%s", str);
+	return sysfs_emit(buf, "%s", str);
 }
 BTRFS_ATTR(, exclusive_operation, btrfs_exclusive_operation_show);
 
@@ -950,7 +947,7 @@ static ssize_t btrfs_generation_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%llu\n", fs_info->generation);
+	return sysfs_emit(buf, "%llu\n", fs_info->generation);
 }
 BTRFS_ATTR(, generation, btrfs_generation_show);
 
@@ -1028,8 +1025,7 @@ static ssize_t btrfs_bg_reclaim_threshold_show(struct kobject *kobj,
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 	ssize_t ret;
 
-	ret = scnprintf(buf, PAGE_SIZE, "%d\n",
-			READ_ONCE(fs_info->bg_reclaim_threshold));
+	ret = sysfs_emit(buf, "%d\n", READ_ONCE(fs_info->bg_reclaim_threshold));
 
 	return ret;
 }
@@ -1471,7 +1467,7 @@ static ssize_t btrfs_devinfo_in_fs_metadata_show(struct kobject *kobj,
 
 	val = !!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+	return sysfs_emit(buf, "%d\n", val);
 }
 BTRFS_ATTR(devid, in_fs_metadata, btrfs_devinfo_in_fs_metadata_show);
 
@@ -1484,7 +1480,7 @@ static ssize_t btrfs_devinfo_missing_show(struct kobject *kobj,
 
 	val = !!test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+	return sysfs_emit(buf, "%d\n", val);
 }
 BTRFS_ATTR(devid, missing, btrfs_devinfo_missing_show);
 
@@ -1498,7 +1494,7 @@ static ssize_t btrfs_devinfo_replace_target_show(struct kobject *kobj,
 
 	val = !!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+	return sysfs_emit(buf, "%d\n", val);
 }
 BTRFS_ATTR(devid, replace_target, btrfs_devinfo_replace_target_show);
 
@@ -1509,8 +1505,7 @@ static ssize_t btrfs_devinfo_scrub_speed_max_show(struct kobject *kobj,
 	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
 						   devid_kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%llu\n",
-			 READ_ONCE(device->scrub_speed_max));
+	return sysfs_emit(buf, "%llu\n", READ_ONCE(device->scrub_speed_max));
 }
 
 static ssize_t btrfs_devinfo_scrub_speed_max_store(struct kobject *kobj,
@@ -1538,7 +1533,7 @@ static ssize_t btrfs_devinfo_writeable_show(struct kobject *kobj,
 
 	val = !!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 
-	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+	return sysfs_emit(buf, "%d\n", val);
 }
 BTRFS_ATTR(devid, writeable, btrfs_devinfo_writeable_show);
 
@@ -1549,14 +1544,14 @@ static ssize_t btrfs_devinfo_error_stats_show(struct kobject *kobj,
 						   devid_kobj);
 
 	if (!device->dev_stats_valid)
-		return scnprintf(buf, PAGE_SIZE, "invalid\n");
+		return sysfs_emit(buf, "invalid\n");
 
 	/*
 	 * Print all at once so we get a snapshot of all values from the same
 	 * time. Keep them in sync and in order of definition of
 	 * btrfs_dev_stat_values.
 	 */
-	return scnprintf(buf, PAGE_SIZE,
+	return sysfs_emit(buf,
 		"write_errs %d\n"
 		"read_errs %d\n"
 		"flush_errs %d\n"