[PATCH 1/2] btrfs-progs: common: introduce fmt_print_start_object

[PATCH 1/2] btrfs-progs: common: introduce fmt_print_start_object

[Sidong Yang]

Introduce a new function that can be used when you need to print an json
object in command like "device stats".

Signed-off-by: Sidong Yang <realwakka@gmail.com>
---
 common/format-output.c | 20 ++++++++++++++++++++
 common/format-output.h |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/common/format-output.c b/common/format-output.c
index 8df93ecb..f31e7259 100644
--- a/common/format-output.c
+++ b/common/format-output.c
@@ -213,6 +213,26 @@ void fmt_print_end_group(struct format_ctx *fctx, const char *name)
 	}
 }
 
+void fmt_print_start_object(struct format_ctx *fctx)
+{
+	if (bconf.output_format == CMD_FORMAT_JSON) {
+		fmt_separator(fctx);
+		fmt_inc_depth(fctx);
+		fctx->memb[fctx->depth] = 0;
+		putchar('{');
+	}
+}
+
+void fmt_print_end_object(struct format_ctx *fctx)
+{
+	if (bconf.output_format == CMD_FORMAT_JSON) {
+		fmt_dec_depth(fctx);
+		putchar('\n');
+		fmt_indent2(fctx->depth);
+		putchar('}');
+	}
+}
+
 /* Use rowspec to print according to currently set output format */
 void fmt_print(struct format_ctx *fctx, const char* key, ...)
 {
diff --git a/common/format-output.h b/common/format-output.h
index bcc2d74d..9d606482 100644
--- a/common/format-output.h
+++ b/common/format-output.h
@@ -87,4 +87,7 @@ void fmt_print_start_group(struct format_ctx *fctx, const char *name,
 		enum json_type jtype);
 void fmt_print_end_group(struct format_ctx *fctx, const char *name);
 
+void fmt_print_start_object(struct format_ctx *fctx);
+void fmt_print_end_object(struct format_ctx *fctx);
+
 #endif
-- 
2.25.1

[PATCH 2/2] btrfs-progs: device stats: add json output format

[Sidong Yang]

Add supports for json formatting, this patch changes hard coded printing
code to formatted print with output formatter. Json output would be
useful for other programs that parse output of the command. but it
changes the text format.

Example text format:

device:                 /dev/vdb
devid			1
write_io_errs:          0
read_io_errs:           0
flush_io_errs:          0
corruption_errs:        0
generation_errs:        0

Example json format:

{
  "__header": {
    "version": "1"
  },
  "device-stats": [
    {
      "device": "/dev/vdb",
      "devid": "1",
      "write_io_errs": "0",
      "read_io_errs": "0",
      "flush_io_errs": "0",
      "corruption_errs": "0",
      "generation_errs": "0"
    }
  ],
}

Signed-off-by: Sidong Yang <realwakka@gmail.com>
---
 cmds/device.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/cmds/device.c b/cmds/device.c
index d72881f8..8b8fc85c 100644
--- a/cmds/device.c
+++ b/cmds/device.c
@@ -36,6 +36,7 @@
 #include "common/path-utils.h"
 #include "common/device-utils.h"
 #include "common/device-scan.h"
+#include "common/format-output.h"
 #include "mkfs/common.h"
 
 static const char * const device_cmd_group_usage[] = {
@@ -459,6 +460,17 @@ out:
 }
 static DEFINE_SIMPLE_COMMAND(device_ready, "ready");
 
+static const struct rowspec device_stats_rowspec[] = {
+	{ .key = "device", .fmt = "%s", .out_text = "device", .out_json = "device" },
+	{ .key = "devid", .fmt = "%u", .out_text = "devid", .out_json = "devid" },
+	{ .key = "write_io_errs", .fmt = "%llu", .out_text = "write_io_errs", .out_json = "write_io_errs" },
+	{ .key = "read_io_errs", .fmt = "%llu", .out_text = "read_io_errs", .out_json = "read_io_errs" },
+	{ .key = "flush_io_errs", .fmt = "%llu", .out_text = "flush_io_errs", .out_json = "flush_io_errs" },
+	{ .key = "corruption_errs", .fmt = "%llu", .out_text = "corruption_errs", .out_json = "corruption_errs" },
+	{ .key = "generation_errs", .fmt = "%llu", .out_text = "generation_errs", .out_json = "generation_errs" },
+	ROWSPEC_END
+};
+
 static const char * const cmd_device_stats_usage[] = {
 	"btrfs device stats [options] <path>|<device>",
 	"Show device IO error statistics",
@@ -482,6 +494,7 @@ static int cmd_device_stats(const struct cmd_struct *cmd, int argc, char **argv)
 	int check = 0;
 	__u64 flags = 0;
 	DIR *dirstream = NULL;
+	struct format_ctx fctx;
 
 	optind = 0;
 	while (1) {
@@ -530,6 +543,8 @@ static int cmd_device_stats(const struct cmd_struct *cmd, int argc, char **argv)
 		goto out;
 	}
 
+	fmt_start(&fctx, device_stats_rowspec, 24, 0);
+	fmt_print_start_group(&fctx, "device-stats", JSON_TYPE_ARRAY);
 	for (i = 0; i < fi_args.num_devices; i++) {
 		struct btrfs_ioctl_get_dev_stats args = {0};
 		char path[BTRFS_DEVICE_PATH_NAME_MAX + 1];
@@ -548,6 +563,7 @@ static int cmd_device_stats(const struct cmd_struct *cmd, int argc, char **argv)
 			err |= 1;
 		} else {
 			char *canonical_path;
+			char devid_str[32];
 			int j;
 			static const struct {
 				const char name[32];
@@ -574,31 +590,36 @@ static int cmd_device_stats(const struct cmd_struct *cmd, int argc, char **argv)
 				snprintf(canonical_path, 32,
 					 "devid:%llu", args.devid);
 			}
+			snprintf(devid_str, 32, "%llu", args.devid);
+			fmt_print_start_object(&fctx);
+			fmt_print(&fctx, "device", canonical_path);
+			fmt_print(&fctx, "devid", di_args[i].devid);
 
 			for (j = 0; j < ARRAY_SIZE(dev_stats); j++) {
 				/* We got fewer items than we know */
 				if (args.nr_items < dev_stats[j].num + 1)
 					continue;
-				printf("[%s].%-16s %llu\n", canonical_path,
-					dev_stats[j].name,
-					(unsigned long long)
-					 args.values[dev_stats[j].num]);
+
+				fmt_print(&fctx, dev_stats[j].name, args.values[dev_stats[j].num]);
 				if ((check == 1)
 				    && (args.values[dev_stats[j].num] > 0))
 					err |= 64;
 			}
-
+			fmt_print_end_object(&fctx);
 			free(canonical_path);
 		}
 	}
 
+	fmt_print_end_group(&fctx, "device-stats");
+	fmt_end(&fctx);
+
 out:
 	free(di_args);
 	close_file_or_dir(fdmnt, dirstream);
 
 	return err;
 }
-static DEFINE_SIMPLE_COMMAND(device_stats, "stats");
+static DEFINE_COMMAND_WITH_FLAGS(device_stats, "stats", CMD_FORMAT_JSON);
 
 static const char * const cmd_device_usage_usage[] = {
 	"btrfs device usage [options] <path> [<path>..]",
-- 
2.25.1