[PATCH 2/2] btrfs-progs: Add -p/--print-missing options for btrfs fi show

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Since a mounted btrfs filesystem contains all the devices info even a
device is removed after mount(like btrfs/003 in xfstests),
we can use the info to print the known missing device if possible.

So -p/--print-missing options are added to print possible missing
devices.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 cmds-filesystem.c | 26 ++++++++++++++++++++------
 man/btrfs.8.in    |  4 +++-
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 4c9933d..77b142c 100644
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -360,7 +360,7 @@ static u64 calc_used_bytes(struct btrfs_ioctl_space_args *si)
 static int print_one_fs(struct btrfs_ioctl_fs_info_args *fs_info,
 		struct btrfs_ioctl_dev_info_args *dev_info,
 		struct btrfs_ioctl_space_args *space_info,
-		char *label, char *path)
+		char *label, char *path, int print_missing)
 {
 	int i;
 	int fd;
@@ -392,7 +392,14 @@ static int print_one_fs(struct btrfs_ioctl_fs_info_args *fs_info,
 		fd = open((char *)tmp_dev_info->path, O_RDONLY);
 		if (fd < 0) {
 			missing = 1;
-			continue;
+			if (print_missing)
+				printf("\tdevid %4llu size %s used %s path %s (missing)\n",
+				       tmp_dev_info->devid,
+				       pretty_size(tmp_dev_info->total_bytes),
+				       pretty_size(tmp_dev_info->bytes_used),
+				       tmp_dev_info->path);
+			else
+				continue;
 		}
 		close(fd);
 		printf("\tdevid %4llu size %s used %s path %s\n",
@@ -440,7 +447,7 @@ static int check_arg_type(char *input)
 	return BTRFS_ARG_UNKNOWN;
 }
 
-static int btrfs_scan_kernel(void *search)
+static int btrfs_scan_kernel(void *search, int print_missing)
 {
 	int ret = 0, fd;
 	FILE *f;
@@ -477,7 +484,8 @@ static int btrfs_scan_kernel(void *search)
 		fd = open(mnt->mnt_dir, O_RDONLY);
 		if ((fd != -1) && !get_df(fd, &space_info_arg)) {
 			print_one_fs(&fs_info_arg, dev_info_arg,
-					space_info_arg, label, mnt->mnt_dir);
+				     space_info_arg, label, mnt->mnt_dir,
+				     print_missing);
 			kfree(space_info_arg);
 			memset(label, 0, sizeof(label));
 		}
@@ -500,6 +508,7 @@ static const char * const cmd_show_usage[] = {
 	"Show the structure of a filesystem",
 	"-d|--all-devices   show only disks under /dev containing btrfs filesystem",
 	"-m|--mounted       show only mounted btrfs",
+	"-p|--print-missing show known missing device if possible",
 	"If no argument is given, structure of all present filesystems is shown.",
 	NULL
 };
@@ -513,6 +522,7 @@ static int cmd_show(int argc, char **argv)
 	int ret;
 	int where = BTRFS_SCAN_LBLKID;
 	int type = 0;
+	int print_missing = 0;
 	char mp[BTRFS_PATH_NAME_MAX + 1];
 	char path[PATH_MAX];
 
@@ -521,9 +531,10 @@ static int cmd_show(int argc, char **argv)
 		static struct option long_options[] = {
 			{ "all-devices", no_argument, NULL, 'd'},
 			{ "mounted", no_argument, NULL, 'm'},
+			{ "print-missing", no_argument, NULL, 'p'},
 			{ NULL, no_argument, NULL, 0 },
 		};
-		int c = getopt_long(argc, argv, "dm", long_options,
+		int c = getopt_long(argc, argv, "dmp", long_options,
 					&long_index);
 		if (c < 0)
 			break;
@@ -534,6 +545,9 @@ static int cmd_show(int argc, char **argv)
 		case 'm':
 			where = BTRFS_SCAN_MOUNTED;
 			break;
+		case 'p':
+			print_missing = 1;
+			break;
 		default:
 			usage(cmd_show_usage);
 		}
@@ -571,7 +585,7 @@ static int cmd_show(int argc, char **argv)
 		goto devs_only;
 
 	/* show mounted btrfs */
-	ret = btrfs_scan_kernel(search);
+	ret = btrfs_scan_kernel(search, print_missing);
 	if (search && !ret)
 		return 0;
 
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 8fea115..db2e355 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -25,7 +25,7 @@ btrfs \- control a btrfs filesystem
 .PP
 \fBbtrfs\fP \fBfilesystem df\fP\fI <path>\fP
 .PP
-\fBbtrfs\fP \fBfilesystem show\fP [\fI--mounted\fP|\fI--all-devices\fP|\fI<uuid>\fP]\fP
+\fBbtrfs\fP \fBfilesystem show\fP [\fI--mounted\fP|\fI--all-devices\fP|\fI--print-missing\fP|\fI<uuid>\fP]\fP
 .PP
 \fBbtrfs\fP \fBfilesystem sync\fP\fI <path> \fP
 .PP
@@ -280,6 +280,8 @@ and unmounted.
 If \fB--mounted\fP is passed, it would probe btrfs kernel to list mounted btrfs filesystem(s);
 If \fB--all-devices\fP is passed, all the devices under /dev are scanned;
 otherwise the devices list is extracted from the /proc/partitions file.
+If \fB--print-missing\fP is passed, btrfs will try its best to print the missing device.
+This option is only useful if the filesystem is already mounted since mounted filesystem may contain the device list.
 .TP
 
 \fBfilesystem sync\fR\fI <path> \fR
-- 
1.8.5.4