[v2] btrfs-progs: device add should check existing FS before adding

Commit Message

Anand Jain Sept. 27, 2013, 5:30 p.m. UTC

as of now, when 'btrfs device add' adds a device it doesn't
check if the given device contains an existing FS. This
patch will change that to check the same. which when true
add will fail, and ask user to use -f option to overwrite.

further, since now we have test_dev_for_mkfs() function
to check if a disk can be used, so this patch will also
use this function to test the given device before adding.

v2: rebase on 20130920, update man page and review comments

Signed-off-by: Anand Jain <[e-mail]>
---
 cmds-device.c  | 36 +++++++++++-------------------------
 man/btrfs.8.in |  6 ++++--
 2 files changed, 15 insertions(+), 27 deletions(-)

Comments

Zach Brown Sept. 27, 2013, 6:32 p.m. UTC | #1

> @@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
>  	int	i, fdmnt, ret=0, e;
>  	DIR	*dirstream = NULL;
>  	int discard = 1;
> +	int force = 0;
> +	char estr[100];
>  
> +		res = test_dev_for_mkfs(argv[i], force, estr);
> +		if (res) {
> +			fprintf(stderr, "%s", estr);
>  			continue;
>  		}

This test_dev_for_mkfs() error string interface is bad.  The caller
should not have to magically guess the string size that the function is
going to use.  Especially because users can trivial provide giant paths
that exhaust that tiny buffer.  If an arbitrarily too small buffer in
the caller was needed at all, its length should have been passed in with
the string pointer.  (Or a string struct that all C projects eventually
grow.)

But all the callers just immediately print it anyway.  Get rid of that
string argument entirely and just have test_dev_for_mkfs() print the
strings.

- z
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Anand Jain Sept. 28, 2013, 2:34 p.m. UTC | #2

On 09/28/2013 02:32 AM, Zach Brown wrote:
>> @@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
>>   	int	i, fdmnt, ret=0, e;
>>   	DIR	*dirstream = NULL;
>>   	int discard = 1;
>> +	int force = 0;
>> +	char estr[100];
>>
>> +		res = test_dev_for_mkfs(argv[i], force, estr);
>> +		if (res) {
>> +			fprintf(stderr, "%s", estr);
>>   			continue;
>>   		}
>
> This test_dev_for_mkfs() error string interface is bad.  The caller
> should not have to magically guess the string size that the function is
> going to use.  Especially because users can trivial provide giant paths
> that exhaust that tiny buffer.  If an arbitrarily too small buffer in
> the caller was needed at all, its length should have been passed in with
> the string pointer.  (Or a string struct that all C projects eventually
> grow.)
>
> But all the callers just immediately print it anyway.  Get rid of that
> string argument entirely and just have test_dev_for_mkfs() print the
> strings.

  Right. But this patch didn't introduce test_dev_for_mkfs()
  revamp of it will be good in a separate patch as it touches
  other functions as well.

Thanks, Anand


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Patch

diff --git a/cmds-device.c b/cmds-device.c
index 12c802e..7cfc347 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -40,6 +40,7 @@  static const char * const cmd_add_dev_usage[] = {
 	"btrfs device add [options] <device> [<device>...] <path>",
 	"Add a device to a filesystem",
 	"-K|--nodiscard    do not perform whole device TRIM",
+	"-f|--force        force overwrite existing filesystem on the disk",
 	NULL
 };
 
@@ -49,14 +50,17 @@  static int cmd_add_dev(int argc, char **argv)
 	int	i, fdmnt, ret=0, e;
 	DIR	*dirstream = NULL;
 	int discard = 1;
+	int force = 0;
+	char estr[100];
 
 	while (1) {
 		int long_index;
 		static struct option long_options[] = {
 			{ "nodiscard", optional_argument, NULL, 'K'},
+			{ "force", no_argument, NULL, 'f'},
 			{ 0, 0, 0, 0 }
 		};
-		int c = getopt_long(argc, argv, "K", long_options,
+		int c = getopt_long(argc, argv, "Kf", long_options,
 					&long_index);
 		if (c < 0)
 			break;
@@ -64,6 +68,9 @@  static int cmd_add_dev(int argc, char **argv)
 		case 'K':
 			discard = 0;
 			break;
+		case 'f':
+			force = 1;
+			break;
 		default:
 			usage(cmd_add_dev_usage);
 		}
@@ -86,19 +93,11 @@  static int cmd_add_dev(int argc, char **argv)
 		struct btrfs_ioctl_vol_args ioctl_args;
 		int	devfd, res;
 		u64 dev_block_count = 0;
-		struct stat st;
 		int mixed = 0;
 
-		res = check_mounted(argv[i]);
-		if (res < 0) {
-			fprintf(stderr, "error checking %s mount status\n",
-				argv[i]);
-			ret++;
-			continue;
-		}
-		if (res == 1) {
-			fprintf(stderr, "%s is mounted\n", argv[i]);
-			ret++;
+		res = test_dev_for_mkfs(argv[i], force, estr);
+		if (res) {
+			fprintf(stderr, "%s", estr);
 			continue;
 		}
 
@@ -108,19 +107,6 @@  static int cmd_add_dev(int argc, char **argv)
 			ret++;
 			continue;
 		}
-		res = fstat(devfd, &st);
-		if (res) {
-			fprintf(stderr, "ERROR: Unable to stat '%s'\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
-		if (!S_ISBLK(st.st_mode)) {
-			fprintf(stderr, "ERROR: '%s' is not a block device\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
 
 		res = btrfs_prepare_device(devfd, argv[i], 1, &dev_block_count,
 					   0, &mixed, discard);
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 60e02bb..a65ed93 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -47,7 +47,7 @@  btrfs \- control a btrfs filesystem
 \fBbtrfs\fP \fB[filesystem] balance status\fP [-v] \fI<path>\fP
 .PP
 .PP
-\fBbtrfs\fP \fBdevice add\fP [-K] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
+\fBbtrfs\fP \fBdevice add\fP [-Kf] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
 \fBbtrfs\fP \fBdevice delete\fP \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
@@ -390,7 +390,7 @@  be verbose
 .RE
 .TP
 
-\fBdevice add\fR\fI [-K] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
+\fBdevice add\fR\fI [-Kf] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
 Add device(s) to the filesystem identified by \fI<path>\fR.
 If applicable, a whole device discard (TRIM) operation is performed.
 .RS
@@ -398,6 +398,8 @@  If applicable, a whole device discard (TRIM) operation is performed.
 \fIOptions\fR
 .IP "\fB-K|--nodiscard\fP" 5
 do not perform discard by default
+.IP "\fB-f|--force\fP" 5
+force overwrite of existing filesystem on the given disk(s)
 .RE
 .TP