-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi all and happy new year.
this is my first patch of the new year. Hooping that this is a good
sign. :-)
The enclosed patch try to address the problem raised by Justin: how
circumvent the check performed by mkfs.btrfs ?
I add a "-f|--force" switch which permits to bypass the check if a
device is already mounted. I update the man page too.
You can pull the change from
http://cassiopea.homelinux.net/git/btrfs-progs-unstable.git
branch
force-mkfs
commit (2900a150cde604f82f1437c931792bfa59c4780b)
Comments are welcome
Regards
G.Baroncelli
- --
gpg key: Goffredo Baroncelli (ghigo) <kreij...@inwind.it>
Key fingerprint = 4769 7E51 5293 D36C 814E C054 BF04 F161 3DC5 0512
On 01/03/2011 12:14 AM, Goffredo Baroncelli wrote:
> On 01/02/2011 08:52 PM, J G wrote:
>> I just encountered some odd behavior from mkbtrfs.
>> The end goal is to restore a backup to newly created BTRFS partitions while
>> using the latest btrfs-tools.
>> Here's the steps to what I did:
>> * Booted SystemRescueCD
>> * Partitioned the drives (two 750GB drives with 12 partitions each)
>> * Created an extra partition on sda as a temporary holding place for the
>> backed up files and so I can update btrfs-tools
>> * Formatted/mounted/restored backup files to the temporary partition which I
>> mounted on /mnt/backup
>> * mount -t proc none /mnt/backup/proc; mount -o bind /dev /mnt/backup/dev
>> * chroot /mnt/backup /bin/bash
>> * Updated btrfs-tools to the latest git pull from today
>> (v0.19-35-g1b444cd-dirty).
>> * mkbtrfs /dev/sda5 /dev/sdb5 -L root
>>
>> mkbtrfs returned with:
>>
>> error checking /dev/sda5 mount status
>>
>> So I used strace to find out how it was checking for the mount status. Now,
>> I'm no expert here, but I'm confused as to just why it failed. The last
>> thing of note:
>>
>> lstat("/boot", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
>> lstat("/boot/sysrcd.dat", 0x7fffb29681e0) = -1 ENOENT (No such file or
>> directory)
>> close(3) = 0
>> munmap(0x7f11df372000, 4096) = 0
>> write(2, "error checking /dev/sda5 mount s"..., 38error checking /dev/sda5
>> mount status
>> ) = 38
>>
>>
>> doesn't explain much. I see that it's checking /proc/mounts to see what's
>> mounted, and then it fails on stating /boot/sysrcd.dat (which doesn't exist
>> in the non-chrooted FS, btw).
>>
>> To make this even weirder, if I format sda5/sdb5 using the SysRescCD version
>> of mkbtrfs (v0.19) and then format sda5/sdb5 using the chroot version, it
>> works fine.
>>
>> Any ideas here? I would expect that mkbtrfs would work inside of a chroot
>> without any assistance from the original root.
>>
>> I have the full strace from the chrooted mkbtrfs failing and from it
>> succeeding, if that's helpful.
>
> On the basis of the provided information, and on the code it seems that
> mkfs.btrfs tries hard to check that the user is not formatting a mounted
> disk (or loop). So mkfs.btrfs scan the /proc/mount file and checks every
> devices. To do the check it needs to access the original file if this is
> a "loop backend". This is reasonable.
>
> In this case in a chroot-ed environment the loop file is not accessible.
>
> If you need a [dirty] "quick hack" to by-pass the problem (not tested):
> - unmount the proc filesystem
> - create an empty file /proc/mounts
> - run btrfs.fsck
> - mount the proc filesystem (removing the fake mounts file)
> - perform a "btrfs device scan"
> - mount the filesystem
>
> Of course the "right" solution is to add a "--force" switch which
> permits to by-pass these checks. Other mkfs.* tools have this switch.
>
>>From the mkfs.ext4 man page:
> [...]
> -F Force mke2fs to create a filesystem,
> even if the specified device is not
> a partition on a block special
> device, or if other parameters do
> not make sense. In order to force
> mke2fs to create a filesystem even
> if the filesystem appears to be in
> use or is mounted (a truly dangerous
> thing to do), this option must be
> specified twice.
>
> [...]
>
>
>>
>> .:Justin:.
>>
>>
>>
>> --
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>> the body of a message to majord...@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> .
>>
>
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>
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diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
index 1e14c6c..f51291c 100644
--- a/man/mkfs.btrfs.8.in
+++ b/man/mkfs.btrfs.8.in
@@ -5,14 +5,14 @@ mkfs.btrfs \- create an btrfs filesystem
.B mkfs.btrfs
[ \fB\-A\fP\fI alloc-start\fP ]
[ \fB\-b\fP\fI byte-count\fP ]
-[ \fB \-d\fP\fI data-profile\fP ]
-[ \fB \-l\fP\fI leafsize\fP ]
-[ \fB \-L\fP\fI label\fP ]
-[ \fB \-m\fP\fI metadata profile\fP ]
-[ \fB \-n\fP\fI nodesize\fP ]
-[ \fB \-s\fP\fI sectorsize\fP ]
-[ \fB \-h\fP ]
-[ \fB \-V\fP ] \fI device\fP [ \fI device ...\fP ]
+[ \fB\-d\fP\fI data-profile\fP ]
+[ \fB\-f\fP ]
+[ \fB\-l\fP\fI leafsize\fP ]
+[ \fB\-L\fP\fI label\fP ]
+[ \fB\-m\fP\fI metadata profile\fP ]
+[ \fB\-n\fP\fI nodesize\fP ]
+[ \fB\-s\fP\fI sectorsize\fP ]
+[ \fB\-V\fP ] \fIdevice\fP [ \fIdevice ...\fP ]
.SH DESCRIPTION
.B mkfs.btrfs
is used to create an btrfs filesystem (usually in a disk partition, or an array
@@ -34,6 +34,9 @@ mkfs.btrfs uses all the available storage for the filesystem.
Specify how the data must be spanned across the devices specified. Valid
values are raid0, raid1, raid10 or single.
.TP
+\fB\-f\fR, \fB\-\-force \fR
+Don't check if the device is already mounted.
+.TP
\fB\-l\fR, \fB\-\-leafsize \fIsize\fR
Specify the leaf size, the least data item in which btrfs stores data. The
default value is the page size.
diff --git a/mkfs.c b/mkfs.c
index 2e99b95..21bcc7a 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -271,6 +271,7 @@ static void print_usage(void)
fprintf(stderr, "\t -A --alloc-start the offset to start the FS\n");
fprintf(stderr, "\t -b --byte-count total number of bytes in the FS\n");
fprintf(stderr, "\t -d --data data profile, raid0, raid1, raid10 or single\n");
+ fprintf(stderr, "\t -f --force don't check if a device is already mounted\n");
fprintf(stderr, "\t -l --leafsize size of btree leaves\n");
fprintf(stderr, "\t -L --label set a label\n");
fprintf(stderr, "\t -m --metadata metadata profile, values like data profile\n");
@@ -332,6 +333,7 @@ static struct option long_options[] = {
{ "sectorsize", 1, NULL, 's' },
{ "data", 1, NULL, 'd' },
{ "version", 0, NULL, 'V' },
+ { "force", 0, NULL, 'f' },
{ 0, 0, 0, 0}
};
@@ -358,10 +360,11 @@ int main(int ac, char **av)
int first_fd;
int ret;
int i;
+ int force=0;
while(1) {
int c;
- c = getopt_long(ac, av, "A:b:l:n:s:m:d:L:V", long_options,
+ c = getopt_long(ac, av, "A:b:l:n:s:m:d:L:Vf", long_options,
&option_index);
if (c < 0)
break;
@@ -401,6 +404,9 @@ int main(int ac, char **av)
case 'V':
print_version();
break;
+ case 'f':
+ force=1;
+ break;
default:
print_usage();
}
@@ -423,13 +429,16 @@ int main(int ac, char **av)
file = av[optind++];
ret = check_mounted(file);
- if (ret < 0) {
- fprintf(stderr, "error checking %s mount status\n", file);
- exit(1);
- }
- if (ret == 1) {
- fprintf(stderr, "%s is mounted\n", file);
- exit(1);
+ if(!force){
+ if (ret < 0) {
+ fprintf(stderr, "error checking %s mount status\n",
+ file);
+ exit(1);
+ }
+ if (ret == 1) {
+ fprintf(stderr, "%s is mounted\n", file);
+ exit(1);
+ }
}
ac--;
fd = open(file, O_RDWR);
@@ -479,15 +488,17 @@ int main(int ac, char **av)
zero_end = 1;
while(ac-- > 0) {
file = av[optind++];
- ret = check_mounted(file);
- if (ret < 0) {
- fprintf(stderr, "error checking %s mount status\n",
- file);
- exit(1);
- }
- if (ret == 1) {
- fprintf(stderr, "%s is mounted\n", file);
- exit(1);
+ if(!force){
+ ret = check_mounted(file);
+ if (ret < 0) {
+ fprintf(stderr, "error checking %s"
+ " mount status\n",file);
+ exit(1);
+ }
+ if (ret == 1) {
+ fprintf(stderr, "%s is mounted\n", file);
+ exit(1);
+ }
}
fd = open(file, O_RDWR);
if (fd < 0) {
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