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btrfs-progs: rescue: add create-control-device subcommand

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Add a new subcommand 'btrfs rescue create-control-device' that creates
/dev/btrfs-control. This is helpful on systems that may not have `mknod`
installed and the device node is missing for some reason.

Issue: #223
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
[ update docs ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Daniel Xu 2020-10-29 16:17:36 -07:00 committed by David Sterba
parent 5c9a753ba0
commit c11874ae81
3 changed files with 46 additions and 4 deletions
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18
Documentation/btrfs-man5.asciidoc
View file

@ -920,16 +920,28 @@ filesystem module:
for a given filesystem
* get the supported features (can be also found under '/sys/fs/btrfs/features')
The device is usually created by a system device node manager (eg. udev), but
can be created manually:
The device is created when btrfs is initialized, either as a module or a
built-in functionality and makes sense only in connection with that. Running
eg. mkfs without the module loaded will not register the device and will
probably warn about that.
In rare cases when the module is loaded but the device is not present (most
likely accidentally deleted), it's possible to recreate it by
--------------------
# mknod --mode=600 /dev/btrfs-control c 10 234
--------------------
or (since 5.11) by a convenience command
--------------------
# btrfs rescue create-control-device
--------------------
The control device is not strictly required but the device scanning will not
work and a workaround would need to be used to mount a multi-device filesystem.
The mount option 'device' can trigger the device scanning during mount.
The mount option 'device' can trigger the device scanning during mount, see
also *btrfs device scan*.
FILESYSTEM WITH MULTIPLE PROFILES

2
btrfs-completion
View file

@ -28,7 +28,7 @@ _btrfs()
commands_balance='start pause cancel resume status'
commands_device='scan add delete remove ready stats usage'
commands_scrub='start cancel resume status'
commands_rescue='chunk-recover super-recover zero-log'
commands_rescue='chunk-recover super-recover zero-log create-control-device'
commands_inspect_internal='inode-resolve logical-resolve subvolid-resolve rootid min-dev-size dump-tree dump-super tree-stats'
commands_property='get set list'
commands_quota='enable disable rescan'

30
cmds/rescue.c
View file

@ -18,6 +18,7 @@
#include "kerncompat.h"
#include <sys/sysmacros.h>
#include <getopt.h>
#include "kernel-shared/ctree.h"
#include "kernel-shared/volumes.h"
@ -264,6 +265,34 @@ out:
}
static DEFINE_SIMPLE_COMMAND(rescue_fix_device_size, "fix-device-size");
static const char * const cmd_rescue_create_control_device_usage[] = {
"btrfs rescue create-control-device",
"Create /dev/btrfs-control (see 'CONTROL DEVICE' in btrfs(5))",
NULL
};
static int cmd_rescue_create_control_device(const struct cmd_struct *cmd,
int argc, char **argv)
{
dev_t device;
int ret;
if (check_argc_exact(argc, 1))
return 1;
device = makedev(10, 234);
ret = mknod("/dev/btrfs-control", S_IFCHR | S_IRUSR | S_IWUSR, device);
if (ret) {
error("could not create /dev/btrfs-control: %m");
return 1;
}
return 0;
}
static DEFINE_SIMPLE_COMMAND(rescue_create_control_device, "create-control-device");
static const char rescue_cmd_group_info[] =
"toolbox for specific rescue operations";
@ -273,6 +302,7 @@ static const struct cmd_group rescue_cmd_group = {
&cmd_struct_rescue_super_recover,
&cmd_struct_rescue_zero_log,
&cmd_struct_rescue_fix_device_size,
&cmd_struct_rescue_create_control_device,
NULL
}
};