btrfs: introduce new ioctl to unregister a btrfs device
Support for a new command that can be used eg. as a command $ btrfs device scan --forget [dev]' (the final name may change though) to undo the effects of 'btrfs device scan [dev]'. For this purpose this patch proposes to use ioctl #5 as it was empty and is next to the SCAN ioctl. The new ioctl BTRFS_IOC_FORGET_DEV works only on the control device (/dev/btrfs-control) to unregister one or all devices, devices that are not mounted. The argument is struct btrfs_ioctl_vol_args, ::name specifies the device path. To unregister all device, the path is an empty string. Again, the devices are removed only if they aren't part of a mounte filesystem. This new ioctl provides: - release of unwanted btrfs_fs_devices and btrfs_devices structures from memory if the device is not going to be mounted - ability to mount filesystem in degraded mode, when one devices is corrupted like in split brain raid1 - running test cases which would require reloading the kernel module but this is not possible eg. due to mounted filesystem or built-in Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: David Sterba <dsterba@suse.com> [ update changelog ] Signed-off-by: David Sterba <dsterba@suse.com>
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@ -2190,6 +2190,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
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ret = PTR_ERR_OR_ZERO(device);
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mutex_unlock(&uuid_mutex);
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break;
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case BTRFS_IOC_FORGET_DEV:
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ret = btrfs_forget_devices(vol->name);
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break;
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case BTRFS_IOC_DEVICES_READY:
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mutex_lock(&uuid_mutex);
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device = btrfs_scan_one_device(vol->name, FMODE_READ,
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@ -1446,6 +1446,17 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
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return 0;
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}
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int btrfs_forget_devices(const char *path)
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{
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int ret;
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mutex_lock(&uuid_mutex);
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ret = btrfs_free_stale_devices(strlen(path) ? path : NULL, NULL);
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mutex_unlock(&uuid_mutex);
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return ret;
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}
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/*
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* Look for a btrfs signature on a device. This may be called out of the mount path
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* and we are not allowed to call set_blocksize during the scan. The superblock
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@ -416,6 +416,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
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fmode_t flags, void *holder);
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struct btrfs_device *btrfs_scan_one_device(const char *path,
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fmode_t flags, void *holder);
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int btrfs_forget_devices(const char *path);
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int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
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void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
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void btrfs_assign_next_active_device(struct btrfs_device *device,
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@ -837,6 +837,8 @@ enum btrfs_err_code {
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struct btrfs_ioctl_vol_args)
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#define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
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struct btrfs_ioctl_vol_args)
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#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
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struct btrfs_ioctl_vol_args)
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/* trans start and trans end are dangerous, and only for
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* use by applications that know how to avoid the
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* resulting deadlocks
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