From 228a73abde5c04428678e917b271f8526cfd90ed Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Fri, 4 Jan 2019 13:31:54 +0800 Subject: [PATCH] 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 Reviewed-by: David Sterba [ update changelog ] Signed-off-by: David Sterba --- fs/btrfs/super.c | 3 +++ fs/btrfs/volumes.c | 11 +++++++++++ fs/btrfs/volumes.h | 1 + include/uapi/linux/btrfs.h | 2 ++ 4 files changed, 17 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 0a3f122dd61f..f9d13a30aa8a 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -2190,6 +2190,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd, ret = PTR_ERR_OR_ZERO(device); mutex_unlock(&uuid_mutex); break; + case BTRFS_IOC_FORGET_DEV: + ret = btrfs_forget_devices(vol->name); + break; case BTRFS_IOC_DEVICES_READY: mutex_lock(&uuid_mutex); device = btrfs_scan_one_device(vol->name, FMODE_READ, diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 7ca31c83e730..fe122e6099ae 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1446,6 +1446,17 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr, return 0; } +int btrfs_forget_devices(const char *path) +{ + int ret; + + mutex_lock(&uuid_mutex); + ret = btrfs_free_stale_devices(strlen(path) ? path : NULL, NULL); + mutex_unlock(&uuid_mutex); + + return ret; +} + /* * Look for a btrfs signature on a device. This may be called out of the mount path * and we are not allowed to call set_blocksize during the scan. The superblock diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 656ea8d85770..3ad9d58d1b66 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -416,6 +416,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices, fmode_t flags, void *holder); struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags, void *holder); +int btrfs_forget_devices(const char *path); int btrfs_close_devices(struct btrfs_fs_devices *fs_devices); void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step); void btrfs_assign_next_active_device(struct btrfs_device *device, diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index e0763bc4158e..c195896d478f 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -837,6 +837,8 @@ enum btrfs_err_code { struct btrfs_ioctl_vol_args) #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \ struct btrfs_ioctl_vol_args) +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \ + struct btrfs_ioctl_vol_args) /* trans start and trans end are dangerous, and only for * use by applications that know how to avoid the * resulting deadlocks -- 2.34.1