From da24927b1e1925da5c1885cb483231dabe027e15 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Mon, 26 Nov 2012 08:44:50 +0000 Subject: [PATCH] Btrfs: get write access when removing a device Steps to reproduce: # mkfs.btrfs -d single -m single # mount -o ro # mount -o ro # mount -o remount,rw # umount # btrfs device delete We can remove a device from a R/O filesystem. The reason is that we just check the R/O flag of the super block object. It is not enough, because the kernel may set the R/O flag only for the mount point. We need invoke mnt_want_write_file() to do a full check. Signed-off-by: Miao Xie Signed-off-by: Chris Mason --- fs/btrfs/ioctl.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 2be49b4c82d6..ee36009f8aa1 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2270,20 +2270,23 @@ out: return ret; } -static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg) +static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg) { + struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root; struct btrfs_ioctl_vol_args *vol_args; int ret; if (!capable(CAP_SYS_ADMIN)) return -EPERM; - if (root->fs_info->sb->s_flags & MS_RDONLY) - return -EROFS; + ret = mnt_want_write_file(file); + if (ret) + return ret; if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running, 1)) { pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n"); + mnt_drop_write_file(file); return -EINPROGRESS; } @@ -2300,6 +2303,7 @@ static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg) kfree(vol_args); out: mutex_unlock(&root->fs_info->volume_mutex); + mnt_drop_write_file(file); atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0); return ret; } @@ -3842,7 +3846,7 @@ long btrfs_ioctl(struct file *file, unsigned int case BTRFS_IOC_ADD_DEV: return btrfs_ioctl_add_dev(root, argp); case BTRFS_IOC_RM_DEV: - return btrfs_ioctl_rm_dev(root, argp); + return btrfs_ioctl_rm_dev(file, argp); case BTRFS_IOC_FS_INFO: return btrfs_ioctl_fs_info(root, argp); case BTRFS_IOC_DEV_INFO: -- 2.20.1