From bbb651e469d99f0088e286fdeb54acca7bb4ad4e Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Mon, 19 Aug 2013 18:51:13 +0200 Subject: [PATCH] Btrfs: don't allow the replace procedure on read only filesystems If you start the replace procedure on a read only filesystem, at the end the procedure fails to write the updated dev_items to the chunk tree. The problem is that this error is not indicated except for a WARN_ON(). If the user now thinks that everything was done as expected and destroys the source device (with mkfs or with a hammer). The next mount fails with "failed to read chunk root" and the filesystem is gone. This commit adds code to fail the attempt to start the replace procedure if the filesystem is mounted read-only. Signed-off-by: Stefan Behrens Cc: # 3.10+ Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 076cc7fff813..559cb161a60a 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -3670,6 +3670,9 @@ static long btrfs_ioctl_dev_replace(struct btrfs_root *root, void __user *arg) switch (p->cmd) { case BTRFS_IOCTL_DEV_REPLACE_CMD_START: + if (root->fs_info->sb->s_flags & MS_RDONLY) + return -EROFS; + if (atomic_xchg( &root->fs_info->mutually_exclusive_operation_running, 1)) {