Steps to reproduce:
# mkfs.btrfs <partition>
# mount -o ro <partition> <mnt0>
# mount -o ro <partition> <mnt1>
# mount -o remount,rw <mnt0>
# umount <mnt0>
# btrfs fi resize 10g <mnt1>
We re-sized 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 <miaox@xxxxxxxxxxxxxx>
---
fs/btrfs/ioctl.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 7d0214b..c4bcba5 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1293,12 +1293,13 @@ out_ra:
return ret;
}
-static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
+static noinline int btrfs_ioctl_resize(struct file *file,
void __user *arg)
{
u64 new_size;
u64 old_size;
u64 devid = 1;
+ struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
struct btrfs_ioctl_vol_args *vol_args;
struct btrfs_trans_handle *trans;
struct btrfs_device *device = NULL;
@@ -1307,12 +1308,13 @@ static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
int ret = 0;
int mod = 0;
- if (root->fs_info->sb->s_flags & MS_RDONLY)
- return -EROFS;
-
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ ret = mnt_want_write_file(file);
+ if (ret)
+ return ret;
+
mutex_lock(&root->fs_info->volume_mutex);
if (root->fs_info->balance_ctl) {
printk(KERN_INFO "btrfs: balance in progress\n");
@@ -1415,6 +1417,7 @@ out_free:
kfree(vol_args);
out:
mutex_unlock(&root->fs_info->volume_mutex);
+ mnt_drop_write_file(file);
return ret;
}
@@ -3759,7 +3762,7 @@ long btrfs_ioctl(struct file *file, unsigned int
case BTRFS_IOC_DEFRAG_RANGE:
return btrfs_ioctl_defrag(file, argp);
case BTRFS_IOC_RESIZE:
- return btrfs_ioctl_resize(root, argp);
+ return btrfs_ioctl_resize(file, argp);
case BTRFS_IOC_ADD_DEV:
return btrfs_ioctl_add_dev(root, argp);
case BTRFS_IOC_RM_DEV:
--
1.7.11.7
--
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