On Tue, Sep 10, 2013 at 12:24:09AM -0400, Jeff Mahoney wrote:
> +static int btrfs_ioctl_set_features(struct file *file, void __user *arg)
> +{
> + struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
> + struct btrfs_super_block *super_block = root->fs_info->super_copy;
> + struct btrfs_ioctl_feature_flags flags[2];
> + struct btrfs_trans_handle *trans;
> + u64 newflags;
> + int ret;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + if (copy_from_user(flags, arg, sizeof(flags)))
> + return -EFAULT;
> +
> + /* Nothing to do */
> + if (!flags[0].compat_flags && !flags[0].compat_ro_flags &&
> + !flags[0].incompat_flags)
> + return 0;
> +
> + ret = check_feature(root, flags[0].compat_flags,
> + flags[1].compat_flags, COMPAT);
> + if (ret)
> + return ret;
> +
> + ret = check_feature(root, flags[0].compat_ro_flags,
> + flags[1].compat_ro_flags, COMPAT_RO);
> + if (ret)
> + return ret;
> +
> + ret = check_feature(root, flags[0].incompat_flags,
> + flags[1].incompat_flags, INCOMPAT);
> + if (ret)
> + return ret;
> +
> + trans = btrfs_start_transaction(root, 1);
It's ok to use 0 here, it's a superblock change and not related the the
metadata (similar to changing the label).
> + if (IS_ERR(trans))
> + return PTR_ERR(trans);
> +
> + spin_lock(&root->fs_info->super_lock);
> + newflags = btrfs_super_compat_flags(super_block);
> + newflags |= flags[0].compat_flags & flags[1].compat_flags;
> + newflags &= ~(flags[0].compat_flags & ~flags[1].compat_flags);
> + btrfs_set_super_compat_flags(super_block, newflags);
> +
> + newflags = btrfs_super_compat_ro_flags(super_block);
> + newflags |= flags[0].compat_ro_flags & flags[1].compat_ro_flags;
> + newflags &= ~(flags[0].compat_ro_flags & ~flags[1].compat_ro_flags);
> + btrfs_set_super_compat_ro_flags(super_block, newflags);
> +
> + newflags = btrfs_super_incompat_flags(super_block);
> + newflags |= flags[0].incompat_flags & flags[1].incompat_flags;
> + newflags &= ~(flags[0].incompat_flags & ~flags[1].incompat_flags);
> + btrfs_set_super_incompat_flags(super_block, newflags);
> + spin_unlock(&root->fs_info->super_lock);
> +
> + return btrfs_end_transaction(trans, root);
I think it's better to use btrfs_commit_transaction. The ioctl is about
to do a permanent change, any crash between ioctl and full commit will
revert to previous state of the features. This is not IMO desirable from
administrators POV.
(Sidenote, IOC_SET_FSLABEL needs the same update.)
> +}
> +
> --- a/include/uapi/linux/btrfs.h 2013-09-09 17:49:10.808003254 -0400
> +++ b/include/uapi/linux/btrfs.h 2013-09-09 17:49:12.483979430 -0400
> @@ -184,6 +184,12 @@ struct btrfs_ioctl_fs_info_args {
> __u64 reserved[124]; /* pad to 1k */
> };
>
> +struct btrfs_ioctl_feature_flags {
> + __u64 compat_flags;
> + __u64 compat_ro_flags;
> + __u64 incompat_flags;
I wonder if it makes sense to add spare bytes here, but does not seem
necessary.
> +};
> @@ -579,4 +585,10 @@ static inline char *btrfs_err_str(enum b
> +#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 54, \
> + struct btrfs_ioctl_feature_flags)
> +#define BTRFS_IOC_SET_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 54, \
> + struct btrfs_ioctl_feature_flags[2])
> +#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 54, \
> + struct btrfs_ioctl_feature_flags[3])
The ioctl number 54 clashes with the OOB dedup merged into 3.12, 55 is
for the in-bound dedup and Anand has claimed 56. I've allocated 57 for
you and updated th wiki page:
https://btrfs.wiki.kernel.org/index.php/Project_ideas#Development_notes.2C_please_read
Stefan's trick to reuse the same number is really neat.
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