On Wed, Jan 20, 2016 at 10:57:07PM +0100, Stanislav Brabec wrote:
> +/**
> + * btrfs_get_default_subvol_id:
> + * @path: Path to mounted btrfs volume
this comment formatting indicate API docs, for private library functions
we don't use "/**".
> + * Searches for the btrfs default subvolume id.
> + *
> + * Returns: default subvolume id or -1 in case of no default
> + * subvolume or error. In case of error, errno is set properly.
> + */
> +__u64 btrfs_get_default_subvol_id(const char *path)
Please, use standard userspace types, for example uint64_t. This is
generic rule, kernel-like types are unacceptable.
> +{
> + int iocret;
> + int fd;
> + DIR *dirstream = NULL;
> + struct btrfs_ioctl_search_args args;
> + struct btrfs_ioctl_search_key *sk = &args.key;
> + struct btrfs_ioctl_search_header *sh;
> + __u64 found = (__u64)-1;
= UINT64_MAX
> +struct btrfs_disk_key {
> + __le64 objectid;
> + __u8 type;
> + __le64 offset;
> +} __attribute__ ((__packed__));
> +
> +struct btrfs_dir_item {
> + struct btrfs_disk_key location;
> + __le64 transid;
> + __le16 data_len;
> + __le16 name_len;
> + __u8 type;
> +} __attribute__ ((__packed__));
again, use int64_t, uint8_t, etc.
> /**
> + * mnt_table_find_target_with_option:
> + * @tb: tab pointer
> + * @path: mountpoint directory
> + * @option: option name (e.g "subvol", "subvolid", ...)
> + * @val: option value
> + * @direction: MNT_ITER_{FORWARD,BACKWARD}
> + *
> + * Try to lookup an entry in the given tab that matches combination of
> + * @path and @option. In difference to mnt_table_find_target(), only
> + * @path iteration is done. No lookup by device name, no canonicalization.
> + *
> + * Returns: a tab entry or NULL.
> + */
if you want to export this function by API then it's necessary to add
to libmount.h.in and libmount.sym, otherwise don't use "/**".
> - DBG(TAB, ul_debug("setting FS root: btrfs subvol"));
> + {
> + /* If fstab entry does not contain "subvol", we have to
> + * check, whether btrfs has default subvolume
> + * defined. */
> +
> + __u64 default_id;
> + const char *target;
> + char default_id_str[16]; /* should be safe for u64 */
char default_id_str[sizeof(stringify_value(UINT64_MAX))];
> +
> + default_id = btrfs_get_default_subvol_id(mnt_fs_get_target(fs));
> + if (default_id == (__u64)-1)
> + goto dflt;
> +
> + /* Volume has default subvolume. Check if it
> + * matches to the one in mountinfo.
> + *
> + * Only kernel >= 4.2 reports subvolid. On older
> + * kernels, there is no reasonable way to detect which
> + * subvolume was mounted. */
> + target = mnt_resolve_spec(mnt_fs_get_target(fs), tb->cache);
> + snprintf(default_id_str, 16, "%llu", (unsigned long long int)default_id);
snprintf(default_id_str, sizeof(default_id_str), ....
> + DBG(TAB, ul_debug("target = %s subvolid = %s", target, &default_id_str));
> + struct libmnt_fs *f = mnt_table_find_target_with_option(tb, target, "subvolid", default_id_str, MNT_ITER_BACKWARD);
> + if (!f)
> + goto dflt;
> +
> + /* Instead of set of BACKREF queries constructing
> + * subvol path, use the one in mountinfo. Kernel does
> + * the evaluation for us. */
> + DBG(TAB, ul_debug("setting FS root: btrfs default subvolid = %s", &default_id_str));
> + if (mnt_fs_get_option(f, "subvol", &vol, &volsz))
> + goto dflt;
> + } else
> + DBG(TAB, ul_debug("setting FS root: btrfs subvol"));
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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