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Diffstat (limited to '')
| -rw-r--r-- | libmount/src/btrfs.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/libmount/src/btrfs.c b/libmount/src/btrfs.c new file mode 100644 index 0000000..a831ce8 --- /dev/null +++ b/libmount/src/btrfs.c @@ -0,0 +1,175 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * This file is part of libmount from util-linux project. + * + * Copyright (C) 2016 David Sterba <dsterba@suse.cz> + * Copyright (C) 2016 Stanislav Brabec <sbrabec@suse.cz> + * + * libmount is free software; you can redistribute it and/or modify it + * under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or + * (at your option) any later version. + * + * Based on kernel ctree.h, rbtree.h and btrfs-progs. + */ +#include <dirent.h> +#include <sys/ioctl.h> +#include <stdlib.h> +#include <stdint.h> +#include <linux/btrfs.h> + +#include "mountP.h" +#include "bitops.h" + + +/* linux/btrfs.h lacks large parts of stuff needed for getting default + * sub-volume. Suppose that if BTRFS_DIR_ITEM_KEY is not defined, all + * declarations are still missing. + */ +#ifndef BTRFS_DIR_ITEM_KEY + +/* + * dir items are the name -> inode pointers in a directory. There is one + * for every name in a directory. + */ +#define BTRFS_DIR_ITEM_KEY 84 + +/* holds pointers to all of the tree roots */ +#define BTRFS_ROOT_TREE_OBJECTID 1ULL + +/* directory objectid inside the root tree */ +#define BTRFS_ROOT_TREE_DIR_OBJECTID 6ULL + +/* + * the key defines the order in the tree, and so it also defines (optimal) + * block layout. objectid corresponds with the inode number. The flags + * tells us things about the object, and is a kind of stream selector. + * so for a given inode, keys with flags of 1 might refer to the inode + * data, flags of 2 may point to file data in the btree and flags == 3 + * may point to extents. + * + * offset is the starting byte offset for this key in the stream. + * + * btrfs_disk_key is in disk byte order. struct btrfs_key is always + * in cpu native order. Otherwise they are identical and their sizes + * should be the same (ie both packed) + */ +struct btrfs_disk_key { + uint64_t objectid; /* little endian */ + uint8_t type; + uint64_t offset; /* little endian */ +} __attribute__ ((__packed__)); + +struct btrfs_dir_item { + struct btrfs_disk_key location; + uint64_t transid; /* little endian */ + uint16_t data_len; /* little endian */ + uint16_t name_len; /* little endian */ + uint8_t type; +} __attribute__ ((__packed__)); + +#define BTRFS_SETGET_STACK_FUNCS(name, type, member, bits) \ +static inline uint##bits##_t btrfs_##name(const type *s) \ +{ \ + return le##bits##_to_cpu(s->member); \ +} + +/* struct btrfs_disk_key */ +BTRFS_SETGET_STACK_FUNCS(disk_key_objectid, struct btrfs_disk_key, + objectid, 64) + +BTRFS_SETGET_STACK_FUNCS(stack_dir_name_len, struct btrfs_dir_item, name_len, 16) + +/* + Red Black Trees +*/ +struct rb_node { + unsigned long __rb_parent_color; + struct rb_node *rb_right; + struct rb_node *rb_left; +} __attribute__((aligned(sizeof(long)))); + /* The alignment might seem pointless, but allegedly CRIS needs it */ + +#endif /* BTRFS_DIR_ITEM_KEY */ + +/* + * btrfs_get_default_subvol_id: + * @path: Path to mounted btrfs volume + * + * Searches for the btrfs default subvolume id. + * + * Returns: default subvolume id or UINT64_MAX (-1) in case of no + * default subvolume or error. In case of error, errno is set + * properly. + */ +uint64_t btrfs_get_default_subvol_id(const char *path) +{ + int iocret; + int fd; + DIR *dirstream; + struct btrfs_ioctl_search_args args; + struct btrfs_ioctl_search_key *sk = &args.key; + struct btrfs_ioctl_search_header *sh; + uint64_t found = UINT64_MAX; + + dirstream = opendir(path); + if (!dirstream) { + DBG(BTRFS, ul_debug("opendir() failed for \"%s\" [errno=%d %m]", path, errno)); + return UINT64_MAX; + } + fd = dirfd(dirstream); + if (fd < 0) { + DBG(BTRFS, ul_debug("dirfd(opendir()) failed for \"%s\" [errno=%d %m]", path, errno)); + goto out; + } + + memset(&args, 0, sizeof(args)); + sk->tree_id = BTRFS_ROOT_TREE_OBJECTID; + sk->min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID; + sk->max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID; + sk->min_type = BTRFS_DIR_ITEM_KEY; + sk->max_type = BTRFS_DIR_ITEM_KEY; + sk->max_offset = UINT64_MAX; + sk->max_transid = UINT64_MAX; + sk->nr_items = 1; + + iocret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args); + if (iocret < 0) { + DBG(BTRFS, ul_debug("ioctl() failed for \"%s\" [errno=%d %m]", path, errno)); + goto out; + } + + /* the ioctl returns the number of items it found in nr_items */ + if (sk->nr_items == 0) { + DBG(BTRFS, ul_debug("root tree dir object id not found")); + goto out; + } + DBG(BTRFS, ul_debug("found %d root tree dir object id items", sk->nr_items)); + + sh = (struct btrfs_ioctl_search_header *)args.buf; + + if (sh->type == BTRFS_DIR_ITEM_KEY) { + struct btrfs_dir_item *di; + int name_len; + char *name; + + di = (struct btrfs_dir_item *)(sh + 1); + name_len = btrfs_stack_dir_name_len(di); + name = (char *)(di + 1); + + if (!strncmp("default", name, name_len)) { + found = btrfs_disk_key_objectid(&di->location); + DBG(BTRFS, ul_debug("\"default\" id is %llu", (unsigned long long)found)); + } else { + DBG(BTRFS, ul_debug("\"default\" id not found in tree root")); + goto out; + } + } else { + DBG(BTRFS, ul_debug("unexpected type found: %d", (int)sh->type)); + goto out; + } + +out: + closedir(dirstream); + return found; +} |