diff options
Diffstat (limited to 'fs/btrfs/backref.c')
| -rw-r--r-- | fs/btrfs/backref.c | 776 |
1 files changed, 776 insertions, 0 deletions
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c new file mode 100644 index 0000000..8855aad --- /dev/null +++ b/fs/btrfs/backref.c @@ -0,0 +1,776 @@ +/* + * Copyright (C) 2011 STRATO. All rights reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License v2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public + * License along with this program; if not, write to the + * Free Software Foundation, Inc., 59 Temple Place - Suite 330, + * Boston, MA 021110-1307, USA. + */ + +#include "ctree.h" +#include "disk-io.h" +#include "backref.h" + +struct __data_ref { + struct list_head list; + u64 inum; + u64 root; + u64 extent_data_item_offset; +}; + +struct __shared_ref { + struct list_head list; + u64 disk_byte; +}; + +static int __inode_info(u64 inum, u64 ioff, u8 key_type, + struct btrfs_root *fs_root, struct btrfs_path *path, + struct btrfs_key *found_key) +{ + int ret; + struct btrfs_key key; + struct extent_buffer *eb; + + key.type = key_type; + key.objectid = inum; + key.offset = ioff; + + ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0); + if (ret < 0) + return ret; + + eb = path->nodes[0]; + if (ret && path->slots[0] >= btrfs_header_nritems(eb)) { + ret = btrfs_next_leaf(fs_root, path); + if (ret) + return ret; + eb = path->nodes[0]; + } + + btrfs_item_key_to_cpu(eb, found_key, path->slots[0]); + if (found_key->type != key.type || found_key->objectid != key.objectid) + return 1; + + return 0; +} + +/* + * this makes the path point to (inum INODE_ITEM ioff) + */ +int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root, + struct btrfs_path *path) +{ + struct btrfs_key key; + return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path, + &key); +} + +static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root, + struct btrfs_path *path, + struct btrfs_key *found_key) +{ + return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path, + found_key); +} + +/* + * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements + * of the path are separated by '/' and the path is guaranteed to be + * 0-terminated. the path is only given within the current file system. + * Therefore, it never starts with a '/'. the caller is responsible to provide + * "size" bytes in "dest". the dest buffer will be filled backwards. finally, + * the start point of the resulting string is returned. this pointer is within + * dest, normally. + * in case the path buffer would overflow, the pointer is decremented further + * as if output was written to the buffer, though no more output is actually + * generated. that way, the caller can determine how much space would be + * required for the path to fit into the buffer. in that case, the returned + * value will be smaller than dest. callers must check this! + */ +static char *iref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path, + struct btrfs_inode_ref *iref, + struct extent_buffer *eb_in, u64 parent, + char *dest, u32 size) +{ + u32 len; + int slot; + u64 next_inum; + int ret; + s64 bytes_left = size - 1; + struct extent_buffer *eb = eb_in; + struct btrfs_key found_key; + + if (bytes_left >= 0) + dest[bytes_left] = '\0'; + + while (1) { + len = btrfs_inode_ref_name_len(eb, iref); + bytes_left -= len; + if (bytes_left >= 0) + read_extent_buffer(eb, dest + bytes_left, + (unsigned long)(iref + 1), len); + if (eb != eb_in) + free_extent_buffer(eb); + ret = inode_ref_info(parent, 0, fs_root, path, &found_key); + if (ret) + break; + next_inum = found_key.offset; + + /* regular exit ahead */ + if (parent == next_inum) + break; + + slot = path->slots[0]; + eb = path->nodes[0]; + /* make sure we can use eb after releasing the path */ + if (eb != eb_in) + atomic_inc(&eb->refs); + btrfs_release_path(path); + + iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref); + parent = next_inum; + --bytes_left; + if (bytes_left >= 0) + dest[bytes_left] = '/'; + } + + btrfs_release_path(path); + + if (ret) + return ERR_PTR(ret); + + return dest + bytes_left; +} + +/* + * this makes the path point to (logical EXTENT_ITEM *) + * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for + * tree blocks and <0 on error. + */ +int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical, + struct btrfs_path *path, struct btrfs_key *found_key) +{ + int ret; + u64 flags; + u32 item_size; + struct extent_buffer *eb; + struct btrfs_extent_item *ei; + struct btrfs_key key; + + key.type = BTRFS_EXTENT_ITEM_KEY; + key.objectid = logical; + key.offset = (u64)-1; + + ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0); + if (ret < 0) + return ret; + ret = btrfs_previous_item(fs_info->extent_root, path, + 0, BTRFS_EXTENT_ITEM_KEY); + if (ret < 0) + return ret; + + btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]); + if (found_key->type != BTRFS_EXTENT_ITEM_KEY || + found_key->objectid > logical || + found_key->objectid + found_key->offset <= logical) + return -ENOENT; + + eb = path->nodes[0]; + item_size = btrfs_item_size_nr(eb, path->slots[0]); + BUG_ON(item_size < sizeof(*ei)); + + ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item); + flags = btrfs_extent_flags(eb, ei); + + if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) + return BTRFS_EXTENT_FLAG_TREE_BLOCK; + if (flags & BTRFS_EXTENT_FLAG_DATA) + return BTRFS_EXTENT_FLAG_DATA; + + return -EIO; +} + +/* + * helper function to iterate extent inline refs. ptr must point to a 0 value + * for the first call and may be modified. it is used to track state. + * if more refs exist, 0 is returned and the next call to + * __get_extent_inline_ref must pass the modified ptr parameter to get the + * next ref. after the last ref was processed, 1 is returned. + * returns <0 on error + */ +static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb, + struct btrfs_extent_item *ei, u32 item_size, + struct btrfs_extent_inline_ref **out_eiref, + int *out_type) +{ + unsigned long end; + u64 flags; + struct btrfs_tree_block_info *info; + + if (!*ptr) { + /* first call */ + flags = btrfs_extent_flags(eb, ei); + if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) { + info = (struct btrfs_tree_block_info *)(ei + 1); + *out_eiref = + (struct btrfs_extent_inline_ref *)(info + 1); + } else { + *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1); + } + *ptr = (unsigned long)*out_eiref; + if ((void *)*ptr >= (void *)ei + item_size) + return -ENOENT; + } + + end = (unsigned long)ei + item_size; + *out_eiref = (struct btrfs_extent_inline_ref *)*ptr; + *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref); + + *ptr += btrfs_extent_inline_ref_size(*out_type); + WARN_ON(*ptr > end); + if (*ptr == end) + return 1; /* last */ + + return 0; +} + +/* + * reads the tree block backref for an extent. tree level and root are returned + * through out_level and out_root. ptr must point to a 0 value for the first + * call and may be modified (see __get_extent_inline_ref comment). + * returns 0 if data was provided, 1 if there was no more data to provide or + * <0 on error. + */ +int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb, + struct btrfs_extent_item *ei, u32 item_size, + u64 *out_root, u8 *out_level) +{ + int ret; + int type; + struct btrfs_tree_block_info *info; + struct btrfs_extent_inline_ref *eiref; + + if (*ptr == (unsigned long)-1) + return 1; + + while (1) { + ret = __get_extent_inline_ref(ptr, eb, ei, item_size, + &eiref, &type); + if (ret < 0) + return ret; + + if (type == BTRFS_TREE_BLOCK_REF_KEY || + type == BTRFS_SHARED_BLOCK_REF_KEY) + break; + + if (ret == 1) + return 1; + } + + /* we can treat both ref types equally here */ + info = (struct btrfs_tree_block_info *)(ei + 1); + *out_root = btrfs_extent_inline_ref_offset(eb, eiref); + *out_level = btrfs_tree_block_level(eb, info); + + if (ret == 1) + *ptr = (unsigned long)-1; + + return 0; +} + +static int __data_list_add(struct list_head *head, u64 inum, + u64 extent_data_item_offset, u64 root) +{ + struct __data_ref *ref; + + ref = kmalloc(sizeof(*ref), GFP_NOFS); + if (!ref) + return -ENOMEM; + + ref->inum = inum; + ref->extent_data_item_offset = extent_data_item_offset; + ref->root = root; + list_add_tail(&ref->list, head); + + return 0; +} + +static int __data_list_add_eb(struct list_head *head, struct extent_buffer *eb, + struct btrfs_extent_data_ref *dref) +{ + return __data_list_add(head, btrfs_extent_data_ref_objectid(eb, dref), + btrfs_extent_data_ref_offset(eb, dref), + btrfs_extent_data_ref_root(eb, dref)); +} + +static int __shared_list_add(struct list_head *head, u64 disk_byte) +{ + struct __shared_ref *ref; + + ref = kmalloc(sizeof(*ref), GFP_NOFS); + if (!ref) + return -ENOMEM; + + ref->disk_byte = disk_byte; + list_add_tail(&ref->list, head); + + return 0; +} + +static int __iter_shared_inline_ref_inodes(struct btrfs_fs_info *fs_info, + u64 logical, u64 inum, + u64 extent_data_item_offset, + u64 extent_offset, + struct btrfs_path *path, + struct list_head *data_refs, + iterate_extent_inodes_t *iterate, + void *ctx) +{ + u64 ref_root; + u32 item_size; + struct btrfs_key key; + struct extent_buffer *eb; + struct btrfs_extent_item *ei; + struct btrfs_extent_inline_ref *eiref; + struct __data_ref *ref; + int ret; + int type; + int last; + unsigned long ptr = 0; + + WARN_ON(!list_empty(data_refs)); + ret = extent_from_logical(fs_info, logical, path, &key); + if (ret & BTRFS_EXTENT_FLAG_DATA) + ret = -EIO; + if (ret < 0) + goto out; + + eb = path->nodes[0]; + ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item); + item_size = btrfs_item_size_nr(eb, path->slots[0]); + + ret = 0; + ref_root = 0; + /* + * as done in iterate_extent_inodes, we first build a list of refs to + * iterate, then free the path and then iterate them to avoid deadlocks. + */ + do { + last = __get_extent_inline_ref(&ptr, eb, ei, item_size, + &eiref, &type); + if (last < 0) { + ret = last; + goto out; + } + if (type == BTRFS_TREE_BLOCK_REF_KEY || + type == BTRFS_SHARED_BLOCK_REF_KEY) { + ref_root = btrfs_extent_inline_ref_offset(eb, eiref); + ret = __data_list_add(data_refs, inum, + extent_data_item_offset, + ref_root); + } + } while (!ret && !last); + + btrfs_release_path(path); + + if (ref_root == 0) { + printk(KERN_ERR "btrfs: failed to find tree block ref " + "for shared data backref %llu\n", logical); + WARN_ON(1); + ret = -EIO; + } + +out: + while (!list_empty(data_refs)) { + ref = list_first_entry(data_refs, struct __data_ref, list); + list_del(&ref->list); + if (!ret) + ret = iterate(ref->inum, extent_offset + + ref->extent_data_item_offset, + ref->root, ctx); + kfree(ref); + } + + return ret; +} + +static int __iter_shared_inline_ref(struct btrfs_fs_info *fs_info, + u64 logical, u64 orig_extent_item_objectid, + u64 extent_offset, struct btrfs_path *path, + struct list_head *data_refs, + iterate_extent_inodes_t *iterate, + void *ctx) +{ + u64 disk_byte; + struct btrfs_key key; + struct btrfs_file_extent_item *fi; + struct extent_buffer *eb; + int slot; + int nritems; + int ret; + int found = 0; + + eb = read_tree_block(fs_info->tree_root, logical, + fs_info->tree_root->leafsize, 0); + if (!eb) + return -EIO; + + /* + * from the shared data ref, we only have the leaf but we need + * the key. thus, we must look into all items and see that we + * find one (some) with a reference to our extent item. + */ + nritems = btrfs_header_nritems(eb); + for (slot = 0; slot < nritems; ++slot) { + btrfs_item_key_to_cpu(eb, &key, slot); + if (key.type != BTRFS_EXTENT_DATA_KEY) + continue; + fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item); + if (!fi) { + free_extent_buffer(eb); + return -EIO; + } + disk_byte = btrfs_file_extent_disk_bytenr(eb, fi); + if (disk_byte != orig_extent_item_objectid) { + if (found) + break; + else + continue; + } + ++found; + ret = __iter_shared_inline_ref_inodes(fs_info, logical, + key.objectid, + key.offset, + extent_offset, path, + data_refs, + iterate, ctx); + if (ret) + break; + } + + if (!found) { + printk(KERN_ERR "btrfs: failed to follow shared data backref " + "to parent %llu\n", logical); + WARN_ON(1); + ret = -EIO; + } + + free_extent_buffer(eb); + return ret; +} + +/* + * calls iterate() for every inode that references the extent identified by + * the given parameters. will use the path given as a parameter and return it + * released. + * when the iterator function returns a non-zero value, iteration stops. + */ +int iterate_extent_inodes(struct btrfs_fs_info *fs_info, + struct btrfs_path *path, + u64 extent_item_objectid, + u64 extent_offset, + iterate_extent_inodes_t *iterate, void *ctx) +{ + unsigned long ptr = 0; + int last; + int ret; + int type; + u64 logical; + u32 item_size; + struct btrfs_extent_inline_ref *eiref; + struct btrfs_extent_data_ref *dref; + struct extent_buffer *eb; + struct btrfs_extent_item *ei; + struct btrfs_key key; + struct list_head data_refs = LIST_HEAD_INIT(data_refs); + struct list_head shared_refs = LIST_HEAD_INIT(shared_refs); + struct __data_ref *ref_d; + struct __shared_ref *ref_s; + + eb = path->nodes[0]; + ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item); + item_size = btrfs_item_size_nr(eb, path->slots[0]); + + /* first we iterate the inline refs, ... */ + do { + last = __get_extent_inline_ref(&ptr, eb, ei, item_size, + &eiref, &type); + if (last == -ENOENT) { + ret = 0; + break; + } + if (last < 0) { + ret = last; + break; + } + + if (type == BTRFS_EXTENT_DATA_REF_KEY) { + dref = (struct btrfs_extent_data_ref *)(&eiref->offset); + ret = __data_list_add_eb(&data_refs, eb, dref); + } else if (type == BTRFS_SHARED_DATA_REF_KEY) { + logical = btrfs_extent_inline_ref_offset(eb, eiref); + ret = __shared_list_add(&shared_refs, logical); + } + } while (!ret && !last); + + /* ... then we proceed to in-tree references and ... */ + while (!ret) { + ++path->slots[0]; + if (path->slots[0] > btrfs_header_nritems(eb)) { + ret = btrfs_next_leaf(fs_info->extent_root, path); + if (ret) { + if (ret == 1) + ret = 0; /* we're done */ + break; + } + eb = path->nodes[0]; + } + btrfs_item_key_to_cpu(eb, &key, path->slots[0]); + if (key.objectid != extent_item_objectid) + break; + if (key.type == BTRFS_EXTENT_DATA_REF_KEY) { + dref = btrfs_item_ptr(eb, path->slots[0], + struct btrfs_extent_data_ref); + ret = __data_list_add_eb(&data_refs, eb, dref); + } else if (key.type == BTRFS_SHARED_DATA_REF_KEY) { + ret = __shared_list_add(&shared_refs, key.offset); + } + } + + btrfs_release_path(path); + + /* + * ... only at the very end we can process the refs we found. this is + * because the iterator function we call is allowed to make tree lookups + * and we have to avoid deadlocks. additionally, we need more tree + * lookups ourselves for shared data refs. + */ + while (!list_empty(&data_refs)) { + ref_d = list_first_entry(&data_refs, struct __data_ref, list); + list_del(&ref_d->list); + if (!ret) + ret = iterate(ref_d->inum, extent_offset + + ref_d->extent_data_item_offset, + ref_d->root, ctx); + kfree(ref_d); + } + + while (!list_empty(&shared_refs)) { + ref_s = list_first_entry(&shared_refs, struct __shared_ref, + list); + list_del(&ref_s->list); + if (!ret) + ret = __iter_shared_inline_ref(fs_info, + ref_s->disk_byte, + extent_item_objectid, + extent_offset, path, + &data_refs, + iterate, ctx); + kfree(ref_s); + } + + return ret; +} + +int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info, + struct btrfs_path *path, + iterate_extent_inodes_t *iterate, void *ctx) +{ + int ret; + u64 offset; + struct btrfs_key found_key; + + ret = extent_from_logical(fs_info, logical, path, + &found_key); + if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK) + ret = -EINVAL; + if (ret < 0) + return ret; + + offset = logical - found_key.objectid; + ret = iterate_extent_inodes(fs_info, path, found_key.objectid, + offset, iterate, ctx); + + return ret; +} + +static int iterate_irefs(u64 inum, struct btrfs_root *fs_root, + struct btrfs_path *path, + iterate_irefs_t *iterate, void *ctx) +{ + int ret; + int slot; + u32 cur; + u32 len; + u32 name_len; + u64 parent = 0; + int found = 0; + struct extent_buffer *eb; + struct btrfs_item *item; + struct btrfs_inode_ref *iref; + struct btrfs_key found_key; + + while (1) { + ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path, + &found_key); + if (ret < 0) + break; + if (ret) { + ret = found ? 0 : -ENOENT; + break; + } + ++found; + + parent = found_key.offset; + slot = path->slots[0]; + eb = path->nodes[0]; + /* make sure we can use eb after releasing the path */ + atomic_inc(&eb->refs); + btrfs_release_path(path); + + item = btrfs_item_nr(eb, slot); + iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref); + + for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) { + name_len = btrfs_inode_ref_name_len(eb, iref); + /* path must be released before calling iterate()! */ + ret = iterate(parent, iref, eb, ctx); + if (ret) { + free_extent_buffer(eb); + break; + } + len = sizeof(*iref) + name_len; + iref = (struct btrfs_inode_ref *)((char *)iref + len); + } + free_extent_buffer(eb); + } + + btrfs_release_path(path); + + return ret; +} + +/* + * returns 0 if the path could be dumped (probably truncated) + * returns <0 in case of an error + */ +static int inode_to_path(u64 inum, struct btrfs_inode_ref *iref, + struct extent_buffer *eb, void *ctx) +{ + struct inode_fs_paths *ipath = ctx; + char *fspath; + char *fspath_min; + int i = ipath->fspath->elem_cnt; + const int s_ptr = sizeof(char *); + u32 bytes_left; + + bytes_left = ipath->fspath->bytes_left > s_ptr ? + ipath->fspath->bytes_left - s_ptr : 0; + + fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr; + fspath = iref_to_path(ipath->fs_root, ipath->btrfs_path, iref, eb, + inum, fspath_min, bytes_left); + if (IS_ERR(fspath)) + return PTR_ERR(fspath); + + if (fspath > fspath_min) { + ipath->fspath->val[i] = (u64)fspath; + ++ipath->fspath->elem_cnt; + ipath->fspath->bytes_left = fspath - fspath_min; + } else { + ++ipath->fspath->elem_missed; + ipath->fspath->bytes_missing += fspath_min - fspath; + ipath->fspath->bytes_left = 0; + } + + return 0; +} + +/* + * this dumps all file system paths to the inode into the ipath struct, provided + * is has been created large enough. each path is zero-terminated and accessed + * from ipath->fspath->val[i]. + * when it returns, there are ipath->fspath->elem_cnt number of paths available + * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the + * number of missed paths in recored in ipath->fspath->elem_missed, otherwise, + * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would + * have been needed to return all paths. + */ +int paths_from_inode(u64 inum, struct inode_fs_paths *ipath) +{ + return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path, + inode_to_path, ipath); +} + +/* + * allocates space to return multiple file system paths for an inode. + * total_bytes to allocate are passed, note that space usable for actual path + * information will be total_bytes - sizeof(struct inode_fs_paths). + * the returned pointer must be freed with free_ipath() in the end. + */ +struct btrfs_data_container *init_data_container(u32 total_bytes) +{ + struct btrfs_data_container *data; + size_t alloc_bytes; + + alloc_bytes = max_t(size_t, total_bytes, sizeof(*data)); + data = kmalloc(alloc_bytes, GFP_NOFS); + if (!data) + return ERR_PTR(-ENOMEM); + + if (total_bytes >= sizeof(*data)) { + data->bytes_left = total_bytes - sizeof(*data); + data->bytes_missing = 0; + } else { + data->bytes_missing = sizeof(*data) - total_bytes; + data->bytes_left = 0; + } + + data->elem_cnt = 0; + data->elem_missed = 0; + + return data; +} + +/* + * allocates space to return multiple file system paths for an inode. + * total_bytes to allocate are passed, note that space usable for actual path + * information will be total_bytes - sizeof(struct inode_fs_paths). + * the returned pointer must be freed with free_ipath() in the end. + */ +struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root, + struct btrfs_path *path) +{ + struct inode_fs_paths *ifp; + struct btrfs_data_container *fspath; + + fspath = init_data_container(total_bytes); + if (IS_ERR(fspath)) + return (void *)fspath; + + ifp = kmalloc(sizeof(*ifp), GFP_NOFS); + if (!ifp) { + kfree(fspath); + return ERR_PTR(-ENOMEM); + } + + ifp->btrfs_path = path; + ifp->fspath = fspath; + ifp->fs_root = fs_root; + + return ifp; +} + +void free_ipath(struct inode_fs_paths *ipath) +{ + kfree(ipath); +} |
