- 根目录:
- fs
- btrfs
- backref.c
/*
* 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"
#include "ulist.h"
#include "transaction.h"
#include "delayed-ref.h"
/*
* this structure records all encountered refs on the way up to the root
*/
struct __prelim_ref {
struct list_head list;
u64 root_id;
struct btrfs_key key;
int level;
int count;
u64 parent;
u64 wanted_disk_byte;
};
static int __add_prelim_ref(struct list_head *head, u64 root_id,
struct btrfs_key *key, int level, u64 parent,
u64 wanted_disk_byte, int count)
{
struct __prelim_ref *ref;
/* in case we're adding delayed refs, we're holding the refs spinlock */
ref = kmalloc(sizeof(*ref), GFP_ATOMIC);
if (!ref)
return -ENOMEM;
ref->root_id = root_id;
if (key)
ref->key = *key;
else
memset(&ref->key, 0, sizeof(ref->key));
ref->level = level;
ref->count = count;
ref->parent = parent;
ref->wanted_disk_byte = wanted_disk_byte;
list_add_tail(&ref->list, head);
return 0;
}
static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
struct ulist *parents,
struct extent_buffer *eb, int level,
u64 wanted_objectid, u64 wanted_disk_byte)
{
int ret;
int slot;
struct btrfs_file_extent_item *fi;
struct btrfs_key key;
u64 disk_byte;
add_parent:
ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
if (ret < 0)
return ret;
if (level != 0)
return 0;
/*
* if the current leaf is full with EXTENT_DATA items, we must
* check the next one if that holds a reference as well.
* ref->count cannot be used to skip this check.
* repeat this until we don't find any additional EXTENT_DATA items.
*/
while (1) {
ret = btrfs_next_leaf(root, path);
if (ret < 0)
return ret;
if (ret)
return 0;
eb = path->nodes[0];
for (slot = 0; slot < btrfs_header_nritems(eb); ++slot) {
btrfs_item_key_to_cpu(eb, &key, slot);
if (key.objectid != wanted_objectid ||
key.type != BTRFS_EXTENT_DATA_KEY)
return 0;
fi = btrfs_item_ptr(eb, slot,
struct btrfs_file_extent_item);
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte == wanted_disk_byte)
goto add_parent;
}
}
return 0;
}
/*
* resolve an indirect backref in the form (root_id, key, level)
* to a logical address
*/
static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
struct __prelim_ref *ref,
struct ulist *parents)
{
struct btrfs_path *path;
struct btrfs_root *root;
struct btrfs_key root_key;
struct btrfs_key key = {0};
struct extent_buffer *eb;
int ret = 0;
int root_level;
int level = ref->level;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
root_key.objectid = ref->root_id;
root_key.type = BTRFS_ROOT_ITEM_KEY;
root_key.offset = (u64)-1;
root = btrfs_read_fs_root_no_name(fs_info, &root_key);
if (IS_ERR(root)) {
ret = PTR_ERR(root);
goto out;
}
rcu_read_lock();
root_level = btrfs_header_level(root->node);
rcu_read_unlock();
if (root_level + 1 == level)
goto out;
path->lowest_level = level;
ret = btrfs_search_slot(NULL, root, &ref->key, path, 0, 0);
pr_debug("search slot in root %llu (level %d, ref count %d) returned "
"%d for key (%llu %u %llu)\n",
(unsigned long long)ref->root_id, level, ref->count, ret,
(unsigned long long)ref->key.objectid, ref->key.type,
(unsigned long long)ref->key.offset);
if (ret < 0)
goto out;
eb = path->nodes[level];
if (!eb) {
WARN_ON(1);
ret = 1;
goto out;
}
if (level == 0) {
if (ret == 1 && path->slots[0] >= btrfs_header_nritems(eb)) {
ret = btrfs_next_leaf(root, path);
if (ret)
goto out;
eb = path->nodes[0];
}
btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
}
/* the last two parameters will only be used for level == 0 */
ret = add_all_parents(root, path, parents, eb, level, key.objectid,
ref->wanted_disk_byte);
out:
btrfs_free_path(path);
return ret;
}
/*
* resolve all indirect backrefs from the list
*/
static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
struct list_head *head)
{
int err;
int ret = 0;
struct __prelim_ref *ref;
struct __prelim_ref *ref_safe;
struct __prelim_ref *new_ref;
struct ulist *parents;
struct ulist_node *node;
parents = ulist_alloc(GFP_NOFS);
if (!parents)
return -ENOMEM;
/*
* _safe allows us to insert directly after the current item without
* iterating over the newly inserted items.
* we're also allowed to re-assign ref during iteration.
*/
list_for_each_entry_safe(ref, ref_safe, head, list) {
if (ref->parent) /* already direct */
continue;
if (ref->count == 0)
continue;
err = __resolve_indirect_ref(fs_info, ref, parents);
if (err) {
if (ret == 0)
ret = err;
continue;
}
/* we put the first parent into the ref at hand */
node = ulist_next(parents, NULL);
ref->parent = node ? node->val : 0;
/* additional parents require new refs being added here */
while ((node = ulist_next(parents, node))) {
new_ref = kmalloc(sizeof(*new_ref), GFP_NOFS);
if (!new_ref) {
ret = -ENOMEM;
break;
}
memcpy(new_ref, ref, sizeof(*ref));
new_ref->parent = node->val;
list_add(&new_ref->list, &ref->list);
}
ulist_reinit(parents);
}
ulist_free(parents);
return ret;
}
/*
* merge two lists of backrefs and adjust counts accordingly
*
* mode = 1: merge identical keys, if key is set
* mode = 2: merge identical parents
*/
static int __merge_refs(struct list_head *head, int mode)
{
struct list_head *pos1;
list_for_each(pos1, head) {
struct list_head *n2;
struct list_head *pos2;
struct __prelim_ref *ref1;
ref1 = list_entry(pos1, struct __prelim_ref, list);
if (mode == 1 && ref1->key.type == 0)
continue;
for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
pos2 = n2, n2 = pos2->next) {
struct __prelim_ref *ref2;
ref2 = list_entry(pos2, struct __prelim_ref, list);
if (mode == 1) {
if (memcmp(&ref1->key, &ref2->key,
sizeof(ref1->key)) ||
ref1->level != ref2->level ||
ref1->root_id != ref2->root_id)
continue;
ref1->count += ref2->count;
} else {
if (ref1->parent != ref2->parent)
continue;
ref1->count += ref2->count;
}
list_del(&ref2->list);
kfree(ref2);
}
}
return 0;
}
/*
* add all currently queued delayed refs from this head whose seq nr is
* smaller or equal that seq to the list
*/
static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
struct btrfs_key *info_key,
struct list_head *prefs)
{
struct btrfs_delayed_extent_op *extent_op = head->extent_op;
struct rb_node *n = &head->node.rb_node;
int sgn;
int ret = 0;
if (extent_op && extent_op->update_key)
btrfs_disk_key_to_cpu(info_key, &extent_op->key);
while ((n = rb_prev(n))) {
struct btrfs_delayed_ref_node *node;
node = rb_entry(n, struct btrfs_delayed_ref_node,
rb_node);
if (node->bytenr != head->node.bytenr)
break;
WARN_ON(node->is_head);
if (node->seq > seq)
continue;
switch (node->action) {
case BTRFS_ADD_DELAYED_EXTENT:
case BTRFS_UPDATE_DELAYED_HEAD:
WARN_ON(1);
continue;
case BTRFS_ADD_DELAYED_REF:
sgn = 1;
break;
case BTRFS_DROP_DELAYED_REF:
sgn = -1;
break;
default:
BUG_ON(1);
}
switch (node->type) {
case BTRFS_TREE_BLOCK_REF_KEY: {
struct btrfs_delayed_tree_ref *ref;
ref = btrfs_delayed_node_to_tree_ref(node);
ret = __add_prelim_ref(prefs, ref->root, info_key,
ref->level + 1, 0, node->bytenr,
node->ref_mod * sgn);
break;
}
case BTRFS_SHARED_BLOCK_REF_KEY: {
struct btrfs_delayed_tree_ref *ref;
ref = btrfs_delayed_node_to_tree_ref(node);
ret = __add_prelim_ref(prefs, ref->root, info_key,
ref->level + 1, ref->parent,
node->bytenr,
node->ref_mod * sgn);
break;
}
case BTRFS_EXTENT_DATA_REF_KEY: {
struct btrfs_delayed_data_ref *ref;
struct btrfs_key key;
ref = btrfs_delayed_node_to_data_ref(node);
key.objectid = ref->objectid;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = ref->offset;
ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
node->bytenr,
node->ref_mod * sgn);
break;
}
case BTRFS_SHARED_DATA_REF_KEY: {
struct btrfs_delayed_data_ref *ref;
struct btrfs_key key;
ref = btrfs_delayed_node_to_data_ref(node);
key.objectid = ref->objectid;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = ref->offset;
ret = __add_prelim_ref(prefs, ref->root, &key, 0,
ref->parent, node->bytenr,
node->ref_mod * sgn);
break;
}
default:
WARN_ON(1);
}
BUG_ON(ret);
}
return 0;
}
/*
* add all inline backrefs for bytenr to the list
*/
static int __add_inline_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
struct btrfs_key *info_key, int *info_level,
struct list_head *prefs)
{
int ret = 0;
int slot;
struct extent_buffer *leaf;
struct btrfs_key key;
unsigned long ptr;
unsigned long end;
struct btrfs_extent_item *ei;
u64 flags;
u64 item_size;
/*
* enumerate all inline refs
*/
leaf = path->nodes[0];
slot = path->slots[0] - 1;
item_size = btrfs_item_size_nr(leaf, slot);
BUG_ON(item_size < sizeof(*ei));
ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
flags = btrfs_extent_flags(leaf, ei);
ptr = (unsigned long)(ei + 1);
end = (unsigned long)ei + item_size;
if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
struct btrfs_tree_block_info *info;
struct btrfs_disk_key disk_key;
info = (struct btrfs_tree_block_info *)ptr;
*info_level = btrfs_tree_block_level(leaf, info);
btrfs_tree_block_key(leaf, info, &disk_key);
btrfs_disk_key_to_cpu(info_key, &disk_key);
ptr += sizeof(struct btrfs_tree_block_info);
BUG_ON(ptr > end);
} else {
BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
}
while (ptr < end) {
struct btrfs_extent_inline_ref *iref;
u64 offset;
int type;
iref = (struct btrfs_extent_inline_ref *)ptr;
type = btrfs_extent_inline_ref_type(leaf, iref);
offset = btrfs_extent_inline_ref_offset(leaf, iref);
switch (type) {
case BTRFS_SHARED_BLOCK_REF_KEY:
ret = __add_prelim_ref(prefs, 0, info_key,
*info_level + 1, offset,
bytenr, 1);
break;
case BTRFS_SHARED_DATA_REF_KEY: {
struct btrfs_shared_data_ref *sdref;
int count;
sdref = (struct btrfs_shared_data_ref *)(iref + 1);
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
bytenr, count);
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
ret = __add_prelim_ref(prefs, offset, info_key,
*info_level + 1, 0, bytenr, 1);
break;
case BTRFS_EXTENT_DATA_REF_KEY: {
struct btrfs_extent_data_ref *dref;
int count;
u64 root;
dref = (struct btrfs_extent_data_ref *)(&iref->offset);
count = btrfs_extent_data_ref_count(leaf, dref);
key.objectid = btrfs_extent_data_ref_objectid(leaf,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0, bytenr,
count);
break;
}
default:
WARN_ON(1);
}
BUG_ON(ret);
ptr += btrfs_extent_inline_ref_size(type);
}
return 0;
}
/*
* add all non-inline backrefs for bytenr to the list
*/
static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
struct btrfs_key *info_key, int info_level,
struct list_head *prefs)
{
struct btrfs_root *extent_root = fs_info->extent_root;
int ret;
int slot;
struct extent_buffer *leaf;
struct btrfs_key key;
while (1) {
ret = btrfs_next_item(extent_root, path);
if (ret < 0)
break;
if (ret) {
ret = 0;
break;
}
slot = path->slots[0];
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.objectid != bytenr)
break;
if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
continue;
if (key.type > BTRFS_SHARED_DATA_REF_KEY)
break;
switch (key.type) {
case BTRFS_SHARED_BLOCK_REF_KEY:
ret = __add_prelim_ref(prefs, 0, info_key,
info_level + 1, key.offset,
bytenr, 1);
break;
case BTRFS_SHARED_DATA_REF_KEY: {
struct btrfs_shared_data_ref *sdref;
int count;
sdref = btrfs_item_ptr(leaf, slot,
struct btrfs_shared_data_ref);
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
bytenr, count);
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
ret = __add_prelim_ref(prefs, key.offset, info_key,
info_level + 1, 0, bytenr, 1);
break;
case BTRFS_EXTENT_DATA_REF_KEY: {
struct btrfs_extent_data_ref *dref;
int count;
u64 root;
dref = btrfs_item_ptr(leaf, slot,
struct btrfs_extent_data_ref);
count = btrfs_extent_data_ref_count(leaf, dref);
key.objectid = btrfs_extent_data_ref_objectid(leaf,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0,
bytenr, count);
break;
}
default:
WARN_ON(1);
}
BUG_ON(ret);
}
return ret;
}
/*
* this adds all existing backrefs (inline backrefs, backrefs and delayed
* refs) for the given bytenr to the refs list, merges duplicates and resolves
* indirect refs to their parent bytenr.
* When roots are found, they're added to the roots list
*
* FIXME some caching might speed things up
*/
static int find_parent_nodes(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 seq, struct ulist *refs, struct ulist *roots)
{
struct btrfs_key key;
struct btrfs_path *path;
struct btrfs_key info_key = { 0 };
struct btrfs_delayed_ref_root *delayed_refs = NULL;
struct btrfs_delayed_ref_head *head = NULL;
int info_level = 0;
int ret;
struct list_head prefs_delayed;
struct list_head prefs;
struct __prelim_ref *ref;
INIT_LIST_HEAD(&prefs);
INIT_LIST_HEAD(&prefs_delayed);
key.objectid = bytenr;
key.type = BTRFS_EXTENT_ITEM_KEY;
key.offset = (u64)-1;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
/*
* grab both a lock on the path and a lock on the delayed ref head.
* We need both to get a consistent picture of how the refs look
* at a specified point in time
*/
again:
ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
if (ret < 0)
goto out;
BUG_ON(ret == 0);
/*
* look if there are updates for this ref queued and lock the head
*/
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
head = btrfs_find_delayed_ref_head(trans, bytenr);
if (head) {
if (!mutex_trylock(&head->mutex)) {
atomic_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(path);
/*
* Mutex was contended, block until it's
* released and try again
*/
mutex_lock(&head->mutex);
mutex_unlock(&head->mutex);
btrfs_put_delayed_ref(&head->node);
goto again;
}
ret = __add_delayed_refs(head, seq, &info_key, &prefs_delayed);
if (ret)
goto out;
}
spin_unlock(&delayed_refs->lock);
if (path->slots[0]) {
struct extent_buffer *leaf;
int slot;
leaf = path->nodes[0];
slot = path->slots[0] - 1;
btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.objectid == bytenr &&
key.type == BTRFS_EXTENT_ITEM_KEY) {
ret = __add_inline_refs(fs_info, path, bytenr,
&info_key, &info_level, &prefs);
if (ret)
goto out;
ret = __add_keyed_refs(fs_info, path, bytenr, &info_key,
info_level, &prefs);
if (ret)
goto out;
}
}
btrfs_release_path(path);
/*
* when adding the delayed refs above, the info_key might not have
* been known yet. Go over the list and replace the missing keys
*/
list_for_each_entry(ref, &prefs_delayed, list) {
if ((ref->key.offset | ref->key.type | ref->key.objectid) == 0)
memcpy(&ref->key, &info_key, sizeof(ref->key));
}
list_splice_init(&prefs_delayed, &prefs);
ret = __merge_refs(&prefs, 1);
if (ret)
goto out;
ret = __resolve_indirect_refs(fs_info, &prefs);
if (ret)
goto out;
ret = __merge_refs(&prefs, 2);
if (ret)
goto out;
while (!list_empty(&prefs)) {
ref = list_first_entry(&prefs, struct __prelim_ref, list);
list_del(&ref->list);
if (ref->count < 0)
WARN_ON(1);
if (ref->count && ref->root_id && ref->parent == 0) {
/* no parent == root of tree */
ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
BUG_ON(ret < 0);
}
if (ref->count && ref->parent) {
ret = ulist_add(refs, ref->parent, 0, GFP_NOFS);
BUG_ON(ret < 0);
}
kfree(ref);
}
out:
if (head)
mutex_unlock(&head->mutex);
btrfs_free_path(path);
while (!list_empty(&prefs)) {
ref = list_first_entry(&prefs, struct __prelim_ref, list);
list_del(&ref->list);
kfree(ref);
}
while (!list_empty(&prefs_delayed)) {
ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
list);
list_del(&ref->list);
kfree(ref);
}
return ret;
}
/*
* Finds all leafs with a reference to the specified combination of bytenr and
* offset. key_list_head will point to a list of corresponding keys (caller must
* free each list element). The leafs will be stored in the leafs ulist, which
* must be freed with ulist_free.
*
* returns 0 on success, <0 on error
*/
static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 num_bytes, u64 seq, struct ulist **leafs)
{
struct ulist *tmp;
int ret;
tmp = ulist_alloc(GFP_NOFS);
if (!tmp)
return -ENOMEM;
*leafs = ulist_alloc(GFP_NOFS);
if (!*leafs) {
ulist_free(tmp);
return -ENOMEM;
}
ret = find_parent_nodes(trans, fs_info, bytenr, seq, *leafs, tmp);
ulist_free(tmp);
if (ret < 0 && ret != -ENOENT) {
ulist_free(*leafs);
return ret;
}
return 0;
}
/*
* walk all backrefs for a given extent to find all roots that reference this
* extent. Walking a backref means finding all extents that reference this
* extent and in turn walk the backrefs of those, too. Naturally this is a
* recursive process, but here it is implemented in an iterative fashion: We
* find all referencing extents for the extent in question and put them on a
* list. In turn, we find all referencing extents for those, further appending
* to the list. The way we iterate the list allows adding more elements after
* the current while iterating. The process stops when we reach the end of the
* list. Found roots are added to the roots list.
*
* returns 0 on success, < 0 on error.
*/
int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 num_bytes, u64 seq, struct ulist **roots)
{
struct ulist *tmp;
struct ulist_node *node = NULL;
int ret;
tmp = ulist_alloc(GFP_NOFS);
if (!tmp)
return -ENOMEM;
*roots = ulist_alloc(GFP_NOFS);
if (!*roots) {
ulist_free(tmp);
return -ENOMEM;
}
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr, seq,
tmp, *roots);
if (ret < 0 && ret != -ENOENT) {
ulist_free(tmp);
ulist_free(*roots);
return ret;
}
node = ulist_next(tmp, node);
if (!node)
break;
bytenr = node->val;
}
ulist_free(tmp);
return 0;
}
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 > 0)
ret = -ENOENT;
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) {
pr_debug("logical %llu is not within any extent\n",
(unsigned long long)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);
pr_debug("logical %llu is at position %llu within the extent (%llu "
"EXTENT_ITEM %llu) flags %#llx size %u\n",
(unsigned long long)logical,
(unsigned long long)(logical - found_key->objectid),
(unsigned long long)found_key->objectid,
(unsigned long long)found_key->offset,
(unsigned long long)flags, item_size);
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 iterate_leaf_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 logical,
u64 orig_extent_item_objectid,
u64 extent_item_pos, u64 root,
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 = 0;
int extent_type;
u64 data_offset;
u64 data_len;
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);
extent_type = btrfs_file_extent_type(eb, fi);
if (extent_type == BTRFS_FILE_EXTENT_INLINE)
continue;
/* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
if (disk_byte != orig_extent_item_objectid)
continue;
data_offset = btrfs_file_extent_offset(eb, fi);
data_len = btrfs_file_extent_num_bytes(eb, fi);
if (extent_item_pos < data_offset ||
extent_item_pos >= data_offset + data_len)
continue;
pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
"root %llu\n", orig_extent_item_objectid,
key.objectid, key.offset, root);
ret = iterate(key.objectid,
key.offset + (extent_item_pos - data_offset),
root, ctx);
if (ret) {
pr_debug("stopping iteration because ret=%d\n", ret);
break;
}
}
free_extent_buffer(eb);
return ret;
}
/*
* calls iterate() for every inode that references the extent identified by
* the given parameters.
* when the iterator function returns a non-zero value, iteration stops.
* path is guaranteed to be in released state when iterate() is called.
*/
int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
struct btrfs_path *path,
u64 extent_item_objectid, u64 extent_item_pos,
iterate_extent_inodes_t *iterate, void *ctx)
{
int ret;
struct list_head data_refs = LIST_HEAD_INIT(data_refs);
struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
struct btrfs_trans_handle *trans;
struct ulist *refs;
struct ulist *roots;
struct ulist_node *ref_node = NULL;
struct ulist_node *root_node = NULL;
struct seq_list seq_elem;
struct btrfs_delayed_ref_root *delayed_refs;
trans = btrfs_join_transaction(fs_info->extent_root);
if (IS_ERR(trans))
return PTR_ERR(trans);
pr_debug("resolving all inodes for extent %llu\n",
extent_item_objectid);
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
btrfs_get_delayed_seq(delayed_refs, &seq_elem);
spin_unlock(&delayed_refs->lock);
ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
extent_item_pos, seq_elem.seq,
&refs);
if (ret)
goto out;
while (!ret && (ref_node = ulist_next(refs, ref_node))) {
ret = btrfs_find_all_roots(trans, fs_info, ref_node->val, -1,
seq_elem.seq, &roots);
if (ret)
break;
while (!ret && (root_node = ulist_next(roots, root_node))) {
pr_debug("root %llu references leaf %llu\n",
root_node->val, ref_node->val);
ret = iterate_leaf_refs(fs_info, path, ref_node->val,
extent_item_objectid,
extent_item_pos, root_node->val,
iterate, ctx);
}
}
ulist_free(refs);
ulist_free(roots);
out:
btrfs_put_delayed_seq(delayed_refs, &seq_elem);
btrfs_end_transaction(trans, fs_info->extent_root);
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 extent_item_pos;
struct btrfs_key found_key;
ret = extent_from_logical(fs_info, logical, path,
&found_key);
btrfs_release_path(path);
if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK)
ret = -EINVAL;
if (ret < 0)
return ret;
extent_item_pos = logical - found_key.objectid;
ret = iterate_extent_inodes(fs_info, path, found_key.objectid,
extent_item_pos, 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()! */
pr_debug("following ref at offset %u for inode %llu in "
"tree %llu\n", cur,
(unsigned long long)found_key.objectid,
(unsigned long long)fs_root->objectid);
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) {
pr_debug("path resolved: %s\n", fspath);
ipath->fspath->val[i] = (u64)(unsigned long)fspath;
++ipath->fspath->elem_cnt;
ipath->fspath->bytes_left = fspath - fspath_min;
} else {
pr_debug("missed path, not enough space. missing bytes: %lu, "
"constructed so far: %s\n",
(unsigned long)(fspath_min - fspath), fspath_min);
++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);
}