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btrfs: fix check_shared for fiemap ioctl 

Only in the case of different root_id or different object_id, check_shared
identified extent as the shared. However, If a extent was referred by
different offset of same file, it should also be identified as shared.
In addition, check_shared's loop scale is at least n^3, so if a extent
has too many references, even causes soft hang up.

First, add all delayed_ref to the ref_tree and calculate the unqiue_refs,
if the unique_refs is greater than one, return BACKREF_FOUND_SHARED.
Then individually add the on-disk reference(inline/keyed) to the ref_tree
and calculate the unique_refs of the ref_tree to check if the unique_refs
is greater than one.Because once there are two references to return
SHARED, so the time complexity is close to the constant.

Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Lu Fengqi 2016-06-13 09:36:46 +08:00 committed by David Sterba
parent b0de6c4c81
commit afce772e87
2 changed files with 369 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

361
fs/btrfs/backref.c
View File

@ -17,6 +17,7 @@
*/
#include <linux/vmalloc.h>
#include <linux/rbtree.h>
#include "ctree.h"
#include "disk-io.h"
#include "backref.h"
@ -34,6 +35,265 @@ struct extent_inode_elem {
struct extent_inode_elem *next;
};
/*
* ref_root is used as the root of the ref tree that hold a collection
* of unique references.
*/
struct ref_root {
struct rb_root rb_root;
/*
* The unique_refs represents the number of ref_nodes with a positive
* count stored in the tree. Even if a ref_node (the count is greater
* than one) is added, the unique_refs will only increase by one.
*/
unsigned int unique_refs;
};
/* ref_node is used to store a unique reference to the ref tree. */
struct ref_node {
struct rb_node rb_node;
/* For NORMAL_REF, otherwise all these fields should be set to 0 */
u64 root_id;
u64 object_id;
u64 offset;
/* For SHARED_REF, otherwise parent field should be set to 0 */
u64 parent;
/* Ref to the ref_mod of btrfs_delayed_ref_node */
int ref_mod;
};
/* Dynamically allocate and initialize a ref_root */
static struct ref_root *ref_root_alloc(void)
{
struct ref_root *ref_tree;
ref_tree = kmalloc(sizeof(*ref_tree), GFP_NOFS);
if (!ref_tree)
return NULL;
ref_tree->rb_root = RB_ROOT;
ref_tree->unique_refs = 0;
return ref_tree;
}
/* Free all nodes in the ref tree, and reinit ref_root */
static void ref_root_fini(struct ref_root *ref_tree)
{
struct ref_node *node;
struct rb_node *next;
while ((next = rb_first(&ref_tree->rb_root)) != NULL) {
node = rb_entry(next, struct ref_node, rb_node);
rb_erase(next, &ref_tree->rb_root);
kfree(node);
}
ref_tree->rb_root = RB_ROOT;
ref_tree->unique_refs = 0;
}
static void ref_root_free(struct ref_root *ref_tree)
{
if (!ref_tree)
return;
ref_root_fini(ref_tree);
kfree(ref_tree);
}
/*
* Compare ref_node with (root_id, object_id, offset, parent)
*
* The function compares two ref_node a and b. It returns an integer less
* than, equal to, or greater than zero , respectively, to be less than, to
* equal, or be greater than b.
*/
static int ref_node_cmp(struct ref_node *a, struct ref_node *b)
{
if (a->root_id < b->root_id)
return -1;
else if (a->root_id > b->root_id)
return 1;
if (a->object_id < b->object_id)
return -1;
else if (a->object_id > b->object_id)
return 1;
if (a->offset < b->offset)
return -1;
else if (a->offset > b->offset)
return 1;
if (a->parent < b->parent)
return -1;
else if (a->parent > b->parent)
return 1;
return 0;
}
/*
* Search ref_node with (root_id, object_id, offset, parent) in the tree
*
* if found, the pointer of the ref_node will be returned;
* if not found, NULL will be returned and pos will point to the rb_node for
* insert, pos_parent will point to pos'parent for insert;
*/
static struct ref_node *__ref_tree_search(struct ref_root *ref_tree,
struct rb_node ***pos,
struct rb_node **pos_parent,
u64 root_id, u64 object_id,
u64 offset, u64 parent)
{
struct ref_node *cur = NULL;
struct ref_node entry;
int ret;
entry.root_id = root_id;
entry.object_id = object_id;
entry.offset = offset;
entry.parent = parent;
*pos = &ref_tree->rb_root.rb_node;
while (**pos) {
*pos_parent = **pos;
cur = rb_entry(*pos_parent, struct ref_node, rb_node);
ret = ref_node_cmp(cur, &entry);
if (ret > 0)
*pos = &(**pos)->rb_left;
else if (ret < 0)
*pos = &(**pos)->rb_right;
else
return cur;
}
return NULL;
}
/*
* Insert a ref_node to the ref tree
* @pos used for specifiy the position to insert
* @pos_parent for specifiy pos's parent
*
* success, return 0;
* ref_node already exists, return -EEXIST;
*/
static int ref_tree_insert(struct ref_root *ref_tree, struct rb_node **pos,
struct rb_node *pos_parent, struct ref_node *ins)
{
struct rb_node **p = NULL;
struct rb_node *parent = NULL;
struct ref_node *cur = NULL;
if (!pos) {
cur = __ref_tree_search(ref_tree, &p, &parent, ins->root_id,
ins->object_id, ins->offset,
ins->parent);
if (cur)
return -EEXIST;
} else {
p = pos;
parent = pos_parent;
}
rb_link_node(&ins->rb_node, parent, p);
rb_insert_color(&ins->rb_node, &ref_tree->rb_root);
return 0;
}
/* Erase and free ref_node, caller should update ref_root->unique_refs */
static void ref_tree_remove(struct ref_root *ref_tree, struct ref_node *node)
{
rb_erase(&node->rb_node, &ref_tree->rb_root);
kfree(node);
}
/*
* Update ref_root->unique_refs
*
* Call __ref_tree_search
* 1. if ref_node doesn't exist, ref_tree_insert this node, and update
* ref_root->unique_refs:
* if ref_node->ref_mod > 0, ref_root->unique_refs++;
* if ref_node->ref_mod < 0, do noting;
*
* 2. if ref_node is found, then get origin ref_node->ref_mod, and update
* ref_node->ref_mod.
* if ref_node->ref_mod is equal to 0,then call ref_tree_remove
*
* according to origin_mod and new_mod, update ref_root->items
* +----------------+--------------+-------------+
* | |new_count <= 0|new_count > 0|
* +----------------+--------------+-------------+
* |origin_count < 0| 0 | 1 |
* +----------------+--------------+-------------+
* |origin_count > 0| -1 | 0 |
* +----------------+--------------+-------------+
*
* In case of allocation failure, -ENOMEM is returned and the ref_tree stays
* unaltered.
* Success, return 0
*/
static int ref_tree_add(struct ref_root *ref_tree, u64 root_id, u64 object_id,
u64 offset, u64 parent, int count)
{
struct ref_node *node = NULL;
struct rb_node **pos = NULL;
struct rb_node *pos_parent = NULL;
int origin_count;
int ret;
if (!count)
return 0;
node = __ref_tree_search(ref_tree, &pos, &pos_parent, root_id,
object_id, offset, parent);
if (node == NULL) {
node = kmalloc(sizeof(*node), GFP_NOFS);
if (!node)
return -ENOMEM;
node->root_id = root_id;
node->object_id = object_id;
node->offset = offset;
node->parent = parent;
node->ref_mod = count;
ret = ref_tree_insert(ref_tree, pos, pos_parent, node);
ASSERT(!ret);
if (ret) {
kfree(node);
return ret;
}
ref_tree->unique_refs += node->ref_mod > 0 ? 1 : 0;
return 0;
}
origin_count = node->ref_mod;
node->ref_mod += count;
if (node->ref_mod > 0)
ref_tree->unique_refs += origin_count > 0 ? 0 : 1;
else if (node->ref_mod <= 0)
ref_tree->unique_refs += origin_count > 0 ? -1 : 0;
if (!node->ref_mod)
ref_tree_remove(ref_tree, node);
return 0;
}
static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
struct btrfs_file_extent_item *fi,
u64 extent_item_pos,
@ -700,6 +960,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
static int __add_inline_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
int *info_level, struct list_head *prefs,
struct ref_root *ref_tree,
u64 *total_refs, u64 inum)
{
int ret = 0;
@ -767,6 +1028,13 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
bytenr, count, GFP_NOFS);
if (ref_tree) {
if (!ret)
ret = ref_tree_add(ref_tree, 0, 0, 0,
bytenr, count);
if (!ret && ref_tree->unique_refs > 1)
ret = BACKREF_FOUND_SHARED;
}
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
@ -794,6 +1062,15 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0,
bytenr, count, GFP_NOFS);
if (ref_tree) {
if (!ret)
ret = ref_tree_add(ref_tree, root,
key.objectid,
key.offset, 0,
count);
if (!ret && ref_tree->unique_refs > 1)
ret = BACKREF_FOUND_SHARED;
}
break;
}
default:
@ -812,7 +1089,8 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
*/
static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
int info_level, struct list_head *prefs, u64 inum)
int info_level, struct list_head *prefs,
struct ref_root *ref_tree, u64 inum)
{
struct btrfs_root *extent_root = fs_info->extent_root;
int ret;
@ -855,6 +1133,13 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
count = btrfs_shared_data_ref_count(leaf, sdref);
ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
bytenr, count, GFP_NOFS);
if (ref_tree) {
if (!ret)
ret = ref_tree_add(ref_tree, 0, 0, 0,
bytenr, count);
if (!ret && ref_tree->unique_refs > 1)
ret = BACKREF_FOUND_SHARED;
}
break;
}
case BTRFS_TREE_BLOCK_REF_KEY:
@ -883,6 +1168,15 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0,
bytenr, count, GFP_NOFS);
if (ref_tree) {
if (!ret)
ret = ref_tree_add(ref_tree, root,
key.objectid,
key.offset, 0,
count);
if (!ret && ref_tree->unique_refs > 1)
ret = BACKREF_FOUND_SHARED;
}
break;
}
default:
@ -909,13 +1203,16 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
* commit root.
* The special case is for qgroup to search roots in commit_transaction().
*
* If check_shared is set to 1, any extent has more than one ref item, will
* be returned BACKREF_FOUND_SHARED immediately.
*
* 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 time_seq, struct ulist *refs,
struct ulist *roots, const u64 *extent_item_pos,
u64 root_objectid, u64 inum)
u64 root_objectid, u64 inum, int check_shared)
{
struct btrfs_key key;
struct btrfs_path *path;
@ -927,6 +1224,7 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
struct list_head prefs;
struct __prelim_ref *ref;
struct extent_inode_elem *eie = NULL;
struct ref_root *ref_tree = NULL;
u64 total_refs = 0;
INIT_LIST_HEAD(&prefs);
@ -958,6 +1256,18 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
again:
head = NULL;
if (check_shared) {
if (!ref_tree) {
ref_tree = ref_root_alloc();
if (!ref_tree) {
ret = -ENOMEM;
goto out;
}
} else {
ref_root_fini(ref_tree);
}
}
ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
if (ret < 0)
goto out;
@ -1002,6 +1312,36 @@ again:
} else {
spin_unlock(&delayed_refs->lock);
}
if (check_shared && !list_empty(&prefs_delayed)) {
/*
* Add all delay_ref to the ref_tree and check if there
* are multiple ref items added.
*/
list_for_each_entry(ref, &prefs_delayed, list) {
if (ref->key_for_search.type) {
ret = ref_tree_add(ref_tree,
ref->root_id,
ref->key_for_search.objectid,
ref->key_for_search.offset,
0, ref->count);
if (ret)
goto out;
} else {
ret = ref_tree_add(ref_tree, 0, 0, 0,
ref->parent, ref->count);
if (ret)
goto out;
}
}
if (ref_tree->unique_refs > 1) {
ret = BACKREF_FOUND_SHARED;
goto out;
}
}
}
if (path->slots[0]) {
@ -1017,11 +1357,13 @@ again:
key.type == BTRFS_METADATA_ITEM_KEY)) {
ret = __add_inline_refs(fs_info, path, bytenr,
&info_level, &prefs,
&total_refs, inum);
ref_tree, &total_refs,
inum);
if (ret)
goto out;
ret = __add_keyed_refs(fs_info, path, bytenr,
info_level, &prefs, inum);
info_level, &prefs,
ref_tree, inum);
if (ret)
goto out;
}
@ -1106,6 +1448,7 @@ again:
out:
btrfs_free_path(path);
ref_root_free(ref_tree);
while (!list_empty(&prefs)) {
ref = list_first_entry(&prefs, struct __prelim_ref, list);
list_del(&ref->list);
@ -1159,8 +1502,8 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
if (!*leafs)
return -ENOMEM;
ret = find_parent_nodes(trans, fs_info, bytenr,
time_seq, *leafs, NULL, extent_item_pos, 0, 0);
ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
*leafs, NULL, extent_item_pos, 0, 0, 0);
if (ret < 0 && ret != -ENOENT) {
free_leaf_list(*leafs);
return ret;
@ -1202,8 +1545,8 @@ static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
ULIST_ITER_INIT(&uiter);
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr,
time_seq, tmp, *roots, NULL, 0, 0);
ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
tmp, *roots, NULL, 0, 0, 0);
if (ret < 0 && ret != -ENOENT) {
ulist_free(tmp);
ulist_free(*roots);
@ -1273,7 +1616,7 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans,
ULIST_ITER_INIT(&uiter);
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
roots, NULL, root_objectid, inum);
roots, NULL, root_objectid, inum, 1);
if (ret == BACKREF_FOUND_SHARED) {
/* this is the only condition under which we return 1 */
ret = 1;

18
fs/btrfs/extent_io.c
View File

@ -20,6 +20,7 @@
#include "locking.h"
#include "rcu-string.h"
#include "backref.h"
#include "transaction.h"
static struct kmem_cache *extent_state_cache;
static struct kmem_cache *extent_buffer_cache;
@ -4487,11 +4488,24 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
flags |= (FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
} else if (fieinfo->fi_extents_max) {
struct btrfs_trans_handle *trans;
u64 bytenr = em->block_start -
(em->start - em->orig_start);
disko = em->block_start + offset_in_extent;
/*
* We need a trans handle to get delayed refs
*/
trans = btrfs_join_transaction(root);
/*
* It's OK if we can't start a trans we can still check
* from commit_root
*/
if (IS_ERR(trans))
trans = NULL;
/*
* As btrfs supports shared space, this information
* can be exported to userspace tools via
@ -4499,9 +4513,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
* then we're just getting a count and we can skip the
* lookup stuff.
*/
ret = btrfs_check_shared(NULL, root->fs_info,
ret = btrfs_check_shared(trans, root->fs_info,
root->objectid,
btrfs_ino(inode), bytenr);
if (trans)
btrfs_end_transaction(trans, root);
if (ret < 0)
goto out_free;
if (ret)