Commit bd989ba3 authored by Jan Schmidt's avatar Jan Schmidt
Browse files

Btrfs: add tree modification log functions



The tree mod log will log modifications made fs-tree nodes. Most
modifications are done by autobalance of the tree. Such changes are recorded
as long as a block entry exists. When released, the log is cleaned.

With the tree modification log, it's possible to reconstruct a consistent
old state of the tree. This is required to do backref walking on a busy
file system.
Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
parent f29021b2
......@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
......@@ -288,6 +289,412 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
return 0;
}
enum mod_log_op {
MOD_LOG_KEY_REPLACE,
MOD_LOG_KEY_ADD,
MOD_LOG_KEY_REMOVE,
MOD_LOG_KEY_REMOVE_WHILE_FREEING,
MOD_LOG_KEY_REMOVE_WHILE_MOVING,
MOD_LOG_MOVE_KEYS,
MOD_LOG_ROOT_REPLACE,
};
struct tree_mod_move {
int dst_slot;
int nr_items;
};
struct tree_mod_root {
u64 logical;
u8 level;
};
struct tree_mod_elem {
struct rb_node node;
u64 index; /* shifted logical */
struct seq_list elem;
enum mod_log_op op;
/* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
int slot;
/* this is used for MOD_LOG_KEY* and MOD_LOG_ROOT_REPLACE */
u64 generation;
/* those are used for op == MOD_LOG_KEY_{REPLACE,REMOVE} */
struct btrfs_disk_key key;
u64 blockptr;
/* this is used for op == MOD_LOG_MOVE_KEYS */
struct tree_mod_move move;
/* this is used for op == MOD_LOG_ROOT_REPLACE */
struct tree_mod_root old_root;
};
static inline void
__get_tree_mod_seq(struct btrfs_fs_info *fs_info, struct seq_list *elem)
{
elem->seq = atomic_inc_return(&fs_info->tree_mod_seq);
list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
}
void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct seq_list *elem)
{
elem->flags = 1;
spin_lock(&fs_info->tree_mod_seq_lock);
__get_tree_mod_seq(fs_info, elem);
spin_unlock(&fs_info->tree_mod_seq_lock);
}
void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct seq_list *elem)
{
struct rb_root *tm_root;
struct rb_node *node;
struct rb_node *next;
struct seq_list *cur_elem;
struct tree_mod_elem *tm;
u64 min_seq = (u64)-1;
u64 seq_putting = elem->seq;
if (!seq_putting)
return;
BUG_ON(!(elem->flags & 1));
spin_lock(&fs_info->tree_mod_seq_lock);
list_del(&elem->list);
list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
if ((cur_elem->flags & 1) && cur_elem->seq < min_seq) {
if (seq_putting > cur_elem->seq) {
/*
* blocker with lower sequence number exists, we
* cannot remove anything from the log
*/
goto out;
}
min_seq = cur_elem->seq;
}
}
/*
* anything that's lower than the lowest existing (read: blocked)
* sequence number can be removed from the tree.
*/
write_lock(&fs_info->tree_mod_log_lock);
tm_root = &fs_info->tree_mod_log;
for (node = rb_first(tm_root); node; node = next) {
next = rb_next(node);
tm = container_of(node, struct tree_mod_elem, node);
if (tm->elem.seq > min_seq)
continue;
rb_erase(node, tm_root);
list_del(&tm->elem.list);
kfree(tm);
}
write_unlock(&fs_info->tree_mod_log_lock);
out:
spin_unlock(&fs_info->tree_mod_seq_lock);
}
/*
* key order of the log:
* index -> sequence
*
* the index is the shifted logical of the *new* root node for root replace
* operations, or the shifted logical of the affected block for all other
* operations.
*/
static noinline int
__tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
{
struct rb_root *tm_root;
struct rb_node **new;
struct rb_node *parent = NULL;
struct tree_mod_elem *cur;
int ret = 0;
BUG_ON(!tm || !tm->elem.seq);
write_lock(&fs_info->tree_mod_log_lock);
tm_root = &fs_info->tree_mod_log;
new = &tm_root->rb_node;
while (*new) {
cur = container_of(*new, struct tree_mod_elem, node);
parent = *new;
if (cur->index < tm->index)
new = &((*new)->rb_left);
else if (cur->index > tm->index)
new = &((*new)->rb_right);
else if (cur->elem.seq < tm->elem.seq)
new = &((*new)->rb_left);
else if (cur->elem.seq > tm->elem.seq)
new = &((*new)->rb_right);
else {
kfree(tm);
ret = -EEXIST;
goto unlock;
}
}
rb_link_node(&tm->node, parent, new);
rb_insert_color(&tm->node, tm_root);
unlock:
write_unlock(&fs_info->tree_mod_log_lock);
return ret;
}
int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
struct tree_mod_elem **tm_ret)
{
struct tree_mod_elem *tm;
u64 seq = 0;
smp_mb();
if (list_empty(&fs_info->tree_mod_seq_list))
return 0;
tm = *tm_ret = kzalloc(sizeof(*tm), flags);
if (!tm)
return -ENOMEM;
__get_tree_mod_seq(fs_info, &tm->elem);
seq = tm->elem.seq;
tm->elem.flags = 0;
return seq;
}
static noinline int
tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb, int slot,
enum mod_log_op op, gfp_t flags)
{
struct tree_mod_elem *tm;
int ret;
ret = tree_mod_alloc(fs_info, flags, &tm);
if (ret <= 0)
return ret;
tm->index = eb->start >> PAGE_CACHE_SHIFT;
if (op != MOD_LOG_KEY_ADD) {
btrfs_node_key(eb, &tm->key, slot);
tm->blockptr = btrfs_node_blockptr(eb, slot);
}
tm->op = op;
tm->slot = slot;
tm->generation = btrfs_node_ptr_generation(eb, slot);
return __tree_mod_log_insert(fs_info, tm);
}
static noinline int
tree_mod_log_insert_key(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
int slot, enum mod_log_op op)
{
return tree_mod_log_insert_key_mask(fs_info, eb, slot, op, GFP_NOFS);
}
static noinline int
tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb, int dst_slot, int src_slot,
int nr_items, gfp_t flags)
{
struct tree_mod_elem *tm;
int ret;
int i;
ret = tree_mod_alloc(fs_info, flags, &tm);
if (ret <= 0)
return ret;
for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
ret = tree_mod_log_insert_key(fs_info, eb, i + dst_slot,
MOD_LOG_KEY_REMOVE_WHILE_MOVING);
BUG_ON(ret < 0);
}
tm->index = eb->start >> PAGE_CACHE_SHIFT;
tm->slot = src_slot;
tm->move.dst_slot = dst_slot;
tm->move.nr_items = nr_items;
tm->op = MOD_LOG_MOVE_KEYS;
return __tree_mod_log_insert(fs_info, tm);
}
static noinline int
tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
struct extent_buffer *old_root,
struct extent_buffer *new_root, gfp_t flags)
{
struct tree_mod_elem *tm;
int ret;
ret = tree_mod_alloc(fs_info, flags, &tm);
if (ret <= 0)
return ret;
tm->index = new_root->start >> PAGE_CACHE_SHIFT;
tm->old_root.logical = old_root->start;
tm->old_root.level = btrfs_header_level(old_root);
tm->generation = btrfs_header_generation(old_root);
tm->op = MOD_LOG_ROOT_REPLACE;
return __tree_mod_log_insert(fs_info, tm);
}
static struct tree_mod_elem *
__tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
int smallest)
{
struct rb_root *tm_root;
struct rb_node *node;
struct tree_mod_elem *cur = NULL;
struct tree_mod_elem *found = NULL;
u64 index = start >> PAGE_CACHE_SHIFT;
read_lock(&fs_info->tree_mod_log_lock);
tm_root = &fs_info->tree_mod_log;
node = tm_root->rb_node;
while (node) {
cur = container_of(node, struct tree_mod_elem, node);
if (cur->index < index) {
node = node->rb_left;
} else if (cur->index > index) {
node = node->rb_right;
} else if (cur->elem.seq < min_seq) {
node = node->rb_left;
} else if (!smallest) {
/* we want the node with the highest seq */
if (found)
BUG_ON(found->elem.seq > cur->elem.seq);
found = cur;
node = node->rb_left;
} else if (cur->elem.seq > min_seq) {
/* we want the node with the smallest seq */
if (found)
BUG_ON(found->elem.seq < cur->elem.seq);
found = cur;
node = node->rb_right;
} else {
found = cur;
break;
}
}
read_unlock(&fs_info->tree_mod_log_lock);
return found;
}
/*
* this returns the element from the log with the smallest time sequence
* value that's in the log (the oldest log item). any element with a time
* sequence lower than min_seq will be ignored.
*/
static struct tree_mod_elem *
tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info, u64 start,
u64 min_seq)
{
return __tree_mod_log_search(fs_info, start, min_seq, 1);
}
/*
* this returns the element from the log with the largest time sequence
* value that's in the log (the most recent log item). any element with
* a time sequence lower than min_seq will be ignored.
*/
static struct tree_mod_elem *
tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
{
return __tree_mod_log_search(fs_info, start, min_seq, 0);
}
static inline void
tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
struct extent_buffer *src, unsigned long dst_offset,
unsigned long src_offset, int nr_items)
{
int ret;
int i;
smp_mb();
if (list_empty(&fs_info->tree_mod_seq_list))
return;
if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
return;
/* speed this up by single seq for all operations? */
for (i = 0; i < nr_items; i++) {
ret = tree_mod_log_insert_key(fs_info, src, i + src_offset,
MOD_LOG_KEY_REMOVE);
BUG_ON(ret < 0);
ret = tree_mod_log_insert_key(fs_info, dst, i + dst_offset,
MOD_LOG_KEY_ADD);
BUG_ON(ret < 0);
}
}
static inline void
tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
int dst_offset, int src_offset, int nr_items)
{
int ret;
ret = tree_mod_log_insert_move(fs_info, dst, dst_offset, src_offset,
nr_items, GFP_NOFS);
BUG_ON(ret < 0);
}
static inline void
tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb,
struct btrfs_disk_key *disk_key, int slot, int atomic)
{
int ret;
ret = tree_mod_log_insert_key_mask(fs_info, eb, slot,
MOD_LOG_KEY_REPLACE,
atomic ? GFP_ATOMIC : GFP_NOFS);
BUG_ON(ret < 0);
}
static void tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb)
{
int i;
int ret;
u32 nritems;
smp_mb();
if (list_empty(&fs_info->tree_mod_seq_list))
return;
if (btrfs_header_level(eb) == 0)
return;
nritems = btrfs_header_nritems(eb);
for (i = nritems - 1; i >= 0; i--) {
ret = tree_mod_log_insert_key(fs_info, eb, i,
MOD_LOG_KEY_REMOVE_WHILE_FREEING);
BUG_ON(ret < 0);
}
}
static inline void
tree_mod_log_set_root_pointer(struct btrfs_root *root,
struct extent_buffer *new_root_node)
{
int ret;
tree_mod_log_free_eb(root->fs_info, root->node);
ret = tree_mod_log_insert_root(root->fs_info, root->node,
new_root_node, GFP_NOFS);
BUG_ON(ret < 0);
}
/*
* check if the tree block can be shared by multiple trees
*/
......@@ -2271,7 +2678,6 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
(unsigned long)btrfs_header_chunk_tree_uuid(split),
BTRFS_UUID_SIZE);
copy_extent_buffer(split, c,
btrfs_node_key_ptr_offset(0),
btrfs_node_key_ptr_offset(mid),
......
......@@ -3114,4 +3114,9 @@ struct seq_list {
u32 flags;
};
void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct seq_list *elem);
void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct seq_list *elem);
#endif
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