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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

fs/btrfs/ctree.c

+407 −1
Original line number Diff line number Diff line
@@ -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),

fs/btrfs/ctree.h

+5 −0
Original line number Diff line number Diff line
@@ -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