/*
* Copyright (C) 2009 Oracle. 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 <linux/sched.h>
#include <linux/sort.h>
#include <linux/ftrace.h>
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"
/*
* delayed back reference update tracking. For subvolume trees
* we queue up extent allocations and backref maintenance for
* delayed processing. This avoids deep call chains where we
* add extents in the middle of btrfs_search_slot, and it allows
* us to buffer up frequently modified backrefs in an rb tree instead
* of hammering updates on the extent allocation tree.
*
* Right now this code is only used for reference counted trees, but
* the long term goal is to get rid of the similar code for delayed
* extent tree modifications.
*/
/*
* entries in the rb tree are ordered by the byte number of the extent
* and by the byte number of the parent block.
*/
static int comp_entry(struct btrfs_delayed_ref_node *ref,
u64 bytenr, u64 parent)
{
if (bytenr < ref->bytenr)
return -1;
if (bytenr > ref->bytenr)
return 1;
if (parent < ref->parent)
return -1;
if (parent > ref->parent)
return 1;
return 0;
}
/*
* insert a new ref into the rbtree. This returns any existing refs
* for the same (bytenr,parent) tuple, or NULL if the new node was properly
* inserted.
*/
static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
u64 bytenr, u64 parent,
struct rb_node *node)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent_node = NULL;
struct btrfs_delayed_ref_node *entry;
int cmp;
while (*p) {
parent_node = *p;
entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
rb_node);
cmp = comp_entry(entry, bytenr, parent);
if (cmp < 0)
p = &(*p)->rb_left;
else if (cmp > 0)
p = &(*p)->rb_right;
else
return entry;
}
entry = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
rb_link_node(node, parent_node, p);
rb_insert_color(node, root);
return NULL;
}
/*
* find an entry based on (bytenr,parent). This returns the delayed
* ref if it was able to find one, or NULL if nothing was in that spot
*/
static struct btrfs_delayed_ref_node *tree_search(struct rb_root *root,
u64 bytenr, u64 parent)
{
struct rb_node *n = root->rb_node;
struct btrfs_delayed_ref_node *entry;
int cmp;
while (n) {
entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
WARN_ON(!entry->in_tree);
cmp = comp_entry(entry, bytenr, parent);
if (cmp < 0)
n = n->rb_left;
else if (cmp > 0)
n = n->rb_right;
else
return entry;
}
return NULL;
}
/*
* Locking on delayed refs is done by taking a lock on the head node,
* which has the (impossible) parent id of (u64)-1. Once a lock is held
* on the head node, you're allowed (and required) to process all the
* delayed refs for a given byte number in the tree.
*
* This will walk forward in the rbtree until it finds a head node it
* is able to lock. It might not lock the delayed ref you asked for,
* and so it will return the one it did lock in next_ret and return 0.
*
* If no locks are taken, next_ret is set to null and 1 is returned. This
* means there are no more unlocked head nodes in the rbtree.
*/
int btrfs_lock_delayed_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_node *ref,
struct btrfs_delayed_ref_head **next_ret)
{
struct rb_node *node;
struct btrfs_delayed_ref_head *head;
int ret = 0;
while (1) {
if (btrfs_delayed_ref_is_head(ref)) {
head = btrfs_delayed_node_to_head(ref);
if (mutex_trylock(&head->mutex)) {
*next_ret = head;
ret = 0;
break;
}
}
node = rb_next(&ref->rb_node);
if (!node) {
ret = 1;
*next_ret = NULL;
break;
}
ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
}
return ret;
}
/*
* This checks to see if there are any delayed refs in the
* btree for a given bytenr. It returns one if it finds any
* and zero otherwise.
*
* If it only finds a head node, it returns 0.
*
* The idea is to use this when deciding if you can safely delete an
* extent from the extent allocation tree. There may be a pending
* ref in the rbtree that adds or removes references, so as long as this
* returns one you need to leave the BTRFS_EXTENT_ITEM in the extent
* allocation tree.
*/
int btrfs_delayed_ref_pending(struct btrfs_trans_handle *trans, u64 bytenr)
{
struct btrfs_delayed_ref_node *ref;
struct btrfs_delayed_ref_root *delayed_refs;
struct rb_node *prev_node;
int ret = 0;
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
ref = tree_search(&delayed_refs->root, bytenr, (u64)-1);
if (ref) {
prev_node = rb_prev(&ref->rb_node);
if (!prev_node)
goto out;
ref = rb_entry(prev_node, struct btrfs_delayed_ref_node,
rb_node);
if (ref->bytenr == bytenr)
ret = 1;
}
out:
spin_unlock(&delayed_refs->lock);
return ret;
}
/*
* helper function to lookup reference count
*
* the head node for delayed ref is used to store the sum of all the
* reference count modifications queued up in the rbtree. This way you
* can check to see what the reference count would be if all of the
* delayed refs are processed.
*/
int btrfs_lookup_extent_ref(struct btrfs_trans_handle *trans,
struct btrfs_root *root, u64 bytenr,
u64 num_bytes, u32 *refs)
{
struct btrfs_delayed_ref_node *ref;
struct btrfs_delayed_ref_head *head;
struct btrfs_delayed_ref_root *delayed_refs;
struct btrfs_path *path;
struct extent_buffer *leaf;
struct btrfs_extent_item *ei;
struct btrfs_key key;
u32 num_refs;
int ret;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
key.objectid = bytenr;
key.type = BTRFS_EXTENT_ITEM_KEY;
key.offset = num_bytes;
delayed_refs = &trans->transaction->delayed_refs;
again:
ret = btrfs_search_slot(trans, root->fs_info->extent_root,
&key, path, 0, 0);
if (ret < 0)
goto out;
if (ret == 0) {
leaf = path->nodes[0];
ei = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_extent_item);
num_refs = btrfs_extent_refs(leaf, ei);
} else {
num_refs = 0;
ret = 0;
}
spin_lock(&delayed_refs->lock);
ref = tree_search(&delayed_refs->root, bytenr, (u64)-1);
if (ref) {
head = btrfs_delayed_node_to_head(ref);
if (mutex_trylock(&head->mutex)) {
num_refs += ref->ref_mod;
mutex_unlock(&head->mutex);
*refs = num_refs;
goto out;
}
atomic_inc(&ref->refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(root->fs_info->extent_root, path);
mutex_lock(&head->mutex);
mutex_unlock(&head->mutex);
btrfs_put_delayed_ref(ref);
goto again;
} else {
*refs = num_refs;
}
out:
spin_unlock(&delayed_refs->lock);
btrfs_free_path(path);
return ret;
}
/*
* helper function to update an extent delayed ref in the
* rbtree. existing and update must both have the same
* bytenr and parent
*
* This may free existing if the update cancels out whatever
* operation it was doing.
*/
static noinline void
update_existing_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_root *delayed_refs,
struct btrfs_delayed_ref_node *existing,
struct btrfs_delayed_ref_node *update)
{
struct btrfs_delayed_ref *existing_ref;
struct btrfs_delayed_ref *ref;
existing_ref = btrfs_delayed_node_to_ref(existing);
ref = btrfs_delayed_node_to_ref(update);
if (ref->pin)
existing_ref->pin = 1;
if (ref->action != existing_ref->action) {
/*
* this is effectively undoing either an add or a
* drop. We decrement the ref_mod, and if it goes
* down to zero we just delete the entry without
* every changing the extent allocation tree.
*/
existing->ref_mod--;
if (existing->ref_mod == 0) {
rb_erase(&existing->rb_node,
&delayed_refs->root);
existing->in_tree = 0;
btrfs_put_delayed_ref(existing);
delayed_refs->num_entries--;
if (trans->delayed_ref_updates)
trans->delayed_ref_updates--;
}
} else {
if (existing_ref->action == BTRFS_ADD_DELAYED_REF) {
/* if we're adding refs, make sure all the
* details match up. The extent could
* have been totally freed and reallocated
* by a different owner before the delayed
* ref entries were removed.
*/
existing_ref->owner_objectid = ref->owner_objectid;
existing_ref->generation = ref->generation;
existing_ref->root = ref->root;
existing->num_bytes = update->num_bytes;
}
/*
* the action on the existing ref matches
* the action on the ref we're trying to add.
* Bump the ref_mod by one so the backref that
* is eventually added/removed has the correct
* reference count
*/
existing->ref_mod += update->ref_mod;
}
}
/*
* helper function to update the accounting in the head ref
* existing and update must have the same bytenr
*/
static noinline void
update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
struct btrfs_delayed_ref_node *update)
{
struct btrfs_delayed_ref_head *existing_ref;
struct btrfs_delayed_ref_head *ref;
existing_ref = btrfs_delayed_node_to_head(existing);
ref = btrfs_delayed_node_to_head(update);
if (ref->must_insert_reserved) {
/* if the extent was freed and then
* reallocated before the delayed ref
* entries were processed, we can end up
* with an existing head ref without
* the must_insert_reserved flag set.
* Set it again here
*/
existing_ref->must_insert_reserved = ref->must_insert_reserved;
/*
* update the num_bytes so we make sure the accounting
* is done correctly
*/
existing->num_bytes = update->num_bytes;
}
/*
* update the reference mod on the head to reflect this new operation
*/
existing->ref_mod += update->ref_mod;
}
/*
* helper function to actually insert a delayed ref into the rbtree.
* this does all the dirty work in terms of maintaining the correct
* overall modification count in the head node and properly dealing
* with updating existing nodes as new modifications are queued.
*/
static noinline int __btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_node *ref,
u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
u64 ref_generation, u64 owner_objectid, int action,
int pin)
{
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_ref *full_ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int count_mod = 1;
int must_insert_reserved = 0;
/*
* the head node stores the sum of all the mods, so dropping a ref
* should drop the sum in the head node by one.
*/
if (parent == (u64)-1 && action == BTRFS_DROP_DELAYED_REF)
count_mod = -1;
/*
* BTRFS_ADD_DELAYED_EXTENT means that we need to update
* the reserved accounting when the extent is finally added, or
* if a later modification deletes the delayed ref without ever
* inserting the extent into the extent allocation tree.
* ref->must_insert_reserved is the flag used to record
* that accounting mods are required.
*
* Once we record must_insert_reserved, switch the action to
* BTRFS_ADD_DELAYED_REF because other special casing is not required.
*/
if (action == BTRFS_ADD_DELAYED_EXTENT) {
must_insert_reserved = 1;
action = BTRFS_ADD_DELAYED_REF;
} else {
must_insert_reserved = 0;
}
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->parent = parent;
ref->ref_mod = count_mod;
ref->in_tree = 1;
ref->num_bytes = num_bytes;
if (btrfs_delayed_ref_is_head(ref)) {
head_ref = btrfs_delayed_node_to_head(ref);
head_ref->must_insert_reserved = must_insert_reserved;
mutex_init(&head_ref->mutex);
} else {
full_ref = btrfs_delayed_node_to_ref(ref);
full_ref->root = ref_root;
full_ref->generation = ref_generation;
full_ref->owner_objectid = owner_objectid;
full_ref->pin = pin;
full_ref->action = action;
}
existing = tree_insert(&delayed_refs->root, bytenr,
parent, &ref->rb_node);
if (existing) {
if (btrfs_delayed_ref_is_head(ref))
update_existing_head_ref(existing, ref);
else
update_existing_ref(trans, delayed_refs, existing, ref);
/*
* we've updated the existing ref, free the newly
* allocated ref
*/
kfree(ref);
} else {
delayed_refs->num_entries++;
trans->delayed_ref_updates++;
}
return 0;
}
/*
* add a delayed ref to the tree. This does all of the accounting required
* to make sure the delayed ref is eventually processed before this
* transaction commits.
*/
int btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
u64 ref_generation, u64 owner_objectid, int action,
int pin)
{
struct btrfs_delayed_ref *ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
ref = kmalloc(sizeof(*ref), GFP_NOFS);
if (!ref)
return -ENOMEM;
/*
* the parent = 0 case comes from cases where we don't actually
* know the parent yet. It will get updated later via a add/drop
* pair.
*/
if (parent == 0)
parent = bytenr;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref) {
kfree(ref);
return -ENOMEM;
}
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
/*
* insert both the head node and the new ref without dropping
* the spin lock
*/
ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
(u64)-1, 0, 0, 0, action, pin);
BUG_ON(ret);
ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
parent, ref_root, ref_generation,
owner_objectid, action, pin);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
/*
* add a delayed ref to the tree. This does all of the accounting required
* to make sure the delayed ref is eventually processed before this
* transaction commits.
*
* The main point of this call is to add and remove a backreference in a single
* shot, taking the lock only once, and only searching for the head node once.
*
* It is the same as doing a ref add and delete in two separate calls.
*/
int btrfs_update_delayed_ref(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes, u64 orig_parent,
u64 parent, u64 orig_ref_root, u64 ref_root,
u64 orig_ref_generation, u64 ref_generation,
u64 owner_objectid, int pin)
{
struct btrfs_delayed_ref *ref;
struct btrfs_delayed_ref *old_ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
ref = kmalloc(sizeof(*ref), GFP_NOFS);
if (!ref)
return -ENOMEM;
old_ref = kmalloc(sizeof(*old_ref), GFP_NOFS);
if (!old_ref) {
kfree(ref);
return -ENOMEM;
}
/*
* the parent = 0 case comes from cases where we don't actually
* know the parent yet. It will get updated later via a add/drop
* pair.
*/
if (parent == 0)
parent = bytenr;
if (orig_parent == 0)
orig_parent = bytenr;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref) {
kfree(ref);
kfree(old_ref);
return -ENOMEM;
}
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
/*
* insert both the head node and the new ref without dropping
* the spin lock
*/
ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
(u64)-1, 0, 0, 0,
BTRFS_ADD_DELAYED_REF, 0);
BUG_ON(ret);
ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
parent, ref_root, ref_generation,
owner_objectid, BTRFS_ADD_DELAYED_REF, 0);
BUG_ON(ret);
ret = __btrfs_add_delayed_ref(trans, &old_ref->node, bytenr, num_bytes,
orig_parent, orig_ref_root,
orig_ref_generation, owner_objectid,
BTRFS_DROP_DELAYED_REF, pin);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
