linux/fs/btrfs/free-space-cache.c
Chris Mason 451d7585a8 Btrfs: add mount -o ssd_spread to spread allocations out
Some SSDs perform best when reusing block numbers often, while
others perform much better when clustering strictly allocates
big chunks of unused space.

The default mount -o ssd will find rough groupings of blocks
where there are a bunch of free blocks that might have some
allocated blocks mixed in.

mount -o ssd_spread will make sure there are no allocated blocks
mixed in.  It should perform better on lower end SSDs.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-06-10 11:29:52 -04:00

724 lines
19 KiB
C

/*
* Copyright (C) 2008 Red Hat. 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 "ctree.h"
#include "free-space-cache.h"
#include "transaction.h"
struct btrfs_free_space {
struct rb_node bytes_index;
struct rb_node offset_index;
u64 offset;
u64 bytes;
};
static int tree_insert_offset(struct rb_root *root, u64 offset,
struct rb_node *node)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct btrfs_free_space *info;
while (*p) {
parent = *p;
info = rb_entry(parent, struct btrfs_free_space, offset_index);
if (offset < info->offset)
p = &(*p)->rb_left;
else if (offset > info->offset)
p = &(*p)->rb_right;
else
return -EEXIST;
}
rb_link_node(node, parent, p);
rb_insert_color(node, root);
return 0;
}
static int tree_insert_bytes(struct rb_root *root, u64 bytes,
struct rb_node *node)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct btrfs_free_space *info;
while (*p) {
parent = *p;
info = rb_entry(parent, struct btrfs_free_space, bytes_index);
if (bytes < info->bytes)
p = &(*p)->rb_left;
else
p = &(*p)->rb_right;
}
rb_link_node(node, parent, p);
rb_insert_color(node, root);
return 0;
}
/*
* searches the tree for the given offset.
*
* fuzzy == 1: this is used for allocations where we are given a hint of where
* to look for free space. Because the hint may not be completely on an offset
* mark, or the hint may no longer point to free space we need to fudge our
* results a bit. So we look for free space starting at or after offset with at
* least bytes size. We prefer to find as close to the given offset as we can.
* Also if the offset is within a free space range, then we will return the free
* space that contains the given offset, which means we can return a free space
* chunk with an offset before the provided offset.
*
* fuzzy == 0: this is just a normal tree search. Give us the free space that
* starts at the given offset which is at least bytes size, and if its not there
* return NULL.
*/
static struct btrfs_free_space *tree_search_offset(struct rb_root *root,
u64 offset, u64 bytes,
int fuzzy)
{
struct rb_node *n = root->rb_node;
struct btrfs_free_space *entry, *ret = NULL;
while (n) {
entry = rb_entry(n, struct btrfs_free_space, offset_index);
if (offset < entry->offset) {
if (fuzzy &&
(!ret || entry->offset < ret->offset) &&
(bytes <= entry->bytes))
ret = entry;
n = n->rb_left;
} else if (offset > entry->offset) {
if (fuzzy &&
(entry->offset + entry->bytes - 1) >= offset &&
bytes <= entry->bytes) {
ret = entry;
break;
}
n = n->rb_right;
} else {
if (bytes > entry->bytes) {
n = n->rb_right;
continue;
}
ret = entry;
break;
}
}
return ret;
}
/*
* return a chunk at least bytes size, as close to offset that we can get.
*/
static struct btrfs_free_space *tree_search_bytes(struct rb_root *root,
u64 offset, u64 bytes)
{
struct rb_node *n = root->rb_node;
struct btrfs_free_space *entry, *ret = NULL;
while (n) {
entry = rb_entry(n, struct btrfs_free_space, bytes_index);
if (bytes < entry->bytes) {
/*
* We prefer to get a hole size as close to the size we
* are asking for so we don't take small slivers out of
* huge holes, but we also want to get as close to the
* offset as possible so we don't have a whole lot of
* fragmentation.
*/
if (offset <= entry->offset) {
if (!ret)
ret = entry;
else if (entry->bytes < ret->bytes)
ret = entry;
else if (entry->offset < ret->offset)
ret = entry;
}
n = n->rb_left;
} else if (bytes > entry->bytes) {
n = n->rb_right;
} else {
/*
* Ok we may have multiple chunks of the wanted size,
* so we don't want to take the first one we find, we
* want to take the one closest to our given offset, so
* keep searching just in case theres a better match.
*/
n = n->rb_right;
if (offset > entry->offset)
continue;
else if (!ret || entry->offset < ret->offset)
ret = entry;
}
}
return ret;
}
static void unlink_free_space(struct btrfs_block_group_cache *block_group,
struct btrfs_free_space *info)
{
rb_erase(&info->offset_index, &block_group->free_space_offset);
rb_erase(&info->bytes_index, &block_group->free_space_bytes);
}
static int link_free_space(struct btrfs_block_group_cache *block_group,
struct btrfs_free_space *info)
{
int ret = 0;
BUG_ON(!info->bytes);
ret = tree_insert_offset(&block_group->free_space_offset, info->offset,
&info->offset_index);
if (ret)
return ret;
ret = tree_insert_bytes(&block_group->free_space_bytes, info->bytes,
&info->bytes_index);
if (ret)
return ret;
return ret;
}
int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
u64 offset, u64 bytes)
{
struct btrfs_free_space *right_info;
struct btrfs_free_space *left_info;
struct btrfs_free_space *info = NULL;
int ret = 0;
info = kzalloc(sizeof(struct btrfs_free_space), GFP_NOFS);
if (!info)
return -ENOMEM;
info->offset = offset;
info->bytes = bytes;
spin_lock(&block_group->tree_lock);
/*
* first we want to see if there is free space adjacent to the range we
* are adding, if there is remove that struct and add a new one to
* cover the entire range
*/
right_info = tree_search_offset(&block_group->free_space_offset,
offset+bytes, 0, 0);
left_info = tree_search_offset(&block_group->free_space_offset,
offset-1, 0, 1);
if (right_info) {
unlink_free_space(block_group, right_info);
info->bytes += right_info->bytes;
kfree(right_info);
}
if (left_info && left_info->offset + left_info->bytes == offset) {
unlink_free_space(block_group, left_info);
info->offset = left_info->offset;
info->bytes += left_info->bytes;
kfree(left_info);
}
ret = link_free_space(block_group, info);
if (ret)
kfree(info);
spin_unlock(&block_group->tree_lock);
if (ret) {
printk(KERN_ERR "btrfs: unable to add free space :%d\n", ret);
BUG_ON(ret == -EEXIST);
}
return ret;
}
int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
u64 offset, u64 bytes)
{
struct btrfs_free_space *info;
int ret = 0;
spin_lock(&block_group->tree_lock);
info = tree_search_offset(&block_group->free_space_offset, offset, 0,
1);
if (info && info->offset == offset) {
if (info->bytes < bytes) {
printk(KERN_ERR "Found free space at %llu, size %llu,"
"trying to use %llu\n",
(unsigned long long)info->offset,
(unsigned long long)info->bytes,
(unsigned long long)bytes);
WARN_ON(1);
ret = -EINVAL;
spin_unlock(&block_group->tree_lock);
goto out;
}
unlink_free_space(block_group, info);
if (info->bytes == bytes) {
kfree(info);
spin_unlock(&block_group->tree_lock);
goto out;
}
info->offset += bytes;
info->bytes -= bytes;
ret = link_free_space(block_group, info);
spin_unlock(&block_group->tree_lock);
BUG_ON(ret);
} else if (info && info->offset < offset &&
info->offset + info->bytes >= offset + bytes) {
u64 old_start = info->offset;
/*
* we're freeing space in the middle of the info,
* this can happen during tree log replay
*
* first unlink the old info and then
* insert it again after the hole we're creating
*/
unlink_free_space(block_group, info);
if (offset + bytes < info->offset + info->bytes) {
u64 old_end = info->offset + info->bytes;
info->offset = offset + bytes;
info->bytes = old_end - info->offset;
ret = link_free_space(block_group, info);
BUG_ON(ret);
} else {
/* the hole we're creating ends at the end
* of the info struct, just free the info
*/
kfree(info);
}
spin_unlock(&block_group->tree_lock);
/* step two, insert a new info struct to cover anything
* before the hole
*/
ret = btrfs_add_free_space(block_group, old_start,
offset - old_start);
BUG_ON(ret);
} else {
spin_unlock(&block_group->tree_lock);
if (!info) {
printk(KERN_ERR "couldn't find space %llu to free\n",
(unsigned long long)offset);
printk(KERN_ERR "cached is %d, offset %llu bytes %llu\n",
block_group->cached,
(unsigned long long)block_group->key.objectid,
(unsigned long long)block_group->key.offset);
btrfs_dump_free_space(block_group, bytes);
} else if (info) {
printk(KERN_ERR "hmm, found offset=%llu bytes=%llu, "
"but wanted offset=%llu bytes=%llu\n",
(unsigned long long)info->offset,
(unsigned long long)info->bytes,
(unsigned long long)offset,
(unsigned long long)bytes);
}
WARN_ON(1);
}
out:
return ret;
}
void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
u64 bytes)
{
struct btrfs_free_space *info;
struct rb_node *n;
int count = 0;
for (n = rb_first(&block_group->free_space_offset); n; n = rb_next(n)) {
info = rb_entry(n, struct btrfs_free_space, offset_index);
if (info->bytes >= bytes)
count++;
printk(KERN_ERR "entry offset %llu, bytes %llu\n",
(unsigned long long)info->offset,
(unsigned long long)info->bytes);
}
printk(KERN_INFO "%d blocks of free space at or bigger than bytes is"
"\n", count);
}
u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group)
{
struct btrfs_free_space *info;
struct rb_node *n;
u64 ret = 0;
for (n = rb_first(&block_group->free_space_offset); n;
n = rb_next(n)) {
info = rb_entry(n, struct btrfs_free_space, offset_index);
ret += info->bytes;
}
return ret;
}
/*
* for a given cluster, put all of its extents back into the free
* space cache. If the block group passed doesn't match the block group
* pointed to by the cluster, someone else raced in and freed the
* cluster already. In that case, we just return without changing anything
*/
static int
__btrfs_return_cluster_to_free_space(
struct btrfs_block_group_cache *block_group,
struct btrfs_free_cluster *cluster)
{
struct btrfs_free_space *entry;
struct rb_node *node;
spin_lock(&cluster->lock);
if (cluster->block_group != block_group)
goto out;
cluster->window_start = 0;
node = rb_first(&cluster->root);
while(node) {
entry = rb_entry(node, struct btrfs_free_space, offset_index);
node = rb_next(&entry->offset_index);
rb_erase(&entry->offset_index, &cluster->root);
link_free_space(block_group, entry);
}
list_del_init(&cluster->block_group_list);
btrfs_put_block_group(cluster->block_group);
cluster->block_group = NULL;
cluster->root.rb_node = NULL;
out:
spin_unlock(&cluster->lock);
return 0;
}
void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
{
struct btrfs_free_space *info;
struct rb_node *node;
struct btrfs_free_cluster *cluster;
struct btrfs_free_cluster *safe;
spin_lock(&block_group->tree_lock);
list_for_each_entry_safe(cluster, safe, &block_group->cluster_list,
block_group_list) {
WARN_ON(cluster->block_group != block_group);
__btrfs_return_cluster_to_free_space(block_group, cluster);
}
while ((node = rb_last(&block_group->free_space_bytes)) != NULL) {
info = rb_entry(node, struct btrfs_free_space, bytes_index);
unlink_free_space(block_group, info);
kfree(info);
if (need_resched()) {
spin_unlock(&block_group->tree_lock);
cond_resched();
spin_lock(&block_group->tree_lock);
}
}
spin_unlock(&block_group->tree_lock);
}
u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
u64 offset, u64 bytes, u64 empty_size)
{
struct btrfs_free_space *entry = NULL;
u64 ret = 0;
spin_lock(&block_group->tree_lock);
entry = tree_search_offset(&block_group->free_space_offset, offset,
bytes + empty_size, 1);
if (!entry)
entry = tree_search_bytes(&block_group->free_space_bytes,
offset, bytes + empty_size);
if (entry) {
unlink_free_space(block_group, entry);
ret = entry->offset;
entry->offset += bytes;
entry->bytes -= bytes;
if (!entry->bytes)
kfree(entry);
else
link_free_space(block_group, entry);
}
spin_unlock(&block_group->tree_lock);
return ret;
}
/*
* given a cluster, put all of its extents back into the free space
* cache. If a block group is passed, this function will only free
* a cluster that belongs to the passed block group.
*
* Otherwise, it'll get a reference on the block group pointed to by the
* cluster and remove the cluster from it.
*/
int btrfs_return_cluster_to_free_space(
struct btrfs_block_group_cache *block_group,
struct btrfs_free_cluster *cluster)
{
int ret;
/* first, get a safe pointer to the block group */
spin_lock(&cluster->lock);
if (!block_group) {
block_group = cluster->block_group;
if (!block_group) {
spin_unlock(&cluster->lock);
return 0;
}
} else if (cluster->block_group != block_group) {
/* someone else has already freed it don't redo their work */
spin_unlock(&cluster->lock);
return 0;
}
atomic_inc(&block_group->count);
spin_unlock(&cluster->lock);
/* now return any extents the cluster had on it */
spin_lock(&block_group->tree_lock);
ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
spin_unlock(&block_group->tree_lock);
/* finally drop our ref */
btrfs_put_block_group(block_group);
return ret;
}
/*
* given a cluster, try to allocate 'bytes' from it, returns 0
* if it couldn't find anything suitably large, or a logical disk offset
* if things worked out
*/
u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
struct btrfs_free_cluster *cluster, u64 bytes,
u64 min_start)
{
struct btrfs_free_space *entry = NULL;
struct rb_node *node;
u64 ret = 0;
spin_lock(&cluster->lock);
if (bytes > cluster->max_size)
goto out;
if (cluster->block_group != block_group)
goto out;
node = rb_first(&cluster->root);
if (!node)
goto out;
entry = rb_entry(node, struct btrfs_free_space, offset_index);
while(1) {
if (entry->bytes < bytes || entry->offset < min_start) {
struct rb_node *node;
node = rb_next(&entry->offset_index);
if (!node)
break;
entry = rb_entry(node, struct btrfs_free_space,
offset_index);
continue;
}
ret = entry->offset;
entry->offset += bytes;
entry->bytes -= bytes;
if (entry->bytes == 0) {
rb_erase(&entry->offset_index, &cluster->root);
kfree(entry);
}
break;
}
out:
spin_unlock(&cluster->lock);
return ret;
}
/*
* here we try to find a cluster of blocks in a block group. The goal
* is to find at least bytes free and up to empty_size + bytes free.
* We might not find them all in one contiguous area.
*
* returns zero and sets up cluster if things worked out, otherwise
* it returns -enospc
*/
int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_block_group_cache *block_group,
struct btrfs_free_cluster *cluster,
u64 offset, u64 bytes, u64 empty_size)
{
struct btrfs_free_space *entry = NULL;
struct rb_node *node;
struct btrfs_free_space *next;
struct btrfs_free_space *last;
u64 min_bytes;
u64 window_start;
u64 window_free;
u64 max_extent = 0;
int total_retries = 0;
int ret;
/* for metadata, allow allocates with more holes */
if (btrfs_test_opt(root, SSD_SPREAD)) {
min_bytes = bytes + empty_size;
} else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
/*
* we want to do larger allocations when we are
* flushing out the delayed refs, it helps prevent
* making more work as we go along.
*/
if (trans->transaction->delayed_refs.flushing)
min_bytes = max(bytes, (bytes + empty_size) >> 1);
else
min_bytes = max(bytes, (bytes + empty_size) >> 4);
} else
min_bytes = max(bytes, (bytes + empty_size) >> 2);
spin_lock(&block_group->tree_lock);
spin_lock(&cluster->lock);
/* someone already found a cluster, hooray */
if (cluster->block_group) {
ret = 0;
goto out;
}
again:
min_bytes = min(min_bytes, bytes + empty_size);
entry = tree_search_bytes(&block_group->free_space_bytes,
offset, min_bytes);
if (!entry) {
ret = -ENOSPC;
goto out;
}
window_start = entry->offset;
window_free = entry->bytes;
last = entry;
max_extent = entry->bytes;
while(1) {
/* out window is just right, lets fill it */
if (window_free >= bytes + empty_size)
break;
node = rb_next(&last->offset_index);
if (!node) {
ret = -ENOSPC;
goto out;
}
next = rb_entry(node, struct btrfs_free_space, offset_index);
/*
* we haven't filled the empty size and the window is
* very large. reset and try again
*/
if (next->offset - (last->offset + last->bytes) > 128 * 1024 ||
next->offset - window_start > (bytes + empty_size) * 2) {
entry = next;
window_start = entry->offset;
window_free = entry->bytes;
last = entry;
max_extent = 0;
total_retries++;
if (total_retries % 64 == 0) {
if (min_bytes >= (bytes + empty_size)) {
ret = -ENOSPC;
goto out;
}
/*
* grow our allocation a bit, we're not having
* much luck
*/
min_bytes *= 2;
goto again;
}
} else {
last = next;
window_free += next->bytes;
if (entry->bytes > max_extent)
max_extent = entry->bytes;
}
}
cluster->window_start = entry->offset;
/*
* now we've found our entries, pull them out of the free space
* cache and put them into the cluster rbtree
*
* The cluster includes an rbtree, but only uses the offset index
* of each free space cache entry.
*/
while(1) {
node = rb_next(&entry->offset_index);
unlink_free_space(block_group, entry);
ret = tree_insert_offset(&cluster->root, entry->offset,
&entry->offset_index);
BUG_ON(ret);
if (!node || entry == last)
break;
entry = rb_entry(node, struct btrfs_free_space, offset_index);
}
ret = 0;
cluster->max_size = max_extent;
atomic_inc(&block_group->count);
list_add_tail(&cluster->block_group_list, &block_group->cluster_list);
cluster->block_group = block_group;
out:
spin_unlock(&cluster->lock);
spin_unlock(&block_group->tree_lock);
return ret;
}
/*
* simple code to zero out a cluster
*/
void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
{
spin_lock_init(&cluster->lock);
spin_lock_init(&cluster->refill_lock);
cluster->root.rb_node = NULL;
cluster->max_size = 0;
INIT_LIST_HEAD(&cluster->block_group_list);
cluster->block_group = NULL;
}