The free space in btrfs is cached in ram to more efficiently search for
free extents on disk. This implements the cache for use by extent-tree.c
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
new file mode 100644
index 0000000..d1e5f0e
--- /dev/null
+++ b/fs/btrfs/free-space-cache.c
@@ -0,0 +1,495 @@
+/*
+ * 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"
+
+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. If contains is set we will return
+ * the free space that contains the given offset. If contains is not set we
+ * will return the free space that starts at or after the given offset and is
+ * at least bytes long.
+ */
+static struct btrfs_free_space *tree_search_offset(struct rb_root *root,
+ u64 offset, u64 bytes,
+ int contains)
+{
+ 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 (!contains &&
+ (!ret || entry->offset < ret->offset) &&
+ (bytes <= entry->bytes))
+ ret = entry;
+ n = n->rb_left;
+ } else if (offset > entry->offset) {
+ if ((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;
+
+
+ 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;
+}
+
+static 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;
+ struct btrfs_free_space *alloc_info;
+ int ret = 0;
+
+ alloc_info = kzalloc(sizeof(struct btrfs_free_space), GFP_NOFS);
+ if (!alloc_info)
+ return -ENOMEM;
+
+ /*
+ * 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, 1);
+ left_info = tree_search_offset(&block_group->free_space_offset,
+ offset-1, 0, 1);
+
+ if (right_info && right_info->offset == offset+bytes) {
+ unlink_free_space(block_group, right_info);
+ info = right_info;
+ info->offset = offset;
+ info->bytes += bytes;
+ } else if (right_info && right_info->offset != offset+bytes) {
+ printk(KERN_ERR "btrfs adding space in the middle of an "
+ "existing free space area. existing: "
+ "offset=%llu, bytes=%llu. new: offset=%llu, "
+ "bytes=%llu\n", (unsigned long long)right_info->offset,
+ (unsigned long long)right_info->bytes,
+ (unsigned long long)offset,
+ (unsigned long long)bytes);
+ BUG();
+ }
+
+ if (left_info) {
+ unlink_free_space(block_group, left_info);
+
+ if (unlikely((left_info->offset + left_info->bytes) !=
+ offset)) {
+ printk(KERN_ERR "btrfs free space to the left "
+ "of new free space isn't "
+ "quite right. existing: offset=%llu, "
+ "bytes=%llu. new: offset=%llu, bytes=%llu\n",
+ (unsigned long long)left_info->offset,
+ (unsigned long long)left_info->bytes,
+ (unsigned long long)offset,
+ (unsigned long long)bytes);
+ BUG();
+ }
+
+ if (info) {
+ info->offset = left_info->offset;
+ info->bytes += left_info->bytes;
+ kfree(left_info);
+ } else {
+ info = left_info;
+ info->bytes += bytes;
+ }
+ }
+
+ if (info) {
+ ret = link_free_space(block_group, info);
+ if (!ret)
+ info = NULL;
+ goto out;
+ }
+
+ info = alloc_info;
+ alloc_info = NULL;
+ info->offset = offset;
+ info->bytes = bytes;
+
+ ret = link_free_space(block_group, info);
+ if (ret)
+ kfree(info);
+out:
+ if (ret) {
+ printk(KERN_ERR "btrfs: unable to add free space :%d\n", ret);
+ if (ret == -EEXIST)
+ BUG();
+ }
+
+ kfree(alloc_info);
+
+ return ret;
+}
+
+static int
+__btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
+ u64 offset, u64 bytes)
+{
+ struct btrfs_free_space *info;
+ int ret = 0;
+
+ 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;
+ goto out;
+ }
+ unlink_free_space(block_group, info);
+
+ if (info->bytes == bytes) {
+ kfree(info);
+ goto out;
+ }
+
+ info->offset += bytes;
+ info->bytes -= bytes;
+
+ ret = link_free_space(block_group, info);
+ 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);
+ }
+
+ /* 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 {
+ WARN_ON(1);
+ }
+out:
+ return ret;
+}
+
+int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
+ u64 offset, u64 bytes)
+{
+ int ret;
+ struct btrfs_free_space *sp;
+
+ mutex_lock(&block_group->alloc_mutex);
+ ret = __btrfs_add_free_space(block_group, offset, bytes);
+ sp = tree_search_offset(&block_group->free_space_offset, offset, 0, 1);
+ BUG_ON(!sp);
+ mutex_unlock(&block_group->alloc_mutex);
+
+ return ret;
+}
+
+int btrfs_add_free_space_lock(struct btrfs_block_group_cache *block_group,
+ u64 offset, u64 bytes)
+{
+ int ret;
+ struct btrfs_free_space *sp;
+
+ ret = __btrfs_add_free_space(block_group, offset, bytes);
+ sp = tree_search_offset(&block_group->free_space_offset, offset, 0, 1);
+ BUG_ON(!sp);
+
+ return ret;
+}
+
+int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
+ u64 offset, u64 bytes)
+{
+ int ret = 0;
+
+ mutex_lock(&block_group->alloc_mutex);
+ ret = __btrfs_remove_free_space(block_group, offset, bytes);
+ mutex_unlock(&block_group->alloc_mutex);
+
+ return ret;
+}
+
+int btrfs_remove_free_space_lock(struct btrfs_block_group_cache *block_group,
+ u64 offset, u64 bytes)
+{
+ int ret;
+
+ ret = __btrfs_remove_free_space(block_group, offset, bytes);
+
+ 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_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;
+}
+
+void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
+{
+ struct btrfs_free_space *info;
+ struct rb_node *node;
+
+ mutex_lock(&block_group->alloc_mutex);
+ 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()) {
+ mutex_unlock(&block_group->alloc_mutex);
+ cond_resched();
+ mutex_lock(&block_group->alloc_mutex);
+ }
+ }
+ mutex_unlock(&block_group->alloc_mutex);
+}
+
+#if 0
+static struct btrfs_free_space *btrfs_find_free_space_offset(struct
+ btrfs_block_group_cache
+ *block_group, u64 offset,
+ u64 bytes)
+{
+ struct btrfs_free_space *ret;
+
+ mutex_lock(&block_group->alloc_mutex);
+ ret = tree_search_offset(&block_group->free_space_offset, offset,
+ bytes, 0);
+ mutex_unlock(&block_group->alloc_mutex);
+
+ return ret;
+}
+
+static struct btrfs_free_space *btrfs_find_free_space_bytes(struct
+ btrfs_block_group_cache
+ *block_group, u64 offset,
+ u64 bytes)
+{
+ struct btrfs_free_space *ret;
+
+ mutex_lock(&block_group->alloc_mutex);
+
+ ret = tree_search_bytes(&block_group->free_space_bytes, offset, bytes);
+ mutex_unlock(&block_group->alloc_mutex);
+
+ return ret;
+}
+#endif
+
+struct btrfs_free_space *btrfs_find_free_space(struct btrfs_block_group_cache
+ *block_group, u64 offset,
+ u64 bytes)
+{
+ struct btrfs_free_space *ret = NULL;
+
+ ret = tree_search_offset(&block_group->free_space_offset, offset,
+ bytes, 0);
+ if (!ret)
+ ret = tree_search_bytes(&block_group->free_space_bytes,
+ offset, bytes);
+
+ return ret;
+}
--
1.6.0.2
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