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free-space-tree.c
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free-space-tree.c
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015 Facebook. All rights reserved.
*/
#include <linux/kernel.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "disk-io.h"
#include "locking.h"
#include "free-space-tree.h"
#include "transaction.h"
#include "block-group.h"
static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path);
void set_free_space_tree_thresholds(struct btrfs_block_group *cache)
{
u32 bitmap_range;
size_t bitmap_size;
u64 num_bitmaps, total_bitmap_size;
/*
* We convert to bitmaps when the disk space required for using extents
* exceeds that required for using bitmaps.
*/
bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
num_bitmaps = div_u64(cache->length + bitmap_range - 1, bitmap_range);
bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
total_bitmap_size = num_bitmaps * bitmap_size;
cache->bitmap_high_thresh = div_u64(total_bitmap_size,
sizeof(struct btrfs_item));
/*
* We allow for a small buffer between the high threshold and low
* threshold to avoid thrashing back and forth between the two formats.
*/
if (cache->bitmap_high_thresh > 100)
cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
else
cache->bitmap_low_thresh = 0;
}
static int add_new_free_space_info(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path)
{
struct btrfs_root *root = trans->fs_info->free_space_root;
struct btrfs_free_space_info *info;
struct btrfs_key key;
struct extent_buffer *leaf;
int ret;
key.objectid = block_group->start;
key.type = BTRFS_FREE_SPACE_INFO_KEY;
key.offset = block_group->length;
ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
if (ret)
goto out;
leaf = path->nodes[0];
info = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_free_space_info);
btrfs_set_free_space_extent_count(leaf, info, 0);
btrfs_set_free_space_flags(leaf, info, 0);
btrfs_mark_buffer_dirty(leaf);
ret = 0;
out:
btrfs_release_path(path);
return ret;
}
EXPORT_FOR_TESTS
struct btrfs_free_space_info *search_free_space_info(
struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path, int cow)
{
struct btrfs_fs_info *fs_info = block_group->fs_info;
struct btrfs_root *root = fs_info->free_space_root;
struct btrfs_key key;
int ret;
key.objectid = block_group->start;
key.type = BTRFS_FREE_SPACE_INFO_KEY;
key.offset = block_group->length;
ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
if (ret < 0)
return ERR_PTR(ret);
if (ret != 0) {
btrfs_warn(fs_info, "missing free space info for %llu",
block_group->start);
ASSERT(0);
return ERR_PTR(-ENOENT);
}
return btrfs_item_ptr(path->nodes[0], path->slots[0],
struct btrfs_free_space_info);
}
/*
* btrfs_search_slot() but we're looking for the greatest key less than the
* passed key.
*/
static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_key *key, struct btrfs_path *p,
int ins_len, int cow)
{
int ret;
ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
if (ret < 0)
return ret;
if (ret == 0) {
ASSERT(0);
return -EIO;
}
if (p->slots[0] == 0) {
ASSERT(0);
return -EIO;
}
p->slots[0]--;
return 0;
}
static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
{
return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
}
static unsigned long *alloc_bitmap(u32 bitmap_size)
{
unsigned long *ret;
unsigned int nofs_flag;
u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
/*
* GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
* into the filesystem as the free space bitmap can be modified in the
* critical section of a transaction commit.
*
* TODO: push the memalloc_nofs_{save,restore}() to the caller where we
* know that recursion is unsafe.
*/
nofs_flag = memalloc_nofs_save();
ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
memalloc_nofs_restore(nofs_flag);
return ret;
}
static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
{
u8 *p = ((u8 *)map) + BIT_BYTE(start);
const unsigned int size = start + len;
int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
while (len - bits_to_set >= 0) {
*p |= mask_to_set;
len -= bits_to_set;
bits_to_set = BITS_PER_BYTE;
mask_to_set = ~0;
p++;
}
if (len) {
mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
*p |= mask_to_set;
}
}
EXPORT_FOR_TESTS
int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path)
{
struct btrfs_fs_info *fs_info = trans->fs_info;
struct btrfs_root *root = fs_info->free_space_root;
struct btrfs_free_space_info *info;
struct btrfs_key key, found_key;
struct extent_buffer *leaf;
unsigned long *bitmap;
char *bitmap_cursor;
u64 start, end;
u64 bitmap_range, i;
u32 bitmap_size, flags, expected_extent_count;
u32 extent_count = 0;
int done = 0, nr;
int ret;
bitmap_size = free_space_bitmap_size(block_group->length,
fs_info->sectorsize);
bitmap = alloc_bitmap(bitmap_size);
if (!bitmap) {
ret = -ENOMEM;
goto out;
}
start = block_group->start;
end = block_group->start + block_group->length;
key.objectid = end - 1;
key.type = (u8)-1;
key.offset = (u64)-1;
while (!done) {
ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
if (ret)
goto out;
leaf = path->nodes[0];
nr = 0;
path->slots[0]++;
while (path->slots[0] > 0) {
btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
ASSERT(found_key.objectid == block_group->start);
ASSERT(found_key.offset == block_group->length);
done = 1;
break;
} else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
u64 first, last;
ASSERT(found_key.objectid >= start);
ASSERT(found_key.objectid < end);
ASSERT(found_key.objectid + found_key.offset <= end);
first = div_u64(found_key.objectid - start,
fs_info->sectorsize);
last = div_u64(found_key.objectid + found_key.offset - start,
fs_info->sectorsize);
le_bitmap_set(bitmap, first, last - first);
extent_count++;
nr++;
path->slots[0]--;
} else {
ASSERT(0);
}
}
ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
if (ret)
goto out;
btrfs_release_path(path);
}
info = search_free_space_info(trans, block_group, path, 1);
if (IS_ERR(info)) {
ret = PTR_ERR(info);
goto out;
}
leaf = path->nodes[0];
flags = btrfs_free_space_flags(leaf, info);
flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
btrfs_set_free_space_flags(leaf, info, flags);
expected_extent_count = btrfs_free_space_extent_count(leaf, info);
btrfs_mark_buffer_dirty(leaf);
btrfs_release_path(path);
if (extent_count != expected_extent_count) {
btrfs_err(fs_info,
"incorrect extent count for %llu; counted %u, expected %u",
block_group->start, extent_count,
expected_extent_count);
ASSERT(0);
ret = -EIO;
goto out;
}
bitmap_cursor = (char *)bitmap;
bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
i = start;
while (i < end) {
unsigned long ptr;
u64 extent_size;
u32 data_size;
extent_size = min(end - i, bitmap_range);
data_size = free_space_bitmap_size(extent_size,
fs_info->sectorsize);
key.objectid = i;
key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
key.offset = extent_size;
ret = btrfs_insert_empty_item(trans, root, path, &key,
data_size);
if (ret)
goto out;
leaf = path->nodes[0];
ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
write_extent_buffer(leaf, bitmap_cursor, ptr,
data_size);
btrfs_mark_buffer_dirty(leaf);
btrfs_release_path(path);
i += extent_size;
bitmap_cursor += data_size;
}
ret = 0;
out:
kvfree(bitmap);
if (ret)
btrfs_abort_transaction(trans, ret);
return ret;
}
EXPORT_FOR_TESTS
int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path)
{
struct btrfs_fs_info *fs_info = trans->fs_info;
struct btrfs_root *root = fs_info->free_space_root;
struct btrfs_free_space_info *info;
struct btrfs_key key, found_key;
struct extent_buffer *leaf;
unsigned long *bitmap;
u64 start, end;
u32 bitmap_size, flags, expected_extent_count;
unsigned long nrbits, start_bit, end_bit;
u32 extent_count = 0;
int done = 0, nr;
int ret;
bitmap_size = free_space_bitmap_size(block_group->length,
fs_info->sectorsize);
bitmap = alloc_bitmap(bitmap_size);
if (!bitmap) {
ret = -ENOMEM;
goto out;
}
start = block_group->start;
end = block_group->start + block_group->length;
key.objectid = end - 1;
key.type = (u8)-1;
key.offset = (u64)-1;
while (!done) {
ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
if (ret)
goto out;
leaf = path->nodes[0];
nr = 0;
path->slots[0]++;
while (path->slots[0] > 0) {
btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
ASSERT(found_key.objectid == block_group->start);
ASSERT(found_key.offset == block_group->length);
done = 1;
break;
} else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
unsigned long ptr;
char *bitmap_cursor;
u32 bitmap_pos, data_size;
ASSERT(found_key.objectid >= start);
ASSERT(found_key.objectid < end);
ASSERT(found_key.objectid + found_key.offset <= end);
bitmap_pos = div_u64(found_key.objectid - start,
fs_info->sectorsize *
BITS_PER_BYTE);
bitmap_cursor = ((char *)bitmap) + bitmap_pos;
data_size = free_space_bitmap_size(found_key.offset,
fs_info->sectorsize);
ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
read_extent_buffer(leaf, bitmap_cursor, ptr,
data_size);
nr++;
path->slots[0]--;
} else {
ASSERT(0);
}
}
ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
if (ret)
goto out;
btrfs_release_path(path);
}
info = search_free_space_info(trans, block_group, path, 1);
if (IS_ERR(info)) {
ret = PTR_ERR(info);
goto out;
}
leaf = path->nodes[0];
flags = btrfs_free_space_flags(leaf, info);
flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
btrfs_set_free_space_flags(leaf, info, flags);
expected_extent_count = btrfs_free_space_extent_count(leaf, info);
btrfs_mark_buffer_dirty(leaf);
btrfs_release_path(path);
nrbits = div_u64(block_group->length, block_group->fs_info->sectorsize);
start_bit = find_next_bit_le(bitmap, nrbits, 0);
while (start_bit < nrbits) {
end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
ASSERT(start_bit < end_bit);
key.objectid = start + start_bit * block_group->fs_info->sectorsize;
key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
if (ret)
goto out;
btrfs_release_path(path);
extent_count++;
start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
}
if (extent_count != expected_extent_count) {
btrfs_err(fs_info,
"incorrect extent count for %llu; counted %u, expected %u",
block_group->start, extent_count,
expected_extent_count);
ASSERT(0);
ret = -EIO;
goto out;
}
ret = 0;
out:
kvfree(bitmap);
if (ret)
btrfs_abort_transaction(trans, ret);
return ret;
}
static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path,
int new_extents)
{
struct btrfs_free_space_info *info;
u32 flags;
u32 extent_count;
int ret = 0;
if (new_extents == 0)
return 0;
info = search_free_space_info(trans, block_group, path, 1);
if (IS_ERR(info)) {
ret = PTR_ERR(info);
goto out;
}
flags = btrfs_free_space_flags(path->nodes[0], info);
extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
extent_count += new_extents;
btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
btrfs_mark_buffer_dirty(path->nodes[0]);
btrfs_release_path(path);
if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
extent_count > block_group->bitmap_high_thresh) {
ret = convert_free_space_to_bitmaps(trans, block_group, path);
} else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
extent_count < block_group->bitmap_low_thresh) {
ret = convert_free_space_to_extents(trans, block_group, path);
}
out:
return ret;
}
EXPORT_FOR_TESTS
int free_space_test_bit(struct btrfs_block_group *block_group,
struct btrfs_path *path, u64 offset)
{
struct extent_buffer *leaf;
struct btrfs_key key;
u64 found_start, found_end;
unsigned long ptr, i;
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
found_start = key.objectid;
found_end = key.objectid + key.offset;
ASSERT(offset >= found_start && offset < found_end);
ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
i = div_u64(offset - found_start,
block_group->fs_info->sectorsize);
return !!extent_buffer_test_bit(leaf, ptr, i);
}
static void free_space_set_bits(struct btrfs_block_group *block_group,
struct btrfs_path *path, u64 *start, u64 *size,
int bit)
{
struct btrfs_fs_info *fs_info = block_group->fs_info;
struct extent_buffer *leaf;
struct btrfs_key key;
u64 end = *start + *size;
u64 found_start, found_end;
unsigned long ptr, first, last;
leaf = path->nodes[0];
btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
found_start = key.objectid;
found_end = key.objectid + key.offset;
ASSERT(*start >= found_start && *start < found_end);
ASSERT(end > found_start);
if (end > found_end)
end = found_end;
ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
first = div_u64(*start - found_start, fs_info->sectorsize);
last = div_u64(end - found_start, fs_info->sectorsize);
if (bit)
extent_buffer_bitmap_set(leaf, ptr, first, last - first);
else
extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
btrfs_mark_buffer_dirty(leaf);
*size -= end - *start;
*start = end;
}
/*
* We can't use btrfs_next_item() in modify_free_space_bitmap() because
* btrfs_next_leaf() doesn't get the path for writing. We can forgo the fancy
* tree walking in btrfs_next_leaf() anyways because we know exactly what we're
* looking for.
*/
static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct btrfs_path *p)
{
struct btrfs_key key;
if (p->slots[0] + 1 < btrfs_header_nritems(p->nodes[0])) {
p->slots[0]++;
return 0;
}
btrfs_item_key_to_cpu(p->nodes[0], &key, p->slots[0]);
btrfs_release_path(p);
key.objectid += key.offset;
key.type = (u8)-1;
key.offset = (u64)-1;
return btrfs_search_prev_slot(trans, root, &key, p, 0, 1);
}
/*
* If remove is 1, then we are removing free space, thus clearing bits in the
* bitmap. If remove is 0, then we are adding free space, thus setting bits in
* the bitmap.
*/
static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path,
u64 start, u64 size, int remove)
{
struct btrfs_root *root = block_group->fs_info->free_space_root;
struct btrfs_key key;
u64 end = start + size;
u64 cur_start, cur_size;
int prev_bit, next_bit;
int new_extents;
int ret;
/*
* Read the bit for the block immediately before the extent of space if
* that block is within the block group.
*/
if (start > block_group->start) {
u64 prev_block = start - block_group->fs_info->sectorsize;
key.objectid = prev_block;
key.type = (u8)-1;
key.offset = (u64)-1;
ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
if (ret)
goto out;
prev_bit = free_space_test_bit(block_group, path, prev_block);
/* The previous block may have been in the previous bitmap. */
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (start >= key.objectid + key.offset) {
ret = free_space_next_bitmap(trans, root, path);
if (ret)
goto out;
}
} else {
key.objectid = start;
key.type = (u8)-1;
key.offset = (u64)-1;
ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
if (ret)
goto out;
prev_bit = -1;
}
/*
* Iterate over all of the bitmaps overlapped by the extent of space,
* clearing/setting bits as required.
*/
cur_start = start;
cur_size = size;
while (1) {
free_space_set_bits(block_group, path, &cur_start, &cur_size,
!remove);
if (cur_size == 0)
break;
ret = free_space_next_bitmap(trans, root, path);
if (ret)
goto out;
}
/*
* Read the bit for the block immediately after the extent of space if
* that block is within the block group.
*/
if (end < block_group->start + block_group->length) {
/* The next block may be in the next bitmap. */
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (end >= key.objectid + key.offset) {
ret = free_space_next_bitmap(trans, root, path);
if (ret)
goto out;
}
next_bit = free_space_test_bit(block_group, path, end);
} else {
next_bit = -1;
}
if (remove) {
new_extents = -1;
if (prev_bit == 1) {
/* Leftover on the left. */
new_extents++;
}
if (next_bit == 1) {
/* Leftover on the right. */
new_extents++;
}
} else {
new_extents = 1;
if (prev_bit == 1) {
/* Merging with neighbor on the left. */
new_extents--;
}
if (next_bit == 1) {
/* Merging with neighbor on the right. */
new_extents--;
}
}
btrfs_release_path(path);
ret = update_free_space_extent_count(trans, block_group, path,
new_extents);
out:
return ret;
}
static int remove_free_space_extent(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path,
u64 start, u64 size)
{
struct btrfs_root *root = trans->fs_info->free_space_root;
struct btrfs_key key;
u64 found_start, found_end;
u64 end = start + size;
int new_extents = -1;
int ret;
key.objectid = start;
key.type = (u8)-1;
key.offset = (u64)-1;
ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
if (ret)
goto out;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
found_start = key.objectid;
found_end = key.objectid + key.offset;
ASSERT(start >= found_start && end <= found_end);
/*
* Okay, now that we've found the free space extent which contains the
* free space that we are removing, there are four cases:
*
* 1. We're using the whole extent: delete the key we found and
* decrement the free space extent count.
* 2. We are using part of the extent starting at the beginning: delete
* the key we found and insert a new key representing the leftover at
* the end. There is no net change in the number of extents.
* 3. We are using part of the extent ending at the end: delete the key
* we found and insert a new key representing the leftover at the
* beginning. There is no net change in the number of extents.
* 4. We are using part of the extent in the middle: delete the key we
* found and insert two new keys representing the leftovers on each
* side. Where we used to have one extent, we now have two, so increment
* the extent count. We may need to convert the block group to bitmaps
* as a result.
*/
/* Delete the existing key (cases 1-4). */
ret = btrfs_del_item(trans, root, path);
if (ret)
goto out;
/* Add a key for leftovers at the beginning (cases 3 and 4). */
if (start > found_start) {
key.objectid = found_start;
key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
key.offset = start - found_start;
btrfs_release_path(path);
ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
if (ret)
goto out;
new_extents++;
}
/* Add a key for leftovers at the end (cases 2 and 4). */
if (end < found_end) {
key.objectid = end;
key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
key.offset = found_end - end;
btrfs_release_path(path);
ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
if (ret)
goto out;
new_extents++;
}
btrfs_release_path(path);
ret = update_free_space_extent_count(trans, block_group, path,
new_extents);
out:
return ret;
}
EXPORT_FOR_TESTS
int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path, u64 start, u64 size)
{
struct btrfs_free_space_info *info;
u32 flags;
int ret;
if (block_group->needs_free_space) {
ret = __add_block_group_free_space(trans, block_group, path);
if (ret)
return ret;
}
info = search_free_space_info(NULL, block_group, path, 0);
if (IS_ERR(info))
return PTR_ERR(info);
flags = btrfs_free_space_flags(path->nodes[0], info);
btrfs_release_path(path);
if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
return modify_free_space_bitmap(trans, block_group, path,
start, size, 1);
} else {
return remove_free_space_extent(trans, block_group, path,
start, size);
}
}
int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
u64 start, u64 size)
{
struct btrfs_block_group *block_group;
struct btrfs_path *path;
int ret;
if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
return 0;
path = btrfs_alloc_path();
if (!path) {
ret = -ENOMEM;
goto out;
}
block_group = btrfs_lookup_block_group(trans->fs_info, start);
if (!block_group) {
ASSERT(0);
ret = -ENOENT;
goto out;
}
mutex_lock(&block_group->free_space_lock);
ret = __remove_from_free_space_tree(trans, block_group, path, start,
size);
mutex_unlock(&block_group->free_space_lock);
btrfs_put_block_group(block_group);
out:
btrfs_free_path(path);
if (ret)
btrfs_abort_transaction(trans, ret);
return ret;
}
static int add_free_space_extent(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path,
u64 start, u64 size)
{
struct btrfs_root *root = trans->fs_info->free_space_root;
struct btrfs_key key, new_key;
u64 found_start, found_end;
u64 end = start + size;
int new_extents = 1;
int ret;
/*
* We are adding a new extent of free space, but we need to merge
* extents. There are four cases here:
*
* 1. The new extent does not have any immediate neighbors to merge
* with: add the new key and increment the free space extent count. We
* may need to convert the block group to bitmaps as a result.
* 2. The new extent has an immediate neighbor before it: remove the
* previous key and insert a new key combining both of them. There is no
* net change in the number of extents.
* 3. The new extent has an immediate neighbor after it: remove the next
* key and insert a new key combining both of them. There is no net
* change in the number of extents.
* 4. The new extent has immediate neighbors on both sides: remove both
* of the keys and insert a new key combining all of them. Where we used
* to have two extents, we now have one, so decrement the extent count.
*/
new_key.objectid = start;
new_key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
new_key.offset = size;
/* Search for a neighbor on the left. */
if (start == block_group->start)
goto right;
key.objectid = start - 1;
key.type = (u8)-1;
key.offset = (u64)-1;
ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
if (ret)
goto out;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
btrfs_release_path(path);
goto right;
}
found_start = key.objectid;
found_end = key.objectid + key.offset;
ASSERT(found_start >= block_group->start &&
found_end > block_group->start);
ASSERT(found_start < start && found_end <= start);
/*
* Delete the neighbor on the left and absorb it into the new key (cases
* 2 and 4).
*/
if (found_end == start) {
ret = btrfs_del_item(trans, root, path);
if (ret)
goto out;
new_key.objectid = found_start;
new_key.offset += key.offset;
new_extents--;
}
btrfs_release_path(path);
right:
/* Search for a neighbor on the right. */
if (end == block_group->start + block_group->length)
goto insert;
key.objectid = end;
key.type = (u8)-1;
key.offset = (u64)-1;
ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
if (ret)
goto out;
btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
btrfs_release_path(path);
goto insert;
}
found_start = key.objectid;
found_end = key.objectid + key.offset;
ASSERT(found_start >= block_group->start &&
found_end > block_group->start);
ASSERT((found_start < start && found_end <= start) ||
(found_start >= end && found_end > end));
/*
* Delete the neighbor on the right and absorb it into the new key
* (cases 3 and 4).
*/
if (found_start == end) {
ret = btrfs_del_item(trans, root, path);
if (ret)
goto out;
new_key.offset += key.offset;
new_extents--;
}
btrfs_release_path(path);
insert:
/* Insert the new key (cases 1-4). */
ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
if (ret)
goto out;
btrfs_release_path(path);
ret = update_free_space_extent_count(trans, block_group, path,
new_extents);
out:
return ret;
}
EXPORT_FOR_TESTS
int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
struct btrfs_block_group *block_group,
struct btrfs_path *path, u64 start, u64 size)
{
struct btrfs_free_space_info *info;
u32 flags;
int ret;
if (block_group->needs_free_space) {
ret = __add_block_group_free_space(trans, block_group, path);
if (ret)
return ret;
}
info = search_free_space_info(NULL, block_group, path, 0);
if (IS_ERR(info))
return PTR_ERR(info);
flags = btrfs_free_space_flags(path->nodes[0], info);
btrfs_release_path(path);
if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
return modify_free_space_bitmap(trans, block_group, path,
start, size, 0);
} else {
return add_free_space_extent(trans, block_group, path, start,
size);