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Code Issues Releases Wiki Activity

Btrfs: groundwork for subvolume and snapshot roots 

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2007-04-09 10:42:37 -04:00 committed by David Woodhouse
parent d6e4a428eb
commit 0f7d52f443
6 changed files with 281 additions and 98 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/btrfs/bit-radix.c
View File

@ -86,7 +86,7 @@ int find_first_radix_bit(struct radix_tree_root *radix, unsigned long *retbits,
int i;
int total_found = 0;
ret = radix_tree_gang_lookup(radix, (void *)&gang, 0, ARRAY_SIZE(gang));
ret = radix_tree_gang_lookup(radix, (void **)gang, 0, ARRAY_SIZE(gang));
for (i = 0; i < ret && nr > 0; i++) {
found = 0;
bits = gang[i];

20
fs/btrfs/ctree.h
View File

@ -232,12 +232,12 @@ struct btrfs_inode_map_item {
struct crypto_hash;
struct btrfs_fs_info {
struct btrfs_root *fs_root;
struct btrfs_root *extent_root;
struct btrfs_root *tree_root;
struct btrfs_root *inode_root;
struct btrfs_key current_insert;
struct btrfs_key last_insert;
struct radix_tree_root fs_roots_radix;
struct radix_tree_root pending_del_radix;
struct radix_tree_root pinned_radix;
u64 last_inode_alloc;
@ -266,6 +266,9 @@ struct btrfs_root {
struct btrfs_root_item root_item;
struct btrfs_key root_key;
struct btrfs_fs_info *fs_info;
struct inode *inode;
u64 objectid;
u64 last_trans;
u32 blocksize;
int ref_cows;
u32 type;
@ -595,7 +598,7 @@ static inline u32 btrfs_key_overflow(struct btrfs_key *key)
static inline void btrfs_set_key_overflow(struct btrfs_key *key, u32 over)
{
BUG_ON(over > BTRFS_KEY_OVERFLOW_MAX);
BUG_ON(over >= BTRFS_KEY_OVERFLOW_MAX);
over = over << BTRFS_KEY_OVERFLOW_SHIFT;
key->flags = (key->flags & ~((u64)BTRFS_KEY_OVERFLOW_MASK)) | over;
}
@ -634,7 +637,7 @@ static inline void btrfs_set_disK_key_overflow(struct btrfs_disk_key *key,
u32 over)
{
u32 flags = btrfs_disk_key_flags(key);
BUG_ON(over > BTRFS_KEY_OVERFLOW_MAX);
BUG_ON(over >= BTRFS_KEY_OVERFLOW_MAX);
over = over << BTRFS_KEY_OVERFLOW_SHIFT;
flags = (flags & ~((u64)BTRFS_KEY_OVERFLOW_MASK)) | over;
btrfs_set_disk_key_flags(key, flags);
@ -748,6 +751,17 @@ static inline void btrfs_set_super_blocknr(struct btrfs_super_block *s, u64 val)
s->blocknr = cpu_to_le64(val);
}
static inline u64 btrfs_super_generation(struct btrfs_super_block *s)
{
return le64_to_cpu(s->generation);
}
static inline void btrfs_set_super_generation(struct btrfs_super_block *s,
u64 val)
{
s->generation = cpu_to_le64(val);
}
static inline u64 btrfs_super_root(struct btrfs_super_block *s)
{
return le64_to_cpu(s->root);

176
fs/btrfs/disk-io.c
View File

@ -4,9 +4,11 @@
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/swap.h>
#include <linux/radix-tree.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
static int check_tree_block(struct btrfs_root *root, struct buffer_head *buf)
{
@ -180,7 +182,7 @@ static int csum_tree_block(struct btrfs_root *root, struct buffer_head *bh,
static int btree_writepage(struct page *page, struct writeback_control *wbc)
{
struct buffer_head *bh;
struct btrfs_root *root = btrfs_sb(page->mapping->host->i_sb);
struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
struct buffer_head *head;
if (!page_has_buffers(page)) {
create_empty_buffers(page, root->fs_info->sb->s_blocksize,
@ -259,10 +261,13 @@ static int __setup_root(int blocksize,
u64 objectid)
{
root->node = NULL;
root->inode = NULL;
root->commit_root = NULL;
root->blocksize = blocksize;
root->ref_cows = 0;
root->fs_info = fs_info;
root->objectid = objectid;
root->last_trans = 0;
memset(&root->root_key, 0, sizeof(root->root_key));
memset(&root->root_item, 0, sizeof(root->root_item));
return 0;
@ -287,10 +292,78 @@ static int find_and_setup_root(int blocksize,
return 0;
}
struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
struct btrfs_key *location)
{
struct btrfs_root *root;
struct btrfs_root *tree_root = fs_info->tree_root;
struct btrfs_path *path;
struct btrfs_leaf *l;
int ret = 0;
printk("read_fs_root looking for %Lu %Lu %u\n", location->objectid, location->offset, location->flags);
root = kmalloc(sizeof(*root), GFP_NOFS);
if (!root) {
printk("failed1\n");
return ERR_PTR(-ENOMEM);
}
if (location->offset == (u64)-1) {
ret = find_and_setup_root(fs_info->sb->s_blocksize,
fs_info->tree_root, fs_info,
location->objectid, root);
if (ret) {
printk("failed2\n");
kfree(root);
return ERR_PTR(ret);
}
goto insert;
}
__setup_root(fs_info->sb->s_blocksize, root, fs_info,
location->objectid);
path = btrfs_alloc_path();
BUG_ON(!path);
ret = btrfs_search_slot(NULL, tree_root, location, path, 0, 0);
if (ret != 0) {
printk("internal search_slot gives us %d\n", ret);
if (ret > 0)
ret = -ENOENT;
goto out;
}
l = btrfs_buffer_leaf(path->nodes[0]);
memcpy(&root->root_item,
btrfs_item_ptr(l, path->slots[0], struct btrfs_root_item),
sizeof(root->root_item));
memcpy(&root->root_key, location, sizeof(*location));
ret = 0;
out:
btrfs_release_path(root, path);
btrfs_free_path(path);
if (ret) {
kfree(root);
return ERR_PTR(ret);
}
root->node = read_tree_block(root,
btrfs_root_blocknr(&root->root_item));
BUG_ON(!root->node);
insert:
printk("inserting %p\n", root);
root->ref_cows = 1;
ret = radix_tree_insert(&fs_info->fs_roots_radix, (unsigned long)root,
root);
if (ret) {
printk("radix_tree_insert gives us %d\n", ret);
brelse(root->node);
kfree(root);
return ERR_PTR(ret);
}
printk("all worked\n");
return root;
}
struct btrfs_root *open_ctree(struct super_block *sb)
{
struct btrfs_root *root = kmalloc(sizeof(struct btrfs_root),
GFP_NOFS);
struct btrfs_root *extent_root = kmalloc(sizeof(struct btrfs_root),
GFP_NOFS);
struct btrfs_root *tree_root = kmalloc(sizeof(struct btrfs_root),
@ -304,9 +377,9 @@ struct btrfs_root *open_ctree(struct super_block *sb)
init_bit_radix(&fs_info->pinned_radix);
init_bit_radix(&fs_info->pending_del_radix);
INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_NOFS);
sb_set_blocksize(sb, 4096);
fs_info->running_transaction = NULL;
fs_info->fs_root = root;
fs_info->tree_root = tree_root;
fs_info->extent_root = extent_root;
fs_info->inode_root = inode_root;
@ -318,6 +391,9 @@ struct btrfs_root *open_ctree(struct super_block *sb)
fs_info->btree_inode->i_nlink = 1;
fs_info->btree_inode->i_size = sb->s_bdev->bd_inode->i_size;
fs_info->btree_inode->i_mapping->a_ops = &btree_aops;
BTRFS_I(fs_info->btree_inode)->root = tree_root;
memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
sizeof(struct btrfs_key));
insert_inode_hash(fs_info->btree_inode);
mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
fs_info->hash_tfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
@ -337,13 +413,12 @@ struct btrfs_root *open_ctree(struct super_block *sb)
BTRFS_SUPER_INFO_OFFSET /
sb->s_blocksize);
if (!fs_info->sb_buffer) {
if (!fs_info->sb_buffer)
return NULL;
}
disk_super = (struct btrfs_super_block *)fs_info->sb_buffer->b_data;
if (!btrfs_super_root(disk_super)) {
if (!btrfs_super_root(disk_super))
return NULL;
}
fs_info->disk_super = disk_super;
tree_root->node = read_tree_block(tree_root,
btrfs_super_root(disk_super));
@ -358,14 +433,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
BTRFS_INODE_MAP_OBJECTID, inode_root);
BUG_ON(ret);
ret = find_and_setup_root(sb->s_blocksize, tree_root, fs_info,
BTRFS_FS_TREE_OBJECTID, root);
BUG_ON(ret);
root->commit_root = root->node;
get_bh(root->node);
root->ref_cows = 1;
root->fs_info->generation = root->root_key.offset + 1;
ret = btrfs_find_highest_inode(root, &root->fs_info->last_inode_alloc);
fs_info->generation = btrfs_super_generation(disk_super) + 1;
ret = btrfs_find_highest_inode(tree_root, &fs_info->last_inode_alloc);
if (ret == 0)
fs_info->highest_inode = fs_info->last_inode_alloc;
memset(&fs_info->kobj, 0, sizeof(fs_info->kobj));
@ -373,7 +442,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
kobject_set_name(&fs_info->kobj, "%s", sb->s_id);
kobject_register(&fs_info->kobj);
mutex_unlock(&fs_info->fs_mutex);
return root;
return tree_root;
}
int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root
@ -398,12 +467,42 @@ int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root
return 0;
}
int del_fs_roots(struct btrfs_fs_info *fs_info)
{
int ret;
struct btrfs_root *gang[8];
int i;
while(1) {
ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
(void **)gang, 0,
ARRAY_SIZE(gang));
if (!ret)
break;
for (i = 0; i < ret; i++) {
radix_tree_delete(&fs_info->fs_roots_radix,
(unsigned long)gang[i]);
if (gang[i]->inode)
iput(gang[i]->inode);
else
printk("no inode for root %p\n", gang[i]);
if (gang[i]->node)
brelse(gang[i]->node);
if (gang[i]->commit_root)
brelse(gang[i]->commit_root);
kfree(gang[i]);
}
}
return 0;
}
int close_ctree(struct btrfs_root *root)
{
int ret;
struct btrfs_trans_handle *trans;
struct btrfs_fs_info *fs_info = root->fs_info;
mutex_lock(&root->fs_info->fs_mutex);
mutex_lock(&fs_info->fs_mutex);
trans = btrfs_start_transaction(root, 1);
btrfs_commit_transaction(trans, root);
/* run commit again to drop the original snapshot */
@ -412,29 +511,26 @@ int close_ctree(struct btrfs_root *root)
ret = btrfs_write_and_wait_transaction(NULL, root);
BUG_ON(ret);
write_ctree_super(NULL, root);
mutex_unlock(&root->fs_info->fs_mutex);
mutex_unlock(&fs_info->fs_mutex);
if (root->node)
btrfs_block_release(root, root->node);
if (root->fs_info->extent_root->node)
btrfs_block_release(root->fs_info->extent_root,
root->fs_info->extent_root->node);
if (root->fs_info->inode_root->node)
btrfs_block_release(root->fs_info->inode_root,
root->fs_info->inode_root->node);
if (root->fs_info->tree_root->node)
btrfs_block_release(root->fs_info->tree_root,
root->fs_info->tree_root->node);
btrfs_block_release(root, root->commit_root);
btrfs_block_release(root, root->fs_info->sb_buffer);
crypto_free_hash(root->fs_info->hash_tfm);
truncate_inode_pages(root->fs_info->btree_inode->i_mapping, 0);
iput(root->fs_info->btree_inode);
kfree(root->fs_info->extent_root);
kfree(root->fs_info->inode_root);
kfree(root->fs_info->tree_root);
kobject_unregister(&root->fs_info->kobj);
kfree(root);
if (fs_info->extent_root->node)
btrfs_block_release(fs_info->extent_root,
fs_info->extent_root->node);
if (fs_info->inode_root->node)
btrfs_block_release(fs_info->inode_root,
fs_info->inode_root->node);
if (fs_info->tree_root->node)
btrfs_block_release(fs_info->tree_root,
fs_info->tree_root->node);
btrfs_block_release(root, fs_info->sb_buffer);
crypto_free_hash(fs_info->hash_tfm);
truncate_inode_pages(fs_info->btree_inode->i_mapping, 0);
iput(fs_info->btree_inode);
del_fs_roots(fs_info);
kfree(fs_info->extent_root);
kfree(fs_info->inode_root);
kfree(fs_info->tree_root);
kobject_unregister(&fs_info->kobj);
return 0;
}

2
fs/btrfs/disk-io.h
View File

@ -39,4 +39,6 @@ int write_ctree_super(struct btrfs_trans_handle *trans,
struct buffer_head *btrfs_find_tree_block(struct btrfs_root *root, u64 blocknr);
int btrfs_csum_data(struct btrfs_root * root, char *data, size_t len,
char *result);
struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
struct btrfs_key *location);
#endif

39
fs/btrfs/super.c
View File

@ -436,7 +436,6 @@ int fixup_tree_root_location(struct btrfs_root *root,
{
struct btrfs_path *path;
struct btrfs_root_item *ri;
int ret;
if (btrfs_key_type(location) != BTRFS_ROOT_ITEM_KEY)
return 0;
@ -447,22 +446,19 @@ int fixup_tree_root_location(struct btrfs_root *root,
BUG_ON(!path);
mutex_lock(&root->fs_info->fs_mutex);
ret = btrfs_lookup_inode(NULL, root, path, location, 0);
if (ret)
goto out;
ri = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]),
path->slots[0],
struct btrfs_root_item);
*sub_root = btrfs_read_fs_root(root->fs_info, location);
if (IS_ERR(*sub_root))
return PTR_ERR(*sub_root);
ri = &(*sub_root)->root_item;
location->objectid = btrfs_root_dirid(ri);
location->flags = 0;
btrfs_set_key_type(location, BTRFS_INODE_ITEM_KEY);
location->offset = 0;
/* FIXME properly select the root */
*sub_root = root->fs_info->fs_root;
out:
btrfs_free_path(path);
mutex_unlock(&root->fs_info->fs_mutex);
return ret;
return 0;
}
@ -494,6 +490,15 @@ static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
if (!inode)
return ERR_PTR(-EACCES);
if (inode->i_state & I_NEW) {
if (sub_root != root) {
ret = radix_tree_insert(
&root->fs_info->fs_roots_radix,
(unsigned long)sub_root,
sub_root);
printk("adding new root for inode %lu\n", inode->i_ino);
igrab(inode);
sub_root->inode = inode;
}
BTRFS_I(inode)->root = sub_root;
memcpy(&BTRFS_I(inode)->location, &location,
sizeof(location));
@ -605,7 +610,7 @@ static int btrfs_fill_super(struct super_block * sb, void * data, int silent)
struct inode * inode;
struct dentry * root_dentry;
struct btrfs_super_block *disk_super;
struct btrfs_root *root;
struct btrfs_root *tree_root;
struct btrfs_inode *bi;
sb->s_maxbytes = MAX_LFS_FILESIZE;
@ -613,14 +618,14 @@ static int btrfs_fill_super(struct super_block * sb, void * data, int silent)
sb->s_op = &btrfs_super_ops;
sb->s_time_gran = 1;
root = open_ctree(sb);
tree_root = open_ctree(sb);
if (!root) {
if (!tree_root) {
printk("btrfs: open_ctree failed\n");
return -EIO;
}
sb->s_fs_info = root;
disk_super = root->fs_info->disk_super;
sb->s_fs_info = tree_root;
disk_super = tree_root->fs_info->disk_super;
printk("read in super total blocks %Lu root %Lu\n",
btrfs_super_total_blocks(disk_super),
btrfs_super_root_dir(disk_super));
@ -630,7 +635,7 @@ static int btrfs_fill_super(struct super_block * sb, void * data, int silent)
bi->location.objectid = inode->i_ino;
bi->location.offset = 0;
bi->location.flags = 0;
bi->root = root->fs_info->tree_root;
bi->root = tree_root;
btrfs_set_key_type(&bi->location, BTRFS_INODE_ITEM_KEY);
if (!inode)

140
fs/btrfs/transaction.c
View File

@ -8,6 +8,8 @@ static int total_trans = 0;
extern struct kmem_cache *btrfs_trans_handle_cachep;
extern struct kmem_cache *btrfs_transaction_cachep;
#define BTRFS_ROOT_TRANS_TAG 0
#define TRANS_MAGIC 0xE1E10E
static void put_transaction(struct btrfs_transaction *transaction)
{
@ -31,9 +33,10 @@ static int join_transaction(struct btrfs_root *root)
GFP_NOFS);
total_trans++;
BUG_ON(!cur_trans);
root->fs_info->generation++;
root->fs_info->running_transaction = cur_trans;
cur_trans->num_writers = 0;
cur_trans->transid = root->root_key.offset + 1;
cur_trans->transid = root->fs_info->generation;
init_waitqueue_head(&cur_trans->writer_wait);
init_waitqueue_head(&cur_trans->commit_wait);
cur_trans->magic = TRANS_MAGIC;
@ -51,13 +54,22 @@ struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
struct btrfs_trans_handle *h =
kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
int ret;
u64 running_trans_id;
/* FIXME, use the right root */
root = root->fs_info->fs_root;
mutex_lock(&root->fs_info->trans_mutex);
ret = join_transaction(root);
BUG_ON(ret);
h->transid = root->fs_info->running_transaction->transid;
running_trans_id = root->fs_info->running_transaction->transid;
if (root != root->fs_info->tree_root && root->last_trans <
running_trans_id) {
radix_tree_tag_set(&root->fs_info->fs_roots_radix,
(unsigned long)root, BTRFS_ROOT_TRANS_TAG);
root->commit_root = root->node;
get_bh(root->node);
}
root->last_trans = running_trans_id;
h->transid = running_trans_id;
h->transaction = root->fs_info->running_transaction;
h->blocks_reserved = num_blocks;
h->blocks_used = 0;
@ -72,9 +84,6 @@ int btrfs_end_transaction(struct btrfs_trans_handle *trans,
{
struct btrfs_transaction *cur_trans;
/* FIXME, use the right root */
root = root->fs_info->fs_root;
WARN_ON(trans->magic != TRANS_MAGIC);
WARN_ON(trans->magic2 != TRANS_MAGIC);
mutex_lock(&root->fs_info->trans_mutex);
@ -145,17 +154,96 @@ static int wait_for_commit(struct btrfs_root *root,
return 0;
}
struct dirty_root {
struct list_head list;
struct btrfs_key snap_key;
struct buffer_head *commit_root;
struct btrfs_root *root;
};
int add_dirty_roots(struct btrfs_trans_handle *trans,
struct radix_tree_root *radix, struct list_head *list)
{
struct dirty_root *dirty;
struct btrfs_root *gang[8];
struct btrfs_root *root;
int i;
int ret;
int err;
printk("add dirty\n");
while(1) {
ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
ARRAY_SIZE(gang),
BTRFS_ROOT_TRANS_TAG);
if (ret == 0)
break;
for (i = 0; i < ret; i++) {
root = gang[i];
radix_tree_tag_clear(radix, (unsigned long)root,
BTRFS_ROOT_TRANS_TAG);
if (root->commit_root == root->node) {
WARN_ON(root->node->b_blocknr !=
btrfs_root_blocknr(&root->root_item));
brelse(root->commit_root);
root->commit_root = NULL;
continue;
}
dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
BUG_ON(!dirty);
memcpy(&dirty->snap_key, &root->root_key,
sizeof(root->root_key));
dirty->commit_root = root->commit_root;
root->commit_root = NULL;
dirty->root = root;
printk("adding dirty root %Lu gen %Lu blocknr %Lu\n", root->root_key.objectid, root->root_key.offset, dirty->commit_root->b_blocknr);
root->root_key.offset = root->fs_info->generation;
btrfs_set_root_blocknr(&root->root_item,
root->node->b_blocknr);
err = btrfs_insert_root(trans, root->fs_info->tree_root,
&root->root_key,
&root->root_item);
BUG_ON(err);
list_add(&dirty->list, list);
}
}
printk("add dirty done\n");
return 0;
}
int drop_dirty_roots(struct btrfs_root *tree_root, struct list_head *list)
{
struct dirty_root *dirty;
struct btrfs_trans_handle *trans;
int ret;
while(!list_empty(list)) {
dirty = list_entry(list->next, struct dirty_root, list);
list_del_init(&dirty->list);
trans = btrfs_start_transaction(tree_root, 1);
printk("drop snapshot root %p, commit_root blocknr %Lu generation %Lu\n", dirty->root, dirty->commit_root->b_blocknr, dirty->snap_key.offset);
ret = btrfs_drop_snapshot(trans, dirty->root,
dirty->commit_root);
BUG_ON(ret);
printk("del root objectid %Lu, offset %Lu\n", dirty->snap_key.objectid, dirty->snap_key.offset);
ret = btrfs_del_root(trans, tree_root, &dirty->snap_key);
BUG_ON(ret);
ret = btrfs_end_transaction(trans, tree_root);
BUG_ON(ret);
kfree(dirty);
}
return 0;
}
int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
struct btrfs_root *root)
{
int ret = 0;
struct buffer_head *snap;
struct btrfs_key snap_key;
struct btrfs_transaction *cur_trans;
struct list_head dirty_fs_roots;
DEFINE_WAIT(wait);
/* FIXME, use the right root */
root = root->fs_info->fs_root;
INIT_LIST_HEAD(&dirty_fs_roots);
mutex_lock(&root->fs_info->trans_mutex);
if (trans->transaction->in_commit) {
@ -184,22 +272,13 @@ printk("already in commit!, waiting\n");
}
finish_wait(&trans->transaction->writer_wait, &wait);
WARN_ON(cur_trans != trans->transaction);
if (root->node != root->commit_root) {
memcpy(&snap_key, &root->root_key, sizeof(snap_key));
root->root_key.offset++;
}
if (btrfs_root_blocknr(&root->root_item) != root->node->b_blocknr) {
btrfs_set_root_blocknr(&root->root_item, root->node->b_blocknr);
ret = btrfs_insert_root(trans, root->fs_info->tree_root,
&root->root_key, &root->root_item);
BUG_ON(ret);
}
add_dirty_roots(trans, &root->fs_info->fs_roots_radix, &dirty_fs_roots);
ret = btrfs_commit_tree_roots(trans, root);
BUG_ON(ret);
cur_trans = root->fs_info->running_transaction;
root->fs_info->running_transaction = NULL;
btrfs_set_super_generation(root->fs_info->disk_super,
root->fs_info->generation + 1);
mutex_unlock(&root->fs_info->trans_mutex);
ret = btrfs_write_and_wait_transaction(trans, root);
BUG_ON(ret);
@ -213,21 +292,8 @@ printk("already in commit!, waiting\n");
put_transaction(cur_trans);
mutex_unlock(&root->fs_info->trans_mutex);
kmem_cache_free(btrfs_trans_handle_cachep, trans);
if (root->node != root->commit_root) {
trans = btrfs_start_transaction(root, 1);
snap = root->commit_root;
root->commit_root = root->node;
get_bh(root->node);
ret = btrfs_drop_snapshot(trans, root, snap);
BUG_ON(ret);
ret = btrfs_del_root(trans, root->fs_info->tree_root,
&snap_key);
BUG_ON(ret);
root->fs_info->generation = root->root_key.offset + 1;
ret = btrfs_end_transaction(trans, root);
BUG_ON(ret);
}
drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
return ret;
}