linux/fs/btrfs/tree-mod-log.c

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// SPDX-License-Identifier: GPL-2.0
#include "tree-mod-log.h"
#include "disk-io.h"
struct tree_mod_root {
u64 logical;
u8 level;
};
struct tree_mod_elem {
struct rb_node node;
u64 logical;
u64 seq;
enum btrfs_mod_log_op op;
/*
* This is used for BTRFS_MOD_LOG_KEY_* and BTRFS_MOD_LOG_MOVE_KEYS
* operations.
*/
int slot;
/* This is used for BTRFS_MOD_LOG_KEY* and BTRFS_MOD_LOG_ROOT_REPLACE. */
u64 generation;
/* Those are used for op == BTRFS_MOD_LOG_KEY_{REPLACE,REMOVE}. */
struct btrfs_disk_key key;
u64 blockptr;
/* This is used for op == BTRFS_MOD_LOG_MOVE_KEYS. */
struct {
int dst_slot;
int nr_items;
} move;
/* This is used for op == BTRFS_MOD_LOG_ROOT_REPLACE. */
struct tree_mod_root old_root;
};
/*
* Pull a new tree mod seq number for our operation.
*/
static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
{
return atomic64_inc_return(&fs_info->tree_mod_seq);
}
/*
* This adds a new blocker to the tree mod log's blocker list if the @elem
* passed does not already have a sequence number set. So when a caller expects
* to record tree modifications, it should ensure to set elem->seq to zero
* before calling btrfs_get_tree_mod_seq.
* Returns a fresh, unused tree log modification sequence number, even if no new
* blocker was added.
*/
u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct btrfs_seq_list *elem)
{
write_lock(&fs_info->tree_mod_log_lock);
if (!elem->seq) {
elem->seq = btrfs_inc_tree_mod_seq(fs_info);
list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
set_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags);
}
write_unlock(&fs_info->tree_mod_log_lock);
return elem->seq;
}
void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
struct btrfs_seq_list *elem)
{
struct rb_root *tm_root;
struct rb_node *node;
struct rb_node *next;
struct tree_mod_elem *tm;
u64 min_seq = BTRFS_SEQ_LAST;
u64 seq_putting = elem->seq;
if (!seq_putting)
return;
write_lock(&fs_info->tree_mod_log_lock);
list_del(&elem->list);
elem->seq = 0;
if (list_empty(&fs_info->tree_mod_seq_list)) {
clear_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags);
} else {
struct btrfs_seq_list *first;
first = list_first_entry(&fs_info->tree_mod_seq_list,
struct btrfs_seq_list, list);
if (seq_putting > first->seq) {
/*
* Blocker with lower sequence number exists, we cannot
* remove anything from the log.
*/
write_unlock(&fs_info->tree_mod_log_lock);
return;
}
min_seq = first->seq;
}
/*
* Anything that's lower than the lowest existing (read: blocked)
* sequence number can be removed from the tree.
*/
tm_root = &fs_info->tree_mod_log;
for (node = rb_first(tm_root); node; node = next) {
next = rb_next(node);
tm = rb_entry(node, struct tree_mod_elem, node);
if (tm->seq >= min_seq)
continue;
rb_erase(node, tm_root);
kfree(tm);
}
write_unlock(&fs_info->tree_mod_log_lock);
}
/*
* Key order of the log:
* node/leaf start address -> sequence
*
* The 'start address' is the logical address of the *new* root node for root
* replace operations, or the logical address of the affected block for all
* other operations.
*/
static noinline int tree_mod_log_insert(struct btrfs_fs_info *fs_info,
struct tree_mod_elem *tm)
{
struct rb_root *tm_root;
struct rb_node **new;
struct rb_node *parent = NULL;
struct tree_mod_elem *cur;
lockdep_assert_held_write(&fs_info->tree_mod_log_lock);
tm->seq = btrfs_inc_tree_mod_seq(fs_info);
tm_root = &fs_info->tree_mod_log;
new = &tm_root->rb_node;
while (*new) {
cur = rb_entry(*new, struct tree_mod_elem, node);
parent = *new;
if (cur->logical < tm->logical)
new = &((*new)->rb_left);
else if (cur->logical > tm->logical)
new = &((*new)->rb_right);
else if (cur->seq < tm->seq)
new = &((*new)->rb_left);
else if (cur->seq > tm->seq)
new = &((*new)->rb_right);
else
return -EEXIST;
}
rb_link_node(&tm->node, parent, new);
rb_insert_color(&tm->node, tm_root);
return 0;
}
/*
* Determines if logging can be omitted. Returns true if it can. Otherwise, it
* returns false with the tree_mod_log_lock acquired. The caller must hold
* this until all tree mod log insertions are recorded in the rb tree and then
* write unlock fs_info::tree_mod_log_lock.
*/
static inline bool tree_mod_dont_log(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb)
{
if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
return true;
if (eb && btrfs_header_level(eb) == 0)
return true;
write_lock(&fs_info->tree_mod_log_lock);
if (list_empty(&(fs_info)->tree_mod_seq_list)) {
write_unlock(&fs_info->tree_mod_log_lock);
return true;
}
return false;
}
/* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
static inline bool tree_mod_need_log(const struct btrfs_fs_info *fs_info,
struct extent_buffer *eb)
{
if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags))
return false;
if (eb && btrfs_header_level(eb) == 0)
return false;
return true;
}
static struct tree_mod_elem *alloc_tree_mod_elem(struct extent_buffer *eb,
int slot,
enum btrfs_mod_log_op op,
gfp_t flags)
{
struct tree_mod_elem *tm;
tm = kzalloc(sizeof(*tm), flags);
if (!tm)
return NULL;
tm->logical = eb->start;
if (op != BTRFS_MOD_LOG_KEY_ADD) {
btrfs_node_key(eb, &tm->key, slot);
tm->blockptr = btrfs_node_blockptr(eb, slot);
}
tm->op = op;
tm->slot = slot;
tm->generation = btrfs_node_ptr_generation(eb, slot);
RB_CLEAR_NODE(&tm->node);
return tm;
}
int btrfs_tree_mod_log_insert_key(struct extent_buffer *eb, int slot,
enum btrfs_mod_log_op op, gfp_t flags)
{
struct tree_mod_elem *tm;
int ret;
if (!tree_mod_need_log(eb->fs_info, eb))
return 0;
tm = alloc_tree_mod_elem(eb, slot, op, flags);
if (!tm)
return -ENOMEM;
if (tree_mod_dont_log(eb->fs_info, eb)) {
kfree(tm);
return 0;
}
ret = tree_mod_log_insert(eb->fs_info, tm);
write_unlock(&eb->fs_info->tree_mod_log_lock);
if (ret)
kfree(tm);
return ret;
}
int btrfs_tree_mod_log_insert_move(struct extent_buffer *eb,
int dst_slot, int src_slot,
int nr_items)
{
struct tree_mod_elem *tm = NULL;
struct tree_mod_elem **tm_list = NULL;
int ret = 0;
int i;
bool locked = false;
if (!tree_mod_need_log(eb->fs_info, eb))
return 0;
tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS);
if (!tm_list)
return -ENOMEM;
tm = kzalloc(sizeof(*tm), GFP_NOFS);
if (!tm) {
ret = -ENOMEM;
goto free_tms;
}
tm->logical = eb->start;
tm->slot = src_slot;
tm->move.dst_slot = dst_slot;
tm->move.nr_items = nr_items;
tm->op = BTRFS_MOD_LOG_MOVE_KEYS;
for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING, GFP_NOFS);
if (!tm_list[i]) {
ret = -ENOMEM;
goto free_tms;
}
}
if (tree_mod_dont_log(eb->fs_info, eb))
goto free_tms;
locked = true;
/*
* When we override something during the move, we log these removals.
* This can only happen when we move towards the beginning of the
* buffer, i.e. dst_slot < src_slot.
*/
for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
ret = tree_mod_log_insert(eb->fs_info, tm_list[i]);
if (ret)
goto free_tms;
}
ret = tree_mod_log_insert(eb->fs_info, tm);
if (ret)
goto free_tms;
write_unlock(&eb->fs_info->tree_mod_log_lock);
kfree(tm_list);
return 0;
free_tms:
for (i = 0; i < nr_items; i++) {
if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
rb_erase(&tm_list[i]->node, &eb->fs_info->tree_mod_log);
kfree(tm_list[i]);
}
if (locked)
write_unlock(&eb->fs_info->tree_mod_log_lock);
kfree(tm_list);
kfree(tm);
return ret;
}
static inline int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
struct tree_mod_elem **tm_list,
int nritems)
{
int i, j;
int ret;
for (i = nritems - 1; i >= 0; i--) {
ret = tree_mod_log_insert(fs_info, tm_list[i]);
if (ret) {
for (j = nritems - 1; j > i; j--)
rb_erase(&tm_list[j]->node,
&fs_info->tree_mod_log);
return ret;
}
}
return 0;
}
int btrfs_tree_mod_log_insert_root(struct extent_buffer *old_root,
struct extent_buffer *new_root,
bool log_removal)
{
struct btrfs_fs_info *fs_info = old_root->fs_info;
struct tree_mod_elem *tm = NULL;
struct tree_mod_elem **tm_list = NULL;
int nritems = 0;
int ret = 0;
int i;
if (!tree_mod_need_log(fs_info, NULL))
return 0;
if (log_removal && btrfs_header_level(old_root) > 0) {
nritems = btrfs_header_nritems(old_root);
tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *),
GFP_NOFS);
if (!tm_list) {
ret = -ENOMEM;
goto free_tms;
}
for (i = 0; i < nritems; i++) {
tm_list[i] = alloc_tree_mod_elem(old_root, i,
BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
if (!tm_list[i]) {
ret = -ENOMEM;
goto free_tms;
}
}
}
tm = kzalloc(sizeof(*tm), GFP_NOFS);
if (!tm) {
ret = -ENOMEM;
goto free_tms;
}
tm->logical = new_root->start;
tm->old_root.logical = old_root->start;
tm->old_root.level = btrfs_header_level(old_root);
tm->generation = btrfs_header_generation(old_root);
tm->op = BTRFS_MOD_LOG_ROOT_REPLACE;
if (tree_mod_dont_log(fs_info, NULL))
goto free_tms;
if (tm_list)
ret = tree_mod_log_free_eb(fs_info, tm_list, nritems);
if (!ret)
ret = tree_mod_log_insert(fs_info, tm);
write_unlock(&fs_info->tree_mod_log_lock);
if (ret)
goto free_tms;
kfree(tm_list);
return ret;
free_tms:
if (tm_list) {
for (i = 0; i < nritems; i++)
kfree(tm_list[i]);
kfree(tm_list);
}
kfree(tm);
return ret;
}
static struct tree_mod_elem *__tree_mod_log_search(struct btrfs_fs_info *fs_info,
u64 start, u64 min_seq,
bool smallest)
{
struct rb_root *tm_root;
struct rb_node *node;
struct tree_mod_elem *cur = NULL;
struct tree_mod_elem *found = NULL;
read_lock(&fs_info->tree_mod_log_lock);
tm_root = &fs_info->tree_mod_log;
node = tm_root->rb_node;
while (node) {
cur = rb_entry(node, struct tree_mod_elem, node);
if (cur->logical < start) {
node = node->rb_left;
} else if (cur->logical > start) {
node = node->rb_right;
} else if (cur->seq < min_seq) {
node = node->rb_left;
} else if (!smallest) {
/* We want the node with the highest seq */
if (found)
BUG_ON(found->seq > cur->seq);
found = cur;
node = node->rb_left;
} else if (cur->seq > min_seq) {
/* We want the node with the smallest seq */
if (found)
BUG_ON(found->seq < cur->seq);
found = cur;
node = node->rb_right;
} else {
found = cur;
break;
}
}
read_unlock(&fs_info->tree_mod_log_lock);
return found;
}
/*
* This returns the element from the log with the smallest time sequence
* value that's in the log (the oldest log item). Any element with a time
* sequence lower than min_seq will be ignored.
*/
static struct tree_mod_elem *tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info,
u64 start, u64 min_seq)
{
return __tree_mod_log_search(fs_info, start, min_seq, true);
}
/*
* This returns the element from the log with the largest time sequence
* value that's in the log (the most recent log item). Any element with
* a time sequence lower than min_seq will be ignored.
*/
static struct tree_mod_elem *tree_mod_log_search(struct btrfs_fs_info *fs_info,
u64 start, u64 min_seq)
{
return __tree_mod_log_search(fs_info, start, min_seq, false);
}
int btrfs_tree_mod_log_eb_copy(struct extent_buffer *dst,
struct extent_buffer *src,
unsigned long dst_offset,
unsigned long src_offset,
int nr_items)
{
struct btrfs_fs_info *fs_info = dst->fs_info;
int ret = 0;
struct tree_mod_elem **tm_list = NULL;
struct tree_mod_elem **tm_list_add, **tm_list_rem;
int i;
bool locked = false;
if (!tree_mod_need_log(fs_info, NULL))
return 0;
if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
return 0;
tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *),
GFP_NOFS);
if (!tm_list)
return -ENOMEM;
tm_list_add = tm_list;
tm_list_rem = tm_list + nr_items;
for (i = 0; i < nr_items; i++) {
tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
BTRFS_MOD_LOG_KEY_REMOVE, GFP_NOFS);
if (!tm_list_rem[i]) {
ret = -ENOMEM;
goto free_tms;
}
tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
BTRFS_MOD_LOG_KEY_ADD, GFP_NOFS);
if (!tm_list_add[i]) {
ret = -ENOMEM;
goto free_tms;
}
}
if (tree_mod_dont_log(fs_info, NULL))
goto free_tms;
locked = true;
for (i = 0; i < nr_items; i++) {
ret = tree_mod_log_insert(fs_info, tm_list_rem[i]);
if (ret)
goto free_tms;
ret = tree_mod_log_insert(fs_info, tm_list_add[i]);
if (ret)
goto free_tms;
}
write_unlock(&fs_info->tree_mod_log_lock);
kfree(tm_list);
return 0;
free_tms:
for (i = 0; i < nr_items * 2; i++) {
if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
kfree(tm_list[i]);
}
if (locked)
write_unlock(&fs_info->tree_mod_log_lock);
kfree(tm_list);
return ret;
}
int btrfs_tree_mod_log_free_eb(struct extent_buffer *eb)
{
struct tree_mod_elem **tm_list = NULL;
int nritems = 0;
int i;
int ret = 0;
if (!tree_mod_need_log(eb->fs_info, eb))
return 0;
nritems = btrfs_header_nritems(eb);
tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS);
if (!tm_list)
return -ENOMEM;
for (i = 0; i < nritems; i++) {
tm_list[i] = alloc_tree_mod_elem(eb, i,
BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
if (!tm_list[i]) {
ret = -ENOMEM;
goto free_tms;
}
}
if (tree_mod_dont_log(eb->fs_info, eb))
goto free_tms;
ret = tree_mod_log_free_eb(eb->fs_info, tm_list, nritems);
write_unlock(&eb->fs_info->tree_mod_log_lock);
if (ret)
goto free_tms;
kfree(tm_list);
return 0;
free_tms:
for (i = 0; i < nritems; i++)
kfree(tm_list[i]);
kfree(tm_list);
return ret;
}
/*
* Returns the logical address of the oldest predecessor of the given root.
* Entries older than time_seq are ignored.
*/
static struct tree_mod_elem *tree_mod_log_oldest_root(struct extent_buffer *eb_root,
u64 time_seq)
{
struct tree_mod_elem *tm;
struct tree_mod_elem *found = NULL;
u64 root_logical = eb_root->start;
bool looped = false;
if (!time_seq)
return NULL;
/*
* The very last operation that's logged for a root is the replacement
* operation (if it is replaced at all). This has the logical address
* of the *new* root, making it the very first operation that's logged
* for this root.
*/
while (1) {
tm = tree_mod_log_search_oldest(eb_root->fs_info, root_logical,
time_seq);
if (!looped && !tm)
return NULL;
/*
* If there are no tree operation for the oldest root, we simply
* return it. This should only happen if that (old) root is at
* level 0.
*/
if (!tm)
break;
/*
* If there's an operation that's not a root replacement, we
* found the oldest version of our root. Normally, we'll find a
* BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
*/
if (tm->op != BTRFS_MOD_LOG_ROOT_REPLACE)
break;
found = tm;
root_logical = tm->old_root.logical;
looped = true;
}
/* If there's no old root to return, return what we found instead */
if (!found)
found = tm;
return found;
}
/*
* tm is a pointer to the first operation to rewind within eb. Then, all
* previous operations will be rewound (until we reach something older than
* time_seq).
*/
static void tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
struct extent_buffer *eb,
u64 time_seq,
struct tree_mod_elem *first_tm)
{
u32 n;
struct rb_node *next;
struct tree_mod_elem *tm = first_tm;
unsigned long o_dst;
unsigned long o_src;
unsigned long p_size = sizeof(struct btrfs_key_ptr);
n = btrfs_header_nritems(eb);
read_lock(&fs_info->tree_mod_log_lock);
while (tm && tm->seq >= time_seq) {
/*
* All the operations are recorded with the operator used for
* the modification. As we're going backwards, we do the
* opposite of each operation here.
*/
switch (tm->op) {
case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING:
BUG_ON(tm->slot < n);
fallthrough;
case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING:
case BTRFS_MOD_LOG_KEY_REMOVE:
btrfs_set_node_key(eb, &tm->key, tm->slot);
btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
btrfs_set_node_ptr_generation(eb, tm->slot,
tm->generation);
n++;
break;
case BTRFS_MOD_LOG_KEY_REPLACE:
BUG_ON(tm->slot >= n);
btrfs_set_node_key(eb, &tm->key, tm->slot);
btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
btrfs_set_node_ptr_generation(eb, tm->slot,
tm->generation);
break;
case BTRFS_MOD_LOG_KEY_ADD:
/* if a move operation is needed it's in the log */
n--;
break;
case BTRFS_MOD_LOG_MOVE_KEYS:
o_dst = btrfs_node_key_ptr_offset(tm->slot);
o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot);
memmove_extent_buffer(eb, o_dst, o_src,
tm->move.nr_items * p_size);
break;
case BTRFS_MOD_LOG_ROOT_REPLACE:
/*
* This operation is special. For roots, this must be
* handled explicitly before rewinding.
* For non-roots, this operation may exist if the node
* was a root: root A -> child B; then A gets empty and
* B is promoted to the new root. In the mod log, we'll
* have a root-replace operation for B, a tree block
* that is no root. We simply ignore that operation.
*/
break;
}
next = rb_next(&tm->node);
if (!next)
break;
tm = rb_entry(next, struct tree_mod_elem, node);
if (tm->logical != first_tm->logical)
break;
}
read_unlock(&fs_info->tree_mod_log_lock);
btrfs_set_header_nritems(eb, n);
}
/*
* Called with eb read locked. If the buffer cannot be rewound, the same buffer
* is returned. If rewind operations happen, a fresh buffer is returned. The
* returned buffer is always read-locked. If the returned buffer is not the
* input buffer, the lock on the input buffer is released and the input buffer
* is freed (its refcount is decremented).
*/
struct extent_buffer *btrfs_tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
struct btrfs_path *path,
struct extent_buffer *eb,
u64 time_seq)
{
struct extent_buffer *eb_rewin;
struct tree_mod_elem *tm;
if (!time_seq)
return eb;
if (btrfs_header_level(eb) == 0)
return eb;
tm = tree_mod_log_search(fs_info, eb->start, time_seq);
if (!tm)
return eb;
if (tm->op == BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
BUG_ON(tm->slot != 0);
eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
if (!eb_rewin) {
btrfs_tree_read_unlock(eb);
free_extent_buffer(eb);
return NULL;
}
btrfs_set_header_bytenr(eb_rewin, eb->start);
btrfs_set_header_backref_rev(eb_rewin,
btrfs_header_backref_rev(eb));
btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
} else {
eb_rewin = btrfs_clone_extent_buffer(eb);
if (!eb_rewin) {
btrfs_tree_read_unlock(eb);
free_extent_buffer(eb);
return NULL;
}
}
btrfs_tree_read_unlock(eb);
free_extent_buffer(eb);
btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb_rewin),
eb_rewin, btrfs_header_level(eb_rewin));
btrfs_tree_read_lock(eb_rewin);
tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
WARN_ON(btrfs_header_nritems(eb_rewin) >
BTRFS_NODEPTRS_PER_BLOCK(fs_info));
return eb_rewin;
}
/*
* Rewind the state of @root's root node to the given @time_seq value.
* If there are no changes, the current root->root_node is returned. If anything
* changed in between, there's a fresh buffer allocated on which the rewind
* operations are done. In any case, the returned buffer is read locked.
* Returns NULL on error (with no locks held).
*/
struct extent_buffer *btrfs_get_old_root(struct btrfs_root *root, u64 time_seq)
{
struct btrfs_fs_info *fs_info = root->fs_info;
struct tree_mod_elem *tm;
struct extent_buffer *eb = NULL;
struct extent_buffer *eb_root;
u64 eb_root_owner = 0;
struct extent_buffer *old;
struct tree_mod_root *old_root = NULL;
u64 old_generation = 0;
u64 logical;
int level;
eb_root = btrfs_read_lock_root_node(root);
tm = tree_mod_log_oldest_root(eb_root, time_seq);
if (!tm)
return eb_root;
if (tm->op == BTRFS_MOD_LOG_ROOT_REPLACE) {
old_root = &tm->old_root;
old_generation = tm->generation;
logical = old_root->logical;
level = old_root->level;
} else {
logical = eb_root->start;
level = btrfs_header_level(eb_root);
}
tm = tree_mod_log_search(fs_info, logical, time_seq);
if (old_root && tm && tm->op != BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
btrfs_tree_read_unlock(eb_root);
free_extent_buffer(eb_root);
old = read_tree_block(fs_info, logical, root->root_key.objectid,
0, level, NULL);
if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
if (!IS_ERR(old))
free_extent_buffer(old);
btrfs_warn(fs_info,
"failed to read tree block %llu from get_old_root",
logical);
} else {
btrfs_tree_read_lock(old);
eb = btrfs_clone_extent_buffer(old);
btrfs_tree_read_unlock(old);
free_extent_buffer(old);
}
} else if (old_root) {
eb_root_owner = btrfs_header_owner(eb_root);
btrfs_tree_read_unlock(eb_root);
free_extent_buffer(eb_root);
eb = alloc_dummy_extent_buffer(fs_info, logical);
} else {
eb = btrfs_clone_extent_buffer(eb_root);
btrfs_tree_read_unlock(eb_root);
free_extent_buffer(eb_root);
}
if (!eb)
return NULL;
if (old_root) {
btrfs_set_header_bytenr(eb, eb->start);
btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
btrfs_set_header_owner(eb, eb_root_owner);
btrfs_set_header_level(eb, old_root->level);
btrfs_set_header_generation(eb, old_generation);
}
btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb), eb,
btrfs_header_level(eb));
btrfs_tree_read_lock(eb);
if (tm)
tree_mod_log_rewind(fs_info, eb, time_seq, tm);
else
WARN_ON(btrfs_header_level(eb) != 0);
WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
return eb;
}
int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
{
struct tree_mod_elem *tm;
int level;
struct extent_buffer *eb_root = btrfs_root_node(root);
tm = tree_mod_log_oldest_root(eb_root, time_seq);
if (tm && tm->op == BTRFS_MOD_LOG_ROOT_REPLACE)
level = tm->old_root.level;
else
level = btrfs_header_level(eb_root);
free_extent_buffer(eb_root);
return level;
}
/*
* Return the lowest sequence number in the tree modification log.
*
* Return the sequence number of the oldest tree modification log user, which
* corresponds to the lowest sequence number of all existing users. If there are
* no users it returns 0.
*/
u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info)
{
u64 ret = 0;
read_lock(&fs_info->tree_mod_log_lock);
if (!list_empty(&fs_info->tree_mod_seq_list)) {
struct btrfs_seq_list *elem;
elem = list_first_entry(&fs_info->tree_mod_seq_list,
struct btrfs_seq_list, list);
ret = elem->seq;
}
read_unlock(&fs_info->tree_mod_log_lock);
return ret;
}