Btrfs: add tree modification log functions
The tree mod log will log modifications made fs-tree nodes. Most
modifications are done by autobalance of the tree. Such changes are recorded
as long as a block entry exists. When released, the log is cleaned.
With the tree modification log, it's possible to reconstruct a consistent
old state of the tree. This is required to do backref walking on a busy
file system.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 56485b3..72b9f97 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/rbtree.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
@@ -288,6 +289,412 @@
return 0;
}
+enum mod_log_op {
+ MOD_LOG_KEY_REPLACE,
+ MOD_LOG_KEY_ADD,
+ MOD_LOG_KEY_REMOVE,
+ MOD_LOG_KEY_REMOVE_WHILE_FREEING,
+ MOD_LOG_KEY_REMOVE_WHILE_MOVING,
+ MOD_LOG_MOVE_KEYS,
+ MOD_LOG_ROOT_REPLACE,
+};
+
+struct tree_mod_move {
+ int dst_slot;
+ int nr_items;
+};
+
+struct tree_mod_root {
+ u64 logical;
+ u8 level;
+};
+
+struct tree_mod_elem {
+ struct rb_node node;
+ u64 index; /* shifted logical */
+ struct seq_list elem;
+ enum mod_log_op op;
+
+ /* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
+ int slot;
+
+ /* this is used for MOD_LOG_KEY* and MOD_LOG_ROOT_REPLACE */
+ u64 generation;
+
+ /* those are used for op == MOD_LOG_KEY_{REPLACE,REMOVE} */
+ struct btrfs_disk_key key;
+ u64 blockptr;
+
+ /* this is used for op == MOD_LOG_MOVE_KEYS */
+ struct tree_mod_move move;
+
+ /* this is used for op == MOD_LOG_ROOT_REPLACE */
+ struct tree_mod_root old_root;
+};
+
+static inline void
+__get_tree_mod_seq(struct btrfs_fs_info *fs_info, struct seq_list *elem)
+{
+ elem->seq = atomic_inc_return(&fs_info->tree_mod_seq);
+ list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
+}
+
+void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
+ struct seq_list *elem)
+{
+ elem->flags = 1;
+ spin_lock(&fs_info->tree_mod_seq_lock);
+ __get_tree_mod_seq(fs_info, elem);
+ spin_unlock(&fs_info->tree_mod_seq_lock);
+}
+
+void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
+ struct seq_list *elem)
+{
+ struct rb_root *tm_root;
+ struct rb_node *node;
+ struct rb_node *next;
+ struct seq_list *cur_elem;
+ struct tree_mod_elem *tm;
+ u64 min_seq = (u64)-1;
+ u64 seq_putting = elem->seq;
+
+ if (!seq_putting)
+ return;
+
+ BUG_ON(!(elem->flags & 1));
+ spin_lock(&fs_info->tree_mod_seq_lock);
+ list_del(&elem->list);
+
+ list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
+ if ((cur_elem->flags & 1) && cur_elem->seq < min_seq) {
+ if (seq_putting > cur_elem->seq) {
+ /*
+ * blocker with lower sequence number exists, we
+ * cannot remove anything from the log
+ */
+ goto out;
+ }
+ min_seq = cur_elem->seq;
+ }
+ }
+
+ /*
+ * anything that's lower than the lowest existing (read: blocked)
+ * sequence number can be removed from the tree.
+ */
+ write_lock(&fs_info->tree_mod_log_lock);
+ tm_root = &fs_info->tree_mod_log;
+ for (node = rb_first(tm_root); node; node = next) {
+ next = rb_next(node);
+ tm = container_of(node, struct tree_mod_elem, node);
+ if (tm->elem.seq > min_seq)
+ continue;
+ rb_erase(node, tm_root);
+ list_del(&tm->elem.list);
+ kfree(tm);
+ }
+ write_unlock(&fs_info->tree_mod_log_lock);
+out:
+ spin_unlock(&fs_info->tree_mod_seq_lock);
+}
+
+/*
+ * key order of the log:
+ * index -> sequence
+ *
+ * the index is the shifted logical of the *new* root node for root replace
+ * operations, or the shifted logical 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;
+ int ret = 0;
+
+ BUG_ON(!tm || !tm->elem.seq);
+
+ write_lock(&fs_info->tree_mod_log_lock);
+ tm_root = &fs_info->tree_mod_log;
+ new = &tm_root->rb_node;
+ while (*new) {
+ cur = container_of(*new, struct tree_mod_elem, node);
+ parent = *new;
+ if (cur->index < tm->index)
+ new = &((*new)->rb_left);
+ else if (cur->index > tm->index)
+ new = &((*new)->rb_right);
+ else if (cur->elem.seq < tm->elem.seq)
+ new = &((*new)->rb_left);
+ else if (cur->elem.seq > tm->elem.seq)
+ new = &((*new)->rb_right);
+ else {
+ kfree(tm);
+ ret = -EEXIST;
+ goto unlock;
+ }
+ }
+
+ rb_link_node(&tm->node, parent, new);
+ rb_insert_color(&tm->node, tm_root);
+unlock:
+ write_unlock(&fs_info->tree_mod_log_lock);
+ return ret;
+}
+
+int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
+ struct tree_mod_elem **tm_ret)
+{
+ struct tree_mod_elem *tm;
+ u64 seq = 0;
+
+ smp_mb();
+ if (list_empty(&fs_info->tree_mod_seq_list))
+ return 0;
+
+ tm = *tm_ret = kzalloc(sizeof(*tm), flags);
+ if (!tm)
+ return -ENOMEM;
+
+ __get_tree_mod_seq(fs_info, &tm->elem);
+ seq = tm->elem.seq;
+ tm->elem.flags = 0;
+
+ return seq;
+}
+
+static noinline int
+tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *eb, int slot,
+ enum mod_log_op op, gfp_t flags)
+{
+ struct tree_mod_elem *tm;
+ int ret;
+
+ ret = tree_mod_alloc(fs_info, flags, &tm);
+ if (ret <= 0)
+ return ret;
+
+ tm->index = eb->start >> PAGE_CACHE_SHIFT;
+ if (op != 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);
+
+ return __tree_mod_log_insert(fs_info, tm);
+}
+
+static noinline int
+tree_mod_log_insert_key(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
+ int slot, enum mod_log_op op)
+{
+ return tree_mod_log_insert_key_mask(fs_info, eb, slot, op, GFP_NOFS);
+}
+
+static noinline int
+tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *eb, int dst_slot, int src_slot,
+ int nr_items, gfp_t flags)
+{
+ struct tree_mod_elem *tm;
+ int ret;
+ int i;
+
+ ret = tree_mod_alloc(fs_info, flags, &tm);
+ if (ret <= 0)
+ return ret;
+
+ for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
+ ret = tree_mod_log_insert_key(fs_info, eb, i + dst_slot,
+ MOD_LOG_KEY_REMOVE_WHILE_MOVING);
+ BUG_ON(ret < 0);
+ }
+
+ tm->index = eb->start >> PAGE_CACHE_SHIFT;
+ tm->slot = src_slot;
+ tm->move.dst_slot = dst_slot;
+ tm->move.nr_items = nr_items;
+ tm->op = MOD_LOG_MOVE_KEYS;
+
+ return __tree_mod_log_insert(fs_info, tm);
+}
+
+static noinline int
+tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *old_root,
+ struct extent_buffer *new_root, gfp_t flags)
+{
+ struct tree_mod_elem *tm;
+ int ret;
+
+ ret = tree_mod_alloc(fs_info, flags, &tm);
+ if (ret <= 0)
+ return ret;
+
+ tm->index = new_root->start >> PAGE_CACHE_SHIFT;
+ 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 = MOD_LOG_ROOT_REPLACE;
+
+ return __tree_mod_log_insert(fs_info, tm);
+}
+
+static struct tree_mod_elem *
+__tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
+ int smallest)
+{
+ struct rb_root *tm_root;
+ struct rb_node *node;
+ struct tree_mod_elem *cur = NULL;
+ struct tree_mod_elem *found = NULL;
+ u64 index = start >> PAGE_CACHE_SHIFT;
+
+ read_lock(&fs_info->tree_mod_log_lock);
+ tm_root = &fs_info->tree_mod_log;
+ node = tm_root->rb_node;
+ while (node) {
+ cur = container_of(node, struct tree_mod_elem, node);
+ if (cur->index < index) {
+ node = node->rb_left;
+ } else if (cur->index > index) {
+ node = node->rb_right;
+ } else if (cur->elem.seq < min_seq) {
+ node = node->rb_left;
+ } else if (!smallest) {
+ /* we want the node with the highest seq */
+ if (found)
+ BUG_ON(found->elem.seq > cur->elem.seq);
+ found = cur;
+ node = node->rb_left;
+ } else if (cur->elem.seq > min_seq) {
+ /* we want the node with the smallest seq */
+ if (found)
+ BUG_ON(found->elem.seq < cur->elem.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, 1);
+}
+
+/*
+ * 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, 0);
+}
+
+static inline void
+tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
+ struct extent_buffer *src, unsigned long dst_offset,
+ unsigned long src_offset, int nr_items)
+{
+ int ret;
+ int i;
+
+ smp_mb();
+ if (list_empty(&fs_info->tree_mod_seq_list))
+ return;
+
+ if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
+ return;
+
+ /* speed this up by single seq for all operations? */
+ for (i = 0; i < nr_items; i++) {
+ ret = tree_mod_log_insert_key(fs_info, src, i + src_offset,
+ MOD_LOG_KEY_REMOVE);
+ BUG_ON(ret < 0);
+ ret = tree_mod_log_insert_key(fs_info, dst, i + dst_offset,
+ MOD_LOG_KEY_ADD);
+ BUG_ON(ret < 0);
+ }
+}
+
+static inline void
+tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
+ int dst_offset, int src_offset, int nr_items)
+{
+ int ret;
+ ret = tree_mod_log_insert_move(fs_info, dst, dst_offset, src_offset,
+ nr_items, GFP_NOFS);
+ BUG_ON(ret < 0);
+}
+
+static inline void
+tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *eb,
+ struct btrfs_disk_key *disk_key, int slot, int atomic)
+{
+ int ret;
+
+ ret = tree_mod_log_insert_key_mask(fs_info, eb, slot,
+ MOD_LOG_KEY_REPLACE,
+ atomic ? GFP_ATOMIC : GFP_NOFS);
+ BUG_ON(ret < 0);
+}
+
+static void tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *eb)
+{
+ int i;
+ int ret;
+ u32 nritems;
+
+ smp_mb();
+ if (list_empty(&fs_info->tree_mod_seq_list))
+ return;
+
+ if (btrfs_header_level(eb) == 0)
+ return;
+
+ nritems = btrfs_header_nritems(eb);
+ for (i = nritems - 1; i >= 0; i--) {
+ ret = tree_mod_log_insert_key(fs_info, eb, i,
+ MOD_LOG_KEY_REMOVE_WHILE_FREEING);
+ BUG_ON(ret < 0);
+ }
+}
+
+static inline void
+tree_mod_log_set_root_pointer(struct btrfs_root *root,
+ struct extent_buffer *new_root_node)
+{
+ int ret;
+ tree_mod_log_free_eb(root->fs_info, root->node);
+ ret = tree_mod_log_insert_root(root->fs_info, root->node,
+ new_root_node, GFP_NOFS);
+ BUG_ON(ret < 0);
+}
+
/*
* check if the tree block can be shared by multiple trees
*/
@@ -2271,7 +2678,6 @@
(unsigned long)btrfs_header_chunk_tree_uuid(split),
BTRFS_UUID_SIZE);
-
copy_extent_buffer(split, c,
btrfs_node_key_ptr_offset(0),
btrfs_node_key_ptr_offset(mid),