Btrfs: update nodatacow code v2
This patch simplifies the nodatacow checker. If all references
were created after the latest snapshot, then we can avoid COW
safely. This patch also updates run_delalloc_nocow to do more
fine-grained checking.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 535cee47..1eb69a9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -848,9 +848,8 @@
return 0;
}
-static int get_reference_status(struct btrfs_root *root, u64 bytenr,
- u64 parent_gen, u64 ref_objectid,
- u64 *min_generation, u32 *ref_count)
+int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, u64 bytenr)
{
struct btrfs_root *extent_root = root->fs_info->extent_root;
struct btrfs_path *path;
@@ -858,8 +857,8 @@
struct btrfs_extent_ref *ref_item;
struct btrfs_key key;
struct btrfs_key found_key;
- u64 root_objectid = root->root_key.objectid;
- u64 ref_generation;
+ u64 ref_root;
+ u64 last_snapshot;
u32 nritems;
int ret;
@@ -872,7 +871,9 @@
if (ret < 0)
goto out;
BUG_ON(ret == 0);
- if (ret < 0 || path->slots[0] == 0)
+
+ ret = -ENOENT;
+ if (path->slots[0] == 0)
goto out;
path->slots[0]--;
@@ -880,14 +881,10 @@
btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
if (found_key.objectid != bytenr ||
- found_key.type != BTRFS_EXTENT_ITEM_KEY) {
- ret = 1;
+ found_key.type != BTRFS_EXTENT_ITEM_KEY)
goto out;
- }
- *ref_count = 0;
- *min_generation = (u64)-1;
-
+ last_snapshot = btrfs_root_last_snapshot(&root->root_item);
while (1) {
leaf = path->nodes[0];
nritems = btrfs_header_nritems(leaf);
@@ -910,25 +907,16 @@
ref_item = btrfs_item_ptr(leaf, path->slots[0],
struct btrfs_extent_ref);
- ref_generation = btrfs_ref_generation(leaf, ref_item);
- /*
- * For (parent_gen > 0 && parent_gen > ref_generation):
- *
- * we reach here through the oldest root, therefore
- * all other reference from same snapshot should have
- * a larger generation.
- */
- if ((root_objectid != btrfs_ref_root(leaf, ref_item)) ||
- (parent_gen > 0 && parent_gen > ref_generation) ||
- (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID &&
- ref_objectid != btrfs_ref_objectid(leaf, ref_item))) {
- *ref_count = 2;
- break;
+ ref_root = btrfs_ref_root(leaf, ref_item);
+ if (ref_root != root->root_key.objectid &&
+ ref_root != BTRFS_TREE_LOG_OBJECTID) {
+ ret = 1;
+ goto out;
}
-
- *ref_count = 1;
- if (*min_generation > ref_generation)
- *min_generation = ref_generation;
+ if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) {
+ ret = 1;
+ goto out;
+ }
path->slots[0]++;
}
@@ -938,89 +926,6 @@
return ret;
}
-int btrfs_cross_ref_exists(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
- struct btrfs_key *key, u64 bytenr)
-{
- struct btrfs_root *old_root;
- struct btrfs_path *path = NULL;
- struct extent_buffer *eb;
- struct btrfs_file_extent_item *item;
- u64 ref_generation;
- u64 min_generation;
- u64 extent_start;
- u32 ref_count;
- int level;
- int ret;
-
- BUG_ON(trans == NULL);
- BUG_ON(key->type != BTRFS_EXTENT_DATA_KEY);
- ret = get_reference_status(root, bytenr, 0, key->objectid,
- &min_generation, &ref_count);
- if (ret)
- return ret;
-
- if (ref_count != 1)
- return 1;
-
- old_root = root->dirty_root->root;
- ref_generation = old_root->root_key.offset;
-
- /* all references are created in running transaction */
- if (min_generation > ref_generation) {
- ret = 0;
- goto out;
- }
-
- path = btrfs_alloc_path();
- if (!path) {
- ret = -ENOMEM;
- goto out;
- }
-
- path->skip_locking = 1;
- /* if no item found, the extent is referenced by other snapshot */
- ret = btrfs_search_slot(NULL, old_root, key, path, 0, 0);
- if (ret)
- goto out;
-
- eb = path->nodes[0];
- item = btrfs_item_ptr(eb, path->slots[0],
- struct btrfs_file_extent_item);
- if (btrfs_file_extent_type(eb, item) != BTRFS_FILE_EXTENT_REG ||
- btrfs_file_extent_disk_bytenr(eb, item) != bytenr) {
- ret = 1;
- goto out;
- }
-
- for (level = BTRFS_MAX_LEVEL - 1; level >= -1; level--) {
- if (level >= 0) {
- eb = path->nodes[level];
- if (!eb)
- continue;
- extent_start = eb->start;
- } else
- extent_start = bytenr;
-
- ret = get_reference_status(root, extent_start, ref_generation,
- 0, &min_generation, &ref_count);
- if (ret)
- goto out;
-
- if (ref_count != 1) {
- ret = 1;
- goto out;
- }
- if (level >= 0)
- ref_generation = btrfs_header_generation(eb);
- }
- ret = 0;
-out:
- if (path)
- btrfs_free_path(path);
- return ret;
-}
-
int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
struct extent_buffer *buf, u32 nr_extents)
{