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Btrfs: update nodatacow code v2

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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>
This commit is contained in:
Yan Zheng
2008-10-30 14:20:02 -04:00
committed by Chris Mason
parent 6643558db2
commit 80ff385665
7 changed files with 154 additions and 213 deletions
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fs/btrfs/extent-tree.c
+18 -113
View File
@@ -848,9 +848,8 @@ out:
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 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
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 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
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 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
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 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
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;
}
if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) {
ret = 1;
goto out;
}
*ref_count = 1;
if (*min_generation > ref_generation)
*min_generation = ref_generation;
path->slots[0]++;
}
@@ -938,89 +926,6 @@ out:
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)
{