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btrfsck: remove extents from the fsck reference tracker as they are freed 

During btrfsck --repair, we make an index of extents that have incorrect
reference counts.  Once we've collect the whole index, we go through
and modify the extent allocation tree to reflect the correct results.

Changing the extent allocation tree may free blocks, and so it may
end up removing a block that had a missing reference structure.  The
fsck code may then circle back around and add the reference back.

The result is an extent that isn't actually used, but is recorded in the
extent allocation tree.

This commit adds a hook called as extents are freed.  The hook searches
the index of incorrect references and updates it to reflect the freeing
of the extent.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2012-02-10 13:28:50 -05:00
parent ae1822f73f
commit 62b7993154
3 changed files with 99 additions and 7 deletions
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94
btrfsck.c
View File

@ -2137,7 +2137,7 @@ static int add_extent_rec(struct cache_tree *extent_cache,
if (inc_ref)
rec->refs++;
if (rec->nr == 1)
rec->nr = nr;
rec->nr = max(nr, max_size);
if (start != rec->start) {
fprintf(stderr, "warning, start mismatch %llu %llu\n",
@ -2175,7 +2175,7 @@ static int add_extent_rec(struct cache_tree *extent_cache,
rec = malloc(sizeof(*rec));
rec->start = start;
rec->max_size = max_size;
rec->nr = nr;
rec->nr = max(nr, max_size);
rec->content_checked = 0;
rec->owner_ref_checked = 0;
INIT_LIST_HEAD(&rec->backrefs);
@ -2722,6 +2722,77 @@ static int add_root_to_pending(struct extent_buffer *buf,
return 0;
}
/* as we fix the tree, we might be deleting blocks that
* we're tracking for repair. This hook makes sure we
* remove any backrefs for blocks as we are fixing them.
*/
static int free_extent_hook(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
u64 bytenr, u64 num_bytes, u64 parent,
u64 root_objectid, u64 owner, u64 offset,
int refs_to_drop)
{
struct extent_record *rec;
struct cache_extent *cache;
int is_data;
struct cache_tree *extent_cache = root->fs_info->fsck_extent_cache;
is_data = owner >= BTRFS_FIRST_FREE_OBJECTID;
cache = find_cache_extent(extent_cache, bytenr, num_bytes);
if (!cache)
return 0;
rec = container_of(cache, struct extent_record, cache);
if (is_data) {
struct data_backref *back;
back = find_data_backref(rec, parent, root_objectid, owner,
offset);
if (!back)
goto out;
if (back->node.found_ref) {
back->found_ref -= refs_to_drop;
if (rec->refs)
rec->refs -= refs_to_drop;
}
if (back->node.found_extent_tree) {
back->num_refs -= refs_to_drop;
if (rec->extent_item_refs)
rec->extent_item_refs -= refs_to_drop;
}
if (back->found_ref == 0)
back->node.found_ref = 0;
if (back->num_refs == 0)
back->node.found_extent_tree = 0;
if (!back->node.found_extent_tree && back->node.found_ref) {
list_del(&back->node.list);
free(back);
}
} else {
struct tree_backref *back;
back = find_tree_backref(rec, parent, root_objectid);
if (!back)
goto out;
if (back->node.found_ref) {
if (rec->refs)
rec->refs--;
back->node.found_ref = 0;
}
if (back->node.found_extent_tree) {
if (rec->extent_item_refs)
rec->extent_item_refs--;
back->node.found_extent_tree = 0;
}
if (!back->node.found_extent_tree && back->node.found_ref) {
list_del(&back->node.list);
free(back);
}
}
maybe_free_extent_rec(extent_cache, rec);
out:
return 0;
}
static int delete_extent_records(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path,
@ -3008,7 +3079,7 @@ static int check_extent_refs(struct btrfs_trans_handle *trans,
while(cache) {
rec = container_of(cache, struct extent_record, cache);
btrfs_pin_extent(root->fs_info,
rec->start, rec->nr);
rec->start, rec->max_size);
cache = next_cache_extent(cache);
}
}
@ -3105,6 +3176,11 @@ static int check_extents(struct btrfs_trans_handle *trans,
cache_tree_init(&nodes);
cache_tree_init(&reada);
if (repair) {
root->fs_info->fsck_extent_cache = &extent_cache;
root->fs_info->free_extent_hook = free_extent_hook;
}
bits_nr = 1024;
bits = malloc(bits_nr * sizeof(struct block_info));
if (!bits) {
@ -3163,6 +3239,12 @@ static int check_extents(struct btrfs_trans_handle *trans,
break;
}
ret = check_extent_refs(trans, root, &extent_cache, repair);
if (repair) {
root->fs_info->fsck_extent_cache = NULL;
root->fs_info->free_extent_hook = NULL;
}
return ret;
}
@ -3267,10 +3349,8 @@ int main(int ac, char **av)
}
ret = check_extents(trans, root, repair);
if (ret) {
fprintf(stderr, "check extents failed with %d!!!!!!!!!\n", ret);
goto out;
}
if (ret)
fprintf(stderr, "Errors found in extent allocation tree\n");
fprintf(stderr, "checking fs roots\n");
ret = check_fs_roots(root, &root_cache);

6
ctree.h
View File

@ -797,6 +797,12 @@ struct btrfs_fs_info {
struct list_head space_info;
int system_allocs;
int readonly;
int (*free_extent_hook)(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
u64 bytenr, u64 num_bytes, u64 parent,
u64 root_objectid, u64 owner, u64 offset,
int refs_to_drop);
struct cache_tree * fsck_extent_cache;
};
/*

6
extent-tree.c
View File

@ -2083,6 +2083,12 @@ static int __free_extent(struct btrfs_trans_handle *trans,
u32 item_size;
u64 refs;
if (root->fs_info->free_extent_hook) {
root->fs_info->free_extent_hook(trans, root, bytenr, num_bytes,
parent, root_objectid, owner_objectid,
owner_offset, refs_to_drop);
}
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;