Josef Bacik wrote on 2016/04/29 09:52 -0400:
On 04/29/2016 01:31 AM, Qu Wenruo wrote:
Josef Bacik wrote on 2016/04/28 10:17 -0400:
On 04/25/2016 11:48 PM, Qu Wenruo wrote:
From: Lu Fengqi <lufq.fnst@xxxxxxxxxxxxxx>
Introduce a new function check_tree_block_backref() to check if a
backref points to correct referencer.
Signed-off-by: Lu Fengqi <lufq.fnst@xxxxxxxxxxxxxx>
Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
cmds-check.c | 95
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 95 insertions(+)
diff --git a/cmds-check.c b/cmds-check.c
index 6633b6e..81dd4f3 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -323,6 +323,8 @@ struct root_item_info {
#define MISSING_BACKREF (1 << 0) /* Completely no backref in
extent tree */
#define BAD_BACKREF (1 << 1) /* Backref mismatch */
#define UNALIGNED_BYTES (1 << 2) /* Some bytes are not aligned */
+#define MISSING_REFERENCER (1 << 3) /* Referencer not found */
+#define BAD_REFERENCER (1 << 4) /* Referencer found, but not
mismatch */
static void *print_status_check(void *p)
{
@@ -8736,6 +8738,99 @@ out:
return ret;
}
+/*
+ * Check if a tree block backref is valid (points to valid tree block)
+ * if level == -1, level will be resolved
+ */
+static int check_tree_block_backref(struct btrfs_fs_info *fs_info,
u64 root_id,
+ u64 bytenr, int level)
+{
+ struct btrfs_root *root;
+ struct btrfs_key key;
+ struct btrfs_path path;
+ struct extent_buffer *eb;
+ struct extent_buffer *node;
+ u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+ int err = 0;
+ int ret;
+
+ /* Query level for level == -1 special case */
+ if (level == -1)
+ level = query_tree_block_level(fs_info, bytenr);
+ if (level < 0) {
+ err = MISSING_REFERENCER;
+ goto out;
+ }
+
+ key.objectid = root_id;
+ key.type = BTRFS_ROOT_ITEM_KEY;
+ key.offset = (u64)-1;
+
+ root = btrfs_read_fs_root(fs_info, &key);
+ if (IS_ERR(root)) {
+ err |= MISSING_REFERENCER;
+ goto out;
+ }
+
+ /* Read out the tree block to get item/node key */
+ eb = read_tree_block(root, bytenr, root->nodesize, 0);
+ /* Impossible, as tree block query has read out the tree block */
+ if (!extent_buffer_uptodate(eb)) {
+ err |= MISSING_REFERENCER;
+ free_extent_buffer(eb);
+ goto out;
+ }
+
+ /* Empty tree, no need to check key */
+ if (!btrfs_header_nritems(eb) && !level) {
+ free_extent_buffer(eb);
+ goto out;
+ }
Actually this is interesting, because we don't actually catch where we
would have btrfs_header_nritems(eb) == 0 and !level. So maybe integrate
that check into check_block, to make sure we have items in node level
extent buffers. Thanks,
Josef
Unfortunately, we can't integrate it into check_tree_block() (or caller
read_tree_block() and its variants).
As this is a valid case.
(And that's why we don't report error here)
For trees like csum tree and uuid tree, they can be empty, and it
doesn't break any thing.
So it's a not something we need to integrate into check_tree_block().
And if you mean check_block() in old fsck codes, we won't use it in new
fsck, so still not a big problem.
But empty trees the root is still level 0, we shouldn't have a node that
is empty, it should just be removed, right? Thanks,
Josef
Oh, You mean any tree level higher than 0 shouldn't have nritems == 0.
That makes sense, I'll send a independent patch for that.
Thanks,
Qu
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