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btrfs: simplify loop in select_reloc_root()

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We have this setup as a loop, but in reality we will never walk back up
the backref tree, if we do then it's a bug.  Get rid of the loop and
handle the case where we have node->new_bytenr set at all.  Previous
check was only if node->new_bytenr != root->node->start, but if it did
then we would hit the WARN_ON() and walk back up the tree.

Instead we want to just return error if ->new_bytenr is set, and then do
the normal updating of the node for the reloc root and carry on.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2024-10-03 11:43:06 -04:00 committed by David Sterba
parent cb7de8ee9c
commit 551d04a32a
1 changed files with 58 additions and 83 deletions
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141
fs/btrfs/relocation.c
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@ -2058,97 +2058,72 @@ struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
int index = 0;
int ret;
next = node;
while (1) {
cond_resched();
next = walk_up_backref(next, edges, &index);
root = next->root;
next = walk_up_backref(node, edges, &index);
root = next->root;
/*
* If there is no root, then our references for this block are
* incomplete, as we should be able to walk all the way up to a
* block that is owned by a root.
*
* This path is only for SHAREABLE roots, so if we come upon a
* non-SHAREABLE root then we have backrefs that resolve
* improperly.
*
* Both of these cases indicate file system corruption, or a bug
* in the backref walking code.
*/
if (!root) {
ASSERT(0);
btrfs_err(trans->fs_info,
"bytenr %llu doesn't have a backref path ending in a root",
node->bytenr);
return ERR_PTR(-EUCLEAN);
}
if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) {
ASSERT(0);
btrfs_err(trans->fs_info,
"bytenr %llu has multiple refs with one ending in a non-shareable root",
node->bytenr);
return ERR_PTR(-EUCLEAN);
}
/*
* If there is no root, then our references for this block are
* incomplete, as we should be able to walk all the way up to a block
* that is owned by a root.
*
* This path is only for SHAREABLE roots, so if we come upon a
* non-SHAREABLE root then we have backrefs that resolve improperly.
*
* Both of these cases indicate file system corruption, or a bug in the
* backref walking code.
*/
if (unlikely(!root)) {
btrfs_err(trans->fs_info,
"bytenr %llu doesn't have a backref path ending in a root",
node->bytenr);
return ERR_PTR(-EUCLEAN);
}
if (unlikely(!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))) {
btrfs_err(trans->fs_info,
"bytenr %llu has multiple refs with one ending in a non-shareable root",
node->bytenr);
return ERR_PTR(-EUCLEAN);
}
if (btrfs_root_id(root) == BTRFS_TREE_RELOC_OBJECTID) {
ret = record_reloc_root_in_trans(trans, root);
if (ret)
return ERR_PTR(ret);
break;
}
ret = btrfs_record_root_in_trans(trans, root);
if (btrfs_root_id(root) == BTRFS_TREE_RELOC_OBJECTID) {
ret = record_reloc_root_in_trans(trans, root);
if (ret)
return ERR_PTR(ret);
root = root->reloc_root;
/*
* We could have raced with another thread which failed, so
* root->reloc_root may not be set, return ENOENT in this case.
*/
if (!root)
return ERR_PTR(-ENOENT);
if (next->new_bytenr != root->node->start) {
/*
* We just created the reloc root, so we shouldn't have
* ->new_bytenr set yet. If it is then we have multiple
* roots pointing at the same bytenr which indicates
* corruption, or we've made a mistake in the backref
* walking code.
*/
ASSERT(next->new_bytenr == 0);
if (next->new_bytenr) {
btrfs_err(trans->fs_info,
"bytenr %llu possibly has multiple roots pointing at the same bytenr %llu",
node->bytenr, next->bytenr);
return ERR_PTR(-EUCLEAN);
}
next->new_bytenr = root->node->start;
btrfs_put_root(next->root);
next->root = btrfs_grab_root(root);
ASSERT(next->root);
mark_block_processed(rc, next);
break;
}
WARN_ON(1);
root = NULL;
next = walk_down_backref(edges, &index);
if (!next || next->level <= node->level)
break;
goto found;
}
if (!root) {
/*
* This can happen if there's fs corruption or if there's a bug
* in the backref lookup code.
*/
ASSERT(0);
ret = btrfs_record_root_in_trans(trans, root);
if (ret)
return ERR_PTR(ret);
root = root->reloc_root;
/*
* We could have raced with another thread which failed, so
* root->reloc_root may not be set, return ENOENT in this case.
*/
if (!root)
return ERR_PTR(-ENOENT);
if (next->new_bytenr) {
/*
* We just created the reloc root, so we shouldn't have
* ->new_bytenr set yet. If it is then we have multiple roots
* pointing at the same bytenr which indicates corruption, or
* we've made a mistake in the backref walking code.
*/
ASSERT(next->new_bytenr == 0);
btrfs_err(trans->fs_info,
"bytenr %llu possibly has multiple roots pointing at the same bytenr %llu",
node->bytenr, next->bytenr);
return ERR_PTR(-EUCLEAN);
}
next->new_bytenr = root->node->start;
btrfs_put_root(next->root);
next->root = btrfs_grab_root(root);
ASSERT(next->root);
mark_block_processed(rc, next);
found:
next = node;
/* setup backref node path for btrfs_reloc_cow_block */
while (1) {