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bcachefs: Fix missing commit in backpointer to missing target

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Fsck wants to do transaction commits from an outer context; it may have
other repair to do (i.e. duplicate backpointers).

But when calling backpointer_not_found() from runtime code, i.e. runtime
self healing, we should be doing the commit - the outer context expects
to just be doing lookups.

This fixes bugs where we get stuck spinning, reported as "RCU lock hold
time warnings.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet
2025-05-09 15:05:19 -04:00
parent a12cb6f758
commit d1041d8eab
1 changed files with 79 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/bcachefs/backpointers.c
+79 -38
View File
@@ -192,7 +192,8 @@ static inline int bch2_backpointers_maybe_flush(struct btree_trans *trans,
static int backpointer_target_not_found(struct btree_trans *trans,
struct bkey_s_c_backpointer bp,
struct bkey_s_c target_k,
struct bkey_buf *last_flushed)
struct bkey_buf *last_flushed,
bool commit)
{
struct bch_fs *c = trans->c;
struct printbuf buf = PRINTBUF;
@@ -228,18 +229,77 @@ static int backpointer_target_not_found(struct btree_trans *trans,
}
if (fsck_err(trans, backpointer_to_missing_ptr,
"%s", buf.buf))
"%s", buf.buf)) {
ret = bch2_backpointer_del(trans, bp.k->p);
if (ret || !commit)
goto out;
/*
* Normally, on transaction commit from inside a transaction,
* we'll return -BCH_ERR_transaction_restart_nested, since a
* transaction commit invalidates pointers given out by peek().
*
* However, since we're updating a write buffer btree, if we
* return a transaction restart and loop we won't see that the
* backpointer has been deleted without an additional write
* buffer flush - and those are expensive.
*
* So we're relying on the caller immediately advancing to the
* next backpointer and starting a new transaction immediately
* after backpointer_get_key() returns NULL:
*/
ret = bch2_trans_commit(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc);
}
out:
fsck_err:
printbuf_exit(&buf);
return ret;
}
struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
struct bkey_s_c_backpointer bp,
struct btree_iter *iter,
unsigned iter_flags,
struct bkey_buf *last_flushed)
static struct btree *__bch2_backpointer_get_node(struct btree_trans *trans,
struct bkey_s_c_backpointer bp,
struct btree_iter *iter,
struct bkey_buf *last_flushed,
bool commit)
{
struct bch_fs *c = trans->c;
BUG_ON(!bp.v->level);
bch2_trans_node_iter_init(trans, iter,
bp.v->btree_id,
bp.v->pos,
0,
bp.v->level - 1,
0);
struct btree *b = bch2_btree_iter_peek_node(trans, iter);
if (IS_ERR_OR_NULL(b))
goto err;
BUG_ON(b->c.level != bp.v->level - 1);
if (extent_matches_bp(c, bp.v->btree_id, bp.v->level,
bkey_i_to_s_c(&b->key), bp))
return b;
if (btree_node_will_make_reachable(b)) {
b = ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node);
} else {
int ret = backpointer_target_not_found(trans, bp, bkey_i_to_s_c(&b->key),
last_flushed, commit);
b = ret ? ERR_PTR(ret) : NULL;
}
err:
bch2_trans_iter_exit(trans, iter);
return b;
}
static struct bkey_s_c __bch2_backpointer_get_key(struct btree_trans *trans,
struct bkey_s_c_backpointer bp,
struct btree_iter *iter,
unsigned iter_flags,
struct bkey_buf *last_flushed,
bool commit)
{
struct bch_fs *c = trans->c;
@@ -277,10 +337,10 @@ struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
bch2_trans_iter_exit(trans, iter);
if (!bp.v->level) {
int ret = backpointer_target_not_found(trans, bp, k, last_flushed);
int ret = backpointer_target_not_found(trans, bp, k, last_flushed, commit);
return ret ? bkey_s_c_err(ret) : bkey_s_c_null;
} else {
struct btree *b = bch2_backpointer_get_node(trans, bp, iter, last_flushed);
struct btree *b = __bch2_backpointer_get_node(trans, bp, iter, last_flushed, commit);
if (b == ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node))
return bkey_s_c_null;
if (IS_ERR_OR_NULL(b))
@@ -295,35 +355,16 @@ struct btree *bch2_backpointer_get_node(struct btree_trans *trans,
struct btree_iter *iter,
struct bkey_buf *last_flushed)
{
struct bch_fs *c = trans->c;
return __bch2_backpointer_get_node(trans, bp, iter, last_flushed, true);
}
BUG_ON(!bp.v->level);
bch2_trans_node_iter_init(trans, iter,
bp.v->btree_id,
bp.v->pos,
0,
bp.v->level - 1,
0);
struct btree *b = bch2_btree_iter_peek_node(trans, iter);
if (IS_ERR_OR_NULL(b))
goto err;
BUG_ON(b->c.level != bp.v->level - 1);
if (extent_matches_bp(c, bp.v->btree_id, bp.v->level,
bkey_i_to_s_c(&b->key), bp))
return b;
if (btree_node_will_make_reachable(b)) {
b = ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node);
} else {
int ret = backpointer_target_not_found(trans, bp, bkey_i_to_s_c(&b->key), last_flushed);
b = ret ? ERR_PTR(ret) : NULL;
}
err:
bch2_trans_iter_exit(trans, iter);
return b;
struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
struct bkey_s_c_backpointer bp,
struct btree_iter *iter,
unsigned iter_flags,
struct bkey_buf *last_flushed)
{
return __bch2_backpointer_get_key(trans, bp, iter, iter_flags, last_flushed, true);
}
static int bch2_check_backpointer_has_valid_bucket(struct btree_trans *trans, struct bkey_s_c k,
@@ -521,7 +562,7 @@ check_existing_bp:
struct bkey_s_c_backpointer other_bp = bkey_s_c_to_backpointer(bp_k);
struct bkey_s_c other_extent =
bch2_backpointer_get_key(trans, other_bp, &other_extent_iter, 0, NULL);
__bch2_backpointer_get_key(trans, other_bp, &other_extent_iter, 0, NULL, false);
ret = bkey_err(other_extent);
if (ret == -BCH_ERR_backpointer_to_overwritten_btree_node)
ret = 0;