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bcachefs: Add an assertion for using multiple btree_trans

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A thread should never be using more than one btree_trans - doing so is
an invitation for deadlocks.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-02-17 20:51:52 -05:00
parent 2c7dd446d9
commit 6623c0fcdf
1 changed files with 9 additions and 0 deletions
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9
fs/bcachefs/btree_iter.c
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@ -2955,6 +2955,15 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
mutex_lock(&c->btree_trans_lock);
list_for_each_entry(pos, &c->btree_trans_list, list) {
/*
* We'd much prefer to be stricter here and completely
* disallow multiple btree_trans in the same thread -
* but the data move path calls bch2_write when we
* already have a btree_trans initialized.
*/
BUG_ON(trans->locking_wait.task->pid == pos->locking_wait.task->pid &&
bch2_trans_locked(pos));
if (trans->locking_wait.task->pid < pos->locking_wait.task->pid) {
list_add_tail(&trans->list, &pos->list);
goto list_add_done;