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bcachefs: gracefully unwind journal res slowpath on shutdown

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bcachefs detects journal stuck conditions in a couple different
places. If the logic in the journal reservation slow path happens to
detect the problem, I've seen instances where the filesystem remains
deadlocked even though it has been shut down. This is occasionally
reproduced by generic/333, and usually manifests as one or more
tasks stuck in the journal reservation slow path.

To help avoid this problem, repeat the journal error check in
__journal_res_get() once under spinlock to cover the case where the
previous lock holder might have triggered shutdown. This also helps
avoid spurious/duplicate stuck reports. Also, wake the journal from
the halt code to make sure blocked callers of the journal res
slowpath have a chance to wake up and observe the pending error.
This survives an overnight looping run of generic/333 without the
aforementioned lockups.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Brian Foster 2023-03-20 13:21:19 -04:00 committed by Kent Overstreet
parent 873555f04d
commit 23fd4f4dc6
1 changed files with 7 additions and 0 deletions
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7
fs/bcachefs/journal.c
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@ -162,6 +162,7 @@ void bch2_journal_halt(struct journal *j)
__journal_entry_close(j, JOURNAL_ENTRY_ERROR_VAL);
if (!j->err_seq)
j->err_seq = journal_cur_seq(j);
journal_wake(j);
spin_unlock(&j->lock);
}
@ -362,6 +363,12 @@ retry:
spin_lock(&j->lock);
/* check once more in case somebody else shut things down... */
if (bch2_journal_error(j)) {
spin_unlock(&j->lock);
return -BCH_ERR_erofs_journal_err;
}
/*
* Recheck after taking the lock, so we don't race with another thread
* that just did journal_entry_open() and call journal_entry_close()