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bcachefs: Fix locking in btree_node_write_done()

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There was a rare recursive locking bug, in __bch2_btree_node_write()
nowrite path -> btree_node_write_done(), in the path that kicks off
another write.

This splits out an inner __btree_node_write_done() that expects to be
run with the btree node lock held.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-02-26 21:35:16 -05:00 committed by Kent Overstreet
parent 75ef2c59bc
commit 39dcace838
1 changed files with 7 additions and 18 deletions
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25
fs/bcachefs/btree_io.c
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@ -1592,29 +1592,13 @@ void bch2_btree_complete_write(struct bch_fs *c, struct btree *b,
bch2_journal_pin_drop(&c->journal, &w->journal);
}
static void btree_node_write_done(struct bch_fs *c, struct btree *b)
static void __btree_node_write_done(struct bch_fs *c, struct btree *b)
{
struct btree_write *w = btree_prev_write(b);
unsigned long old, new, v;
bch2_btree_complete_write(c, b, w);
v = READ_ONCE(b->flags);
do {
old = new = v;
if (old & (1U << BTREE_NODE_need_write))
goto do_write;
new &= ~(1U << BTREE_NODE_write_in_flight);
new &= ~(1U << BTREE_NODE_write_in_flight_inner);
} while ((v = cmpxchg(&b->flags, old, new)) != old);
wake_up_bit(&b->flags, BTREE_NODE_write_in_flight);
return;
do_write:
six_lock_read(&b->c.lock, NULL, NULL);
v = READ_ONCE(b->flags);
do {
old = new = v;
@ -1637,7 +1621,12 @@ do_write:
if (new & (1U << BTREE_NODE_write_in_flight))
__bch2_btree_node_write(c, b, true);
}
static void btree_node_write_done(struct bch_fs *c, struct btree *b)
{
six_lock_read(&b->c.lock, NULL, NULL);
__btree_node_write_done(c, b);
six_unlock_read(&b->c.lock);
}
@ -1992,7 +1981,7 @@ err:
b->written += sectors_to_write;
nowrite:
btree_bounce_free(c, bytes, used_mempool, data);
btree_node_write_done(c, b);
__btree_node_write_done(c, b);
}
/*