diff options
| author | Kent Overstreet <kent.overstreet@gmail.com> | 2022-02-27 09:56:33 -0500 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-10-22 17:09:26 -0400 |
| commit | bf3efff5e4fc2dcd6e6c15578d3f08c301a13229 (patch) | |
| tree | cca40f2591a81ba52e14350a663266b83c78e43f /fs/bcachefs/btree_io.c | |
| parent | 6f5f747c318be4adf3824ee7716a7886da35f9a3 (diff) | |
| download | lwn-bf3efff5e4fc2dcd6e6c15578d3f08c301a13229.tar.gz lwn-bf3efff5e4fc2dcd6e6c15578d3f08c301a13229.zip | |
bcachefs: Fix race leading to btree node write getting stuck
Checking btree_node_may_write() isn't atomic with the other btree flags,
dirty and need_write in particular. There was a rare race where we'd
unblock a node from writing while __btree_node_flush() was setting
need_write, and no thread would notice that the node was now both able
to write and needed to be written.
Fix this by adding btree node flags for will_make_reachable and
write_blocked that can be checked in the cmpxchg loop in
__bch2_btree_node_write.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Diffstat (limited to 'fs/bcachefs/btree_io.c')
| -rw-r--r-- | fs/bcachefs/btree_io.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/bcachefs/btree_io.c b/fs/bcachefs/btree_io.c index 540bfe07c128..53f83340f69a 100644 --- a/fs/bcachefs/btree_io.c +++ b/fs/bcachefs/btree_io.c @@ -1606,7 +1606,8 @@ static void __btree_node_write_done(struct bch_fs *c, struct btree *b) if ((old & (1U << BTREE_NODE_dirty)) && (old & (1U << BTREE_NODE_need_write)) && !(old & (1U << BTREE_NODE_never_write)) && - btree_node_may_write(b)) { + !(old & (1U << BTREE_NODE_write_blocked)) && + !(old & (1U << BTREE_NODE_will_make_reachable))) { new &= ~(1U << BTREE_NODE_dirty); new &= ~(1U << BTREE_NODE_need_write); new |= (1U << BTREE_NODE_write_in_flight); @@ -1778,10 +1779,13 @@ void __bch2_btree_node_write(struct bch_fs *c, struct btree *b, unsigned flags) !(old & (1 << BTREE_NODE_need_write))) return; - if (!btree_node_may_write(b)) + if (old & + ((1 << BTREE_NODE_never_write)| + (1 << BTREE_NODE_write_blocked))) return; - if (old & (1 << BTREE_NODE_never_write)) + if (b->written && + (old & (1 << BTREE_NODE_will_make_reachable))) return; if (old & (1 << BTREE_NODE_write_in_flight)) |