[PATCH 5.19 046/192] btrfs: zoned: fix API misuse of zone finish waiting

Greg Kroah-Hartman
2022-09-13T14:16:26Z

From: Naohiro Aota <naohiro.aota@wdc.com>

commit d5b81ced74afded85619ffbbe9c32ba9d82c9b1e upstream.

The commit 2ce543f47843 ("btrfs: zoned: wait until zone is finished when
allocation didn't progress") implemented a zone finish waiting mechanism
to the write path of zoned mode. However, using
wait_var_event()/wake_up_all() on fs_info->zone_finish_wait is wrong and
wait_var_event() just hangs because no one ever wakes it up once it goes
into sleep.

Instead, we can simply use wait_on_bit_io() and clear_and_wake_up_bit()
on fs_info->flags with a proper barrier installed.

Fixes: 2ce543f47843 ("btrfs: zoned: wait until zone is finished when allocation didn't progress")
CC: stable@vger.kernel.org # 5.16+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/ctree.h | 2 --
fs/btrfs/disk-io.c | 1 -
fs/btrfs/inode.c | 7 +++----
fs/btrfs/zoned.c | 3 +--
4 files changed, 4 insertions(+), 9 deletions(-)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1065,8 +1065,6 @@ struct btrfs_fs_info {

spinlock_t zone_active_bgs_lock;
struct list_head zone_active_bgs;
- /* Waiters when BTRFS_FS_NEED_ZONE_FINISH is set */
- wait_queue_head_t zone_finish_wait;

#ifdef CONFIG_BTRFS_FS_REF_VERIFY
spinlock_t ref_verify_lock;
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3173,7 +3173,6 @@ void btrfs_init_fs_info(struct btrfs_fs_
init_waitqueue_head(&fs_info->transaction_blocked_wait);
init_waitqueue_head(&fs_info->async_submit_wait);
init_waitqueue_head(&fs_info->delayed_iputs_wait);
- init_waitqueue_head(&fs_info->zone_finish_wait);

/* Usable values until the real ones are cached from the superblock */
fs_info->nodesize = 4096;
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1643,10 +1643,9 @@ static noinline int run_delalloc_zoned(s
done_offset = end;

if (done_offset == start) {
- struct btrfs_fs_info *info = inode->root->fs_info;
-
- wait_var_event(&info->zone_finish_wait,
- !test_bit(BTRFS_FS_NEED_ZONE_FINISH, &info->flags));
+ wait_on_bit_io(&inode->root->fs_info->flags,
+ BTRFS_FS_NEED_ZONE_FINISH,
+ TASK_UNINTERRUPTIBLE);
continue;
}

--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2016,8 +2016,7 @@ static int do_zone_finish(struct btrfs_b
/* For active_bg_list */
btrfs_put_block_group(block_group);

- clear_bit(BTRFS_FS_NEED_ZONE_FINISH, &fs_info->flags);
- wake_up_all(&fs_info->zone_finish_wait);
+ clear_and_wake_up_bit(BTRFS_FS_NEED_ZONE_FINISH, &fs_info->flags);

return 0;
}