2023-10-07 07:40:56

by Kemeng Shi

Subject: [PATCH v2] fuse: remove unneeded lock which protecting update of congestion_threshold

Commit 670d21c6e17f6 ("fuse: remove reliance on bdi congestion") change how
congestion_threshold is used and lock in
fuse_conn_congestion_threshold_write is not needed anymore.
1. Access to supe_block is removed along with removing of bdi congestion.
Then down_read(&fc->killsb) which protecting access to super_block is no
needed.
2. Compare num_background and congestion_threshold without holding
bg_lock. Then there is no need to hold bg_lock to update
congestion_threshold.

Signed-off-by: Kemeng Shi <[email protected]>
---
fs/fuse/control.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index ab62e4624256..1bf928e277fe 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -174,11 +174,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
if (!fc)
goto out;

- down_read(&fc->killsb);
- spin_lock(&fc->bg_lock);
- fc->congestion_threshold = val;
- spin_unlock(&fc->bg_lock);
- up_read(&fc->killsb);
+ WRITE_ONCE(fc->congestion_threshold, val);
fuse_conn_put(fc);
out:
return ret;
--
2.30.0

2024-03-06 10:10:19

by Miklos Szeredi

Subject: Re: [PATCH v2] fuse: remove unneeded lock which protecting update of congestion_threshold

On Sat, 7 Oct 2023 at 09:40, Kemeng Shi <[email protected]> wrote:
>
> Commit 670d21c6e17f6 ("fuse: remove reliance on bdi congestion") change how
> congestion_threshold is used and lock in
> fuse_conn_congestion_threshold_write is not needed anymore.
> 1. Access to supe_block is removed along with removing of bdi congestion.
> Then down_read(&fc->killsb) which protecting access to super_block is no
> needed.
> 2. Compare num_background and congestion_threshold without holding
> bg_lock. Then there is no need to hold bg_lock to update
> congestion_threshold.
>
> Signed-off-by: Kemeng Shi <[email protected]>

Applied, thanks.

Miklos