linux-kernel - Re: [PATCH 5.10/5.15 1/1] fuse: don't increment nlink in link()

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Message-ID: <CAOssrKddunTkNzY1ydgg-rpi1aTuq-ghgJcVuQOXnK1GH5HCtg@mail.gmail.com>
Date: Mon, 23 Jun 2025 12:21:09 +0200
From: Miklos Szeredi <mszeredi@...hat.com>
To: "d.privalov" <d.privalov@....ru>
Cc: stable@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Marcel Holtmann <marcel@...tmann.org>, Johan Hedberg <johan.hedberg@...il.com>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, linux-bluetooth@...r.kernel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	lvc-project@...uxtesting.org
Subject: Re: [PATCH 5.10/5.15 1/1] fuse: don't increment nlink in link()

On Wed, Jun 18, 2025 at 2:00 PM d.privalov <d.privalov@....ru> wrote:
>
> From: Miklos Szeredi <mszeredi@...hat.com>
>
> commit 97f044f690bac2b094bfb7fb2d177ef946c85880 upstream.
>
> The fuse_iget() call in create_new_entry() already updated the inode with
> all the new attributes and incremented the attribute version.
>
> Incrementing the nlink will result in the wrong count.  This wasn't noticed
> because the attributes were invalidated right after this.
>
> Updating ctime is still needed for the writeback case when the ctime is not
> refreshed.
>
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> Signed-off-by: Dmitriy Privalov <d.privalov@....ru>
> ---
>  fs/fuse/dir.c | 29 ++++++++++-------------------
>  1 file changed, 10 insertions(+), 19 deletions(-)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index 4488a53a192d..7055fdc1b8ce 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -807,7 +807,7 @@ void fuse_flush_time_update(struct inode *inode)
>         mapping_set_error(inode->i_mapping, err);
>  }
>
> -void fuse_update_ctime(struct inode *inode)
> +static void fuse_update_ctime_in_cache(struct inode *inode)
>  {

Backport is wrong.  In the original patch we have

-       fuse_invalidate_attr(inode);

And that line comes from 371e8fd02969 ("fuse: move
fuse_invalidate_attr() into fuse_update_ctime()") in v5.16.

The fix is to not introduce fuse_update_ctime_in_cache(), because
fuse_update_ctime() is already doing that.

Thanks,
Miklos