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From: Miklos Szeredi <miklos@szeredi.hu>
To: Chengguang Xu <cgxu519@mykernel.net>
Cc: overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate
Date: Tue, 20 Jul 2021 16:35:14 +0200	[thread overview]
Message-ID: <CAJfpegsT3PaVggkcx+OdoxOCR2hWYeLs1rTr_p3nNMimnknCug@mail.gmail.com> (raw)
In-Reply-To: <20210424140316.485444-1-cgxu519@mykernel.net>

On Sat, 24 Apr 2021 at 16:04, Chengguang Xu <cgxu519@mykernel.net> wrote:
>
> Lower files may be shared in overlayfs so strictly checking write
> perssmion on lower file will cause interferes between different
> overlayfs instances.

How so?

i_writecount on lower inode is not modified by overlayfs (at least not
in this codepath).  Which means that there should be no interference
between overlayfs instances sharing a lower directory tree.

Thanks,
Miklos



>
> Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
> ---
>  fs/overlayfs/inode.c | 6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 28c71978eb2e..17d1add0af1a 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -31,12 +31,6 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>                 goto out;
>
>         if (attr->ia_valid & ATTR_SIZE) {
> -               struct inode *realinode = d_inode(ovl_dentry_real(dentry));
> -
> -               err = -ETXTBSY;
> -               if (atomic_read(&realinode->i_writecount) < 0)
> -                       goto out_drop_write;
> -
>                 /* Truncate should trigger data copy up as well */
>                 full_copy_up = true;
>         }
> --
> 2.27.0
>
>

  parent reply	other threads:[~2021-07-20 14:54 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-24 14:03 Chengguang Xu
2021-04-24 14:03 ` [RFC PATCH 2/2] ovl: enhance write permission check for writable open Chengguang Xu
2021-07-21 13:14   ` Miklos Szeredi
2021-04-28 12:18 ` 回复:[RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-07-20 14:35 ` Miklos Szeredi [this message]
2021-07-20 15:19   ` [RFC " Miklos Szeredi
2021-07-20 16:01     ` Chengguang Xu
2021-07-20 16:01     ` Miklos Szeredi
2021-07-20 16:04       ` Chengguang Xu

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