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From: Amir Goldstein <amir73il@gmail.com>
To: Chengguang Xu <cgxu519@mykernel.net>, Miklos Szeredi <miklos@szeredi.hu>
Cc: overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH] ovl: fix incorrect extent info in metacopy case
Date: Thu, 25 Jun 2020 11:35:17 +0300
Message-ID: <CAOQ4uxh9gzdRJp4g1yjQy9nDMASdsdvkzBGhGL2_+3rOBJZFAw@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxi53CzBwXxygKMhDDSaGpX0CcfV6jiaKRFVbrFHW7PbxA@mail.gmail.com>

On Wed, Jun 24, 2020 at 3:53 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Wed, Jun 24, 2020 at 1:23 PM Chengguang Xu <cgxu519@mykernel.net> wrote:
> >
> > In metacopy case, we should use ovl_inode_realdata() instead of
> > ovl_inode_real() to get real inode which has data, so that
> > we can get correct information of extentes in ->fiemap operation.
> >
> > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
>
> looks right

Miklos,

Not related to this patch, I noticed something that could be odd with
ovl_fiemap().

When passed the flag FIEMAP_FLAG_SYNC, ->fiemap() will trigger writeback
of lower inode pages.

This behavior is border line for overlayfs.
I did not check if filemap_write_and_wait() ends up being a noop on read-only
fs or if it can return an error.
Following ovl_fsync() practice, we may want to silently drop the
FIEMAP_FLAG_SYNC flag? but that could result in unexpected results.

Am I overthinking this?

Thanks,
Amir.

  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 10:20 Chengguang Xu
2020-06-24 12:53 ` Amir Goldstein
2020-06-25  8:35   ` Amir Goldstein [this message]
2020-06-25  9:46     ` cgxu

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