linux-ext4 - Re: [PATCH] fscrypt: Copy the memcg information to the ciphertext page

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Date:   Thu, 2 Feb 2023 17:07:24 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        stable@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH] fscrypt: Copy the memcg information to the ciphertext
 page

On Thu, Feb 02, 2023 at 11:30:42AM -1000, Tejun Heo wrote:
> > The bug we're discussing here is that when ext4 writes out a pagecache page in
> > an encrypted file, it first encrypts the data into a bounce page, then passes
> > the bounce page (which don't have a memcg) to wbc_account_cgroup_owner().  Maybe
> > the proper fix is to just pass the pagecache page to wbc_account_cgroup_owner()
> > instead?  See below for ext4 (a separate patch would be needed for f2fs):
> 
> Yeah, this makes sense to me and is the right thing to do no matter what.
> wbc_account_cgroup_owner() should be fed the origin page so that the IO can
> be blamed on the owner of that page.

Thanks.  These patches fix this for ext4 and f2fs:

    * https://lore.kernel.org/r/20230203005503.141557-1-ebiggers@kernel.org
    * https://lore.kernel.org/r/20230203010239.216421-1-ebiggers@kernel.org

- Eric