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Date:   Tue, 8 Nov 2022 20:03:37 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Lukas Czerner <lczerner@redhat.com>
Cc:     Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.com>,
        Eric Sandeen <sandeen@redhat.com>, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/2] shmem: implement user/group quota support for tmpfs
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References: <20221108133010.75226-1-lczerner@redhat.com>
 <20221108133010.75226-2-lczerner@redhat.com>
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On Tue, Nov 08, 2022 at 02:30:09PM +0100, Lukas Czerner wrote:
> +	err = shmem_get_folio(inode, index, &folio, SGP_WRITE);
> +	if (err)
> +		return err;
> +
> +	page = folio_file_page(folio, index);
> +	if (PageHWPoison(page)) {
> +		folio_unlock(folio);
> +		folio_put(folio);
> +		return -EIO;
> +	}
> +
> +	/* Write data, or zeroout the portion of the page */
> +	if (data)
> +		memcpy(page_address(page) + offset, data, len);
> +	else
> +		memset(page_address(page) + offset, 0, len);
> +
> +	SetPageUptodate(page);

This is suspicious.  There is no per-page Uptodate bit, there is only a
per-folio Uptodate bit.  So this should be folio_mark_uptodate().
Except that you've only done one of the pages in the folio, so you
have no business setting the uptodate bit at all.