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Message-ID: <cedbd75d-4a0f-74fb-3a6e-547862cc431e@redhat.com>
Date:   Tue, 27 Jun 2023 20:04:58 +0200
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Subject: Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local_{page, folio}()
To:     Matthew Wilcox <willy@infradead.org>,
        Sumitra Sharma <sumitraartsy@gmail.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ira Weiny <ira.weiny@intel.com>,
        Fabio <fmdefrancesco@gmail.com>, Deepak R Varma <drv@mailo.com>
References: <20230627135115.GA452832@sumitra.com>
 <ZJsg5GL79MIOzbRf@casper.infradead.org>
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From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <ZJsg5GL79MIOzbRf@casper.infradead.org>
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Hi Matthew,

On 6/27/23 19:48, Matthew Wilcox wrote:
> On Tue, Jun 27, 2023 at 06:51:15AM -0700, Sumitra Sharma wrote:
>> +++ b/fs/vboxsf/file.c
>> @@ -234,7 +234,7 @@ static int vboxsf_read_folio(struct file *file, struct folio *folio)
>>  	u8 *buf;
>>  	int err;
>>  
>> -	buf = kmap(page);
>> +	buf = kmap_local_folio(folio, off);
> 
> Did you test this?  'off' is the offset in the _file_.  Whereas
> kmap_local_folio() takes the offset within the _folio_.  They have
> different types (loff_t vs size_t) to warn you that they're different
> things.


Ah yes you are completely right, off is the offset in the file
and buf should point to the *start* of a mapping of the page.

Regards,

Hans