linux-kernel - Re: block: Don't invalidate pagecache for invalid falloc modes

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Message-ID: <d5e95ca1-aa20-43da-92f8-3860e744337e@kernel.dk>
Date:   Wed, 11 Oct 2023 14:53:15 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Mike Snitzer <snitzer@...nel.org>
Cc:     Sarthak Kukreti <sarthakkukreti@...omium.org>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        stable@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: block: Don't invalidate pagecache for invalid falloc modes

On 10/11/23 2:50 PM, Mike Snitzer wrote:
> On Wed, Oct 11 2023 at  4:20P -0400,
> Jens Axboe <axboe@...nel.dk> wrote:
> 
>> On 10/11/23 2:12 PM, Sarthak Kukreti wrote:
>>> Only call truncate_bdev_range() if the fallocate mode is
>>> supported. This fixes a bug where data in the pagecache
>>> could be invalidated if the fallocate() was called on the
>>> block device with an invalid mode.
>>
>> Fix looks fine, but would be nicer if we didn't have to duplicate the
>> truncate_bdev_range() in each switch clause. Can we check this upfront
>> instead?
> 
> No, if you look at the function (rather than just the patch in
> isolation) we need to make the call for each case rather than collapse
> to a single call at the front (that's the reason for this fix, because
> otherwise the default: error case will invalidate the page cache too).

Yes that part is clear, but it might look cleaner to check a valid mask
first rather than have 3 duplicate calls.

> Just so you're aware, I also had this feedback that shaped the patch a
> bit back in April:
> https://listman.redhat.com/archives/dm-devel/2023-April/053986.html
> 
>> Also, please wrap commit messages at 72-74 chars.
> 
> Not seeing where the header should be wrapped.  You referring to the
> Fixes: line?  I've never seen those wrapped.

I'm referring to the commit message itself.

-- 
Jens Axboe