linux-kernel - Re: [PATCH 2/2] loop: Better discard support for block devices

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Message-ID: <CACVXFVN63UDefvBnYTQ==tWwYqGJbCS_HK==-1jVa5sVc=-Upw@mail.gmail.com>
Date:   Tue, 27 Nov 2018 10:55:20 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     evgreen@...omium.org
Cc:     Jens Axboe <axboe@...nel.dk>, gwendal@...omium.org,
        asavery@...omium.org, linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] loop: Better discard support for block devices

On Tue, Nov 27, 2018 at 2:55 AM Evan Green <evgreen@...omium.org> wrote:
>
> On Tue, Oct 30, 2018 at 4:06 PM Evan Green <evgreen@...omium.org> wrote:
> >
> > If the backing device for a loop device is a block device,

This shouldn't be a very common use case wrt. loop.

> > then mirror the discard properties of the underlying block
> > device into the loop device. While in there, differentiate
> > between REQ_OP_DISCARD and REQ_OP_WRITE_ZEROES, which are
> > different for block devices, but which the loop device had
> > just been lumping together.
> >
> > Signed-off-by: Evan Green <evgreen@...omium.org>
>
> Any thoughts on this patch? This fixes issues for us when using a loop
> device backed by a block device, where we see many logs like:
>
> [  372.767286] print_req_error: I/O error, dev loop5, sector 88125696

Seems not see any explanation about this IO error and the fix in your patch.
Could you describe it a bit more?


thanks,
Ming Lei