Date:   Fri, 22 Feb 2019 11:15:32 +0500
From:   Roman Mamedov <rm@romanrm.net>
To:     "Martin K. Petersen" <martin.petersen@oracle.com>
Cc:     Jeff Mahoney <jeffm@suse.com>, Keith Busch <keith.busch@intel.com>,
        Ric Wheeler <ricwheeler@gmail.com>,
        Dave Chinner <david@fromorbit.com>,
        lsf-pc@lists.linux-foundation.org,
        linux-xfs <linux-xfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-ext4 <linux-ext4@vger.kernel.org>,
        linux-btrfs <linux-btrfs@vger.kernel.org>,
        linux-block@vger.kernel.org
Subject: Re: [LSF/MM TOPIC] More async operations for file systems - async
 discard?
Message-ID: <20190222111532.4ead81dc@natsu>
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        <20190220234723.GA5999@localhost.localdomain>
        <45c27fea-6d74-2adc-fe9d-e314ce4f3672@suse.com>
        <yq17edsil17.fsf@oracle.com>
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On Thu, 21 Feb 2019 22:01:24 -0500
"Martin K. Petersen" <martin.petersen@oracle.com> wrote:

> Consequently, many of the modern devices that claim to support discard
> to make us software folks happy (or to satisfy a purchase order
> requirements) complete the commands without doing anything at all.
> We're simply wasting queue slots.

Any example of such devices? Let alone "many"? Where you would issue a
full-device blkdiscard, but then just read back old data.

I know only one model(PLEXTOR PX-512M6M) of dozens tested, which is peculiar
that it ignores trim specifically for the 1st sector of the entire disk. But
implying there are "many" which no-op it entirely, seems like imagining the
world already works like you would assume it to.

-- 
With respect,
Roman