linux-kernel - Re: zram hot

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Date:   Mon, 26 Jun 2017 11:58:18 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Sami Kerola <kerolasa@....fi>, Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Karel Zak <kzak@...hat.com>,
        util-linux <util-linux@...r.kernel.org>
Subject: Re: zram hot_add device busy

On (06/26/17 11:39), Sergey Senozhatsky wrote:
[..]
> ok... I don't think I see what we can do in zram about the
> issue in question.

... check init_done() in reset_store() and avoid the whole ->bd_openers
branch if the device is already reset?

// not compile tested. just a sketch. //

---

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index debee952dcc1..79b1a957a6bd 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1047,6 +1047,14 @@ static ssize_t reset_store(struct device *dev,
                return -EINVAL;
 
        zram = dev_to_zram(dev);
+
+       down_write(&zram->init_lock);
+       if (!init_done(zram)) {
+               up_write(&zram->init_lock);
+               return len;
+       }
+       up_write(&zram->init_lock);
+
        bdev = bdget_disk(zram->disk, 0);
        if (!bdev)
                return -ENOMEM;

---

	-ss