linux-kernel - Re: [PATCH 3.15 093/122] zram: revalidate disk after capacity change

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Message-ID: <20140709053957.GD9824@bbox>
Date:	Wed, 9 Jul 2014 14:39:57 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Sasha Levin <sasha.levin@...cle.com>,
	"Alexander E. Patrakov" <patrakov@...il.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3.15 093/122] zram: revalidate disk after capacity change

Hello Greg,

On Tue, Jul 08, 2014 at 08:02:26AM -0700, Greg Kroah-Hartman wrote:
> On Tue, Jul 08, 2014 at 07:56:17PM +0900, Sergey Senozhatsky wrote:
> > On (07/07/14 16:57), Greg Kroah-Hartman wrote:
> > > Date: Mon,  7 Jul 2014 16:57:35 -0700
> > > From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > To: linux-kernel@...r.kernel.org
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
> > >  stable@...r.kernel.org, Minchan Kim <minchan@...nel.org>, "Alexander E.
> > >  Patrakov" <patrakov@...il.com>, Sergey Senozhatsky
> > >  <sergey.senozhatsky@...il.com>, Nitin Gupta <ngupta@...are.org>, Jerome
> > >  Marchand <jmarchan@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>,
> > >  Linus Torvalds <torvalds@...ux-foundation.org>
> > > Subject: [PATCH 3.15 093/122] zram: revalidate disk after capacity change
> > > X-Mailer: git-send-email 2.0.0.254.g50f84e3
> > > User-Agent: quilt/0.63-1
> > > 
> > > 3.15-stable review patch.  If anyone has any objections, please let me know.
> > > 
> > > ------------------
> > > 
> > > From: Minchan Kim <minchan@...nel.org>
> > > 
> > > commit 2e32baea46ce542c561a519414c840295b229c8f upstream.
> > > 
> > > Alexander reported mkswap on /dev/zram0 is failed if other process is
> > > opening the block device file.
> > > 
> > > Step is as follows,
> > > 
> > > 0. Reset the unused zram device.
> > > 1. Use a program that opens /dev/zram0 with O_RDWR and sleeps
> > >    until killed.
> > > 2. While that program sleeps, echo the correct value to
> > >    /sys/block/zram0/disksize.
> > > 3. Verify (e.g. in /proc/partitions) that the disk size is applied
> > >    correctly. It is.
> > > 4. While that program still sleeps, attempt to mkswap /dev/zram0.
> > >    This fails: mkswap: error: swap area needs to be at least 40 KiB
> > > 
> > > When I investigated, the size get by ioctl(fd, BLKGETSIZE64, xxx) on
> > > mkswap to get a size of blockdev was zero although zram0 has right size by
> > > 2.
> > > 
> > > The reason is zram didn't revalidate disk after changing capacity so that
> > > size of blockdev's inode is not uptodate until all of file is close.
> > > 
> > > This patch should fix the BUG.
> > > 
> > > Signed-off-by: Minchan Kim <minchan@...nel.org>
> > > Reported-by: Alexander E. Patrakov <patrakov@...il.com>
> > > Tested-by: Alexander E. Patrakov <patrakov@...il.com>
> > > Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> > > Cc: Nitin Gupta <ngupta@...are.org>
> > > Acked-by: Jerome Marchand <jmarchan@...hat.com>
> > > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > > Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > Hello,
> > 
> > this patch is known to cause problems. please see
> > https://lkml.org/lkml/2014/7/3/885
> 
> Did the fix ever get merged to Linus's tree?  If not, why not?  I'd
> rather just take that fix as well.

Not yet.
Because Andrew picked his tree(ie, mmotm) today.

> 
> thanks,
> 
> greg k-h
> --
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-- 
Kind regards,
Minchan Kim
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