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

[Minchan Kim]

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@xxxxxxxxxxxxxxxxxxx>
> > > To: linux-kernel@xxxxxxxxxxxxxxx
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>,
> > >  stable@xxxxxxxxxxxxxxx, Minchan Kim <minchan@xxxxxxxxxx>, "Alexander E.
> > >  Patrakov" <patrakov@xxxxxxxxx>, Sergey Senozhatsky
> > >  <sergey.senozhatsky@xxxxxxxxx>, Nitin Gupta <ngupta@xxxxxxxxxx>, Jerome
> > >  Marchand <jmarchan@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>,
> > >  Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > 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@xxxxxxxxxx>
> > > 
> > > 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@xxxxxxxxxx>
> > > Reported-by: Alexander E. Patrakov <patrakov@xxxxxxxxx>
> > > Tested-by: Alexander E. Patrakov <patrakov@xxxxxxxxx>
> > > Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> > > Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
> > > Acked-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
> > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > 
> > 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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