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

[Greg Kroah-Hartman]

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.

thanks,

greg k-h
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