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SubjectRe: [PATCH 3.15 093/122] zram: revalidate disk after capacity change
On (07/07/14 16:57), Greg Kroah-Hartman wrote:
> Date: Mon, 7 Jul 2014 16:57:35 -0700
> From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> To: linux-kernel@vger.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
> stable@vger.kernel.org, Minchan Kim <minchan@kernel.org>, "Alexander E.
> Patrakov" <patrakov@gmail.com>, Sergey Senozhatsky
> <sergey.senozhatsky@gmail.com>, Nitin Gupta <ngupta@vflare.org>, Jerome
> Marchand <jmarchan@redhat.com>, Andrew Morton <akpm@linux-foundation.org>,
> Linus Torvalds <torvalds@linux-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@kernel.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@kernel.org>
> Reported-by: Alexander E. Patrakov <patrakov@gmail.com>
> Tested-by: Alexander E. Patrakov <patrakov@gmail.com>
> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Cc: Nitin Gupta <ngupta@vflare.org>
> Acked-by: Jerome Marchand <jmarchan@redhat.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Hello,

this patch is known to cause problems. please see
https://lkml.org/lkml/2014/7/3/885

-ss


> ---
> drivers/block/zram/zram_drv.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -622,8 +622,10 @@ static void zram_reset_device(struct zra
> memset(&zram->stats, 0, sizeof(zram->stats));
>
> zram->disksize = 0;
> - if (reset_capacity)
> + if (reset_capacity) {
> set_capacity(zram->disk, 0);
> + revalidate_disk(zram->disk);
> + }
> up_write(&zram->init_lock);
> }
>
> @@ -664,6 +666,7 @@ static ssize_t disksize_store(struct dev
> zram->comp = comp;
> zram->disksize = disksize;
> set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> + revalidate_disk(zram->disk);
> up_write(&zram->init_lock);
> return len;
>
>
>


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