linux-kernel - Re: [PATCHv2 00/10] cleaned up on-demand device creation

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Date:	Fri, 17 Apr 2015 08:23:29 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCHv2 00/10] cleaned up on-demand device creation

Hello,

On Thu, Apr 16, 2015 at 08:55:46PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> resending on-demand device creation patch set. sadly, I managed to create a
> mess; so here is my take to clean it up, fold patches and, hopefully, see
> them in 4.1.

Thanks for handling this quickly. I acknowlege dynamic device management part
but I want to review your patchset carefully one more time because you changed
a lot although it's just refactoring. Really sorry for late review. It's totally
my bad. Probably, I will have time to review next week so I feel it's too late
to merge it into 4.1 but I think there is no urgency to merge it.

> 
> this mess will not happen again.
> 
> 
> Andrew picked up some of the commits lined up for 4.1, which required manual
> editing. sorry for that inconvenience.
> 
> 
> unfortunately, commit c72c6160d967ed26a0b136dbab337f821d233509
>   Author: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
>   Date:   Wed Apr 15 16:15:55 2015 -0700
> 
>      zram: move compact_store() to sysfs functions area
> 
> 
> ended up to be different: from a cosmetic change it has transformed into
> a functional change.
> 
> I fix it in 0001-zram-enable-compaction-support-in-zram.patch.
> 

So Andrew, could you pick 0001 in this merge window? Without it, zram cannot
use compaction feature of zsmalloc so zsmalloc's compaciton feature will be
void.

> 
> the rest is functionally identical to what we had in linux-next and mmotm for
> quite some time: in linux-next since Wed Apr 8 09:44:43 2015 +1000
> (commit 273b0791dae2f0b).
> 
> it would be nice to see it in 4.1, if possible.
> 
> no functional change in zram_drv.c file, compared to zram_drv.c from
> linux-next-20150415 (yes, actually checked). just a couple of additional
> comment tweaks.
> 
> like:
> 
> -/* allocate and initialize new zram device. the function returns
> - * '>= 0' device_id upon success, and negative value otherwise. */
> +/*
> + * Allocate and initialize new zram device. the function returns
> + * '>= 0' device_id upon success, and negative value otherwise.
> + */
> 
> or
> 
>         /*
>          * First, make ->disksize device attr RO, closing
> -        * ZRAM_CTL_REMOVE vs disksize_store() race window
> +        * zram_remove() vs disksize_store() race window
>          */
> 
> 
> I also picked up the remaining part of Julia Lawall's
> <Julia.Lawall@...6.fr> ("zram: fix error return code") commit.
> 
> Documentation is identical to linux-next-20150415 version.
> 
> 
> 8<-------
> 
> We currently don't support zram on-demand device creation.  The only way
> to have N zram devices is to specify num_devices module parameter (default
> value 1).  That means that if, for some reason, at some point, user wants
> to have N + 1 devies he/she must umount all the existing devices, unload
> the module, load the module passing num_devices equals to N + 1.  And do
> this again, if needed.
> 
> This patchset introduces zram-control sysfs class, which has two sysfs
> attrs:
> 
>  - zram_add     -- add a new zram device
>  - zram_remove  -- remove a specific (device_id) zram device
> 
>     Usage example:
>         # add a new specific zram device
>         cat /sys/class/zram-control/zram_add
>         1
> 
>         # remove a specific zram device
>         echo 4 > /sys/class/zram-control/zram_remove
> 
> The patchset also does some cleanups and huge code reorganization.
> 
> 
> -ss
> 
> 
> Sergey Senozhatsky (10):
>   zram: enable compaction support in zram
>   zram: cosmetic ZRAM_ATTR_RO code formatting tweak
>   zram: use idr instead of `zram_devices' array
>   zram: factor out device reset from reset_store()
>   zram: reorganize code layout
>   zram: remove max_num_devices limitation
>   zram: report every added and removed device
>   zram: trivial: correct flag operations comment
>   zram: return zram device_id value from zram_add()
>   zram: add dynamic device add/remove functionality
> 
>  Documentation/ABI/testing/sysfs-class-zram |  24 +
>  Documentation/blockdev/zram.txt            |  31 +-
>  drivers/block/zram/zram_drv.c              | 939 +++++++++++++++++------------
>  drivers/block/zram/zram_drv.h              |   6 -
>  4 files changed, 597 insertions(+), 403 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-zram
> 
> -- 
> 2.4.0.rc1.29.gecc46a1
> 

-- 
Kind regards,
Minchan Kim
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