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* [PATCH v5] zram: break the strict dependency from lzo
@ 2020-11-15 10:15 Rui Salvaterra
  2020-11-19 22:26 ` Minchan Kim
  0 siblings, 1 reply; 6+ messages in thread
From: Rui Salvaterra @ 2020-11-15 10:15 UTC (permalink / raw)
  To: minchan, ngupta, sergey.senozhatsky.work
  Cc: linux-block, linux-kernel, Rui Salvaterra

From the beginning, the zram block device always enabled CRYPTO_LZO, since
lzo-rle is hardcoded as the fallback compression algorithm. As a consequence, on
systems where another compression algorithm is chosen (e.g. CRYPTO_ZSTD), the
lzo kernel module becomes unused, while still having to be built/loaded.

This patch removes the hardcoded lzo-rle dependency and allows the user to
select the default compression algorithm for zram at build time. The previous
behaviour is kept, as the default algorithm is still lzo-rle.

Suggested-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
---
v5: incorporate Minchan's feedback. Allow the user to choose a default algorithm.
v4: incorporate Sergey's feedback and fix a small typo.
v3: fix the default selection when lzo isn't present. Rebase against 5.10-rc1.
v2: fix the dependency on CRYPTO.

I believe this is the final version, but it does deserve some comment. Given the
choice of having more preprocessor #if/#endif directives in C files or making
the kconfig a bit more complex, I went for the latter. However, since kconfig
choices can only be boolean, I had to devise a way to make a string selection
based on the boolean choice, hence the ZRAM_DEF_COMP symbol.
I also tried to make the ZRAM_AUTOSEL_ALGO definition a bit less painful to the
eye, while still allowing for the compression algorithms to be selected as
modules, as per Sergey's suggestion.

 drivers/block/zram/Kconfig    | 49 ++++++++++++++++++++++++++++++++++-
 drivers/block/zram/zcomp.c    |  2 ++
 drivers/block/zram/zram_drv.c |  2 +-
 3 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index fe7a4b7d30cf..cde089c30ffb 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -2,7 +2,6 @@
 config ZRAM
 	tristate "Compressed RAM block device support"
 	depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
-	select CRYPTO_LZO
 	help
 	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
 	  Pages written to these disks are compressed and stored in memory
@@ -14,6 +13,54 @@ config ZRAM
 
 	  See Documentation/admin-guide/blockdev/zram.rst for more information.
 
+choice
+	prompt "Default zram compression algorithm"
+	depends on ZRAM
+
+config ZRAM_DEF_COMP_LZORLE
+	bool "lzo-rle"
+	depends on CRYPTO_LZO
+
+config ZRAM_DEF_COMP_ZSTD
+	bool "zstd"
+	depends on CRYPTO_ZSTD
+
+config ZRAM_DEF_COMP_LZ4
+	bool "lz4"
+	depends on CRYPTO_LZ4
+
+config ZRAM_DEF_COMP_LZO
+	bool "lzo"
+	depends on CRYPTO_LZO
+
+config ZRAM_DEF_COMP_LZ4HC
+	bool "lz4hc"
+	depends on CRYPTO_LZ4HC
+
+config ZRAM_DEF_COMP_842
+	bool "842"
+	depends on CRYPTO_842
+
+endchoice
+
+config ZRAM_DEF_COMP
+	string
+	default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
+	default "zstd" if ZRAM_DEF_COMP_ZSTD
+	default "lz4" if ZRAM_DEF_COMP_LZ4
+	default "lzo" if ZRAM_DEF_COMP_LZO
+	default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
+	default "842" if ZRAM_DEF_COMP_842
+
+config ZRAM_AUTOSEL_ALGO
+	def_bool y
+	depends on ZRAM && \
+		!(CRYPTO_LZ4=m   || CRYPTO_LZ4=y   || \
+		  CRYPTO_LZ4HC=m || CRYPTO_LZ4HC=y || \
+		  CRYPTO_842=m   || CRYPTO_842=y   || \
+		  CRYPTO_ZSTD=m  || CRYPTO_ZSTD=y)
+	select CRYPTO_LZO
+
 config ZRAM_WRITEBACK
        bool "Write back incompressible or idle page to backing device"
        depends on ZRAM
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 33e3b76c4fa9..052aa3f65514 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -15,8 +15,10 @@
 #include "zcomp.h"
 
 static const char * const backends[] = {
+#if IS_ENABLED(CONFIG_CRYPTO_LZO)
 	"lzo",
 	"lzo-rle",
+#endif
 #if IS_ENABLED(CONFIG_CRYPTO_LZ4)
 	"lz4",
 #endif
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 1b697208d661..9ddccb968c68 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -42,7 +42,7 @@ static DEFINE_IDR(zram_index_idr);
 static DEFINE_MUTEX(zram_index_mutex);
 
 static int zram_major;
-static const char *default_compressor = "lzo-rle";
+static const char *default_compressor = CONFIG_ZRAM_DEF_COMP;
 
 /* Module params (documentation at end) */
 static unsigned int num_devices = 1;
-- 
2.29.2


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v5] zram: break the strict dependency from lzo
  2020-11-15 10:15 [PATCH v5] zram: break the strict dependency from lzo Rui Salvaterra
@ 2020-11-19 22:26 ` Minchan Kim
  2020-11-20  9:10   ` Rui Salvaterra
  0 siblings, 1 reply; 6+ messages in thread
From: Minchan Kim @ 2020-11-19 22:26 UTC (permalink / raw)
  To: Rui Salvaterra; +Cc: ngupta, sergey.senozhatsky.work, linux-block, linux-kernel

On Sun, Nov 15, 2020 at 10:15:14AM +0000, Rui Salvaterra wrote:
> From the beginning, the zram block device always enabled CRYPTO_LZO, since
> lzo-rle is hardcoded as the fallback compression algorithm. As a consequence, on
> systems where another compression algorithm is chosen (e.g. CRYPTO_ZSTD), the
> lzo kernel module becomes unused, while still having to be built/loaded.
> 
> This patch removes the hardcoded lzo-rle dependency and allows the user to
> select the default compression algorithm for zram at build time. The previous
> behaviour is kept, as the default algorithm is still lzo-rle.
> 
> Suggested-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> Suggested-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
> ---
> v5: incorporate Minchan's feedback. Allow the user to choose a default algorithm.
> v4: incorporate Sergey's feedback and fix a small typo.
> v3: fix the default selection when lzo isn't present. Rebase against 5.10-rc1.
> v2: fix the dependency on CRYPTO.
> 
> I believe this is the final version, but it does deserve some comment. Given the
> choice of having more preprocessor #if/#endif directives in C files or making
> the kconfig a bit more complex, I went for the latter. However, since kconfig
> choices can only be boolean, I had to devise a way to make a string selection
> based on the boolean choice, hence the ZRAM_DEF_COMP symbol.
> I also tried to make the ZRAM_AUTOSEL_ALGO definition a bit less painful to the
> eye, while still allowing for the compression algorithms to be selected as
> modules, as per Sergey's suggestion.
> 
>  drivers/block/zram/Kconfig    | 49 ++++++++++++++++++++++++++++++++++-
>  drivers/block/zram/zcomp.c    |  2 ++
>  drivers/block/zram/zram_drv.c |  2 +-
>  3 files changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
> index fe7a4b7d30cf..cde089c30ffb 100644
> --- a/drivers/block/zram/Kconfig
> +++ b/drivers/block/zram/Kconfig
> @@ -2,7 +2,6 @@
>  config ZRAM
>  	tristate "Compressed RAM block device support"
>  	depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
> -	select CRYPTO_LZO
>  	help
>  	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
>  	  Pages written to these disks are compressed and stored in memory
> @@ -14,6 +13,54 @@ config ZRAM
>  
>  	  See Documentation/admin-guide/blockdev/zram.rst for more information.
>  
> +choice
> +	prompt "Default zram compression algorithm"
> +	depends on ZRAM
> +
> +config ZRAM_DEF_COMP_LZORLE
> +	bool "lzo-rle"
> +	depends on CRYPTO_LZO
> +
> +config ZRAM_DEF_COMP_ZSTD
> +	bool "zstd"
> +	depends on CRYPTO_ZSTD
> +
> +config ZRAM_DEF_COMP_LZ4
> +	bool "lz4"
> +	depends on CRYPTO_LZ4
> +
> +config ZRAM_DEF_COMP_LZO
> +	bool "lzo"
> +	depends on CRYPTO_LZO
> +
> +config ZRAM_DEF_COMP_LZ4HC
> +	bool "lz4hc"
> +	depends on CRYPTO_LZ4HC
> +
> +config ZRAM_DEF_COMP_842
> +	bool "842"
> +	depends on CRYPTO_842
> +
> +endchoice
> +
> +config ZRAM_DEF_COMP
> +	string
> +	default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
> +	default "zstd" if ZRAM_DEF_COMP_ZSTD
> +	default "lz4" if ZRAM_DEF_COMP_LZ4
> +	default "lzo" if ZRAM_DEF_COMP_LZO
> +	default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
> +	default "842" if ZRAM_DEF_COMP_842
> +
> +config ZRAM_AUTOSEL_ALGO
> +	def_bool y
> +	depends on ZRAM && \
> +		!(CRYPTO_LZ4=m   || CRYPTO_LZ4=y   || \
> +		  CRYPTO_LZ4HC=m || CRYPTO_LZ4HC=y || \
> +		  CRYPTO_842=m   || CRYPTO_842=y   || \
> +		  CRYPTO_ZSTD=m  || CRYPTO_ZSTD=y)
> +	select CRYPTO_LZO
> +

Hi Rui,

What's the purpose of ZRAM_AUTOSEL_ALGO?
If you and Sergey already discussed, sorry about the missing it.

Below doesn't work for your goal?

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index fe7a4b7d30cf..7f3c50f5f87e 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -2,7 +2,6 @@
 config ZRAM
        tristate "Compressed RAM block device support"
        depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
-       select CRYPTO_LZO
        help
          Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
          Pages written to these disks are compressed and stored in memory
@@ -14,6 +13,32 @@ config ZRAM

          See Documentation/admin-guide/blockdev/zram.rst for more information.

+
+choice
+       prompt "zram default compressor"
+       default ZRAM_COMP_LZO_DEF
+       depends on ZRAM || CRYPTO_LZ4
+       help
+         a
+
+config ZRAM_COMP_LZO_DEF
+       bool "lzo"
+       select CRYPTO_LZO
+       help
+         b
+
+config ZRAM_COMP_LZ4_DEF
+       bool "lz4"
+       depends on CRYPTO_LZ4
+       help
+         c
+endchoice
+
+config ZRAM_DEF_COMP
+       string
+       default "lzo" if ZRAM_COMP_LZO_DEF
+       default "lz4" if ZRAM_COMP_LZ4_DEF


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v5] zram: break the strict dependency from lzo
  2020-11-19 22:26 ` Minchan Kim
@ 2020-11-20  9:10   ` Rui Salvaterra
  2020-11-20 21:40     ` Minchan Kim
  0 siblings, 1 reply; 6+ messages in thread
From: Rui Salvaterra @ 2020-11-20  9:10 UTC (permalink / raw)
  To: Minchan Kim; +Cc: ngupta, sergey.senozhatsky.work, linux-block, linux-kernel

Hi, Minchan,

On Thu, 19 Nov 2020 at 22:26, Minchan Kim <minchan@kernel.org> wrote:
>
> What's the purpose of ZRAM_AUTOSEL_ALGO?
> If you and Sergey already discussed, sorry about the missing it.

The purpose of ZRAM_AUTOSEL_ALGO is to make sure at least one of the
required compression algorithms is enabled, either as a module or
built-in. I believe Sergey agreed with the reasoning behind it, but
he'll let us know if I misunderstood. :)

> Below doesn't work for your goal?

Unfortunately, it doesn't. :( It breaks the dependency chain, allowing
you to deselect all compression algorithms in the crypto menu, and
consequently disabling zram. This is only my opinion (and I know
select directives should be very well justified), but I believe that
it should be zram to make sure its required libraries are enabled, and
not the other way around. Having to select a compression algorithm in
the crypto menu for the zram block device to appear in the block
devices menu seems backwards to me.

Thanks,
Rui

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v5] zram: break the strict dependency from lzo
  2020-11-20  9:10   ` Rui Salvaterra
@ 2020-11-20 21:40     ` Minchan Kim
  2020-11-21  0:44       ` Rui Salvaterra
  0 siblings, 1 reply; 6+ messages in thread
From: Minchan Kim @ 2020-11-20 21:40 UTC (permalink / raw)
  To: Rui Salvaterra; +Cc: ngupta, sergey.senozhatsky.work, linux-block, linux-kernel

On Fri, Nov 20, 2020 at 09:10:13AM +0000, Rui Salvaterra wrote:
> Hi, Minchan,
> 
> On Thu, 19 Nov 2020 at 22:26, Minchan Kim <minchan@kernel.org> wrote:
> >
> > What's the purpose of ZRAM_AUTOSEL_ALGO?
> > If you and Sergey already discussed, sorry about the missing it.
> 
> The purpose of ZRAM_AUTOSEL_ALGO is to make sure at least one of the
> required compression algorithms is enabled, either as a module or
> built-in. I believe Sergey agreed with the reasoning behind it, but
> he'll let us know if I misunderstood. :)
> 
> > Below doesn't work for your goal?
> 
> Unfortunately, it doesn't. :( It breaks the dependency chain, allowing
> you to deselect all compression algorithms in the crypto menu, and

Hi Rui,

I don't understand it. Please see below.  ZRAM_COMP_LZO_DEF select
CRYPTO_LZO, not relying on it. If system supports other CRYPTO module
it will show on choice list. Otherwise, default lzo will be always
there and select CRYPTO_LZO.

Do I miss your point?

+
+choice
+       prompt "zram default compressor"
+       default ZRAM_COMP_LZO_DEF
+       depends on ZRAM || CRYPTO_LZ4
+       help
+         a
+
+config ZRAM_COMP_LZO_DEF
+       bool "lzo"
+       select CRYPTO_LZO
+       help
+         b
+
+config ZRAM_COMP_LZ4_DEF
+       bool "lz4"
+       depends on CRYPTO_LZ4
+       help
+         c
+endchoice
+
+config ZRAM_DEF_COMP
+       string
+       default "lzo" if ZRAM_COMP_LZO_DEF
+       default "lz4" if ZRAM_COMP_LZ4_DEF



^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v5] zram: break the strict dependency from lzo
  2020-11-20 21:40     ` Minchan Kim
@ 2020-11-21  0:44       ` Rui Salvaterra
  2020-11-22  9:40         ` Rui Salvaterra
  0 siblings, 1 reply; 6+ messages in thread
From: Rui Salvaterra @ 2020-11-21  0:44 UTC (permalink / raw)
  To: Minchan Kim; +Cc: ngupta, sergey.senozhatsky.work, linux-block, linux-kernel

Hi, Minchan,

On Fri, 20 Nov 2020 at 21:40, Minchan Kim <minchan@kernel.org> wrote:
>
> Do I miss your point?

Well, it's quite possible I mis{read,applied} your patch. It's late
here, I'll test it with fresher brains tomorrow to see if it's
functionally equivalent.

Thanks,
Rui

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH v5] zram: break the strict dependency from lzo
  2020-11-21  0:44       ` Rui Salvaterra
@ 2020-11-22  9:40         ` Rui Salvaterra
  0 siblings, 0 replies; 6+ messages in thread
From: Rui Salvaterra @ 2020-11-22  9:40 UTC (permalink / raw)
  To: Minchan Kim; +Cc: ngupta, sergey.senozhatsky.work, linux-block, linux-kernel

Hi, Minchan,

On Sat, 21 Nov 2020 at 00:44, Rui Salvaterra <rsalvaterra@gmail.com> wrote:
>
> Well, it's quite possible I mis{read,applied} your patch.

And I obviously did. Your kconfig suggestion does basically the same,
in a more simplified way. I guess a v6 is in order.

Thanks,
Rui

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-11-22  9:40 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-15 10:15 [PATCH v5] zram: break the strict dependency from lzo Rui Salvaterra
2020-11-19 22:26 ` Minchan Kim
2020-11-20  9:10   ` Rui Salvaterra
2020-11-20 21:40     ` Minchan Kim
2020-11-21  0:44       ` Rui Salvaterra
2020-11-22  9:40         ` Rui Salvaterra

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