linux-kernel - [PATCH v2] f2fs: compress: Allow modular (de)compression algorithms

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Date:   Fri, 26 Feb 2021 11:06:40 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH v2] f2fs: compress: Allow modular (de)compression algorithms

If F2FS_FS is modular, enabling the compressions options
F2FS_FS_{LZ4,LZ4HZ,LZO,LZORLE,ZSTD} will make the (de)compression
algorithms {LZ4,LZ4HC,LZO,ZSTD}_{,DE}COMPRESS builtin instead of
modular, as the former depend on an intermediate boolean
F2FS_FS_COMPRESSION, which in-turn depends on tristate F2FS_FS.

Indeed, if a boolean symbol A depends directly on a tristate symbol B
and selects another tristate symbol C:

    tristate B

    tristate C

    bool A
      depends on B
      select C

and B is modular, then C will also be modular.

However, if there is an intermediate boolean D in the dependency chain
between A and B:

    tristate B

    tristate C

    bool D
      depends on B

    bool A
      depends on D
      select C

then the modular state won't propagate from B to C, and C will be
builtin instead of modular.

As modular dependency propagation through intermediate symbols is
obscure, fix this in a robust way by moving the selection of tristate
(de)compression algorithms from the boolean compression options to the
tristate main F2FS_FS option.

Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
v2:
  - Move the selects to F2FS_FS instead of adding direct dependencies
    on F2FS_FS.
---
 fs/f2fs/Kconfig | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
index 62e638a49bbf089a..cca79029a577151c 100644
--- a/fs/f2fs/Kconfig
+++ b/fs/f2fs/Kconfig
@@ -7,6 +7,15 @@ config F2FS_FS
 	select CRYPTO_CRC32
 	select F2FS_FS_XATTR if FS_ENCRYPTION
 	select FS_ENCRYPTION_ALGS if FS_ENCRYPTION
+	select LZ4_COMPRESS if F2FS_FS_LZ4
+	select LZ4_DECOMPRESS if F2FS_FS_LZ4
+	select LZ4HC_COMPRESS if F2FS_FS_LZ4HC
+	select LZO_COMPRESS if F2FS_FS_LZO
+	select LZO_COMPRESS if F2FS_FS_LZORLE
+	select LZO_DECOMPRESS if F2FS_FS_LZO
+	select LZO_DECOMPRESS if F2FS_FS_LZORLE
+	select ZSTD_COMPRESS if F2FS_FS_ZSTD
+	select ZSTD_DECOMPRESS if F2FS_FS_ZSTD
 	help
 	  F2FS is based on Log-structured File System (LFS), which supports
 	  versatile "flash-friendly" features. The design has been focused on
@@ -94,8 +103,6 @@ config F2FS_FS_COMPRESSION
 config F2FS_FS_LZO
 	bool "LZO compression support"
 	depends on F2FS_FS_COMPRESSION
-	select LZO_COMPRESS
-	select LZO_DECOMPRESS
 	default y
 	help
 	  Support LZO compress algorithm, if unsure, say Y.
@@ -103,8 +110,6 @@ config F2FS_FS_LZO
 config F2FS_FS_LZ4
 	bool "LZ4 compression support"
 	depends on F2FS_FS_COMPRESSION
-	select LZ4_COMPRESS
-	select LZ4_DECOMPRESS
 	default y
 	help
 	  Support LZ4 compress algorithm, if unsure, say Y.
@@ -113,7 +118,6 @@ config F2FS_FS_LZ4HC
 	bool "LZ4HC compression support"
 	depends on F2FS_FS_COMPRESSION
 	depends on F2FS_FS_LZ4
-	select LZ4HC_COMPRESS
 	default y
 	help
 	  Support LZ4HC compress algorithm, LZ4HC has compatible on-disk
@@ -122,8 +126,6 @@ config F2FS_FS_LZ4HC
 config F2FS_FS_ZSTD
 	bool "ZSTD compression support"
 	depends on F2FS_FS_COMPRESSION
-	select ZSTD_COMPRESS
-	select ZSTD_DECOMPRESS
 	default y
 	help
 	  Support ZSTD compress algorithm, if unsure, say Y.
@@ -132,8 +134,6 @@ config F2FS_FS_LZORLE
 	bool "LZO-RLE compression support"
 	depends on F2FS_FS_COMPRESSION
 	depends on F2FS_FS_LZO
-	select LZO_COMPRESS
-	select LZO_DECOMPRESS
 	default y
 	help
 	  Support LZO-RLE compress algorithm, if unsure, say Y.
-- 
2.25.1