[RFC PATCH 17/18] beamfs: add Kconfig and Makefile

[Aurelien DESBRIERES <aurelien@hackers.camp>]

Hook beamfs into fs/Kconfig, among the miscellaneous filesystems, and
into fs/Makefile.

Besides BEAMFS_FS there are two debugging options: BEAMFS_DEBUG_TREE
enables the tree checker, and BEAMFS_ORDERED_META writes metadata
blocks synchronously in dependency order, an experiment kept to
measure ordering questions. Both default to off.

The Makefile adds the warnings the module is developed with; whether
they stop the build is left to CONFIG_WERROR.

Assisted-by: LLM
Signed-off-by: Aurelien DESBRIERES <aurelien@hackers.camp>
---
 fs/Kconfig         |  1 +
 fs/Makefile        |  1 +
 fs/beamfs/Kconfig  | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/beamfs/Makefile | 21 +++++++++++++++
 4 files changed, 87 insertions(+)
 create mode 100644 fs/beamfs/Kconfig
 create mode 100644 fs/beamfs/Makefile

diff --git a/fs/Kconfig b/fs/Kconfig
index 46313f65ee54..7c864b9549d4 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -313,6 +313,7 @@ source "fs/affs/Kconfig"
 source "fs/ecryptfs/Kconfig"
 source "fs/hfs/Kconfig"
 source "fs/hfsplus/Kconfig"
+source "fs/beamfs/Kconfig"
 source "fs/befs/Kconfig"
 source "fs/jffs2/Kconfig"
 # UBIFS File system configuration
diff --git a/fs/Makefile b/fs/Makefile
index 16f1108b64e1..632c15c85254 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_XFS_FS)		+= xfs/
 obj-$(CONFIG_9P_FS)		+= 9p/
 obj-$(CONFIG_AFS_FS)		+= afs/
 obj-$(CONFIG_NILFS2_FS)		+= nilfs2/
+obj-$(CONFIG_BEAMFS_FS)		+= beamfs/
 obj-$(CONFIG_BEFS_FS)		+= befs/
 obj-y				+= hostfs/
 obj-$(CONFIG_CACHEFILES)	+= cachefiles/
diff --git a/fs/beamfs/Kconfig b/fs/beamfs/Kconfig
new file mode 100644
index 000000000000..56be9beeb588
--- /dev/null
+++ b/fs/beamfs/Kconfig
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# beamfs filesystem configuration
+#
+
+config BEAMFS_FS
+	tristate "beamfs filesystem support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	select FS_IOMAP
+	select CRC32
+	select REED_SOLOMON
+	select REED_SOLOMON_ENC8
+	select REED_SOLOMON_DEC8
+	help
+	  beamfs is a block-device filesystem that corrects corrupted bytes
+	  in place, on a single device, without a second copy to repair
+	  from. Data and directory blocks carry Reed-Solomon RS(255,239)
+	  parity over GF(2^8) inside the block, indirect blocks carry it in
+	  a region of their own, and every read decodes.
+
+	  Up to eight corrupted bytes per 255-byte codeword are corrected.
+	  A codeword the decoder reports as uncorrectable fails the read
+	  with -EIO. Nothing is guaranteed beyond eight bytes per codeword.
+
+	  It is meant for storage that takes bit flips the device does not
+	  correct itself, such as single-event upsets. See
+	  Documentation/filesystems/beamfs.rst.
+
+	  To compile this file system support as a module, choose M here:
+	  the module will be called beamfs.
+
+	  If unsure, say N.
+
+config BEAMFS_DEBUG_TREE
+	bool "beamfs: check the indirect tree invariant at every store"
+	depends on BEAMFS_FS
+	help
+	  Record every pointer installed in an indirect block and check
+	  each later store to the same slot against that record. A slot
+	  that held a live pointer and reads back as zero is reported
+	  with a stack trace at the instant it happens, instead of being
+	  counted by fsck long after.
+
+	  Costs one hash lookup and sixteen bytes per live pointer. Say
+	  N for production.
+
+config BEAMFS_ORDERED_META
+	bool "Write metadata in dependency order (slow, experimental)"
+	depends on BEAMFS_FS
+	default n
+	help
+	  Write every metadata block to the medium before anything names
+	  it: one synchronous write per level of indirection, up to four
+	  for a block reached through the triple indirect.
+
+	  This exists to answer a question, not to be enabled. beamfs
+	  relies on mark_buffer_dirty for ordering and mark_buffer_dirty
+	  gives none, and this forces the safe order at whatever cost in
+	  speed so that the hypothesis can be measured rather than
+	  argued. A journal is how the same property is had for one
+	  sequential write instead.
+
+	  Say N.
diff --git a/fs/beamfs/Makefile b/fs/beamfs/Makefile
new file mode 100644
index 000000000000..d01ad86a0c14
--- /dev/null
+++ b/fs/beamfs/Makefile
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the beamfs filesystem.
+#
+
+obj-$(CONFIG_BEAMFS_FS) += beamfs.o
+
+beamfs-y := treecheck.o super.o inode.o dir.o dirent.o file.o \
+	    file_inline.o scrub.o indparity.o rsbench.o budget.o clock.o \
+	    alert.o edac.o alloc.o namei.o
+
+# define_trace.h includes beamfs_trace.h by name, from super.c.
+CFLAGS_super.o += -I$(src)
+
+# The warnings the module is developed with. Whether they stop the
+# build is left to CONFIG_WERROR.
+ccflags-y += -Wall -Wextra -Wformat=2 -Werror=format
+ccflags-y += -Wmissing-prototypes -Wmissing-declarations
+ccflags-y += -Wundef -Wstrict-prototypes
+# The VFS passes handlers more arguments than most of them use.
+ccflags-y += -Wno-unused-parameter
-- 
2.55.0