[Buildroot] [PATCH 2/2] fs/btrfs: Introducing btrfs rootfs support.
Robert J. Heywood
robert.heywood at codethink.co.uk
Thu Aug 23 22:01:56 UTC 2018
This patch makes it possible to format the rootfs using btrfs.
It introduces the option; BR2_TARGET_ROOTFS_BTRFS
When selected, the user is able to specify the filesystem size,
label, options, and node and sector sizes.
The new files are based on fs/ext2/{Config.in,ext2.mk}
Signed-off-by: Robert J. Heywood <robert.heywood at codethink.co.uk>
---
fs/Config.in | 1 +
fs/btrfs/Config.in | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/btrfs.mk | 39 +++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+)
create mode 100644 fs/btrfs/Config.in
create mode 100644 fs/btrfs/btrfs.mk
diff --git a/fs/Config.in b/fs/Config.in
index c25b01c3de..24f22fd7e3 100644
--- a/fs/Config.in
+++ b/fs/Config.in
@@ -1,6 +1,7 @@
menu "Filesystem images"
source "fs/axfs/Config.in"
+source "fs/btrfs/Config.in"
source "fs/cloop/Config.in"
source "fs/cpio/Config.in"
source "fs/cramfs/Config.in"
diff --git a/fs/btrfs/Config.in b/fs/btrfs/Config.in
new file mode 100644
index 0000000000..52fbfd983a
--- /dev/null
+++ b/fs/btrfs/Config.in
@@ -0,0 +1,51 @@
+config BR2_TARGET_ROOTFS_BTRFS
+ bool "btrfs root filesystem"
+ select BR2_PACKAGE_HOST_BTRFS_PROGS
+ help
+ Build a btrfs root filesystem. If you enable this option, you
+ probably want to enable the btrfs-progs package too.
+
+
+if BR2_TARGET_ROOTFS_BTRFS
+
+config BR2_TARGET_ROOTFS_BTRFS_LABEL
+ string "filesystem label"
+
+config BR2_TARGET_ROOTFS_BTRFS_SIZE
+ string "filesystem size"
+ default "100m"
+ help
+ The size of the filesystem image in bytes.
+ Suffix with k, m, g or t for power-of-two kilo-, mega-, giga-
+ or terabytes.
+
+config BR2_TARGET_ROOTFS_BTRFS_SIZE_SECTOR
+ string "sector size"
+ default 4096
+ help
+ This value should be set to the page size in bytes. The default
+ value of 4096 is the the most common page size for most systems.
+ If the sectorsize differs from the page size, the created
+ filesystem may not be mountable by the kernel.
+ Therefore it is recommended to leave this value at 4096. Unless
+ you know that your kernel uses a different page size.
+ Suffix with k for power-of-two kilobytes.
+
+config BR2_TARGET_ROOTFS_BTRFS_SIZE_NODE
+ string "btree node size"
+ default 16384
+ help
+ The tree block size in which btrfs stores metadata in bytes.
+ This must be a multiple of the sectorsize, but not larger than
+ 64KiB (65536).
+ Suffix with k for power-of-two kilobytes.
+
+config BR2_TARGET_ROOTFS_BTRFS_FEATURES
+ string "Filesystem Features"
+ help
+ A comma separated string of features that can be enabled
+ during creation time.
+ For a list of available options, use:
+ `.../host/bin/mkfs.btrfs -O list-all`
+
+endif # BR2_TARGET_ROOTFS_BTRFS
diff --git a/fs/btrfs/btrfs.mk b/fs/btrfs/btrfs.mk
new file mode 100644
index 0000000000..37b2937825
--- /dev/null
+++ b/fs/btrfs/btrfs.mk
@@ -0,0 +1,39 @@
+################################################################################
+#
+# Build the btrfs root filesystem image
+#
+################################################################################
+
+BTRFS_SIZE = $(call qstrip,$(BR2_TARGET_ROOTFS_BTRFS_SIZE))
+ifeq ($(BR2_TARGET_ROOTFS_BTRFS)-$(BTRFS_SIZE),y-)
+$(error BR2_TARGET_ROOTFS_BTRFS_SIZE cannot be empty)
+endif
+
+BTRFS_SIZE_NODE = $(call qstrip,$(BR2_TARGET_ROOTFS_BTRFS_SIZE_NODE))
+BTRFS_SIZE_SECTOR = $(call qstrip,$(BR2_TARGET_ROOTFS_BTRFS_SIZE_SECTOR))
+BTRFS_FEATURES = $(call qstrip,$(BR2_TARGET_ROOTFS_BTRFS_FEATURES))
+# qstrip results in stripping consecutive spaces into a single one. So the
+# variable is not qstrip-ed to preserve the integrity of the string value.
+BTRFS_LABEL := $(subst ",,$(BR2_TARGET_ROOTFS_BTRFS_LABEL))
+# ")
+
+BTRFS_OPTS = \
+ -r '$(TARGET_DIR)' \
+ -L '$(BTRFS_LABEL)' \
+ $(if $(BTRFS_SIZE_NODE),--nodesize '$(BTRFS_SIZE_NODE)') \
+ $(if $(BTRFS_SIZE_SECTOR),--sectorsize '$(BTRFS_SIZE_SECTOR)') \
+ $(if $(BTRFS_FEATURES),--features '$(BTRFS_FEATURES)')
+
+ROOTFS_BTRFS_DEPENDENCIES = host-btrfs-progs
+
+define ROOTFS_BTRFS_CMD
+ rm -f $@
+ truncate -s $(BTRFS_SIZE) $@
+ $(HOST_DIR)/bin/mkfs.btrfs $(BTRFS_OPTS) $@ \
+ || { ret=$$?; \
+ echo "*** Maybe you need to increase the filesystem size (BR2_TARGET_ROOTFS_BTRFS_SIZE)" 1>&2; \
+ exit $$ret; \
+ }
+endef
+
+$(eval $(rootfs))
--
2.11.0
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