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authorDavid Howells <dhowells@redhat.com>2006-09-30 20:45:40 +0200
committerJens Axboe <axboe@nelson.home.kernel.dk>2006-09-30 20:52:31 +0200
commit9361401eb7619c033e2394e4f9f6d410d6719ac7 (patch)
tree04b94a71f2366988c17740d1c16cfbdec41d5d2e /block
parentd366e40a1cabd453be6e2609caa7e12f9ca17b1f (diff)
downloadlinux-0-day-9361401eb7619c033e2394e4f9f6d410d6719ac7.tar.gz
[PATCH] BLOCK: Make it possible to disable the block layer [try #6]
Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/Kconfig20
-rw-r--r--block/Kconfig.iosched3
-rw-r--r--block/Makefile2
3 files changed, 24 insertions, 1 deletions
diff --git a/block/Kconfig b/block/Kconfig
index b6f5f0a..9af6c61 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -1,6 +1,24 @@
#
# Block layer core configuration
#
+config BLOCK
+ bool "Enable the block layer"
+ default y
+ help
+ This permits the block layer to be removed from the kernel if it's not
+ needed (on some embedded devices for example). If this option is
+ disabled, then blockdev files will become unusable and some
+ filesystems (such as ext3) will become unavailable.
+
+ This option will also disable SCSI character devices and USB storage
+ since they make use of various block layer definitions and
+ facilities.
+
+ Say Y here unless you know you really don't want to mount disks and
+ suchlike.
+
+if BLOCK
+
#XXX - it makes sense to enable this only for 32-bit subarch's, not for x86_64
#for instance.
config LBD
@@ -33,4 +51,6 @@ config LSF
If unsure, say Y.
+endif
+
source block/Kconfig.iosched
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 48d090e..903f0d3 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -1,3 +1,4 @@
+if BLOCK
menu "IO Schedulers"
@@ -67,3 +68,5 @@ config DEFAULT_IOSCHED
default "noop" if DEFAULT_NOOP
endmenu
+
+endif
diff --git a/block/Makefile b/block/Makefile
index c05de0e..4b84d0d 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -2,7 +2,7 @@
# Makefile for the kernel block layer
#
-obj-y := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
+obj-$(CONFIG_BLOCK) := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_AS) += as-iosched.o