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authorDavid Howells2006-09-30 13:45:40 -0500
committerJens Axboe2006-09-30 13:52:31 -0500
commit9361401eb7619c033e2394e4f9f6d410d6719ac7 (patch)
tree04b94a71f2366988c17740d1c16cfbdec41d5d2e /block/Kconfig
parentd366e40a1cabd453be6e2609caa7e12f9ca17b1f (diff)
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[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/Kconfig')
-rw-r--r--block/Kconfig20
1 files changed, 20 insertions, 0 deletions
diff --git a/block/Kconfig b/block/Kconfig
index b6f5f0a7965..9af6c614dfd 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -1,6 +1,24 @@
1# 1#
2# Block layer core configuration 2# Block layer core configuration
3# 3#
4config BLOCK
5 bool "Enable the block layer"
6 default y
7 help
8 This permits the block layer to be removed from the kernel if it's not
9 needed (on some embedded devices for example). If this option is
10 disabled, then blockdev files will become unusable and some
11 filesystems (such as ext3) will become unavailable.
12
13 This option will also disable SCSI character devices and USB storage
14 since they make use of various block layer definitions and
15 facilities.
16
17 Say Y here unless you know you really don't want to mount disks and
18 suchlike.
19
20if BLOCK
21
4#XXX - it makes sense to enable this only for 32-bit subarch's, not for x86_64 22#XXX - it makes sense to enable this only for 32-bit subarch's, not for x86_64
5#for instance. 23#for instance.
6config LBD 24config LBD
@@ -33,4 +51,6 @@ config LSF
33 51
34 If unsure, say Y. 52 If unsure, say Y.
35 53
54endif
55
36source block/Kconfig.iosched 56source block/Kconfig.iosched