[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>
2006-09-30 18:45:40 +00:00
|
|
|
if BLOCK
|
2005-04-16 22:20:36 +00:00
|
|
|
|
|
|
|
|
menu "IO Schedulers"
|
|
|
|
|
|
|
|
|
|
config IOSCHED_NOOP
|
|
|
|
|
bool
|
|
|
|
|
default y
|
|
|
|
|
---help---
|
|
|
|
|
The no-op I/O scheduler is a minimal scheduler that does basic merging
|
|
|
|
|
and sorting. Its main uses include non-disk based block devices like
|
|
|
|
|
memory devices, and specialised software or hardware environments
|
|
|
|
|
that do their own scheduling and require only minimal assistance from
|
|
|
|
|
the kernel.
|
|
|
|
|
|
|
|
|
|
config IOSCHED_DEADLINE
|
|
|
|
|
tristate "Deadline I/O scheduler"
|
|
|
|
|
default y
|
|
|
|
|
---help---
|
2009-10-03 07:37:51 +00:00
|
|
|
The deadline I/O scheduler is simple and compact. It will provide
|
|
|
|
|
CSCAN service with FIFO expiration of requests, switching to
|
|
|
|
|
a new point in the service tree and doing a batch of IO from there
|
|
|
|
|
in case of expiry.
|
2005-04-16 22:20:36 +00:00
|
|
|
|
|
|
|
|
config IOSCHED_CFQ
|
|
|
|
|
tristate "CFQ I/O scheduler"
|
|
|
|
|
default y
|
|
|
|
|
---help---
|
|
|
|
|
The CFQ I/O scheduler tries to distribute bandwidth equally
|
|
|
|
|
among all processes in the system. It should provide a fair
|
2009-10-03 07:40:47 +00:00
|
|
|
and low latency working environment, suitable for both desktop
|
|
|
|
|
and server systems.
|
|
|
|
|
|
2007-02-17 19:08:22 +00:00
|
|
|
This is the default I/O scheduler.
|
2005-04-16 22:20:36 +00:00
|
|
|
|
2009-12-03 17:59:43 +00:00
|
|
|
config CFQ_GROUP_IOSCHED
|
|
|
|
|
bool "CFQ Group Scheduling support"
|
2010-04-26 17:27:56 +00:00
|
|
|
depends on IOSCHED_CFQ && BLK_CGROUP
|
2009-12-03 17:59:43 +00:00
|
|
|
default n
|
|
|
|
|
---help---
|
|
|
|
|
Enable group IO scheduling in CFQ.
|
|
|
|
|
|
2005-10-30 23:02:19 +00:00
|
|
|
choice
|
|
|
|
|
prompt "Default I/O scheduler"
|
2006-06-19 08:06:48 +00:00
|
|
|
default DEFAULT_CFQ
|
2005-10-30 23:02:19 +00:00
|
|
|
help
|
|
|
|
|
Select the I/O scheduler which will be used by default for all
|
|
|
|
|
block devices.
|
|
|
|
|
|
|
|
|
|
config DEFAULT_DEADLINE
|
2005-11-04 07:44:58 +00:00
|
|
|
bool "Deadline" if IOSCHED_DEADLINE=y
|
2005-10-30 23:02:19 +00:00
|
|
|
|
|
|
|
|
config DEFAULT_CFQ
|
2005-11-04 07:44:58 +00:00
|
|
|
bool "CFQ" if IOSCHED_CFQ=y
|
2005-10-30 23:02:19 +00:00
|
|
|
|
|
|
|
|
config DEFAULT_NOOP
|
|
|
|
|
bool "No-op"
|
|
|
|
|
|
|
|
|
|
endchoice
|
|
|
|
|
|
|
|
|
|
config DEFAULT_IOSCHED
|
|
|
|
|
string
|
|
|
|
|
default "deadline" if DEFAULT_DEADLINE
|
|
|
|
|
default "cfq" if DEFAULT_CFQ
|
|
|
|
|
default "noop" if DEFAULT_NOOP
|
|
|
|
|
|
2005-04-16 22:20:36 +00:00
|
|
|
endmenu
|
[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>
2006-09-30 18:45:40 +00:00
|
|
|
|
|
|
|
|
endif
|
