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9361401eb7
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>
57 lines
1.7 KiB
Plaintext
57 lines
1.7 KiB
Plaintext
#
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# Block layer core configuration
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#
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config BLOCK
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bool "Enable the block layer"
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default y
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help
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This permits the block layer to be removed from the kernel if it's not
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needed (on some embedded devices for example). If this option is
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disabled, then blockdev files will become unusable and some
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filesystems (such as ext3) will become unavailable.
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This option will also disable SCSI character devices and USB storage
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since they make use of various block layer definitions and
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facilities.
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Say Y here unless you know you really don't want to mount disks and
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suchlike.
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if BLOCK
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#XXX - it makes sense to enable this only for 32-bit subarch's, not for x86_64
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#for instance.
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config LBD
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bool "Support for Large Block Devices"
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depends on X86 || (MIPS && 32BIT) || PPC32 || (S390 && !64BIT) || SUPERH || UML
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help
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Say Y here if you want to attach large (bigger than 2TB) discs to
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your machine, or if you want to have a raid or loopback device
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bigger than 2TB. Otherwise say N.
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config BLK_DEV_IO_TRACE
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bool "Support for tracing block io actions"
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depends on SYSFS
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select RELAY
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select DEBUG_FS
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help
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Say Y here, if you want to be able to trace the block layer actions
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on a given queue. Tracing allows you to see any traffic happening
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on a block device queue. For more information (and the user space
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support tools needed), fetch the blktrace app from:
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git://brick.kernel.dk/data/git/blktrace.git
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config LSF
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bool "Support for Large Single Files"
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depends on X86 || (MIPS && 32BIT) || PPC32 || ARCH_S390_31 || SUPERH || UML
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help
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Say Y here if you want to be able to handle very large files (bigger
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than 2TB), otherwise say N.
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If unsure, say Y.
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endif
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source block/Kconfig.iosched
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