[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>
diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index a03e862..a304b34 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -166,7 +166,7 @@
config MTD_BLOCK
tristate "Caching block device access to MTD devices"
- depends on MTD
+ depends on MTD && BLOCK
---help---
Although most flash chips have an erase size too large to be useful
as block devices, it is possible to use MTD devices which are based
@@ -188,7 +188,7 @@
config MTD_BLOCK_RO
tristate "Readonly block device access to MTD devices"
- depends on MTD_BLOCK!=y && MTD
+ depends on MTD_BLOCK!=y && MTD && BLOCK
help
This allows you to mount read-only file systems (such as cramfs)
from an MTD device, without the overhead (and danger) of the caching
@@ -199,7 +199,7 @@
config FTL
tristate "FTL (Flash Translation Layer) support"
- depends on MTD
+ depends on MTD && BLOCK
---help---
This provides support for the original Flash Translation Layer which
is part of the PCMCIA specification. It uses a kind of pseudo-
@@ -215,7 +215,7 @@
config NFTL
tristate "NFTL (NAND Flash Translation Layer) support"
- depends on MTD
+ depends on MTD && BLOCK
---help---
This provides support for the NAND Flash Translation Layer which is
used on M-Systems' DiskOnChip devices. It uses a kind of pseudo-
@@ -238,7 +238,7 @@
config INFTL
tristate "INFTL (Inverse NAND Flash Translation Layer) support"
- depends on MTD
+ depends on MTD && BLOCK
---help---
This provides support for the Inverse NAND Flash Translation
Layer which is used on M-Systems' newer DiskOnChip devices. It
@@ -255,7 +255,7 @@
config RFD_FTL
tristate "Resident Flash Disk (Flash Translation Layer) support"
- depends on MTD
+ depends on MTD && BLOCK
---help---
This provides support for the flash translation layer known
as the Resident Flash Disk (RFD), as used by the Embedded BIOS