[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>

1 files changed, 24 insertions, 7 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index 4fd9efac29ab..1453d2d164f7 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -4,6 +4,8 @@
 
 menu "File systems"
 
+if BLOCK
+
 config EXT2_FS
         tristate "Second extended fs support"
         help
@@ -399,6 +401,8 @@ config ROMFS_FS
           If you don't know whether you need it, then you don't need it:
           answer N.
 
+endif
+
 config INOTIFY
         bool "Inotify file change notification support"
         default y
@@ -530,6 +534,7 @@ config FUSE_FS
           If you want to develop a userspace FS, or if you want to use
           a filesystem based on FUSE, answer Y or M.
 
+if BLOCK
 menu "CD-ROM/DVD Filesystems"
 
 config ISO9660_FS
@@ -597,7 +602,9 @@ config UDF_NLS
         depends on (UDF_FS=m && NLS) || (UDF_FS=y && NLS=y)
 
 endmenu
+endif
 
+if BLOCK
 menu "DOS/FAT/NT Filesystems"
 
 config FAT_FS
@@ -782,6 +789,7 @@ config NTFS_RW
           It is perfectly safe to say N here.
 
 endmenu
+endif
 
 menu "Pseudo filesystems"
 
@@ -939,7 +947,7 @@ menu "Miscellaneous filesystems"
 
 config ADFS_FS
         tristate "ADFS file system support (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         help
           The Acorn Disc Filing System is the standard file system of the
           RiscOS operating system which runs on Acorn's ARM-based Risc PC
@@ -967,7 +975,7 @@ config ADFS_FS_RW
 
 config AFFS_FS
         tristate "Amiga FFS file system support (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         help
           The Fast File System (FFS) is the common file system used on hard
           disks by Amiga(tm) systems since AmigaOS Version 1.3 (34.20).  Say Y
@@ -989,7 +997,7 @@ config AFFS_FS
 
 config HFS_FS
         tristate "Apple Macintosh file system support (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         select NLS
         help
           If you say Y here, you will be able to mount Macintosh-formatted
@@ -1002,6 +1010,7 @@ config HFS_FS
 
 config HFSPLUS_FS
         tristate "Apple Extended HFS file system support"
+        depends on BLOCK
         select NLS
         select NLS_UTF8
         help
@@ -1015,7 +1024,7 @@ config HFSPLUS_FS
 
 config BEFS_FS
         tristate "BeOS file system (BeFS) support (read only) (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         select NLS
         help
           The BeOS File System (BeFS) is the native file system of Be, Inc's
@@ -1042,7 +1051,7 @@ config BEFS_DEBUG
 
 config BFS_FS
         tristate "BFS file system support (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         help
           Boot File System (BFS) is a file system used under SCO UnixWare to
           allow the bootloader access to the kernel image and other important
@@ -1064,7 +1073,7 @@ config BFS_FS
 
 config EFS_FS
         tristate "EFS file system support (read only) (EXPERIMENTAL)"
-        depends on EXPERIMENTAL
+        depends on BLOCK && EXPERIMENTAL
         help
           EFS is an older file system used for non-ISO9660 CD-ROMs and hard
           disk partitions by SGI's IRIX operating system (IRIX 6.0 and newer
@@ -1079,7 +1088,7 @@ config EFS_FS
 
 config JFFS_FS
         tristate "Journalling Flash File System (JFFS) support"
-        depends on MTD
+        depends on MTD && BLOCK
         help
           JFFS is the Journaling Flash File System developed by Axis
           Communications in Sweden, aimed at providing a crash/powerdown-safe
@@ -1264,6 +1273,7 @@ endchoice
 
 config CRAMFS
         tristate "Compressed ROM file system support (cramfs)"
+        depends on BLOCK
         select ZLIB_INFLATE
         help
           Saying Y here includes support for CramFs (Compressed ROM File
@@ -1283,6 +1293,7 @@ config CRAMFS
 
 config VXFS_FS
         tristate "FreeVxFS file system support (VERITAS VxFS(TM) compatible)"
+        depends on BLOCK
         help
           FreeVxFS is a file system driver that support the VERITAS VxFS(TM)
           file system format.  VERITAS VxFS(TM) is the standard file system
@@ -1300,6 +1311,7 @@ config VXFS_FS
 
 config HPFS_FS
         tristate "OS/2 HPFS file system support"
+        depends on BLOCK
         help
           OS/2 is IBM's operating system for PC's, the same as Warp, and HPFS
           is the file system used for organizing files on OS/2 hard disk
@@ -1316,6 +1328,7 @@ config HPFS_FS
 
 config QNX4FS_FS
         tristate "QNX4 file system support (read only)"
+        depends on BLOCK
         help
           This is the file system used by the real-time operating systems
           QNX 4 and QNX 6 (the latter is also called QNX RTP).
@@ -1343,6 +1356,7 @@ config QNX4FS_RW
 
 config SYSV_FS
         tristate "System V/Xenix/V7/Coherent file system support"
+        depends on BLOCK
         help
           SCO, Xenix and Coherent are commercial Unix systems for Intel
           machines, and Version 7 was used on the DEC PDP-11. Saying Y
@@ -1381,6 +1395,7 @@ config SYSV_FS
 
 config UFS_FS
         tristate "UFS file system support (read only)"
+        depends on BLOCK
         help
           BSD and derivate versions of Unix (such as SunOS, FreeBSD, NetBSD,
           OpenBSD and NeXTstep) use a file system called UFS. Some System V
@@ -1959,11 +1974,13 @@ config GENERIC_ACL
 
 endmenu
 
+if BLOCK
 menu "Partition Types"
 
 source "fs/partitions/Kconfig"
 
 endmenu
+endif
 
 source "fs/nls/Kconfig"