path: root/mm
diff options
authorDavid Howells <>2006-09-30 20:45:40 +0200
committerJens Axboe <>2006-09-30 20:52:31 +0200
commit9361401eb7619c033e2394e4f9f6d410d6719ac7 (patch)
tree04b94a71f2366988c17740d1c16cfbdec41d5d2e /mm
parentd366e40a1cabd453be6e2609caa7e12f9ca17b1f (diff)
[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 <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'mm')
5 files changed, 14 insertions, 4 deletions
diff --git a/mm/Makefile b/mm/Makefile
index 4f2166a833b..12b3a4eee88 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -12,7 +12,7 @@ obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
readahead.o swap.o truncate.o vmscan.o \
prio_tree.o util.o mmzone.o vmstat.o $(mmu-y)
-ifeq ($(CONFIG_MMU),y)
obj-y += bounce.o
obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o thrash.o
diff --git a/mm/filemap.c b/mm/filemap.c
index d6846de0888..c4fe97f5ace 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2020,6 +2020,7 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
*count = inode->i_sb->s_maxbytes - *pos;
} else {
loff_t isize;
if (bdev_read_only(I_BDEV(inode)))
return -EPERM;
@@ -2031,6 +2032,9 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
if (*pos + *count > isize)
*count = isize - *pos;
+ return -EPERM;
return 0;
diff --git a/mm/migrate.c b/mm/migrate.c
index 7f50e3ff54c..ba2453f9483 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -409,6 +409,7 @@ int migrate_page(struct address_space *mapping,
* Migration function for pages with buffers. This function can only be used
* if the underlying filesystem guarantees that no other references to "page"
@@ -466,6 +467,7 @@ int buffer_migrate_page(struct address_space *mapping,
return 0;
* Writeback a page to clean the dirty state
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index ecf27839c20..c0d4ce144de 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -807,9 +807,11 @@ int fastcall set_page_dirty(struct page *page)
if (likely(mapping)) {
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
- if (spd)
- return (*spd)(page);
- return __set_page_dirty_buffers(page);
+ if (!spd)
+ spd = __set_page_dirty_buffers;
+ return (*spd)(page);
if (!PageDirty(page)) {
if (!TestSetPageDirty(page))
diff --git a/mm/truncate.c b/mm/truncate.c
index cd3e34b816d..8fde6580657 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -35,8 +35,10 @@ void do_invalidatepage(struct page *page, unsigned long offset)
void (*invalidatepage)(struct page *, unsigned long);
invalidatepage = page->mapping->a_ops->invalidatepage;
if (!invalidatepage)
invalidatepage = block_invalidatepage;
if (invalidatepage)
(*invalidatepage)(page, offset);