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authorNick Piggin <npiggin@suse.de>2008-02-08 04:19:49 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 09:22:30 -0800
commit9db5579be4bb5320c3248f6acf807aedf05ae143 (patch)
treefde09bbeb427946b30d2e0fb6b00494a42488052 /drivers/block/Makefile
parentdaeb51e62cacde31c8245866e1096ff79a0c83fe (diff)
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rewrite rd
This is a rewrite of the ramdisk block device driver. The old one is really difficult because it effectively implements a block device which serves data out of its own buffer cache. It relies on the dirty bit being set, to pin its backing store in cache, however there are non trivial paths which can clear the dirty bit (eg. try_to_free_buffers()), which had recently lead to data corruption. And in general it is completely wrong for a block device driver to do this. The new one is more like a regular block device driver. It has no idea about vm/vfs stuff. It's backing store is similar to the buffer cache (a simple radix-tree of pages), but it doesn't know anything about page cache (the pages in the radix tree are not pagecache pages). There is one slight downside -- direct block device access and filesystem metadata access goes through an extra copy and gets stored in RAM twice. However, this downside is only slight, because the real buffercache of the device is now reclaimable (because we're not playing crazy games with it), so under memory intensive situations, footprint should effectively be the same -- maybe even a slight advantage to the new driver because it can also reclaim buffer heads. The fact that it now goes through all the regular vm/fs paths makes it much more useful for testing, too. text data bss dec hex filename 2837 849 384 4070 fe6 drivers/block/rd.o 3528 371 12 3911 f47 drivers/block/brd.o Text is larger, but data and bss are smaller, making total size smaller. A few other nice things about it: - Similar structure and layout to the new loop device handlinag. - Dynamic ramdisk creation. - Runtime flexible buffer head size (because it is no longer part of the ramdisk code). - Boot / load time flexible ramdisk size, which could easily be extended to a per-ramdisk runtime changeable size (eg. with an ioctl). - Can use highmem for the backing store. [akpm@linux-foundation.org: fix build] [byron.bbradley@gmail.com: make rd_size non-static] Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Byron Bradley <byron.bbradley@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block/Makefile')
-rw-r--r--drivers/block/Makefile2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index 7691505a2e1..01c972415cb 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -11,7 +11,7 @@ obj-$(CONFIG_AMIGA_FLOPPY) += amiflop.o
obj-$(CONFIG_PS3_DISK) += ps3disk.o
obj-$(CONFIG_ATARI_FLOPPY) += ataflop.o
obj-$(CONFIG_AMIGA_Z2RAM) += z2ram.o
-obj-$(CONFIG_BLK_DEV_RAM) += rd.o
+obj-$(CONFIG_BLK_DEV_RAM) += brd.o
obj-$(CONFIG_BLK_DEV_LOOP) += loop.o
obj-$(CONFIG_BLK_DEV_PS2) += ps2esdi.o
obj-$(CONFIG_BLK_DEV_XD) += xd.o