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Commit 95d402f0 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
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dm: add bufio 



The dm-bufio interface allows you to do cached I/O on devices,
holding recently-read blocks in memory and performing delayed writes.

We don't use buffer cache or page cache already present in the kernel, because:
* we need to handle block sizes larger than a page
* we can't allocate memory to perform reads or we'd have deadlocks

Currently, when a cache is required, we limit its size to a fraction of
available memory.  Usage can be viewed and changed in
/sys/module/dm_bufio/parameters/ .

The first user is thin provisioning, but more dm users are planned.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 3cf2e4ba

drivers/md/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -208,6 +208,14 @@ config DM_DEBUG 


	  If unsure, say N.



config DM_BUFIO

       tristate

       depends on BLK_DEV_DM && EXPERIMENTAL

       ---help---

	 This interface allows you to do buffered I/O on a device and acts

	 as a cache, holding recently-read blocks in memory and performing

	 delayed writes.



config DM_CRYPT

	tristate "Crypt target support"

	depends on BLK_DEV_DM

drivers/md/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ obj-$(CONFIG_MD_MULTIPATH) += multipath.o 
obj-$(CONFIG_MD_FAULTY)		+= faulty.o

obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o

obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o

obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o

obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o

obj-$(CONFIG_DM_DELAY)		+= dm-delay.o

obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o