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: Mikulas Patocka <[email protected]> Signed-off-by: Alasdair G Kergon <[email protected]>
agners · Oct 31, 2011 · 95d402f · 95d402f
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commit 95d402f
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diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
@@ -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

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
@@ -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