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authorMartin K. Petersen <martin.petersen@oracle.com>2010-03-16 20:30:01 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2010-04-01 15:58:56 -0700
commit9b2ff973b075293e16e148e57a1856498e23e95d (patch)
tree2aac23425e42c6ac2f5949aaa4347c141bb17373 /lib
parente548510b30a5b74f9be9c501d955ca90c7d1a8d0 (diff)
block: Backport of various I/O topology fixes from 2.6.33 and 2.6.34
block: Backport of various I/O topology fixes from 2.6.33 and 2.6.34 The stacking code incorrectly scaled up the data offset in some cases causing misaligned devices to report alignment. Rewrite the stacking algorithm to remedy this. (Upstream commit 9504e0864b58b4a304820dcf3755f1da80d5e72f) The top device misalignment flag would not be set if the added bottom device was already misaligned as opposed to causing a stacking failure. Also massage the reporting so that an error is only returned if adding the bottom device caused the misalignment. I.e. don't return an error if the top is already flagged as misaligned. (Upstream commit fe0b393f2c0a0d23a9bc9ed7dc51a1ee511098bd) lcm() was defined to take integer-sized arguments. The supplied arguments are multiplied, however, causing us to overflow given sufficiently large input. That in turn led to incorrect optimal I/O size reporting in some cases. Switch lcm() over to unsigned long similar to gcd() and move the function from blk-settings.c to lib. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile2
-rw-r--r--lib/lcm.c15
2 files changed, 16 insertions, 1 deletions
diff --git a/lib/Makefile b/lib/Makefile
index 2e78277eff9d..452f188c11e0 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -21,7 +21,7 @@ lib-y += kobject.o kref.o klist.o
obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
- string_helpers.o gcd.o
+ string_helpers.o gcd.o lcm.o
ifeq ($(CONFIG_DEBUG_KOBJECT),y)
CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/lcm.c b/lib/lcm.c
new file mode 100644
index 000000000000..157cd88a6ffc
--- /dev/null
+++ b/lib/lcm.c
@@ -0,0 +1,15 @@
+#include <linux/kernel.h>
+#include <linux/gcd.h>
+#include <linux/module.h>
+
+/* Lowest common multiple */
+unsigned long lcm(unsigned long a, unsigned long b)
+{
+ if (a && b)
+ return (a * b) / gcd(a, b);
+ else if (b)
+ return b;
+
+ return a;
+}
+EXPORT_SYMBOL_GPL(lcm);