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Subject[58/93] /dev/mem: introduce size_inside_page()
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Wu Fengguang <fengguang.wu@intel.com>

commit f222318e9c3a315723e3524fb9d6566b2430db44 upstream

/dev/mem: introduce size_inside_page()

[ cebbert@redhat.com : backport to 2.6.32 ]
[ subset of original patch, for just /dev/kmem ]

Introduce size_inside_page() to replace duplicate /dev/mem code.

Also apply it to /dev/kmem, whose alignment logic was buggy.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/char/mem.c | 40 +++++++++++++++++-----------------------
1 file changed, 17 insertions(+), 23 deletions(-)

--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -35,6 +35,19 @@
# include <linux/efi.h>
#endif

+static inline unsigned long size_inside_page(unsigned long start,
+ unsigned long size)
+{
+ unsigned long sz;
+
+ if (-start & (PAGE_SIZE - 1))
+ sz = -start & (PAGE_SIZE - 1);
+ else
+ sz = PAGE_SIZE;
+
+ return min_t(unsigned long, sz, size);
+}
+
/*
* Architectures vary in how they handle caching for addresses
* outside of main memory.
@@ -430,15 +443,7 @@ static ssize_t read_kmem(struct file *fi
}
#endif
while (low_count > 0) {
- /*
- * Handle first page in case it's not aligned
- */
- if (-p & (PAGE_SIZE - 1))
- sz = -p & (PAGE_SIZE - 1);
- else
- sz = PAGE_SIZE;
-
- sz = min_t(unsigned long, sz, low_count);
+ sz = size_inside_page(p, low_count);

/*
* On ia64 if a page has been mapped somewhere as
@@ -462,10 +467,8 @@ static ssize_t read_kmem(struct file *fi
if (!kbuf)
return -ENOMEM;
while (count > 0) {
- int len = count;
+ int len = size_inside_page(p, count);

- if (len > PAGE_SIZE)
- len = PAGE_SIZE;
len = vread(kbuf, (char *)p, len);
if (!len)
break;
@@ -510,15 +513,8 @@ do_write_kmem(void *p, unsigned long rea

while (count > 0) {
char *ptr;
- /*
- * Handle first page in case it's not aligned
- */
- if (-realp & (PAGE_SIZE - 1))
- sz = -realp & (PAGE_SIZE - 1);
- else
- sz = PAGE_SIZE;

- sz = min_t(unsigned long, sz, count);
+ sz = size_inside_page(realp, count);

/*
* On ia64 if a page has been mapped somewhere as
@@ -578,10 +574,8 @@ static ssize_t write_kmem(struct file *
if (!kbuf)
return wrote ? wrote : -ENOMEM;
while (count > 0) {
- int len = count;
+ int len = size_inside_page(p, count);

- if (len > PAGE_SIZE)
- len = PAGE_SIZE;
if (len) {
written = copy_from_user(kbuf, buf, len);
if (written) {



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