[PATCH] Forcing capacity sizes for block devices

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Make the size attribute of block devices writable via sysfs. This
allows userspace to force
device boundaries in cases where the device driver is unable to detect
the correct size, as
with spec-incompliant SD card readers. Also see
http://marc.info/?t=125555550200010&r=1&w=2

diff -uprN -X linux-2.6.32-vanilla/Documentation/dontdiff
linux-2.6.32-vanilla/block/genhd.c linux-2.6.32-patched/block/genhd.c
--- linux-2.6.32-vanilla/block/genhd.c	2009-12-03 04:51:21.000000000 +0100
+++ linux-2.6.32-patched/block/genhd.c	2009-12-15 14:38:24.962463446 +0100
@@ -865,7 +865,7 @@ static DEVICE_ATTR(range, S_IRUGO, disk_
 static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);
 static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
 static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
-static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
+static DEVICE_ATTR(size, S_IRUGO | S_IWUSR, part_size_show, part_size_set);
 static DEVICE_ATTR(alignment_offset, S_IRUGO,
disk_alignment_offset_show, NULL);
 static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
diff -uprN -X linux-2.6.32-vanilla/Documentation/dontdiff
linux-2.6.32-vanilla/fs/partitions/check.c
linux-2.6.32-patched/fs/partitions/check.c
--- linux-2.6.32-vanilla/fs/partitions/check.c	2009-12-03
04:51:21.000000000 +0100
+++ linux-2.6.32-patched/fs/partitions/check.c	2009-12-19
10:38:58.745294907 +0100
@@ -219,6 +219,18 @@ ssize_t part_size_show(struct device *de
 	return sprintf(buf, "%llu\n",(unsigned long long)p->nr_sects);
 }

+ssize_t part_size_set(struct device *dev,
+		      struct device_attribute *attr, char *buf, size_t len)
+{
+	struct hd_struct *p = dev_to_part(dev);
+	unsigned long long val;
+	if (strict_strtoull(buf, 0, &val))
+		return -EINVAL;
+
+	p->nr_sects = val;
+	return len;
+}
+
 ssize_t part_alignment_offset_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
diff -uprN -X linux-2.6.32-vanilla/Documentation/dontdiff
linux-2.6.32-vanilla/include/linux/genhd.h
linux-2.6.32-patched/include/linux/genhd.h
--- linux-2.6.32-vanilla/include/linux/genhd.h	2009-12-03
04:51:21.000000000 +0100
+++ linux-2.6.32-patched/include/linux/genhd.h	2009-12-19
10:40:30.900871273 +0100
@@ -549,6 +549,9 @@ extern void blk_unregister_region(dev_t

 extern ssize_t part_size_show(struct device *dev,
 			      struct device_attribute *attr, char *buf);
+extern ssize_t part_size_set(struct device *dev,
+			     struct device_attribute *attr, char *buf,
+			     size_t len);
 extern ssize_t part_stat_show(struct device *dev,
 			      struct device_attribute *attr, char *buf);
 extern ssize_t part_inflight_show(struct device *dev,

Signed-off-by: Clemens Fruhwirth <clemens@xxxxxxxxxxxxx>
Reviewed-by: Grant Grundler <grundler@xxxxxxxxxx>
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