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authorJames Bottomley <JBottomley@Odin.com>2015-03-05 18:47:01 -0800
committerJames Bottomley <JBottomley@Odin.com>2015-04-10 16:27:48 -0700
commitb9f28d863594c429e1df35a0474d2663ca28b307 (patch)
tree75a15cd66637d33e6d8e6e0c6cdd67e44790b376 /include/linux/string_helpers.h
parentcad2e03d8607793fd71a830b4b41fc8e9e9995ea (diff)
sd, mmc, virtio_blk, string_helpers: fix block size units
The current string_get_size() overflows when the device size goes over 2^64 bytes because the string helper routine computes the suffix from the size in bytes. However, the entirety of Linux thinks in terms of blocks, not bytes, so this will artificially induce an overflow on very large devices. Fix this by making the function string_get_size() take blocks and the block size instead of bytes. This should allow us to keep working until the current SCSI standard overflows. Also fix virtio_blk and mmc (both of which were also artificially multiplying by the block size to pass a byte side to string_get_size()). The mathematics of this is pretty simple: we're taking a product of size in blocks (S) and block size (B) and trying to re-express this in exponential form: S*B = R*N^E (where N, the exponent is either 1000 or 1024) and R < N. Mathematically, S = RS*N^ES and B=RB*N^EB, so if RS*RB < N it's easy to see that S*B = RS*RB*N^(ES+EB). However, if RS*BS > N, we can see that this can be re-expressed as RS*BS = R*N (where R = RS*BS/N < N) so the whole exponent becomes R*N^(ES+EB+1) [jejb: fix incorrect 32 bit do_div spotted by kbuild test robot <fengguang.wu@intel.com>] Acked-by: Ulf Hansson <ulf.hansson@linaro.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: James Bottomley <JBottomley@Odin.com>
Diffstat (limited to 'include/linux/string_helpers.h')
-rw-r--r--include/linux/string_helpers.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index 657571817260..263328063730 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -10,7 +10,7 @@ enum string_size_units {
STRING_UNITS_2, /* use binary powers of 2^10 */
};
-void string_get_size(u64 size, enum string_size_units units,
+void string_get_size(u64 size, u64 blk_size, enum string_size_units units,
char *buf, int len);
#define UNESCAPE_SPACE 0x01