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authorJames Bottomley <JBottomley@Odin.com>2015-03-06 05:47:01 +0300
committerJames Bottomley <JBottomley@Odin.com>2015-04-11 02:27:48 +0300
commitb9f28d863594c429e1df35a0474d2663ca28b307 (patch)
tree75a15cd66637d33e6d8e6e0c6cdd67e44790b376 /drivers/block
parentcad2e03d8607793fd71a830b4b41fc8e9e9995ea (diff)
downloadlinux-b9f28d863594c429e1df35a0474d2663ca28b307.tar.xz
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 'drivers/block')
-rw-r--r--drivers/block/virtio_blk.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 655e570b9b31..5ea2f0bbbc7c 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -342,7 +342,7 @@ static void virtblk_config_changed_work(struct work_struct *work)
struct request_queue *q = vblk->disk->queue;
char cap_str_2[10], cap_str_10[10];
char *envp[] = { "RESIZE=1", NULL };
- u64 capacity, size;
+ u64 capacity;
/* Host must always specify the capacity. */
virtio_cread(vdev, struct virtio_blk_config, capacity, &capacity);
@@ -354,9 +354,10 @@ static void virtblk_config_changed_work(struct work_struct *work)
capacity = (sector_t)-1;
}
- size = capacity * queue_logical_block_size(q);
- string_get_size(size, STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
- string_get_size(size, STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
+ string_get_size(capacity, queue_logical_block_size(q),
+ STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
+ string_get_size(capacity, queue_logical_block_size(q),
+ STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
dev_notice(&vdev->dev,
"new size: %llu %d-byte logical blocks (%s/%s)\n",