[PATCH] fix small highmem bio bounce bvec handling glitch

[Christophe Saout <christophe@saout.de>]

Hi,

[Oops, forgot to Cc LKML]

while going through the bio highmem handling code I noticed a small
glitch. __end_that_request_first might modify the bv_offset and bv_len
if the segment was partially completed. The bio-read-bounce-back code
should use the unmodified bv_offset when copying the segment data:

--- linux.orig/mm/highmem.c	2004-01-21 19:08:45.000000000 +0100
+++ linux/mm/highmem.c	2004-02-26 15:47:14.574722576 +0100
@@ -294,7 +294,12 @@
 		if (tovec->bv_page == fromvec->bv_page)
 			continue;
 
-		vfrom = page_address(fromvec->bv_page) + fromvec->bv_offset;
+		/*
+		 * fromvec->bv_offset and fromvec->bv_len might have been
+		 * modified by the block layer, so use the original copy,
+		 * bounce_copy_vec already uses tovec->bv_len
+		 */
+		vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 
 		bounce_copy_vec(tovec, vfrom);
 	}