diskio: sanitize the reduced transfer sizes

Simply shift the size left by 1 when computing the transfer sizes.
This will always end with the values ..., 1, 0 as it should.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/core/fs/diskio.c b/core/fs/diskio.c
index 6afba21..cdbed79 100644 (file)
--- a/core/fs/diskio.c
+++ b/core/fs/diskio.c
@@ -74,8 +74,8 @@ static int chs_rdwr_sectors(struct disk *disk, void *buf,
            if (retry--)
                continue;
 
-            /* if we are reading ONE sector and go here, just make it _faile_ */
-            chunk = chunk == 1 ? 0 : ((chunk+1) >> 1);
+           /* For any starting value, this will always end with ..., 1, 0 */
+           chunk >>= 1;
             if (chunk) {
                MaxTransfer = chunk;
                retry = RETRY_COUNT;
@@ -163,13 +163,16 @@ static int edd_rdwr_sectors(struct disk *disk, void *buf,
                break;
            if (retry--)
                continue;
-           chunk = chunk == 1 ? 0 : ((chunk+1) >> 1);
+
+           /* For any starting value, this will always end with ..., 1, 0 */
+           chunk >>= 1;
            if (chunk) {
                MaxTransfer = chunk;
                retry = RETRY_COUNT;
                 pkt.blocks = chunk;
                continue;
            }
+
            /*** XXX: Consider falling back to CHS here?! ***/
             printf("reading sectors error(EDD)\n");
            return done;        /* Failure */