[PATCH] fs/bio.c: tweaks

- Calculate a variable in bvec_alloc_bs() only once needed, not earlier
  (bio.o down from 18408 to 18376 Bytes, 32 Bytes saved, probably due to
  data locality improvements).

- Init variable idx to silence a gcc warning which already existed in the
  unmodified original base file (bvec_alloc_bs() handles idx correctly, so
  there's no need for the warning):

	fs/bio.c: In function `bio_alloc_bioset':
	fs/bio.c:169: warning: `idx' may be used uninitialized in this function
Signed-off-by: Andreas Mohr <andi@lisas.de>
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/bio.c

@@ -79,7 +79,6 @@ static struct bio_set *fs_bio_set;
 static inline struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx, struct bio_set *bs)
 {
 	struct bio_vec *bvl;
-	struct biovec_slab *bp;
 
 	/*
 	 * see comment near bvec_array define!
@@ -98,10 +97,12 @@ static inline struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned lon
 	 * idx now points to the pool we want to allocate from
 	 */
 
-	bp = bvec_slabs + *idx;
 	bvl = mempool_alloc(bs->bvec_pools[*idx], gfp_mask);
-	if (bvl)
+	if (bvl) {
+		struct biovec_slab *bp = bvec_slabs + *idx;
+
 		memset(bvl, 0, bp->nr_vecs * sizeof(struct bio_vec));
+	}
 
 	return bvl;
 }
@@ -166,7 +167,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 
 		bio_init(bio);
 		if (likely(nr_iovecs)) {
-			unsigned long idx;
+			unsigned long idx = 0; /* shut up gcc */
 
 			bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
 			if (unlikely(!bvl)) {