[PATCH] pktcdvd: Reduce stack usage

Reduce stack usage in the pkt_start_write() function.  Even though it's not
currently a real problem, the pages and offsets arrays can be eliminated,
which saves approximately 1000 bytes of stack space.

Signed-off-by: Peter Osterlund <petero2@telia.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 26 deletions

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 89d8fe014efa..93e44d0292ab 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -645,7 +645,7 @@ static void pkt_copy_bio_data(struct bio *src_bio, int seg, int offs, struct pag
  * b) The data can be used as cache to avoid read requests if we receive a
  *    new write request for the same zone.
  */
-static void pkt_make_local_copy(struct packet_data *pkt, struct page **pages, int *offsets)
+static void pkt_make_local_copy(struct packet_data *pkt, struct bio_vec *bvec)
 {
         int f, p, offs;
 
@@ -653,15 +653,15 @@ static void pkt_make_local_copy(struct packet_data *pkt, struct page **pages, in
         p = 0;
         offs = 0;
         for (f = 0; f < pkt->frames; f++) {
-                if (pages[f] != pkt->pages[p]) {
-                        void *vfrom = kmap_atomic(pages[f], KM_USER0) + offsets[f];
+                if (bvec[f].bv_page != pkt->pages[p]) {
+                        void *vfrom = kmap_atomic(bvec[f].bv_page, KM_USER0) + bvec[f].bv_offset;
                         void *vto = page_address(pkt->pages[p]) + offs;
                         memcpy(vto, vfrom, CD_FRAMESIZE);
                         kunmap_atomic(vfrom, KM_USER0);
-                        pages[f] = pkt->pages[p];
-                        offsets[f] = offs;
+                        bvec[f].bv_page = pkt->pages[p];
+                        bvec[f].bv_offset = offs;
                 } else {
-                        BUG_ON(offsets[f] != offs);
+                        BUG_ON(bvec[f].bv_offset != offs);
                 }
                 offs += CD_FRAMESIZE;
                 if (offs >= PAGE_SIZE) {
@@ -991,18 +991,17 @@ try_next_bio:
 static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
 {
         struct bio *bio;
-        struct page *pages[PACKET_MAX_SIZE];
-        int offsets[PACKET_MAX_SIZE];
         int f;
         int frames_write;
+        struct bio_vec *bvec = pkt->w_bio->bi_io_vec;
 
         for (f = 0; f < pkt->frames; f++) {
-                pages[f] = pkt->pages[(f * CD_FRAMESIZE) / PAGE_SIZE];
-                offsets[f] = (f * CD_FRAMESIZE) % PAGE_SIZE;
+                bvec[f].bv_page = pkt->pages[(f * CD_FRAMESIZE) / PAGE_SIZE];
+                bvec[f].bv_offset = (f * CD_FRAMESIZE) % PAGE_SIZE;
         }
 
         /*
-         * Fill-in pages[] and offsets[] with data from orig_bios.
+         * Fill-in bvec with data from orig_bios.
          */
         frames_write = 0;
         spin_lock(&pkt->lock);
@@ -1024,11 +1023,11 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
                         }
 
                         if (src_bvl->bv_len - src_offs >= CD_FRAMESIZE) {
-                                pages[f] = src_bvl->bv_page;
-                                offsets[f] = src_bvl->bv_offset + src_offs;
+                                bvec[f].bv_page = src_bvl->bv_page;
+                                bvec[f].bv_offset = src_bvl->bv_offset + src_offs;
                         } else {
                                 pkt_copy_bio_data(bio, segment, src_offs,
-                                                  pages[f], offsets[f]);
+                                                  bvec[f].bv_page, bvec[f].bv_offset);
                         }
                         src_offs += CD_FRAMESIZE;
                         frames_write++;
@@ -1042,7 +1041,7 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
         BUG_ON(frames_write != pkt->write_size);
 
         if (test_bit(PACKET_MERGE_SEGS, &pd->flags) || (pkt->write_size < pkt->frames)) {
-                pkt_make_local_copy(pkt, pages, offsets);
+                pkt_make_local_copy(pkt, bvec);
                 pkt->cache_valid = 1;
         } else {
                 pkt->cache_valid = 0;
@@ -1055,17 +1054,9 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
         pkt->w_bio->bi_bdev = pd->bdev;
         pkt->w_bio->bi_end_io = pkt_end_io_packet_write;
         pkt->w_bio->bi_private = pkt;
-        for (f = 0; f < pkt->frames; f++) {
-                if ((f + 1 < pkt->frames) && (pages[f + 1] == pages[f]) &&
-                    (offsets[f + 1] = offsets[f] + CD_FRAMESIZE)) {
-                        if (!bio_add_page(pkt->w_bio, pages[f], CD_FRAMESIZE * 2, offsets[f]))
-                                BUG();
-                        f++;
-                } else {
-                        if (!bio_add_page(pkt->w_bio, pages[f], CD_FRAMESIZE, offsets[f]))
-                                BUG();
-                }
-        }
+        for (f = 0; f < pkt->frames; f++)
+                if (!bio_add_page(pkt->w_bio, bvec[f].bv_page, CD_FRAMESIZE, bvec[f].bv_offset))
+                        BUG();
         VPRINTK("pktcdvd: vcnt=%d\n", pkt->w_bio->bi_vcnt);
 
         atomic_set(&pkt->io_wait, 1);