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Commit 72772323 authored by Peter Osterlund's avatar Peter Osterlund Committed by Linus Torvalds
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[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: default avatarPeter Osterlund <petero2@telia.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 948423e5

drivers/block/pktcdvd.c

+17 −26
Original line number Diff line number Diff line
@@ -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 @@ static int pkt_handle_queue(struct pktcdvd_device *pd) 
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]))

	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);