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[PATCH] pktcdvd: Reduce stack usage

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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>
This commit is contained in:
Peter Osterlund 2006-02-14 13:52:56 -08:00 committed by Linus Torvalds
parent 948423e5cc
commit 7277232374
1 changed files with 17 additions and 26 deletions
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43
drivers/block/pktcdvd.c
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@ -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);