[PATCH v2 5/7] scsi_debug: prepare to enable clustering

Akinobu Mita
2014-01-19T13:52:02Z

Currently, clustering support for scsi_debug is disabled. This is
because there are for_each_sg() loops which assume that each sg list
element is consisted with a single page. But enabling clustering
support, each sg list element for scsi commands can be consisted with
multiple pages.

This replaces these for_each_sg() loops with sg mapping iterator which
is capable of handling each sg list element is consisted with multiple
pages.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
---
Change from previous version:
- remove unnecessary irqsave/irqrestore while iterating sg mapping

drivers/scsi/scsi_debug.c | 109 +++++++++++++++++++++++++---------------------
1 file changed, 59 insertions(+), 50 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index a102519..004b985 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1789,23 +1789,27 @@ static int dif_verify(struct sd_dif_tuple *sdt, const void *data,
static void dif_copy_prot(struct scsi_cmnd *SCpnt, sector_t sector,
unsigned int sectors, bool read)
{
- unsigned int i, resid;
- struct scatterlist *psgl;
+ size_t resid;
void *paddr;
const void *dif_store_end = dif_storep + sdebug_store_sectors;
+ struct sg_mapping_iter miter;

/* Bytes of protection data to copy into sgl */
resid = sectors * sizeof(*dif_storep);

- scsi_for_each_prot_sg(SCpnt, psgl, scsi_prot_sg_count(SCpnt), i) {
- int len = min(psgl->length, resid);
+ sg_miter_start(&miter, scsi_prot_sglist(SCpnt),
+ scsi_prot_sg_count(SCpnt), SG_MITER_ATOMIC |
+ (read ? SG_MITER_TO_SG : SG_MITER_FROM_SG));
+
+ while (sg_miter_next(&miter) && resid > 0) {
+ size_t len = min(miter.length, resid);
void *start = dif_store(sector);
- int rest = 0;
+ size_t rest = 0;

if (dif_store_end < start + len)
rest = start + len - dif_store_end;

- paddr = kmap_atomic(sg_page(psgl)) + psgl->offset;
+ paddr = miter.addr;

if (read)
memcpy(paddr, start, len - rest);
@@ -1821,8 +1825,8 @@ static void dif_copy_prot(struct scsi_cmnd *SCpnt, sector_t sector,

sector += len / sizeof(*dif_storep);
resid -= len;
- kunmap_atomic(paddr);
}
+ sg_miter_stop(&miter);
}

static int prot_verify_read(struct scsi_cmnd *SCpnt, sector_t start_sec,
@@ -1929,55 +1933,62 @@ void dump_sector(unsigned char *buf, int len)
static int prot_verify_write(struct scsi_cmnd *SCpnt, sector_t start_sec,
unsigned int sectors, u32 ei_lba)
{
- int i, j, ret;
+ int ret;
struct sd_dif_tuple *sdt;
- struct scatterlist *dsgl;
- struct scatterlist *psgl = scsi_prot_sglist(SCpnt);
- void *daddr, *paddr;
+ void *daddr;
sector_t sector = start_sec;
int ppage_offset;
+ int dpage_offset;
+ struct sg_mapping_iter diter;
+ struct sg_mapping_iter piter;

BUG_ON(scsi_sg_count(SCpnt) == 0);
BUG_ON(scsi_prot_sg_count(SCpnt) == 0);

- ppage_offset = 0;
-
- /* For each data page */
- scsi_for_each_sg(SCpnt, dsgl, scsi_sg_count(SCpnt), i) {
- daddr = kmap_atomic(sg_page(dsgl)) + dsgl->offset;
- paddr = kmap_atomic(sg_page(psgl)) + psgl->offset;
-
- /* For each sector-sized chunk in data page */
- for (j = 0; j < dsgl->length; j += scsi_debug_sector_size) {
+ sg_miter_start(&piter, scsi_prot_sglist(SCpnt),
+ scsi_prot_sg_count(SCpnt),
+ SG_MITER_ATOMIC | SG_MITER_FROM_SG);
+ sg_miter_start(&diter, scsi_sglist(SCpnt), scsi_sg_count(SCpnt),
+ SG_MITER_ATOMIC | SG_MITER_FROM_SG);
+
+ /* For each protection page */
+ while (sg_miter_next(&piter)) {
+ dpage_offset = 0;
+ if (WARN_ON(!sg_miter_next(&diter))) {
+ ret = 0x01;
+ goto out;
+ }

+ for (ppage_offset = 0; ppage_offset < piter.length;
+ ppage_offset += sizeof(struct sd_dif_tuple)) {
/* If we're at the end of the current
- * protection page advance to the next one
+ * data page advance to the next one
*/
- if (ppage_offset >= psgl->length) {
- kunmap_atomic(paddr);
- psgl = sg_next(psgl);
- BUG_ON(psgl == NULL);
- paddr = kmap_atomic(sg_page(psgl))
- + psgl->offset;
- ppage_offset = 0;
+ if (dpage_offset >= diter.length) {
+ if (WARN_ON(!sg_miter_next(&diter))) {
+ ret = 0x01;
+ goto out;
+ }
+ dpage_offset = 0;
}

- sdt = paddr + ppage_offset;
+ sdt = piter.addr + ppage_offset;
+ daddr = diter.addr + dpage_offset;

- ret = dif_verify(sdt, daddr + j, sector, ei_lba);
+ ret = dif_verify(sdt, daddr, sector, ei_lba);
if (ret) {
- dump_sector(daddr + j, scsi_debug_sector_size);
+ dump_sector(daddr, scsi_debug_sector_size);
goto out;
}

sector++;
ei_lba++;
- ppage_offset += sizeof(struct sd_dif_tuple);
+ dpage_offset += scsi_debug_sector_size;
}
-
- kunmap_atomic(paddr);
- kunmap_atomic(daddr);
+ diter.consumed = dpage_offset;
+ sg_miter_stop(&diter);
}
+ sg_miter_stop(&piter);

dif_copy_prot(SCpnt, start_sec, sectors, false);
dix_writes++;
@@ -1986,8 +1997,8 @@ static int prot_verify_write(struct scsi_cmnd *SCpnt, sector_t start_sec,

out:
dif_errors++;
- kunmap_atomic(paddr);
- kunmap_atomic(daddr);
+ sg_miter_stop(&diter);
+ sg_miter_stop(&piter);
return ret;
}

@@ -2311,11 +2322,11 @@ static int resp_report_luns(struct scsi_cmnd * scp,
static int resp_xdwriteread(struct scsi_cmnd *scp, unsigned long long lba,
unsigned int num, struct sdebug_dev_info *devip)
{
- int i, j, ret = -1;
+ int j;
unsigned char *kaddr, *buf;
unsigned int offset;
- struct scatterlist *sg;
struct scsi_data_buffer *sdb = scsi_in(scp);
+ struct sg_mapping_iter miter;

/* better not to use temporary buffer. */
buf = kmalloc(scsi_bufflen(scp), GFP_ATOMIC);
@@ -2328,22 +2339,20 @@ static int resp_xdwriteread(struct scsi_cmnd *scp, unsigned long long lba,
scsi_sg_copy_to_buffer(scp, buf, scsi_bufflen(scp));

offset = 0;
- for_each_sg(sdb->table.sgl, sg, sdb->table.nents, i) {
- kaddr = (unsigned char *)kmap_atomic(sg_page(sg));
- if (!kaddr)
- goto out;
+ sg_miter_start(&miter, sdb->table.sgl, sdb->table.nents,
+ SG_MITER_ATOMIC | SG_MITER_TO_SG);

- for (j = 0; j < sg->length; j++)
- *(kaddr + sg->offset + j) ^= *(buf + offset + j);
+ while (sg_miter_next(&miter)) {
+ kaddr = miter.addr;
+ for (j = 0; j < miter.length; j++)
+ *(kaddr + j) ^= *(buf + offset + j);

- offset += sg->length;
- kunmap_atomic(kaddr);
+ offset += miter.length;
}
- ret = 0;
-out:
+ sg_miter_stop(&miter);
kfree(buf);

- return ret;
+ return 0;
}

/* When timer goes off this function is called. */
--
1.8.3.2