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sg: convert the direct IO path to use the block layer
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This patch converts the direct IO path (SG_FLAG_DIRECT_IO) to use the
block layer functions (blk_get_request, blk_execute_rq_nowait,
blk_rq_map_user, etc) instead of scsi_execute_async().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Douglas Gilbert <dougg@torque.net>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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FUJITA Tomonori authored and Jens Axboe committed Oct 9, 2008
1 parent 10865df commit 6e5a30c
Showing 1 changed file with 27 additions and 146 deletions.
173 changes: 27 additions & 146 deletions drivers/scsi/sg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,7 @@ typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */
char sg_io_owned; /* 1 -> packet belongs to SG_IO */
volatile char done; /* 0->before bh, 1->before read, 2->read */
struct request *rq;
struct bio *bio;
} Sg_request;

typedef struct sg_fd { /* holds the state of a file descriptor */
Expand Down Expand Up @@ -1679,21 +1680,29 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
sg_io_hdr_t *hp = &srp->header;
int dxfer_len = (int) hp->dxfer_len;
int dxfer_dir = hp->dxfer_direction;
unsigned long uaddr = (unsigned long)hp->dxferp;
Sg_scatter_hold *req_schp = &srp->data;
Sg_scatter_hold *rsv_schp = &sfp->reserve;
struct request_queue *q = sfp->parentdp->device->request_queue;
unsigned long alignment = queue_dma_alignment(q) | q->dma_pad_mask;

SCSI_LOG_TIMEOUT(4, printk("sg_start_req: dxfer_len=%d\n", dxfer_len));

if ((dxfer_len <= 0) || (dxfer_dir == SG_DXFER_NONE))
return __sg_start_req(srp, hp, cmd);

#ifdef SG_ALLOW_DIO_CODE
if (sg_allow_dio && (hp->flags & SG_FLAG_DIRECT_IO) &&
(dxfer_dir != SG_DXFER_UNKNOWN) && (0 == hp->iovec_count) &&
(!sfp->parentdp->device->host->unchecked_isa_dma)) {
res = sg_build_direct(srp, sfp, dxfer_len);
if (res <= 0) /* -ve -> error, 0 -> done, 1 -> try indirect */
return res;
(!sfp->parentdp->device->host->unchecked_isa_dma) &&
!(uaddr & alignment) && !(dxfer_len & alignment)) {
res = __sg_start_req(srp, hp, cmd);
if (!res)
res = sg_build_direct(srp, sfp, dxfer_len);

return res;
}
#endif
if ((!sg_res_in_use(sfp)) && (dxfer_len <= rsv_schp->bufflen))
sg_link_reserve(sfp, srp, dxfer_len);
else {
Expand All @@ -1718,8 +1727,11 @@ sg_finish_rem_req(Sg_request * srp)
else
sg_remove_scat(req_schp);

if (srp->rq)
if (srp->rq) {
if (srp->bio)
blk_rq_unmap_user(srp->bio);
blk_put_request(srp->rq);
}

sg_remove_request(sfp, srp);
}
Expand All @@ -1746,151 +1758,23 @@ sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
return tablesize; /* number of scat_gath elements allocated */
}

#ifdef SG_ALLOW_DIO_CODE
/* vvvvvvvv following code borrowed from st driver's direct IO vvvvvvvvv */
/* TODO: hopefully we can use the generic block layer code */

/* Pin down user pages and put them into a scatter gather list. Returns <= 0 if
- mapping of all pages not successful
(i.e., either completely successful or fails)
*/
static int
st_map_user_pages(struct scatterlist *sgl, const unsigned int max_pages,
unsigned long uaddr, size_t count, int rw)
{
unsigned long end = (uaddr + count + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;
const int nr_pages = end - start;
int res, i, j;
struct page **pages;

/* User attempted Overflow! */
if ((uaddr + count) < uaddr)
return -EINVAL;

/* Too big */
if (nr_pages > max_pages)
return -ENOMEM;

/* Hmm? */
if (count == 0)
return 0;

if ((pages = kmalloc(max_pages * sizeof(*pages), GFP_ATOMIC)) == NULL)
return -ENOMEM;

/* Try to fault in all of the necessary pages */
down_read(&current->mm->mmap_sem);
/* rw==READ means read from drive, write into memory area */
res = get_user_pages(
current,
current->mm,
uaddr,
nr_pages,
rw == READ,
0, /* don't force */
pages,
NULL);
up_read(&current->mm->mmap_sem);

/* Errors and no page mapped should return here */
if (res < nr_pages)
goto out_unmap;

for (i=0; i < nr_pages; i++) {
/* FIXME: flush superflous for rw==READ,
* probably wrong function for rw==WRITE
*/
flush_dcache_page(pages[i]);
/* ?? Is locking needed? I don't think so */
/* if (!trylock_page(pages[i]))
goto out_unlock; */
}

sg_set_page(sgl, pages[0], 0, uaddr & ~PAGE_MASK);
if (nr_pages > 1) {
sgl[0].length = PAGE_SIZE - sgl[0].offset;
count -= sgl[0].length;
for (i=1; i < nr_pages ; i++)
sg_set_page(&sgl[i], pages[i], count < PAGE_SIZE ? count : PAGE_SIZE, 0);
}
else {
sgl[0].length = count;
}

kfree(pages);
return nr_pages;

out_unmap:
if (res > 0) {
for (j=0; j < res; j++)
page_cache_release(pages[j]);
res = 0;
}
kfree(pages);
return res;
}


/* And unmap them... */
static int
st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages,
int dirtied)
{
int i;

for (i=0; i < nr_pages; i++) {
struct page *page = sg_page(&sgl[i]);

if (dirtied)
SetPageDirty(page);
/* unlock_page(page); */
/* FIXME: cache flush missing for rw==READ
* FIXME: call the correct reference counting function
*/
page_cache_release(page);
}

return 0;
}

/* ^^^^^^^^ above code borrowed from st driver's direct IO ^^^^^^^^^ */
#endif


/* Returns: -ve -> error, 0 -> done, 1 -> try indirect */
static int
sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len)
{
#ifdef SG_ALLOW_DIO_CODE
sg_io_hdr_t *hp = &srp->header;
Sg_scatter_hold *schp = &srp->data;
int sg_tablesize = sfp->parentdp->sg_tablesize;
int mx_sc_elems, res;
struct scsi_device *sdev = sfp->parentdp->device;

if (((unsigned long)hp->dxferp &
queue_dma_alignment(sdev->request_queue)) != 0)
return 1;
int res;
struct request *rq = srp->rq;
struct request_queue *q = sfp->parentdp->device->request_queue;

mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
if (mx_sc_elems <= 0) {
return 1;
}
res = st_map_user_pages(schp->buffer, mx_sc_elems,
(unsigned long)hp->dxferp, dxfer_len,
(SG_DXFER_TO_DEV == hp->dxfer_direction) ? 1 : 0);
if (res <= 0) {
sg_remove_scat(schp);
return 1;
}
schp->k_use_sg = res;
res = blk_rq_map_user(q, rq, NULL, hp->dxferp, dxfer_len, GFP_ATOMIC);
if (res)
return res;
srp->bio = rq->bio;
schp->dio_in_use = 1;
hp->info |= SG_INFO_DIRECT_IO;
return 0;
#else
return 1;
#endif
}

static int
Expand Down Expand Up @@ -2069,11 +1953,7 @@ sg_remove_scat(Sg_scatter_hold * schp)
if (schp->buffer && (schp->sglist_len > 0)) {
struct scatterlist *sg = schp->buffer;

if (schp->dio_in_use) {
#ifdef SG_ALLOW_DIO_CODE
st_unmap_user_pages(sg, schp->k_use_sg, TRUE);
#endif
} else {
if (!schp->dio_in_use) {
int k;

for (k = 0; (k < schp->k_use_sg) && sg_page(sg);
Expand All @@ -2083,8 +1963,9 @@ sg_remove_scat(Sg_scatter_hold * schp)
k, sg_page(sg), sg->length));
sg_page_free(sg_page(sg), sg->length);
}

kfree(schp->buffer);
}
kfree(schp->buffer);
}
memset(schp, 0, sizeof (*schp));
}
Expand Down

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