This patch reimplements scsi_execute_async(). In the new version it's a lot less
hackish and also has additional features. Namely:
1. Possibility to insert commands both in tail and in head of the queue.
2. Possibility to explicitly specify if the last SG element has space for padding.
This patch based on the previous patches posted by Tejun Heo. Comparing to them
it has the following improvements:
1. It uses BIOs chaining instead of kmalloc()ing the whole bio.
2. It uses SGs chaining instead of kmalloc()ing one big SG in case if direct
mapping failed (e.g. because of DMA alignment or padding).
3. If direct mapping failed, if possible, it copies only the last SG element,
not the whole SG.
4. When needed, copy_page() is used instead of memcpy() to copy the whole pages.
Also this patch adds and exports functions sg_copy() and sg_copy_elem(), which
cop one SG to another and one SG element to another respectively.
At the moment SCST is the only user of this functionality. It needs it, because
its target drivers, which are, basically, SCSI drivers, can deal only with SGs,
not with BIOs. But, according the latest discussions, there are other potential
users for of this functionality, so I'm sending this patch in a hope that it will be
also useful for them and eventually will be merged in the mainline kernel.
This patch requires previously sent patch with subject "[PATCH]: Rename REQ_COPY_USER
to more descriptive REQ_HAS_TAIL_SPACE_FOR_PADDING".
It's against 2.6.30.1, but if necessary, I can update it to any necessary
kernel version.
Signed-off-by: Vladislav Bolkhovitin <vst@xxxxxxxx>
block/blk-map.c | 408 ++++++++++++++++++++++++++++++++++++++++++++
drivers/scsi/scsi_lib.c | 108 +++++++++++
include/linux/blkdev.h | 3
include/linux/scatterlist.h | 7
include/scsi/scsi_device.h | 11 +
lib/scatterlist.c | 147 +++++++++++++++
6 files changed, 683 insertions(+), 1 deletion(-)
diff -upkr linux-2.6.30.1/block/blk-map.c linux-2.6.30.1/block/blk-map.c
--- linux-2.6.30.1/block/blk-map.c 2009-07-10 21:13:25.000000000 +0400
+++ linux-2.6.30.1/block/blk-map.c 2009-07-14 19:24:36.000000000 +0400
@@ -5,6 +5,7 @@
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
+#include <linux/scatterlist.h>
#include <scsi/sg.h> /* for struct sg_iovec */
#include "blk.h"
@@ -272,6 +273,413 @@ int blk_rq_unmap_user(struct bio *bio)
}
EXPORT_SYMBOL(blk_rq_unmap_user);
+struct blk_kern_sg_hdr {
+ struct scatterlist *orig_sgp;
+ union {
+ struct sg_table new_sg_table;
+ struct scatterlist *saved_sg;
+ };
+ bool tail_only;
+};
+
+#define BLK_KERN_SG_HDR_ENTRIES (1 + (sizeof(struct blk_kern_sg_hdr) - 1) / \
+ sizeof(struct scatterlist))
+
+/**
+ * blk_rq_unmap_kern_sg - "unmaps" data buffers in the request
+ * @req: request to unmap
+ * @do_copy: sets copy data between buffers, if needed, or not
+ *
+ * Description:
+ * It frees all additional buffers allocated for SG->BIO mapping.
+ */
+void blk_rq_unmap_kern_sg(struct request *req, int do_copy)
+{
+ struct blk_kern_sg_hdr *hdr = (struct blk_kern_sg_hdr *)req->end_io_data;
+
+ if (hdr == NULL)
+ goto out;
+
+ if (hdr->tail_only) {
+ /* Tail element only was copied */
+ struct scatterlist *saved_sg = hdr->saved_sg;
+ struct scatterlist *tail_sg = hdr->orig_sgp;
+
+ if ((rq_data_dir(req) == READ) && do_copy)
+ sg_copy_elem(saved_sg, tail_sg, tail_sg->length,
+ KM_BIO_DST_IRQ, KM_BIO_SRC_IRQ);
+
+ __free_pages(sg_page(tail_sg), get_order(tail_sg->length));
+ *tail_sg = *saved_sg;
+ kfree(hdr);
+ } else {
+ /* The whole SG was copied */
+ struct sg_table new_sg_table = hdr->new_sg_table;
+ struct scatterlist *new_sgl = new_sg_table.sgl +
+ BLK_KERN_SG_HDR_ENTRIES;
+ struct scatterlist *orig_sgl = hdr->orig_sgp;
+
+ if ((rq_data_dir(req) == READ) && do_copy)
+ sg_copy(orig_sgl, new_sgl, 0, KM_BIO_DST_IRQ,
+ KM_BIO_SRC_IRQ);
+
+ sg_free_table(&new_sg_table);
+ }
+
+out:
+ return;
+}
+EXPORT_SYMBOL(blk_rq_unmap_kern_sg);
+
+static int blk_rq_handle_align_tail_only(struct request *rq,
+ struct scatterlist *sg_to_copy,
+ gfp_t gfp, gfp_t page_gfp)
+{
+ int res = 0;
+ struct scatterlist *tail_sg = sg_to_copy;
+ struct scatterlist *saved_sg;
+ struct blk_kern_sg_hdr *hdr;
+ int saved_sg_nents;
+ struct page *pg;
+
+ saved_sg_nents = 1 + BLK_KERN_SG_HDR_ENTRIES;
+
+ saved_sg = kmalloc(sizeof(*saved_sg) * saved_sg_nents, gfp);
+ if (saved_sg == NULL)
+ goto out_nomem;
+
+ sg_init_table(saved_sg, saved_sg_nents);
+
+ hdr = (struct blk_kern_sg_hdr *)saved_sg;
+ saved_sg += BLK_KERN_SG_HDR_ENTRIES;
+ saved_sg_nents -= BLK_KERN_SG_HDR_ENTRIES;
+
+ hdr->tail_only = true;
+ hdr->orig_sgp = tail_sg;
+ hdr->saved_sg = saved_sg;
+
+ *saved_sg = *tail_sg;
+
+ pg = alloc_pages(page_gfp, get_order(tail_sg->length));
+ if (pg == NULL)
+ goto err_free_saved_sg;
+
+ sg_assign_page(tail_sg, pg);
+ tail_sg->offset = 0;
+
+ if (rq_data_dir(rq) == WRITE)
+ sg_copy_elem(tail_sg, saved_sg, saved_sg->length,
+ KM_USER1, KM_USER0);
+
+ rq->end_io_data = hdr;
+ rq->cmd_flags |= REQ_HAS_TAIL_SPACE_FOR_PADDING;
+
+out:
+ return res;
+
+err_free_saved_sg:
+ kfree(saved_sg);
+
+out_nomem:
+ res = -ENOMEM;
+ goto out;
+}
+
+static int blk_rq_handle_align(struct request *rq, struct scatterlist **psgl,
+ int *pnents, struct scatterlist *sgl_to_copy,
+ int nents_to_copy, gfp_t gfp, gfp_t page_gfp)
+{
+ int res = 0, i;
+ struct scatterlist *sgl = *psgl;
+ int nents = *pnents;
+ struct sg_table sg_table;
+ struct scatterlist *sg;
+ struct scatterlist *new_sgl;
+ size_t len = 0, to_copy;
+ int new_sgl_nents;
+ struct blk_kern_sg_hdr *hdr;
+
+ if (sgl != sgl_to_copy) {
+ /* copy only the last element */
+ res = blk_rq_handle_align_tail_only(rq, sgl_to_copy,
+ gfp, page_gfp);
+ if (res == 0)
+ goto out;
+ /* else go through */
+ }
+
+ for_each_sg(sgl, sg, nents, i)
+ len += sg->length;
+ to_copy = len;
+
+ new_sgl_nents = PFN_UP(len) + BLK_KERN_SG_HDR_ENTRIES;
+
+ res = sg_alloc_table(&sg_table, new_sgl_nents, gfp);
+ if (res != 0)
+ goto out;
+
+ new_sgl = sg_table.sgl;
+ hdr = (struct blk_kern_sg_hdr *)new_sgl;
+ new_sgl += BLK_KERN_SG_HDR_ENTRIES;
+ new_sgl_nents -= BLK_KERN_SG_HDR_ENTRIES;
+
+ hdr->tail_only = false;
+ hdr->orig_sgp = sgl;
+ hdr->new_sg_table = sg_table;
+
+ for_each_sg(new_sgl, sg, new_sgl_nents, i) {
+ struct page *pg;
+
+ pg = alloc_page(page_gfp);
+ if (pg == NULL)
+ goto err_free_new_sgl;
+
+ sg_assign_page(sg, pg);
+ sg->length = min_t(size_t, PAGE_SIZE, len);
+
+ len -= PAGE_SIZE;
+ }
+
+ if (rq_data_dir(rq) == WRITE) {
+ /*
+ * We need to limit amount of copied data to to_copy, because
+ * sgl might have the last element not marked as last in
+ * SG chaining.
+ */
+ sg_copy(new_sgl, sgl, to_copy, KM_USER0, KM_USER1);
+ }
+
+ rq->end_io_data = hdr;
+ rq->cmd_flags |= REQ_HAS_TAIL_SPACE_FOR_PADDING;
+
+ *psgl = new_sgl;
+ *pnents = new_sgl_nents;
+
+out:
+ return res;
+
+err_free_new_sgl:
+ for_each_sg(new_sgl, sg, new_sgl_nents, i) {
+ struct page *pg = sg_page(sg);
+ if (pg == NULL)
+ break;
+ __free_page(pg);
+ }
+ sg_free_table(&sg_table);
+
+ res = -ENOMEM;
+ goto out;
+}
+
+static void bio_map_kern_endio(struct bio *bio, int err)
+{
+ bio_put(bio);
+}
+
+static int __blk_rq_map_kern_sg(struct request *rq, struct scatterlist *sgl,
+ int nents, gfp_t gfp, struct scatterlist **sgl_to_copy,
+ int *nents_to_copy)
+{
+ int res;
+ struct request_queue *q = rq->q;
+ int rw = rq_data_dir(rq);
+ int max_nr_vecs, i;
+ size_t tot_len;
+ bool need_new_bio;
+ struct scatterlist *sg, *prev_sg = NULL;
+ struct bio *bio = NULL, *hbio = NULL, *tbio = NULL;
+
+ *sgl_to_copy = NULL;
+
+ if (unlikely((sgl == 0) || (nents <= 0))) {
+ WARN_ON(1);
+ res = -EINVAL;
+ goto out;
+ }
+
+ /*
+ * Let's keep each bio allocation inside a single page to decrease
+ * probability of failure.
+ */
+ max_nr_vecs = min_t(size_t,
+ ((PAGE_SIZE - sizeof(struct bio)) / sizeof(struct bio_vec)),
+ BIO_MAX_PAGES);
+
+ need_new_bio = true;
+ tot_len = 0;
+ for_each_sg(sgl, sg, nents, i) {
+ struct page *page = sg_page(sg);
+ void *page_addr = page_address(page);
+ size_t len = sg->length, l;
+ size_t offset = sg->offset;
+
+ tot_len += len;
+ prev_sg = sg;
+
+ /*
+ * Each segment must be aligned on DMA boundary and
+ * not on stack. The last one may have unaligned
+ * length as long as the total length is aligned to
+ * DMA padding alignment.
+ */
+ if (i == nents - 1)
+ l = 0;
+ else
+ l = len;
+ if (((sg->offset | l) & queue_dma_alignment(q)) ||
+ (page_addr && object_is_on_stack(page_addr + sg->offset))) {
+ res = -EINVAL;
+ goto out_need_copy;
+ }
+
+ while (len > 0) {
+ size_t bytes;
+ int rc;
+
+ if (need_new_bio) {
+ bio = bio_kmalloc(gfp, max_nr_vecs);
+ if (bio == NULL) {
+ res = -ENOMEM;
+ goto out_free_bios;
+ }
+
+ if (rw == WRITE)
+ bio->bi_rw |= 1 << BIO_RW;
+
+ bio->bi_end_io = bio_map_kern_endio;
+
+ if (hbio == NULL)
+ hbio = tbio = bio;
+ else
+ tbio = tbio->bi_next = bio;
+ }
+
+ bytes = min_t(size_t, len, PAGE_SIZE - offset);
+
+ rc = bio_add_pc_page(q, bio, page, bytes, offset);
+ if (rc < bytes) {
+ if (unlikely(need_new_bio || (rc < 0))) {
+ if (rc < 0)
+ res = rc;
+ else
+ res = -EIO;
+ goto out_need_copy;
+ } else {
+ need_new_bio = true;
+ len -= rc;
+ offset += rc;
+ continue;
+ }
+ }
+
+ need_new_bio = false;
+ offset = 0;
+ len -= bytes;
+ page = nth_page(page, 1);
+ }
+ }
+
+ if (hbio == NULL) {
+ res = -EINVAL;
+ goto out_free_bios;
+ }
+
+ /* Total length must be aligned on DMA padding alignment */
+ if ((tot_len & q->dma_pad_mask) &&
+ !(rq->cmd_flags & REQ_HAS_TAIL_SPACE_FOR_PADDING)) {
+ res = -EINVAL;
+ if (sgl->offset == 0) {
+ *sgl_to_copy = prev_sg;
+ *nents_to_copy = 1;
+ goto out_free_bios;
+ } else
+ goto out_need_copy;
+ }
+
+ while (hbio != NULL) {
+ bio = hbio;
+ hbio = hbio->bi_next;
+ bio->bi_next = NULL;
+
+ blk_queue_bounce(q, &bio);
+
+ res = blk_rq_append_bio(q, rq, bio);
+ if (unlikely(res != 0)) {
+ bio->bi_next = hbio;
+ hbio = bio;
+ goto out_free_bios;
+ }
+ }
+
+ rq->buffer = rq->data = NULL;
+
+out:
+ return res;
+
+out_need_copy:
+ *sgl_to_copy = sgl;
+ *nents_to_copy = nents;
+
+out_free_bios:
+ while (hbio != NULL) {
+ bio = hbio;
+ hbio = hbio->bi_next;
+ bio_put(bio);
+ }
+ goto out;
+}
+
+/**
+ * blk_rq_map_kern_sg - map kernel data to a request, for REQ_TYPE_BLOCK_PC
+ * @rq: request to fill
+ * @sgl: area to map
+ * @nents: number of elements in @sgl
+ * @gfp: memory allocation flags
+ *
+ * Description:
+ * Data will be mapped directly if possible. Otherwise a bounce
+ * buffer will be used.
+ */
+int blk_rq_map_kern_sg(struct request *rq, struct scatterlist *sgl,
+ int nents, gfp_t gfp)
+{
+ int res;
+ struct scatterlist *sg_to_copy = NULL;
+ int nents_to_copy = 0;
+
+ if (unlikely((sgl == 0) || (sgl->length == 0) ||
+ (nents <= 0) || (rq->end_io_data != NULL))) {
+ WARN_ON(1);
+ res = -EINVAL;
+ goto out;
+ }
+
+ res = __blk_rq_map_kern_sg(rq, sgl, nents, gfp, &sg_to_copy,
+ &nents_to_copy);
+ if (unlikely(res != 0)) {
+ if (sg_to_copy == NULL)
+ goto out;
+
+ res = blk_rq_handle_align(rq, &sgl, &nents, sg_to_copy,
+ nents_to_copy, gfp, rq->q->bounce_gfp | gfp);
+ if (unlikely(res != 0))
+ goto out;
+
+ res = __blk_rq_map_kern_sg(rq, sgl, nents, gfp, &sg_to_copy,
+ &nents_to_copy);
+ if (res != 0) {
+ blk_rq_unmap_kern_sg(rq, 0);
+ goto out;
+ }
+ }
+
+ rq->buffer = rq->data = NULL;
+
+out:
+ return res;
+}
+EXPORT_SYMBOL(blk_rq_map_kern_sg);
+
/**
* blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
* @q: request queue where request should be inserted
diff -upkr linux-2.6.30.1/drivers/scsi/scsi_lib.c linux-2.6.30.1/drivers/scsi/scsi_lib.c
--- linux-2.6.30.1/drivers/scsi/scsi_lib.c 2009-07-10 21:13:25.000000000 +0400
+++ linux-2.6.30.1/drivers/scsi/scsi_lib.c 2009-07-08 21:24:29.000000000 +0400
@@ -277,6 +277,100 @@ int scsi_execute_req(struct scsi_device
}
EXPORT_SYMBOL(scsi_execute_req);
+struct scsi_io_context {
+ void *blk_data;
+ void *data;
+ void (*done)(void *data, char *sense, int result, int resid);
+ char sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+static struct kmem_cache *scsi_io_context_cache;
+
+static void scsi_end_async(struct request *req, int error)
+{
+ struct scsi_io_context *sioc = req->end_io_data;
+
+ req->end_io_data = sioc->blk_data;
+ blk_rq_unmap_kern_sg(req, (error == 0));
+
+ if (sioc->done)
+ sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
+
+ kmem_cache_free(scsi_io_context_cache, sioc);
+ __blk_put_request(req->q, req);
+}
+
+/**
+ * scsi_execute_async - insert request
+ * @sdev: scsi device
+ * @cmd: scsi command
+ * @cmd_len: length of scsi cdb
+ * @data_direction: DMA_TO_DEVICE, DMA_FROM_DEVICE, or DMA_NONE
+ * @sgl: data buffer scatterlist
+ * @nents: number of elements in the sgl
+ * @timeout: request timeout in seconds
+ * @retries: number of times to retry request
+ * @privdata: data passed to done()
+ * @done: callback function when done
+ * @gfp: memory allocation flags
+ * @flags: one or more SCSI_ASYNC_EXEC_FLAG_* flags
+ */
+int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
+ int cmd_len, int data_direction, struct scatterlist *sgl,
+ int nents, int timeout, int retries, void *privdata,
+ void (*done)(void *, char *, int, int), gfp_t gfp,
+ int flags)
+{
+ struct request *req;
+ struct scsi_io_context *sioc;
+ int err = 0;
+ int write = (data_direction == DMA_TO_DEVICE);
+
+ sioc = kmem_cache_zalloc(scsi_io_context_cache, gfp);
+ if (sioc == NULL)
+ return DRIVER_ERROR << 24;
+
+ req = blk_get_request(sdev->request_queue, write, gfp);
+ if (req == NULL)
+ goto free_sense;
+ req->cmd_type = REQ_TYPE_BLOCK_PC;
+ req->cmd_flags |= REQ_QUIET;
+
+ if (flags & SCSI_ASYNC_EXEC_FLAG_HAS_TAIL_SPACE_FOR_PADDING)
+ req->cmd_flags |= REQ_HAS_TAIL_SPACE_FOR_PADDING;
+
+ if (sgl != NULL) {
+ err = blk_rq_map_kern_sg(req, sgl, nents, gfp);
+ if (err)
+ goto free_req;
+ }
+
+ sioc->blk_data = req->end_io_data;
+ sioc->data = privdata;
+ sioc->done = done;
+
+ req->cmd_len = cmd_len;
+ memset(req->cmd, 0, BLK_MAX_CDB); /* ATAPI hates garbage after CDB */
+ memcpy(req->cmd, cmd, req->cmd_len);
+ req->sense = sioc->sense;
+ req->sense_len = 0;
+ req->timeout = timeout;
+ req->retries = retries;
+ req->end_io_data = sioc;
+
+ blk_execute_rq_nowait(req->q, NULL, req,
+ flags & SCSI_ASYNC_EXEC_FLAG_AT_HEAD, scsi_end_async);
+ return 0;
+
+free_req:
+ blk_put_request(req);
+
+free_sense:
+ kmem_cache_free(scsi_io_context_cache, sioc);
+ return DRIVER_ERROR << 24;
+}
+EXPORT_SYMBOL_GPL(scsi_execute_async);
+
/*
* Function: scsi_init_cmd_errh()
*
@@ -1743,12 +1837,20 @@ int __init scsi_init_queue(void)
{
int i;
+ scsi_io_context_cache = kmem_cache_create("scsi_io_context",
+ sizeof(struct scsi_io_context),
+ 0, 0, NULL);
+ if (!scsi_io_context_cache) {
+ printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
+ return -ENOMEM;
+ }
+
scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
sizeof(struct scsi_data_buffer),
0, 0, NULL);
if (!scsi_sdb_cache) {
printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
- return -ENOMEM;
+ goto cleanup_io_context;
}
for (i = 0; i < SG_MEMPOOL_NR; i++) {
@@ -1784,6 +1886,9 @@ cleanup_sdb:
}
kmem_cache_destroy(scsi_sdb_cache);
+cleanup_io_context:
+ kmem_cache_destroy(scsi_io_context_cache);
+
return -ENOMEM;
}
@@ -1791,6 +1896,7 @@ void scsi_exit_queue(void)
{
int i;
+ kmem_cache_destroy(scsi_io_context_cache);
kmem_cache_destroy(scsi_sdb_cache);
for (i = 0; i < SG_MEMPOOL_NR; i++) {
diff -upkr linux-2.6.30.1/include/linux/blkdev.h linux-2.6.30.1/include/linux/blkdev.h
--- linux-2.6.30.1/include/linux/blkdev.h 2009-07-10 21:13:25.000000000 +0400
+++ linux-2.6.30.1/include/linux/blkdev.h 2009-07-13 13:56:45.000000000 +0400
@@ -807,6 +807,9 @@ extern int blk_rq_map_kern(struct reques
extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
struct rq_map_data *, struct sg_iovec *, int,
unsigned int, gfp_t);
+extern int blk_rq_map_kern_sg(struct request *rq,
+ struct scatterlist *sgl, int nents, gfp_t gfp);
+extern void blk_rq_unmap_kern_sg(struct request *req, int do_copy);
extern int blk_execute_rq(struct request_queue *, struct gendisk *,
struct request *, int);
extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
diff -upkr linux-2.6.30.1/include/linux/scatterlist.h linux-2.6.30.1/include/linux/scatterlist.h
--- linux-2.6.30.1/include/linux/scatterlist.h 2009-06-10 07:05:27.000000000 +0400
+++ linux-2.6.30.1/include/linux/scatterlist.h 2009-07-13 13:56:24.000000000 +0400
@@ -218,6 +218,13 @@ size_t sg_copy_from_buffer(struct scatte
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen);
+int sg_copy_elem(struct scatterlist *dst_sg, struct scatterlist *src_sg,
+ size_t copy_len, enum km_type d_km_type,
+ enum km_type s_km_type);
+int sg_copy(struct scatterlist *dst_sg,
+ struct scatterlist *src_sg, size_t copy_len,
+ enum km_type d_km_type, enum km_type s_km_type);
+
/*
* Maximum number of entries that will be allocated in one piece, if
* a list larger than this is required then chaining will be utilized.
diff -upkr linux-2.6.30.1/include/scsi/scsi_device.h linux-2.6.30.1/include/scsi/scsi_device.h
--- linux-2.6.30.1/include/scsi/scsi_device.h 2009-07-10 21:13:25.000000000 +0400
+++ linux-2.6.30.1/include/scsi/scsi_device.h 2009-07-08 21:24:29.000000000 +0400
@@ -372,6 +372,17 @@ extern int scsi_execute_req(struct scsi_
struct scsi_sense_hdr *, int timeout, int retries,
int *resid);
+#define SCSI_ASYNC_EXEC_FLAG_AT_HEAD 1
+#define SCSI_ASYNC_EXEC_FLAG_HAS_TAIL_SPACE_FOR_PADDING 2
+
+#define SCSI_EXEC_REQ_FIFO_DEFINED
+extern int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
+ int cmd_len, int data_direction,
+ struct scatterlist *sgl, int nents, int timeout,
+ int retries, void *privdata,
+ void (*done)(void *, char *, int, int),
+ gfp_t gfp, int flags);
+
static inline int __must_check scsi_device_reprobe(struct scsi_device *sdev)
{
return device_reprobe(&sdev->sdev_gendev);
diff -upkr linux-2.6.30.1/lib/scatterlist.c linux-2.6.30.1/lib/scatterlist.c
--- linux-2.6.30.1/lib/scatterlist.c 2009-06-10 07:05:27.000000000 +0400
+++ linux-2.6.30.1/lib/scatterlist.c 2009-07-14 19:22:49.000000000 +0400
@@ -485,3 +485,150 @@ size_t sg_copy_to_buffer(struct scatterl
return sg_copy_buffer(sgl, nents, buf, buflen, 1);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
+
+/*
+ * Can switch to the next dst_sg element, so, to copy to strictly only
+ * one dst_sg element, it must be either last in the chain, or
+ * copy_len == dst_sg->length.
+ */
+static int __sg_copy_elem(struct scatterlist **pdst_sg, size_t *pdst_len,
+ size_t *pdst_offs, struct scatterlist *src_sg,
+ size_t copy_len,
+ enum km_type d_km_type, enum km_type s_km_type)
+{
+ int res = 0;
+ struct scatterlist *dst_sg;
+ size_t src_len, dst_len, src_offs, dst_offs;
+ struct page *src_page, *dst_page;
+
+ if (copy_len == 0)
+ copy_len = 0x7FFFFFFF; /* copy all */
+
+ dst_sg = *pdst_sg;
+ dst_len = *pdst_len;
+ dst_offs = *pdst_offs;
+ dst_page = sg_page(dst_sg);
+
+ src_page = sg_page(src_sg);
+ src_len = src_sg->length;
+ src_offs = src_sg->offset;
+
+ do {
+ void *saddr, *daddr;
+ size_t n;
+
+ saddr = kmap_atomic(src_page +
+ (src_offs >> PAGE_SHIFT), s_km_type) +
+ (src_offs & ~PAGE_MASK);
+ daddr = kmap_atomic(dst_page +
+ (dst_offs >> PAGE_SHIFT), d_km_type) +
+ (dst_offs & ~PAGE_MASK);
+
+ if (((src_offs & ~PAGE_MASK) == 0) &&
+ ((dst_offs & ~PAGE_MASK) == 0) &&
+ (src_len >= PAGE_SIZE) && (dst_len >= PAGE_SIZE) &&
+ (copy_len >= PAGE_SIZE)) {
+ copy_page(daddr, saddr);
+ n = PAGE_SIZE;
+ } else {
+ n = min_t(size_t, PAGE_SIZE - (dst_offs & ~PAGE_MASK),
+ PAGE_SIZE - (src_offs & ~PAGE_MASK));
+ n = min(n, src_len);
+ n = min(n, dst_len);
+ n = min_t(size_t, n, copy_len);
+ memcpy(daddr, saddr, n);
+ }
+ dst_offs += n;
+ src_offs += n;
+
+ kunmap_atomic(saddr, s_km_type);
+ kunmap_atomic(daddr, d_km_type);
+
+ res += n;
+ copy_len -= n;
+ if (copy_len == 0)
+ goto out;
+
+ src_len -= n;
+ dst_len -= n;
+ if (dst_len == 0) {
+ dst_sg = sg_next(dst_sg);
+ if (dst_sg == NULL)
+ goto out;
+ dst_page = sg_page(dst_sg);
+ dst_len = dst_sg->length;
+ dst_offs = dst_sg->offset;
+ }
+ } while (src_len > 0);
+
+out:
+ *pdst_sg = dst_sg;
+ *pdst_len = dst_len;
+ *pdst_offs = dst_offs;
+ return res;
+}
+
+/**
+ * sg_copy_elem - copy one SG element to another
+ * @dst_sg: destination SG element
+ * @src_sg: source SG element
+ * @copy_len: maximum amount of data to copy. If 0, then copy all.
+ * @d_km_type: kmap_atomic type for the destination SG
+ * @s_km_type: kmap_atomic type for the source SG
+ *
+ * Description:
+ * Data from the source SG element will be copied to the destination SG
+ * element. Returns number of bytes copied. Can switch to the next dst_sg
+ * element, so, to copy to strictly only one dst_sg element, it must be
+ * either last in the chain, or copy_len == dst_sg->length.
+ */
+int sg_copy_elem(struct scatterlist *dst_sg, struct scatterlist *src_sg,
+ size_t copy_len, enum km_type d_km_type,
+ enum km_type s_km_type)
+{
+ size_t dst_len = dst_sg->length, dst_offs = dst_sg->offset;
+
+ return __sg_copy_elem(&dst_sg, &dst_len, &dst_offs, src_sg,
+ copy_len, d_km_type, s_km_type);
+}
+EXPORT_SYMBOL(sg_copy_elem);
+
+/**
+ * sg_copy - copy one SG vector to another
+ * @dst_sg: destination SG
+ * @src_sg: source SG
+ * @copy_len: maximum amount of data to copy. If 0, then copy all.
+ * @d_km_type: kmap_atomic type for the destination SG
+ * @s_km_type: kmap_atomic type for the source SG
+ *
+ * Description:
+ * Data from the source SG vector will be copied to the destination SG
+ * vector. End of the vectors will be determined by sg_next() returning
+ * NULL. Returns number of bytes copied.
+ */
+int sg_copy(struct scatterlist *dst_sg,
+ struct scatterlist *src_sg, size_t copy_len,
+ enum km_type d_km_type, enum km_type s_km_type)
+{
+ int res = 0;
+ size_t dst_len, dst_offs;
+
+ if (copy_len == 0)
+ copy_len = 0x7FFFFFFF; /* copy all */
+
+ dst_len = dst_sg->length;
+ dst_offs = dst_sg->offset;
+
+ do {
+ copy_len -= __sg_copy_elem(&dst_sg, &dst_len, &dst_offs,
+ src_sg, copy_len, d_km_type, s_km_type);
+ if ((copy_len == 0) || (dst_sg == NULL))
+ goto out;
+
+ src_sg = sg_next(src_sg);
+ } while (src_sg != NULL);
+
+out:
+ return res;
+}
+EXPORT_SYMBOL(sg_copy);
--
Home page of SCST and target drivers: http://scst.sourceforge.net
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