[PATCH 25/35] libfc: Add routine to copy data from a buffer to a SG list

Robert Love
2009-09-11T23:59:05Z

When handling the multi-frame responses of fc pass-thru requests,
a code segment similar to fc_fcp_recv_data (routine to receive
inbound SCSI data) is used in the response handler. This patch
is to add a routine, called fc_copy_buffer_to_sglist(), to handle
the common function of copying data from a buffer to a scatter-
gather list in order to avoid code duplication.

Signed-off-by: Robert Love <robert.w.love@intel.com>
---

drivers/scsi/libfc/fc_fcp.c | 56 +++++++-------------------------------
drivers/scsi/libfc/fc_libfc.c | 60 +++++++++++++++++++++++++++++++++++++++++
drivers/scsi/libfc/fc_libfc.h | 8 +++++
3 files changed, 78 insertions(+), 46 deletions(-)

diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index e4ff27e..a474773 100644
--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -324,7 +324,7 @@ static void fc_fcp_recv_data(struct fc_fcp_pkt *fsp, struct fc_frame *fp)
size_t len;
void *buf;
struct scatterlist *sg;
- size_t remaining;
+ u32 nents;

fh = fc_frame_header_get(fp);
offset = ntohl(fh->fh_parm_offset);
@@ -348,55 +348,19 @@ static void fc_fcp_recv_data(struct fc_fcp_pkt *fsp, struct fc_frame *fp)
if (offset != fsp->xfer_len)
fsp->state |= FC_SRB_DISCONTIG;

- crc = 0;
- if (fr_flags(fp) & FCPHF_CRC_UNCHECKED)
- crc = crc32(~0, (u8 *) fh, sizeof(*fh));
-
sg = scsi_sglist(sc);
- remaining = len;
-
- while (remaining > 0 && sg) {
- size_t off;
- void *page_addr;
- size_t sg_bytes;
-
- if (offset >= sg->length) {
- offset -= sg->length;
- sg = sg_next(sg);
- continue;
- }
- sg_bytes = min(remaining, sg->length - offset);
+ nents = scsi_sg_count(sc);

- /*
- * The scatterlist item may be bigger than PAGE_SIZE,
- * but we are limited to mapping PAGE_SIZE at a time.
- */
- off = offset + sg->offset;
- sg_bytes = min(sg_bytes, (size_t)
- (PAGE_SIZE - (off & ~PAGE_MASK)));
- page_addr = kmap_atomic(sg_page(sg) + (off >> PAGE_SHIFT),
- KM_SOFTIRQ0);
- if (!page_addr)
- break; /* XXX panic? */
-
- if (fr_flags(fp) & FCPHF_CRC_UNCHECKED)
- crc = crc32(crc, buf, sg_bytes);
- memcpy((char *)page_addr + (off & ~PAGE_MASK), buf,
- sg_bytes);
-
- kunmap_atomic(page_addr, KM_SOFTIRQ0);
- buf += sg_bytes;
- offset += sg_bytes;
- remaining -= sg_bytes;
- copy_len += sg_bytes;
- }
-
- if (fr_flags(fp) & FCPHF_CRC_UNCHECKED) {
+ if (!(fr_flags(fp) & FCPHF_CRC_UNCHECKED)) {
+ copy_len = fc_copy_buffer_to_sglist(buf, len, sg, &nents,
+ &offset, KM_SOFTIRQ0, NULL);
+ } else {
+ crc = crc32(~0, (u8 *) fh, sizeof(*fh));
+ copy_len = fc_copy_buffer_to_sglist(buf, len, sg, &nents,
+ &offset, KM_SOFTIRQ0, &crc);
buf = fc_frame_payload_get(fp, 0);
- if (len % 4) {
+ if (len % 4)
crc = crc32(crc, buf + len, 4 - (len % 4));
- len += 4 - (len % 4);
- }

if (~crc != le32_to_cpu(fr_crc(fp))) {
crc_err:
diff --git a/drivers/scsi/libfc/fc_libfc.c b/drivers/scsi/libfc/fc_libfc.c
index 01418ae..295eafb 100644
--- a/drivers/scsi/libfc/fc_libfc.c
+++ b/drivers/scsi/libfc/fc_libfc.c
@@ -72,3 +72,63 @@ static void __exit libfc_exit(void)
fc_destroy_rport();
}
module_exit(libfc_exit);
+
+/**
+ * fc_copy_buffer_to_sglist() - This routine copies the data of a buffer
+ * into a scatter-gather list (SG list).
+ *
+ * @buf: pointer to the data buffer.
+ * @len: the byte-length of the data buffer.
+ * @sg: pointer to the pointer of the SG list.
+ * @nents: pointer to the remaining number of entries in the SG list.
+ * @offset: pointer to the current offset in the SG list.
+ * @km_type: dedicated page table slot type for kmap_atomic.
+ * @crc: pointer to the 32-bit crc value.
+ * If crc is NULL, CRC is not calculated.
+ */
+u32 fc_copy_buffer_to_sglist(void *buf, size_t len,
+ struct scatterlist *sg,
+ u32 *nents, size_t *offset,
+ enum km_type km_type, u32 *crc)
+{
+ size_t remaining = len;
+ u32 copy_len = 0;
+
+ while (remaining > 0 && sg) {
+ size_t off, sg_bytes;
+ void *page_addr;
+
+ if (*offset >= sg->length) {
+ /*
+ * Check for end and drop resources
+ * from the last iteration.
+ */
+ if (!(*nents))
+ break;
+ --(*nents);
+ *offset -= sg->length;
+ sg = sg_next(sg);
+ continue;
+ }
+ sg_bytes = min(remaining, sg->length - *offset);
+
+ /*
+ * The scatterlist item may be bigger than PAGE_SIZE,
+ * but we are limited to mapping PAGE_SIZE at a time.
+ */
+ off = *offset + sg->offset;
+ sg_bytes = min(sg_bytes,
+ (size_t)(PAGE_SIZE - (off & ~PAGE_MASK)));
+ page_addr = kmap_atomic(sg_page(sg) + (off >> PAGE_SHIFT),
+ km_type);
+ if (crc)
+ *crc = crc32(*crc, buf, sg_bytes);
+ memcpy((char *)page_addr + (off & ~PAGE_MASK), buf, sg_bytes);
+ kunmap_atomic(page_addr, km_type);
+ buf += sg_bytes;
+ *offset += sg_bytes;
+ remaining -= sg_bytes;
+ copy_len += sg_bytes;
+ }
+ return copy_len;
+}
diff --git a/drivers/scsi/libfc/fc_libfc.h b/drivers/scsi/libfc/fc_libfc.h
index 0530149..e4b5e92 100644
--- a/drivers/scsi/libfc/fc_libfc.h
+++ b/drivers/scsi/libfc/fc_libfc.h
@@ -101,4 +101,12 @@ void fc_destroy_fcp(void);
*/
const char *fc_els_resp_type(struct fc_frame *);

+/*
+ * Copies a buffer into an sg list
+ */
+u32 fc_copy_buffer_to_sglist(void *buf, size_t len,
+ struct scatterlist *sg,
+ u32 *nents, size_t *offset,
+ enum km_type km_type, u32 *crc);
+
#endif /* _FC_LIBFC_H_ */