[SCSI] libfc: Add routine to copy data from a buffer to a SG list

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>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

3 files changed, 78 insertions, 46 deletions

diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index 866f78ac4ec2..98279fe0d0c7 100644
--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -323,7 +323,7 @@ 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);
@@ -347,55 +347,19 @@ 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);
-
-                /*
-                 * 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;
-        }
+        nents = scsi_sg_count(sc);
 
-        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 01418ae8cb84..295eafb0316f 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 0530149ac174..e4b5e9280cb0 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_ */