[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>
diff --git a/drivers/scsi/libfc/fc_libfc.c b/drivers/scsi/libfc/fc_libfc.c
index 01418ae..295eafb0 100644
--- a/drivers/scsi/libfc/fc_libfc.c
+++ b/drivers/scsi/libfc/fc_libfc.c
@@ -72,3 +72,63 @@
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;
+}