[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_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index 866f78a..98279fe 100644 (file)
--- 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 01418ae..295eafb 100644 (file)
--- 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 (file)
--- 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_ */