svn commit: r334484 - head/sys/compat/linuxkpi/common/include/linux

[Hans Petter Selasky]

Author: hselasky
Date: Fri Jun  1 12:09:07 2018
New Revision: 334484
URL: https://svnweb.freebsd.org/changeset/base/334484

Log:
  Implement the __sg_alloc_table_from_pages() function based on the existing
  sg_alloc_table_from_pages() function in the LinuxKPI.
  
  This basically allow segments to have a limit, max_segment.
  
  Submitted by:	Johannes Lundberg <johalun0 at gmail.com>
  MFC after:	1 week
  Sponsored by:	Mellanox Technologies
  Sponsored by:	Limelight Networks

Modified:
  head/sys/compat/linuxkpi/common/include/linux/scatterlist.h

Modified: head/sys/compat/linuxkpi/common/include/linux/scatterlist.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/scatterlist.h	Fri Jun  1 11:42:09 2018	(r334483)
+++ head/sys/compat/linuxkpi/common/include/linux/scatterlist.h	Fri Jun  1 12:09:07 2018	(r334484)
@@ -64,6 +64,8 @@ struct sg_page_iter {
 	} internal;
 };
 
+#define	SCATTERLIST_MAX_SEGMENT	(-1U & ~(PAGE_SIZE - 1))
+
 #define	SG_MAX_SINGLE_ALLOC	(PAGE_SIZE / sizeof(struct scatterlist))
 
 #define	SG_MAGIC		0x87654321UL
@@ -286,18 +288,26 @@ sg_alloc_table(struct sg_table *table, unsigned int ne
 }
 
 static inline int
-sg_alloc_table_from_pages(struct sg_table *sgt,
+__sg_alloc_table_from_pages(struct sg_table *sgt,
     struct page **pages, unsigned int count,
     unsigned long off, unsigned long size,
-    gfp_t gfp_mask)
+    unsigned int max_segment, gfp_t gfp_mask)
 {
-	unsigned int i, segs, cur;
+	unsigned int i, segs, cur, len;
 	int rc;
 	struct scatterlist *s;
 
+	if (__predict_false(!max_segment || offset_in_page(max_segment)))
+		return (-EINVAL);
+
+	len = 0;
 	for (segs = i = 1; i < count; ++i) {
-		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
+		len += PAGE_SIZE;
+		if (len >= max_segment ||
+		    page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
 			++segs;
+			len = 0;
+		}
 	}
 	if (__predict_false((rc = sg_alloc_table(sgt, segs, gfp_mask))))
 		return (rc);
@@ -307,10 +317,13 @@ sg_alloc_table_from_pages(struct sg_table *sgt,
 		unsigned long seg_size;
 		unsigned int j;
 
-		for (j = cur + 1; j < count; ++j)
-			if (page_to_pfn(pages[j]) !=
+		len = 0;
+		for (j = cur + 1; j < count; ++j) {
+			len += PAGE_SIZE;
+			if (len >= max_segment || page_to_pfn(pages[j]) !=
 			    page_to_pfn(pages[j - 1]) + 1)
 				break;
+		}
 
 		seg_size = ((j - cur) << PAGE_SHIFT) - off;
 		sg_set_page(s, pages[cur], min(size, seg_size), off);
@@ -321,6 +334,16 @@ sg_alloc_table_from_pages(struct sg_table *sgt,
 	return (0);
 }
 
+static inline int
+sg_alloc_table_from_pages(struct sg_table *sgt,
+    struct page **pages, unsigned int count,
+    unsigned long off, unsigned long size,
+    gfp_t gfp_mask)
+{
+
+	return (__sg_alloc_table_from_pages(sgt, pages, count, off, size,
+	    SCATTERLIST_MAX_SEGMENT, gfp_mask));
+}
 
 static inline int
 sg_nents(struct scatterlist *sg)