3 files changed, 27 insertions, 20 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8723abeb018e..bbd7a0a08692 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -564,6 +564,11 @@ static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
         return mempool_alloc(sgp->pool, gfp_mask);
 }
 
+static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
+{
+        __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, false, scsi_sg_free);
+}
+
 static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
                               gfp_t gfp_mask)
 {
@@ -572,19 +577,12 @@ static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
         BUG_ON(!nents);
 
         ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
-                               gfp_mask, scsi_sg_alloc);
+                               NULL, gfp_mask, scsi_sg_alloc);
         if (unlikely(ret))
-                __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS,
-                                scsi_sg_free);
-
+                scsi_free_sgtable(sdb);
         return ret;
 }
 
-static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
-{
-        __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
-}
-
 /*
  * Function:    scsi_release_buffers()
  *
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index a964f7285600..f4ec8bbcb372 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -229,10 +229,10 @@ void sg_init_one(struct scatterlist *, const void *, unsigned int);
 typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
 typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 
-void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
+void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_fn *);
 void sg_free_table(struct sg_table *);
-int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
-                     sg_alloc_fn *);
+int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
+                     struct scatterlist *, gfp_t, sg_alloc_fn *);
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 int sg_alloc_table_from_pages(struct sg_table *sgt,
         struct page **pages, unsigned int n_pages,
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 3a8e8e8fb2a5..b4415fceb7e7 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -165,6 +165,7 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
  * __sg_free_table - Free a previously mapped sg table
  * @table:      The sg table header to use
  * @max_ents:   The maximum number of entries per single scatterlist
+ * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk
  * @free_fn:    Free function
  *
  *  Description:
@@ -174,7 +175,7 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
  *
  **/
 void __sg_free_table(struct sg_table *table, unsigned int max_ents,
-                     sg_free_fn *free_fn)
+                     bool skip_first_chunk, sg_free_fn *free_fn)
 {
         struct scatterlist *sgl, *next;
 
@@ -202,7 +203,10 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
                 }
 
                 table->orig_nents -= sg_size;
-                free_fn(sgl, alloc_size);
+                if (!skip_first_chunk) {
+                        free_fn(sgl, alloc_size);
+                        skip_first_chunk = false;
+                }
                 sgl = next;
         }
 
@@ -217,7 +221,7 @@ EXPORT_SYMBOL(__sg_free_table);
  **/
 void sg_free_table(struct sg_table *table)
 {
-        __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
+        __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
 }
 EXPORT_SYMBOL(sg_free_table);
 
@@ -241,8 +245,8 @@ EXPORT_SYMBOL(sg_free_table);
  *
  **/
 int __sg_alloc_table(struct sg_table *table, unsigned int nents,
-                     unsigned int max_ents, gfp_t gfp_mask,
-                     sg_alloc_fn *alloc_fn)
+                     unsigned int max_ents, struct scatterlist *first_chunk,
+                     gfp_t gfp_mask, sg_alloc_fn *alloc_fn)
 {
         struct scatterlist *sg, *prv;
         unsigned int left;
@@ -269,7 +273,12 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 
                 left -= sg_size;
 
-                sg = alloc_fn(alloc_size, gfp_mask);
+                if (first_chunk) {
+                        sg = first_chunk;
+                        first_chunk = NULL;
+                } else {
+                        sg = alloc_fn(alloc_size, gfp_mask);
+                }
                 if (unlikely(!sg)) {
                         /*
                          * Adjust entry count to reflect that the last
@@ -324,9 +333,9 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
         int ret;
 
         ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
-                               gfp_mask, sg_kmalloc);
+                               NULL, gfp_mask, sg_kmalloc);
         if (unlikely(ret))
-                __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
+                __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
 
         return ret;
 }