SG: work with the SCSI fixed maximum allocations.

SCSI sg table allocation has a maximum size (of SCSI_MAX_SG_SEGMENTS,
currently 128) and this will cause a BUG_ON() in SCSI if something
tries an allocation over it.  This patch adds a size limit to the
chaining allocator to allow the specification of the maximum
allocation size for chaining, so we always chain in units of the
maximum SCSI allocation size.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3b5121c4c081..eb4911a61641 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -761,9 +761,11 @@ int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 
         BUG_ON(!cmd->use_sg);
 
-        ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg, gfp_mask, scsi_sg_alloc);
+        ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg,
+                               SCSI_MAX_SG_SEGMENTS, gfp_mask, scsi_sg_alloc);
         if (unlikely(ret))
-                __sg_free_table(&cmd->sg_table, scsi_sg_free);
+                __sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS,
+                                scsi_sg_free);
 
         cmd->request_buffer = cmd->sg_table.sgl;
         return ret;
@@ -773,7 +775,7 @@ EXPORT_SYMBOL(scsi_alloc_sgtable);
 
 void scsi_free_sgtable(struct scsi_cmnd *cmd)
 {
-        __sg_free_table(&cmd->sg_table, scsi_sg_free);
+        __sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
 }
 
 EXPORT_SYMBOL(scsi_free_sgtable);