scsi: core: don’t preallocate small SGL in case of NO_SG_CHAIN [Linux 5.3]

This Linux kernel change "scsi: core: don’t preallocate small SGL in case of NO_SG_CHAIN" is included in the Linux 5.3 release. This change is authored by Ming Lei <ming.lei [at] redhat.com> on Thu Jun 6 16:34:09 2019 +0800. The commit for this change in Linux stable tree is 3e99b3b (patch).

scsi: core: don't preallocate small SGL in case of NO_SG_CHAIN

The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't
support SG_CHAIN, preallocation of small SGL can't work at all.

Fix this issue by not using small preallocation in case of NO_SG_CHAIN.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/scsi/scsi_lib.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 45b43e9..30cbea5 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -43,9 +43,13 @@
  * Size of integrity metadata is usually small, 1 inline sg should
  * cover normal cases.
  */
+#ifdef CONFIG_ARCH_NO_SG_CHAIN
+#define  SCSI_INLINE_PROT_SG_CNT  0
+#define  SCSI_INLINE_SG_CNT  0
+#else
 #define  SCSI_INLINE_PROT_SG_CNT  1
-
 #define  SCSI_INLINE_SG_CNT  2
+#endif

 static struct kmem_cache *scsi_sdb_cache;
 static struct kmem_cache *scsi_sense_cache;

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