[PATCH V3 0/2] scsi: core: avoid big pre-allocation for sg list

[Ming Lei <ming.lei@redhat.com>]

Hi,

Since supporting to blk-mq, big pre-allocation for sg list is introduced,
this way is very unfriendly wrt. memory consumption.

There were Red Hat internal reports that some scsi_debug based tests
can't be run any more because of too big pre-allocation.

Also lpfc users commplained that 1GB+ ram is pre-allocatd for single
HBA.

sg_alloc_table_chained() is improved to support variant size of 1st
pre-allocated SGL in the 1st patch as suggested by Christoph.

The other two patches try to address this issue by allocating sg list runtime,
meantime pre-allocating one or two inline sg entries for small IO. This
ways follows NVMe's approach wrt. sg list allocation.

V3:
	- improve sg_alloc_table_chained() to accept variant size of
	the 1st pre-allocated SGL
	- applies the improved sg API to address the big pre-allocation
	issue

V2:
	- move inline sg table initializetion into one helper
	- introduce new helper for getting inline sg
	- comment log fix

Ming Lei (3):
  lib/sg_pool.c: improve APIs for allocating sg pool
  scsi: core: avoid to pre-allocate big chunk for protection meta data
  scsi: core: avoid to pre-allocate big chunk for sg list

 drivers/scsi/scsi_lib.c     | 36 +++++++++++++++++++++++----------
 include/linux/scatterlist.h | 27 ++++++++++++++++++++-----
 lib/scatterlist.c           | 36 +++++++++++++++++++++------------
 lib/sg_pool.c               | 49 ++++++++++++++++++++++++++++++---------------
 4 files changed, 103 insertions(+), 45 deletions(-)

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>
-- 
2.9.5