[PATCH V4 0/3] 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.

V4:
	- add parameter to sg_alloc_table_chained()/sg_free_table_chained()
	directly, and update current callers

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/nvme/host/fc.c            |  7 ++++---
 drivers/nvme/host/rdma.c          |  7 ++++---
 drivers/nvme/target/loop.c        |  4 ++--
 drivers/scsi/scsi_lib.c           | 31 ++++++++++++++++++++++---------
 include/linux/scatterlist.h       | 11 +++++++----
 lib/scatterlist.c                 | 36 +++++++++++++++++++++++-------------
 lib/sg_pool.c                     | 37 +++++++++++++++++++++++++++----------
 net/sunrpc/xprtrdma/svc_rdma_rw.c |  5 +++--
 8 files changed, 92 insertions(+), 46 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>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: netdev@vger.kernel.org
Cc: linux-nvme@lists.infradead.org

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2.9.5