While working of this "[PATCH v4] Make SCSI Status CONDITION MET
equivalent to GOOD" the author had trouble finding how to add another
corner case check in the scsi_io_completion() function (scsi_lib.c).
That function is executed at the completion of every SCSI command but
only 20 or so of its hundred of lines of code are executed for the vast
majority of invocations (i.e. the fastpath).
This patch refactors scsi_io_completion() by taking the bulk of its
error processing code into three static helper functions, leaving only
the 20 or so code lines that constitute the fastpath. In this process
comments were added and tweaked, plus variables renamed. The last two
patches in this set are optional: adding conditional hints along the
fastpath and converting 3 BUG() calls in scsi_io_completion() to WARNs
as requested by a reviewer.
There is no attempt in this patchset to change the logic of the original
scsi_io_completion() although the last patch attempts to continue from
awkward situations rather than crashing the calling thread (and possibly
the kernel). Some conditional checks are saved by reducing the number of
redundant tests (e.g. multiple checks that the 'result' variable is
non-zero). Also De Morgan's laws are applied to some complex conditions
to simplify them from the reader's perspective. The fact remains, this
is a very complex function.
This patch is against Martin Petersen's 4.17/scsi-queue branch.
Note: to apply this patchset to the lk 4.15 production kernels (tested
on lk 4.15.13), these two lines near the end of scsi_io_completion():
__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
and
__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
need that trailing 0 changed to 'false', prior to applying 4/7 .
ChangeLog since v4
- introduce bool do_print to simplify conditionals in the case of
a recovered error sense key in 2/7 rather than 3/7
ChangeLog since v3
- make use of bools sense_valid and sense_current consistent in 3/7
and 4/7
Douglas Gilbert (7):
scsi_io_completion comment on end_request return
scsi_io_completion rename variables
scsi_io_completion_nz_result function added
scsi_io_completion_action helper added
scsi_io_completion_reprep helper added
scsi_io_completion hints on fastpatch
scsi_io_completion convert BUGs to WARNs
drivers/scsi/scsi_lib.c | 378 +++++++++++++++++++++++++++---------------------
1 file changed, 214 insertions(+), 164 deletions(-)
--
2.14.1
