Bart Van Assche wrote:

On Sat, 2018-04-07 at 12:53 -0400, Wakko Warner wrote:

quoted

Bart Van Assche wrote:

quoted

On Thu, 2018-04-05 at 22:06 -0400, Wakko Warner wrote:

quoted

I know now why scsi_print_command isn't doing anything.  cmd->cmnd is null.
I added a dev_printk in scsi_print_command where the 2 if statements return.
Logs:
[  29.866415] sr 3:0:0:0: cmd->cmnd is NULL

That's something that should never happen. As one can see in
scsi_setup_scsi_cmnd() and scsi_setup_fs_cmnd() both functions initialize
that pointer. Since I have not yet been able to reproduce myself what you
reported, would it be possible for you to bisect this issue? You will need
to follow something like the following procedure (see also
https://git-scm.com/docs/git-bisect):

After doing 3 successful compiles with good/bad, I got this error and was
not able to compile any more kernels:
  CC      scripts/mod/devicetable-offsets.s
scripts/mod/empty.c:1:0: error: code model kernel does not support PIC mode
 /* empty file to figure out endianness / word size */
 
scripts/mod/devicetable-offsets.c:1:0: error: code model kernel does not support PIC mode
 #include <linux/kbuild.h>
 
scripts/Makefile.build:153: recipe for target 'scripts/mod/devicetable-offsets.s' failed

I don't think it found the bad commit.

Have you tried to modify the kernel Makefile as indicated in the following
e-mail? This should make the kernel build:

https://lists.ubuntu.com/archives/kernel-team/2016-May/077178.html

Thanks.  That helped.

I finished with git bisect.  Here's the output:
84c8590646d5b35804bac60eb58b145839b5893e is the first bad commit
commit 84c8590646d5b35804bac60eb58b145839b5893e
Author: Ming Lei [off-list ref]
Date:   Fri Nov 11 20:05:32 2016 +0800

    target: avoid accessing .bi_vcnt directly
    
    When the bio is full, bio_add_pc_page() will return zero,
    so use this information tell when the bio is full.
    
    Also replace access to .bi_vcnt for pr_debug() with bio_segments().
    
    Reviewed-by: Christoph Hellwig [off-list ref]
    Signed-off-by: Ming Lei [off-list ref]
    Reviewed-by: Sagi Grimberg [off-list ref]
    Signed-off-by: Jens Axboe [off-list ref]

:040000 040000 a3ebbb71c52ee4eb8c3be4d033b81179211bf704 de39a328dbd1b18519946b3ad46d9302886e0dd0 M      drivers

I did a diff between HEAD^ and HEAD and manually patched the file from
4.15.14.  It's not an exact revert.  I'm running it now and it's working.
I'll do a better test later on.  Here's the patch:

--- a/drivers/target/target_core_pscsi.c	2018-02-04 14:31:31.077316617 -0500
+++ b/drivers/target/target_core_pscsi.c	2018-04-08 11:43:49.588641374 -0400

@@ -915,7 +915,9 @@
 					bio, page, bytes, off);
 			pr_debug("PSCSI: bio->bi_vcnt: %d nr_vecs: %d\n",
 				bio_segments(bio), nr_vecs);
-			if (rc != bytes) {
+			if (rc != bytes)
+				goto fail;
+			if (bio->bi_vcnt > nr_vecs) {
 				pr_debug("PSCSI: Reached bio->bi_vcnt max:"
 					" %d i: %d bio: %p, allocating another"
 					" bio\n", bio->bi_vcnt, i, bio);

I really appreciate your time and assistance with this.

-- 
 Microsoft has beaten Volkswagen's world record.  Volkswagen only created 22
 million bugs.