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    SubjectRe: 4.15.14 crash with iscsi target and dvd
    Ming Lei wrote:
    > On Tue, Apr 10, 2018 at 08:45:25PM -0400, Wakko Warner wrote:
    > > Sorry for the delay. I reverted my change, added this one. I didn't
    > > reboot, I just unloaded and loaded this one.
    > > Note: /dev/sr1 as seen from the initiator is /dev/sr0 (physical disc) on the
    > > target.
    > >
    > > Doesn't crash, however on the initiator I see this:
    > > [9273849.707777] ISO 9660 Extensions: RRIP_1991A
    > > [9273863.359718] scsi_io_completion: 13 callbacks suppressed
    > > [9273863.359788] sr 26:0:0:0: [sr1] tag#1 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=0x08
    > > [9273863.359909] sr 26:0:0:0: [sr1] tag#1 Sense Key : 0x2 [current]
    > > [9273863.359974] sr 26:0:0:0: [sr1] tag#1 ASC=0x8 ASCQ=0x0
    > > [9273863.360036] sr 26:0:0:0: [sr1] tag#1 CDB: opcode=0x28 28 00 00 22 f6 96 00 00 80 00
    > > [9273863.360116] blk_update_request: 13 callbacks suppressed
    > > [9273863.360177] blk_update_request: I/O error, dev sr1, sector 9165400
    > > [9273875.864648] sr 26:0:0:0: [sr1] tag#1 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=0x08
    > > [9273875.864738] sr 26:0:0:0: [sr1] tag#1 Sense Key : 0x2 [current]
    > > [9273875.864801] sr 26:0:0:0: [sr1] tag#1 ASC=0x8 ASCQ=0x0
    > > [9273875.864890] sr 26:0:0:0: [sr1] tag#1 CDB: opcode=0x28 28 00 00 22 f7 16 00 00 80 00
    > > [9273875.864971] blk_update_request: I/O error, dev sr1, sector 9165912
    > >
    > > To cause this, I mounted the dvd as seen in the first line and ran this
    > > command: find /cdrom2 -type f | xargs -tn1 cat > /dev/null
    > > I did some various tests. Each test was done after umount and mount to
    > > clear the cache.
    > > cat <file> > /dev/null causes the message.
    > > dd if=<file> of=/dev/null bs=2048 doesn't
    > > using bs=4096 doesn't
    > > using bs=64k doesn't
    > > using bs=128k does
    > > cat uses a blocksize of 128k.
    > >
    > > The following was done without being mounted.
    > > ddrescue -f -f /dev/sr1 /dev/null
    > > doesn't cause the message
    > > dd if=/dev/sr1 of=/dev/null bs=128k
    > > doesn't cause the message
    > > using bs=256k causes the message once:
    > > [9275916.857409] sr 27:0:0:0: [sr1] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=0x08
    > > [9275916.857482] sr 27:0:0:0: [sr1] tag#0 Sense Key : 0x2 [current]
    > > [9275916.857520] sr 27:0:0:0: [sr1] tag#0 ASC=0x8 ASCQ=0x0
    > > [9275916.857556] sr 27:0:0:0: [sr1] tag#0 CDB: opcode=0x28 28 00 00 00 00 00 00 00 80 00
    > > [9275916.857614] blk_update_request: I/O error, dev sr1, sector 0
    > >
    > > If I access the disc from the target natively either by mounting and
    > > accessing files or working with the device directly (ie dd) no errors are
    > > logged on the target.
    >
    > OK, thanks for your test.
    >
    > Could you test the following patch and see if there is still the failure
    > message?
    >
    > diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
    > index 0d99b242e82e..6137287b52fb 100644
    > --- a/drivers/target/target_core_pscsi.c
    > +++ b/drivers/target/target_core_pscsi.c
    > @@ -913,9 +913,11 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
    >
    > rc = bio_add_pc_page(pdv->pdv_sd->request_queue,
    > bio, page, bytes, off);
    > + if (rc != bytes)
    > + goto fail;
    > pr_debug("PSCSI: bio->bi_vcnt: %d nr_vecs: %d\n",
    > bio_segments(bio), nr_vecs);
    > - if (rc != bytes) {
    > + if (/*rc != bytes*/0) {
    > pr_debug("PSCSI: Reached bio->bi_vcnt max:"
    > " %d i: %d bio: %p, allocating another"
    > " bio\n", bio->bi_vcnt, i, bio);

    Target doesn't crash but the errors on the initiator are still there.

    Seems that if I do large transfers, I see this in the initiator's logs.
    With the previous patch, I burned 3 dvds at the same time, compared the
    files to the originals and I have a script that catalogs the files. The
    files consist of debian packages and source files. The 3 operations did not
    show any errors in the kernel log on either end.

    I did this test:
    initiator: dd if=/dev/sr1 bs=512k count=1024 | md5sum
    target: dd if=/dev/sr0 bs=512k count=1024 | md5sum

    Result: the same. It's OK even with the i/o errors shown on the initiator.

    The above patch was added on top of the one you gave me before, but I don't
    believe that that would be an issue.

    ... Now if someone could help me with a kvm virtualization problem I'm
    having with 4.16 that wasn't there with 4.15...

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

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