Date:   Mon, 22 Jul 2019 19:42:27 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: Linux 5.3-rc1

On 7/22/19 4:45 PM, James Bottomley wrote:
> [linux-scsi added to cc]
> On Mon, 2019-07-22 at 15:21 -0700, Guenter Roeck wrote:
>> On Sun, Jul 21, 2019 at 02:33:38PM -0700, Linus Torvalds wrote:
>>
>> [ ... ]
>>>
>>> Go test,
>>>
>>
>> Things looked pretty good until a few days ago. Unfortunately,
>> the last few days brought in a couple of issues.
>>
>> riscv:virt:defconfig:scsi[virtio]
>> riscv:virt:defconfig:scsi[virtio-pci]
>>
>> Boot tests crash with no useful backtrace. Bisect points to
>> merge ac60602a6d8f ("Merge tag 'dma-mapping-5.3-1'"). Log is at
>> https://kerneltests.org/builders/qemu-riscv64-master/builds/238/steps
>> /qemubuildcommand_1/logs/stdio
>>
>> ppc:mpc8544ds:mpc85xx_defconfig:sata-sii3112
>> ppc64:pseries:pseries_defconfig:sata-sii3112
>> ppc64:pseries:pseries_defconfig:little:sata-sii3112
>> ppc64:ppce500:corenet64_smp_defconfig:e5500:sata-sii3112
>>
>> ata1: lost interrupt (Status 0x50)
>> ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
>> ata1.00: failed command: READ DMA
>>
>> and many similar errors. Boot ultimately times out. Bisect points to
>> merge
>> f65420df914a ("Merge tag 'scsi-fixes'").
>>
>> Logs:
>> https://kerneltests.org/builders/qemu-ppc64-master/builds/1212/steps/
>> qemubuildcommand/logs/stdio
>> https://kerneltests.org/builders/qemu-ppc-master/builds/1255/steps/qe
>> mubuildcommand/logs/stdio
>>
>> Guenter
>>
>> ---
>> riscv bisect log
>>
>> # bad: [5f9e832c137075045d15cd6899ab0505cfb2ca4b] Linus 5.3-rc1
>> # good: [bdd17bdef7d8da4d8eee254abb4c92d8a566bdc1] scsi: core: take
>> the DMA max mapping size into account
>> git bisect start 'HEAD' 'bdd17bdef7d8'
>> # good: [237f83dfbe668443b5e31c3c7576125871cca674] Merge
>> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
>> git bisect good 237f83dfbe668443b5e31c3c7576125871cca674
>> # good: [be8454afc50f43016ca8b6130d9673bdd0bd56ec] Merge tag 'drm-
>> next-2019-07-16' of git://anongit.freedesktop.org/drm/drm
>> git bisect good be8454afc50f43016ca8b6130d9673bdd0bd56ec
>> # good: [d4df33b0e9925c158b313a586fb1557cf29cfdf4] Merge branch 'for-
>> linus-5.2' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb
>> git bisect good d4df33b0e9925c158b313a586fb1557cf29cfdf4
>> # good: [f90b8fda3a9d72a9422ea80ae95843697f94ea4a] ARM: dts: gemini:
>> Set DIR-685 SPI CS as active low
>> git bisect good f90b8fda3a9d72a9422ea80ae95843697f94ea4a
>> # good: [31cc088a4f5d83481c6f5041bd6eb06115b974af] Merge tag 'drm-
>> next-2019-07-19' of git://anongit.freedesktop.org/drm/drm
>> git bisect good 31cc088a4f5d83481c6f5041bd6eb06115b974af
>> # good: [ad21a4ce040cc41b4a085417169b558e86af56b7] dt-bindings:
>> pinctrl: aspeed: Fix 'compatible' schema errors
>> git bisect good ad21a4ce040cc41b4a085417169b558e86af56b7
>> # good: [e6023adc5c6af79ac8ac5b17939f58091fa0d870] Merge branch
>> 'core-urgent-for-linus' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>> git bisect good e6023adc5c6af79ac8ac5b17939f58091fa0d870
>> # bad: [ac60602a6d8f6830dee89f4b87ee005f62eb7171] Merge tag 'dma-
>> mapping-5.3-1' of git://git.infradead.org/users/hch/dma-mapping
>> git bisect bad ac60602a6d8f6830dee89f4b87ee005f62eb7171
>> # good: [6e67d77d673d785631b0c52314b60d3c68ebe809] perf vendor events
>> s390: Add JSON files for machine type 8561
>> git bisect good 6e67d77d673d785631b0c52314b60d3c68ebe809
>> # good: [a0d14b8909de55139b8702fe0c7e80b69763dcfb] x86/mm, tracing:
>> Fix CR2 corruption
>> git bisect good a0d14b8909de55139b8702fe0c7e80b69763dcfb
>> # good: [6879298bd0673840cadd1fb36d7225485504ceb4] x86/entry/64:
>> Prevent clobbering of saved CR2 value
>> git bisect good 6879298bd0673840cadd1fb36d7225485504ceb4
>> # good: [449fa54d6815be8c2c1f68fa9dbbae9384a7c03e] dma-direct:
>> correct the physical addr in dma_direct_sync_sg_for_cpu/device
>> git bisect good 449fa54d6815be8c2c1f68fa9dbbae9384a7c03e
>> # good: [e0c5c5e308ee9b3548844f0d88da937782b895ef] Merge tag 'perf-
>> core-for-mingo-5.3-20190715' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into
>> perf/urgent
>> git bisect good e0c5c5e308ee9b3548844f0d88da937782b895ef
>> # good: [c6dd78fcb8eefa15dd861889e0f59d301cb5230c] Merge branch 'x86-
>> urgent-for-linus' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>> git bisect good c6dd78fcb8eefa15dd861889e0f59d301cb5230c
>> # first bad commit: [ac60602a6d8f6830dee89f4b87ee005f62eb7171] Merge
>> tag 'dma-mapping-5.3-1' of git://git.infradead.org/users/hch/dma-
>> mapping
>>
>> ---------
>> ppc/ppc64 bisect log
>>
>> # bad: [5f9e832c137075045d15cd6899ab0505cfb2ca4b] Linus 5.3-rc1
>> # good: [abdfd52a295fb5731ab07b5c9013e2e39f4d1cbe] Merge tag 'armsoc-
>> defconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
>> git bisect start 'HEAD' 'abdfd52a295f'
>> # bad: [e6023adc5c6af79ac8ac5b17939f58091fa0d870] Merge branch 'core-
>> urgent-for-linus' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>> git bisect bad e6023adc5c6af79ac8ac5b17939f58091fa0d870
>> # bad: [f65420df914a85e33b2c8b1cab310858b2abb7c0] Merge tag 'scsi-
>> fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
>> git bisect bad f65420df914a85e33b2c8b1cab310858b2abb7c0
>> # good: [168c79971b4a7be7011e73bf488b740a8e1135c8] Merge tag 'kbuild-
>> v5.3-2' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
>> git bisect good 168c79971b4a7be7011e73bf488b740a8e1135c8
>> # good: [106d45f350c7cac876844dc685845cba4ffdb70b] scsi: zfcp: fix
>> request object use-after-free in send path causing wrong traces
>> git bisect good 106d45f350c7cac876844dc685845cba4ffdb70b
>> # good: [bdd17bdef7d8da4d8eee254abb4c92d8a566bdc1] scsi: core: take
>> the DMA max mapping size into account
>> git bisect good bdd17bdef7d8da4d8eee254abb4c92d8a566bdc1
>> # good: [09a4460ba4434ef0327cd26bf25f2d7afb973251] scsi: IB/iser: set
>> virt_boundary_mask in the scsi host
>> git bisect good 09a4460ba4434ef0327cd26bf25f2d7afb973251
>> # good: [ce0ad853109733d772d26224297fda0de313bf13] scsi: mpt3sas: set
>> an unlimited max_segment_size for SAS 3.0 HBAs
>> git bisect good ce0ad853109733d772d26224297fda0de313bf13
>> # good: [07d9aa14346489d6facae5777ceb267a1dcadbc5] scsi:
>> megaraid_sas: set an unlimited max_segment_size
>> git bisect good 07d9aa14346489d6facae5777ceb267a1dcadbc5
>> # first bad commit: [f65420df914a85e33b2c8b1cab310858b2abb7c0] Merge
>> tag 'scsi-fixes' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
> 
> When a bisect lands on a merge commit it usually indicates bad
> interaction between two trees.  The way to find it is to do a bisect,
> but merge up to the other side of the scsi-fixes pull before running
> tests so the interaction is exposed in the bisect.
> 

Can you provide instructions for dummies ?

> However my money is on:
> 
> 
> commit bdd17bdef7d8da4d8eee254abb4c92d8a566bdc1
> Author: Christoph Hellwig <hch@....de>
> Date:   Mon Jun 17 14:19:54 2019 +0200
> 
>      scsi: core: take the DMA max mapping size into account
>   
> Now that I look at the code again:
> 
> 
> +       shost->max_sectors = min_t(unsigned int, shost->max_sectors,
> +                       dma_max_mapping_size(dev) << SECTOR_SHIFT);
> 
> That shift looks to be the wrong way around (should be >>).  I bet
> something is giving a very large number which becomes zero on left
> shift, meaning max_sectors gets set to zero.
> 

That does indeed look bad, but changing it doesn't make a difference.

Thanks,
Guenter

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