RE: [External] regression caused by patch 6180bb446ab624b9ab8bf201ed251ca87f07b413 ("dax: fix detection of dax support for non-persistent memory block devices")

[Adrian Huang12 <ahuang12@lenovo.com>]

Hi Mikulas,

> -----Original Message-----
> From: Mikulas Patocka <mpatocka@redhat.com>
> Sent: Monday, September 14, 2020 11:49 PM
> To: Coly Li <colyli@suse.de>; Dan Williams <dan.j.williams@intel.com>; Dave
> Jiang <dave.jiang@intel.com>
> Cc: Jan Kara <jack@suse.com>; Vishal Verma <vishal.l.verma@intel.com>;
> Adrian Huang12 <ahuang12@lenovo.com>; Ira Weiny <ira.weiny@intel.com>;
> Mike Snitzer <snitzer@redhat.com>; Pankaj Gupta
> <pankaj.gupta.linux@gmail.com>; linux-nvdimm@lists.01.org
> Subject: [External] regression caused by patch
> 6180bb446ab624b9ab8bf201ed251ca87f07b413 ("dax: fix detection of dax
> support for non-persistent memory block devices")
> 
> Hi
> 
> The patch 6180bb446ab624b9ab8bf201ed251ca87f07b413 ("dax: fix
> detection of dax support for non-persistent memory block devices") causes
> crash when attempting to mount the ext4 filesystem on /dev/pmem0
> ("mkfs.ext4 /dev/pmem0; mount -t ext4 /dev/pmem0 /mnt/test"). The device
> /dev/pmem0 is emulated using the "memmap" kernel parameter.
> 

Could you please test the following patch? Thanks.
https://lists.01.org/hyperkitty/list/linux-nvdimm@lists.01.org/thread/2JDBSE2WK75LSGCFEOY3RXRN3CNLBPB2/

 > The patch causes infinite recursion and double-fault exception:
> 
> __generic_fsdax_supported
> bdev_dax_supported
> __bdev_dax_supported
> dax_supported
> dax_dev->ops->dax_supported
> generic_fsdax_supported
> __generic_fsdax_supported
> 
> Mikulas
> 
> 
> 
> [   17.500619] traps: PANIC: double fault, error_code: 0x0
> [   17.500619] double fault: 0000 [#1] PREEMPT SMP
> [   17.500620] CPU: 0 PID: 1326 Comm: mount Not tainted 5.9.0-rc1-bisect #10
> [   17.500620] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> [   17.500621] RIP: 0010:__generic_fsdax_supported+0x6a/0x500
> [   17.500622] Code: ff ff ff ff ff 7f 00 48 21 f3 48 01 c3 48 c1 e3 09 f6 c7 0e 0f
> 85 fa 01 00 00 48 85 ff 49 89 fd 74 11 be 00 10 00 00 4c 89 e7 <e8> b1 fe ff ff
> 84 c0 75 11 31 c0 48 83 c4 48 5b 5d 41 5c 41 5d 41
> [   17.500623] RSP: 0018:ffff88940b4fdff8 EFLAGS: 00010286
> [   17.500624] RAX: 0000000000000000 RBX: 00000007fffff000 RCX:
> 0000000000000000
> [   17.500625] RDX: 0000000000001000 RSI: 0000000000001000 RDI:
> ffff88940b34c300
> [   17.500625] RBP: 0000000000000000 R08: 0000000004000000 R09:
> 8080808080808080
> [   17.500626] R10: 0000000000000000 R11: fefefefefefefeff R12:
> ffff88940b34c300
> [   17.500626] R13: ffff88940b3dc000 R14: ffff88940badd000 R15:
> 0000000000000001
> [   17.500627] FS:  00000000f7c25780(0000) GS:ffff88940fa00000(0000)
> knlGS:0000000000000000
> [   17.500628] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> [   17.500628] CR2: ffff88940b4fdfe8 CR3: 000000140bd15000 CR4:
> 00000000000006b0
> [   17.500628] Call Trace:
> [   17.500629] Modules linked in: uvesafb cfbfillrect cfbimgblt cn cfbcopyarea fb
> fbdev ipv6 tun autofs4 binfmt_misc configfs af_packet virtio_rng rng_core
> mousedev evdev pcspkr virtio_balloon button raid10 raid456 async_raid6_recov
> async_memcpy async_pq raid6_pq async_xor xor async_tx libcrc32c raid1 raid0
> md_mod sd_mod t10_pi virtio_scsi virtio_net net_failover psmouse scsi_mod
> failover
> [   17.500638] ---[ end trace 3c877fcb5b865459 ]---
> [   17.500638] RIP: 0010:__generic_fsdax_supported+0x6a/0x500
> [   17.500639] Code: ff ff ff ff ff 7f 00 48 21 f3 48 01 c3 48 c1 e3 09 f6 c7 0e 0f
> 85 fa 01 00 00 48 85 ff 49 89 fd 74 11 be 00 10 00 00 4c 89 e7 <e8> b1 fe ff ff
> 84 c0 75 11 31 c0 48 83 c4 48 5b 5d 41 5c 41 5d 41
> [   17.500640] RSP: 0018:ffff88940b4fdff8 EFLAGS: 00010286
> [   17.500641] RAX: 0000000000000000 RBX: 00000007fffff000 RCX:
> 0000000000000000
> [   17.500641] RDX: 0000000000001000 RSI: 0000000000001000 RDI:
> ffff88940b34c300
> [   17.500642] RBP: 0000000000000000 R08: 0000000004000000 R09:
> 8080808080808080
> [   17.500642] R10: 0000000000000000 R11: fefefefefefefeff R12:
> ffff88940b34c300
> [   17.500643] R13: ffff88940b3dc000 R14: ffff88940badd000 R15:
> 0000000000000001
> [   17.500643] FS:  00000000f7c25780(0000) GS:ffff88940fa00000(0000)
> knlGS:0000000000000000
> [   17.500644] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> [   17.500644] CR2: ffff88940b4fdfe8 CR3: 000000140bd15000 CR4:
> 00000000000006b0
> [   17.500645] Kernel panic - not syncing: Fatal exception in interrupt
> [   17.500941] Kernel Offset: disabled
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