[REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing crash shortly after bootup

[John Stultz]

Hey all,
  In testing Linus' HEAD today I found another[1] regression in the block merge.

This time I see a crash on my hikey960 board shortly after booting
ASOP. See the log below.

I bisected the issue down to "block: split bio_kmalloc from bio_alloc_bioset":
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3175199ab0ac8c874ec25c6bf169f74888917435

But unfortunately that does not revert cleanly against Linus' HEAD.

It seems like the issue is that the function is no longer handling the
case where the bio_set *bs is NULL as is done here:
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/block/blk-crypto-fallback.c#n230

If there's anything I can do to help debug this issue, please let me know!

thanks
-john

[1]: "add a disk_uevent helper" also was giving me trouble as reported here:
https://lore.kernel.org/lkml/CALAqxLU3B8YcS_MTnr2Lpasvn8oLJvD2qO4hkfkZeEwVNfeHXg@xxxxxxxxxxxxxx/


[   34.600558] Unable to handle kernel read from unreadable memory at
virtual address 0000000000000068
[   34.609819] Mem abort info:
[   34.612644]   ESR = 0x96000005
[   34.615707]   EC = 0x25: DABT (current EL), IL = 32 bits
[   34.621157]   SET = 0, FnV = 0
[   34.624288]   EA = 0, S1PTW = 0
[   34.628312] Data abort info:
[   34.631236]   ISV = 0, ISS = 0x00000005
[   34.635222]   CM = 0, WnR = 0
[   34.638186] user pgtable: 4k pages, 39-bit VAs, pgdp=000000000774f000
[   34.644639] [0000000000000068] pgd=0000000000000000,
p4d=0000000000000000, pud=0000000000000000
[   34.653381] Internal error: Oops: 96000005 [#1] PREEMPT SMP
[   34.658954] Modules linked in:
[   34.662007] CPU: 0 PID: 173 Comm: kworker/u16:3 Not tainted
5.11.0-04196-ga8e8932e4ae #559
[   34.670270] Hardware name: HiKey960 (DT)
[   34.674190] Workqueue: writeback wb_workfn (flush-8:48)
[   34.679429] pstate: 80400005 (Nzcv daif +PAN -UAO -TCO BTYPE=--)
[   34.685435] pc : bio_alloc_bioset+0x14/0x230
[   34.689720] lr : bio_clone_fast+0x28/0x80
[   34.693728] sp : ffffffc012a13530
[   34.697036] x29: ffffffc012a13530 x28: 0000000000003400
[   34.702351] x27: 0000000000000000 x26: ffffff8001993040
[   34.703203] dwmmc_k3 ff3ff000.dwmmc2: Unexpected interrupt latency
[   34.707662] x25: 0000000000000001 x24: ffffff8001fc8800
[   34.719145] x23: ffffffffffffffff x22: ffffffc012a137e8
[   34.724456] x21: 0000000000000c00 x20: ffffff8001fc8800
[   34.729767] x19: 0000000000000800 x18: fffffffe013efe80
[   34.735078] x17: 0000000000000068 x16: fffffffe012aa440
[   34.740389] x15: 0000000000001000 x14: ffffff8001fc8800
[   34.745700] x13: ffffff805c3e4000 x12: 00000000001ce000
[   34.751009] x11: 00000000000000fb x10: 0000000000001000
[   34.756320] x9 : 0000000000000033 x8 : 00000000000d9000
[   34.761631] x7 : 0000000000000000 x6 : 000000000000a000
[   34.766941] x5 : 0000000000000c00 x4 : 0000000000001000
[   34.772251] x3 : 0000000000000000 x2 : 0000000000000000
[   34.777561] x1 : 0000000000000000 x0 : 0000000000000c00
[   34.782873] Call trace:
[   34.784901] ueventd: LoadWithAliases was unable to load platform:regulatory
[   34.785313]  bio_alloc_bioset+0x14/0x230
[   34.796189]  bio_clone_fast+0x28/0x80
[   34.799848]  bio_split+0x50/0xd0
[   34.803072]  blk_crypto_fallback_encrypt_bio+0x2ec/0x5e8
[   34.808384]  blk_crypto_fallback_bio_prep+0xfc/0x140
[   34.813345]  __blk_crypto_bio_prep+0x13c/0x150
[   34.817784]  submit_bio_noacct+0x3c0/0x548
[   34.821880]  submit_bio+0x48/0x200
[   34.825278]  ext4_io_submit+0x50/0x68
[   34.828939]  ext4_writepages+0x558/0xca8
[   34.832860]  do_writepages+0x58/0x108
[   34.836522]  __writeback_single_inode+0x44/0x510
[   34.841137]  writeback_sb_inodes+0x1e0/0x4a8
[   34.845404]  __writeback_inodes_wb+0x78/0xe8
[   34.849670]  wb_writeback+0x274/0x3e8
[   34.853328]  wb_workfn+0x308/0x5f0
[   34.856726]  process_one_work+0x1ec/0x4d0
[   34.860734]  worker_thread+0x44/0x478
[   34.864392]  kthread+0x140/0x150
[   34.867618]  ret_from_fork+0x10/0x30
[   34.871197] Code: a9ba7bfd 910003fd f9000bf3 7900bfa1 (f9403441)
[   34.877289] ---[ end trace e6c2a3ab108278f0 ]---
[   34.893636] Kernel panic - not syncing: Oops: Fatal exception