Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables

[Guenter Roeck]

On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote:
> Now that the page table allocator can free page table allocations
> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations
> to avoid needlessly wasting memory.
> 
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>

Something in the sparc32 patches in linux-next causes all my sparc32 emulations
to crash. bisect points to this patch, but reverting it doesn't help, and neither
does reverting the rest of the series.

Guenter

---
Bisect log:

# bad: [bdecf38f228bcca73b31ada98b5b7ba1215eb9c9] Add linux-next specific files for 20200515
# good: [2ef96a5bb12be62ef75b5828c0aab838ebb29cb8] Linux 5.7-rc5
git bisect start 'HEAD' 'v5.7-rc5'
# bad: [3674d7aa7a8e61d993886c2fb7c896c5ef85e988] Merge remote-tracking branch 'crypto/master'
git bisect bad 3674d7aa7a8e61d993886c2fb7c896c5ef85e988
# bad: [1ab4d6ff0a3ee4b29441d8b0076bc8d4734bd16e] Merge remote-tracking branch 'hwmon-staging/hwmon-next'
git bisect bad 1ab4d6ff0a3ee4b29441d8b0076bc8d4734bd16e
# good: [dccfae3ab84387c94f2efc574d41efae005eeee5] Merge remote-tracking branch 'tegra/for-next'
git bisect good dccfae3ab84387c94f2efc574d41efae005eeee5
# bad: [20f9d1287c9f0047b81497197c9f4893485bbe15] Merge remote-tracking branch 'djw-vfs/vfs-for-next'
git bisect bad 20f9d1287c9f0047b81497197c9f4893485bbe15
# bad: [6537897637b5b91f921cb0ac6c465a593f4a665e] Merge remote-tracking branch 'sparc-next/master'
git bisect bad 6537897637b5b91f921cb0ac6c465a593f4a665e
# good: [bca1583e0693e0ba76450b684c5910f7083eeef4] Merge remote-tracking branch 'mips/mips-next'
git bisect good bca1583e0693e0ba76450b684c5910f7083eeef4
# good: [1f12096aca212af8fad3ef58d5673cde691a1452] Merge the lockless page table walk rework into next
git bisect good 1f12096aca212af8fad3ef58d5673cde691a1452
# good: [23a457b8d57dc8d0cc1dbd1882993dd2fcc4b0c0] s390: nvme reipl
git bisect good 23a457b8d57dc8d0cc1dbd1882993dd2fcc4b0c0
# good: [f57f5010c0c3fe2d924a957ddf1d17fbebb54d47] Merge remote-tracking branch 'risc-v/for-next'
git bisect good f57f5010c0c3fe2d924a957ddf1d17fbebb54d47
# good: [1d5fd6c33b04e5d5b665446c3b56f2148f0f1272] sh: add missing DECLARE_EXPORT() for __ashiftrt_r4_xx
git bisect good 1d5fd6c33b04e5d5b665446c3b56f2148f0f1272
# bad: [8c8f3156dd40f8bdc58f2ac461374bc804c28e3b] sparc32: mm: Reduce allocation size for PMD and PTE tables
git bisect bad 8c8f3156dd40f8bdc58f2ac461374bc804c28e3b
# good: [8e958839e4b9fb6ea4385ff2c52d1333a3a618de] sparc32: mm: Restructure sparc32 MMU page-table layout
git bisect good 8e958839e4b9fb6ea4385ff2c52d1333a3a618de
# good: [3f407976ac2953116cb8880a7a18b63bcc81829d] sparc32: mm: Change pgtable_t type to pte_t * instead of struct page *
git bisect good 3f407976ac2953116cb8880a7a18b63bcc81829d
# first bad commit: [8c8f3156dd40f8bdc58f2ac461374bc804c28e3b] sparc32: mm: Reduce allocation size for PMD and PTE tables

---
Log messages:

Lots of:

BUG: scheduling while atomic: kthreadd/2/0xffffffff
Modules linked in:
CPU: 0 PID: 2 Comm: kthreadd Tainted: G        W         5.7.0-rc5-next-20200515 #1
[f04f2c94 :
here+0x16c/0x250 ]
[f04f2df0 :
schedule+0x78/0x11c ]
[f003f100 :
kthreadd+0x188/0x1a4 ]
[f0008448 :
ret_from_kernel_thread+0xc/0x38 ]
[00000000 :
0x0 ]

followed by:

Kernel panic - not syncing: Aiee, killing interrupt handler!
CPU: 0 PID: 19 Comm: cryptomgr_test Tainted: G        W         5.7.0-rc5-next-20200515 #1
[f0024400 :
do_exit+0x7c8/0xa88 ]
[f0075540 :
__module_put_and_exit+0xc/0x18 ]
[f0221428 :
cryptomgr_test+0x28/0x48 ]
[f003edc0 :
kthread+0xf4/0x12c ]
[f0008448 :
ret_from_kernel_thread+0xc/0x38 ]
[00000000 :
0x0 ]