Re: [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS

[Florian Fainelli]

On 11/7/20 7:22 AM, Stefan Agner wrote:
> Most architectures define MAX_PHYSMEM_BITS in asm/sparsemem.h and don't
> include it in asm/pgtable.h. Include asm/sparsemem.h directly to get
> the MAX_PHYSMEM_BITS define on all architectures.
> 
> This fixes a crash when accessing zram on 32-bit ARM platform with LPAE and
> more than 4GB of memory:
>   Unable to handle kernel NULL pointer dereference at virtual address 00000000
>   pgd = a27bd01c
>   [00000000] *pgd=236a0003, *pmd=1ffa64003
>   Internal error: Oops: 207 [#1] SMP ARM
>   Modules linked in: mdio_bcm_unimac(+) brcmfmac cfg80211 brcmutil raspberrypi_hwmon hci_uart crc32_arm_ce bcm2711_thermal phy_generic genet
>   CPU: 0 PID: 123 Comm: mkfs.ext4 Not tainted 5.9.6 #1
>   Hardware name: BCM2711
>   PC is at zs_map_object+0x94/0x338
>   LR is at zram_bvec_rw.constprop.0+0x330/0xa64
>   pc : [<c0602b38>]    lr : [<c0bda6a0>]    psr: 60000013
>   sp : e376bbe0  ip : 00000000  fp : c1e2921c
>   r10: 00000002  r9 : c1dda730  r8 : 00000000
>   r7 : e8ff7a00  r6 : 00000000  r5 : 02f9ffa0  r4 : e3710000
>   r3 : 000fdffe  r2 : c1e0ce80  r1 : ebf979a0  r0 : 00000000
>   Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>   Control: 30c5383d  Table: 235c2a80  DAC: fffffffd
>   Process mkfs.ext4 (pid: 123, stack limit = 0x495a22e6)
>   Stack: (0xe376bbe0 to 0xe376c000)
>   ...
>   [<c0602b38>] (zs_map_object) from [<c0bda6a0>] (zram_bvec_rw.constprop.0+0x330/0xa64)
>   [<c0bda6a0>] (zram_bvec_rw.constprop.0) from [<c0bdaf78>] (zram_submit_bio+0x1a4/0x40c)
>   [<c0bdaf78>] (zram_submit_bio) from [<c085806c>] (submit_bio_noacct+0xd0/0x3c8)
>   [<c085806c>] (submit_bio_noacct) from [<c08583b0>] (submit_bio+0x4c/0x190)
>   [<c08583b0>] (submit_bio) from [<c06496b4>] (submit_bh_wbc+0x188/0x1b8)
>   [<c06496b4>] (submit_bh_wbc) from [<c064ce98>] (__block_write_full_page+0x340/0x5e4)
>   [<c064ce98>] (__block_write_full_page) from [<c064d3ec>] (block_write_full_page+0x128/0x170)
>   [<c064d3ec>] (block_write_full_page) from [<c0591ae8>] (__writepage+0x14/0x68)
>   [<c0591ae8>] (__writepage) from [<c0593efc>] (write_cache_pages+0x1bc/0x494)
>   [<c0593efc>] (write_cache_pages) from [<c059422c>] (generic_writepages+0x58/0x8c)
>   [<c059422c>] (generic_writepages) from [<c0594c24>] (do_writepages+0x48/0xec)
>   [<c0594c24>] (do_writepages) from [<c0589330>] (__filemap_fdatawrite_range+0xf0/0x128)
>   [<c0589330>] (__filemap_fdatawrite_range) from [<c05894bc>] (file_write_and_wait_range+0x48/0x98)
>   [<c05894bc>] (file_write_and_wait_range) from [<c064f3f8>] (blkdev_fsync+0x1c/0x44)
>   [<c064f3f8>] (blkdev_fsync) from [<c064408c>] (do_fsync+0x3c/0x70)
>   [<c064408c>] (do_fsync) from [<c0400374>] (__sys_trace_return+0x0/0x2c)
>   Exception stack(0xe376bfa8 to 0xe376bff0)
>   bfa0:                   0003d2e0 b6f7b6f0 00000003 00046e40 00001000 00000000
>   bfc0: 0003d2e0 b6f7b6f0 00000000 00000076 00000000 00000000 befcbb20 befcbb28
>   bfe0: b6f4e060 befcbad8 b6f23e0c b6dc4a80
>   Code: e5927000 e0050391 e0871005 e5918018 (e5983000)
> 
> Fixes: 61989a80fb3a ("staging: zsmalloc: zsmalloc memory allocation library")
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>

BTW, I can confirm on behalf of a colleague here that this patch fixes
zsmalloc on a 32-bit platform with 4GB of DRAM and with a 3GB user/1GB
kernel split. Thanks!
-- 
Florian