On Mon, Aug 29, 2022 at 4:11 AM Liu Shixin <liushixin2@xxxxxxxxxx> wrote: > > On 2022/8/29 4:44, Vitaly Wool wrote: > > On Sat, Aug 27, 2022 at 12:12 PM Liu Shixin <liushixin2@xxxxxxxxxx> wrote: > >> If zswap initial failed or has not been initial, frontswap_ops will be > >> NULL. In such situation, swap device would enable failed with following > >> stack trace: > >> > >> Unable to handle kernel access to user memory outside uaccess routines at virtual address 0000000000000000 > >> Mem abort info: > >> ESR = 0x0000000096000004 > >> EC = 0x25: DABT (current EL), IL = 32 bits > >> SET = 0, FnV = 0 > >> EA = 0, S1PTW = 0 > >> FSC = 0x04: level 0 translation fault > >> Data abort info: > >> ISV = 0, ISS = 0x00000004 > >> CM = 0, WnR = 0 > >> user pgtable: 4k pages, 48-bit VAs, pgdp=00000020a4fab000 > >> [0000000000000000] pgd=0000000000000000, p4d=0000000000000000 > >> Internal error: Oops: 96000004 [#1] SMP > >> Modules linked in: zram fsl_dpaa2_eth pcs_lynx phylink ahci_qoriq crct10dif_ce ghash_ce sbsa_gwdt fsl_mc_dpio nvme lm90 nvme_core at803x xhci_plat_hcd rtc_fsl_ftm_alarm xgmac_mdio ahci_platform i2c_imx ip6_tables ip_tables fuse > >> Unloaded tainted modules: cppc_cpufreq():1 > >> CPU: 10 PID: 761 Comm: swapon Not tainted 6.0.0-rc2-00454-g22100432cf14 #1 > >> Hardware name: SolidRun Ltd. SolidRun CEX7 Platform, BIOS EDK II Jun 21 2022 > >> pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > >> pc : frontswap_init+0x38/0x60 > >> lr : __do_sys_swapon+0x8a8/0x9f4 > >> sp : ffff80000969bcf0 > >> x29: ffff80000969bcf0 x28: ffff37bee0d8fc00 x27: ffff80000a7f5000 > >> x26: fffffcdefb971e80 x25: ffffaba797453b90 x24: 0000000000000064 > >> x23: ffff37c1f209d1a8 x22: ffff37bee880e000 x21: ffffaba797748560 > >> x20: ffff37bee0d8fce4 x19: ffffaba797748488 x18: 0000000000000014 > >> x17: 0000000030ec029a x16: ffffaba795a479b0 x15: 0000000000000000 > >> x14: 0000000000000000 x13: 0000000000000030 x12: 0000000000000001 > >> x11: ffff37c63c0aba18 x10: 0000000000000000 x9 : ffffaba7956b8c88 > >> x8 : ffff80000969bcd0 x7 : 0000000000000000 x6 : 0000000000000000 > >> x5 : 0000000000000001 x4 : 0000000000000000 x3 : ffffaba79730f000 > >> x2 : ffff37bee0d8fc00 x1 : 0000000000000000 x0 : 0000000000000000 > >> Call trace: > >> frontswap_init+0x38/0x60 > >> __do_sys_swapon+0x8a8/0x9f4 > >> __arm64_sys_swapon+0x28/0x3c > >> invoke_syscall+0x78/0x100 > >> el0_svc_common.constprop.0+0xd4/0xf4 > >> do_el0_svc+0x38/0x4c > >> el0_svc+0x34/0x10c > >> el0t_64_sync_handler+0x11c/0x150 > >> el0t_64_sync+0x190/0x194 > >> Code: d000e283 910003fd f9006c41 f946d461 (f9400021) > >> ---[ end trace 0000000000000000 ]--- > >> > > Well, this issue you are seeing is in fact introduced by the following patch: > > > > author Christoph Hellwig <hch@xxxxxx> 2022-01-21 22:15:10 -0800 > > frontswap: remove support for multiple ops > > > > So I would rather see that one reverted and fixed. > > > > Thanks, > > Vitaly > It is surely introduced by the previous patch ,but is it need to revert that patch? Do we have > any plans to add new backend in the future? I believe we do. Besides, this patch introduces the bug you have hit, before this patch frontswap just wouldn't go doing anything on an empty list. It's my bad I didn't NAK that patch then, but we have an opportunity to do it the right way now. Thanks, Vitaly > Thanks, > > > >> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx> > >> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx> > >> --- > >> mm/frontswap.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/mm/frontswap.c b/mm/frontswap.c > >> index 1a97610308cb..620f95af81dd 100644 > >> --- a/mm/frontswap.c > >> +++ b/mm/frontswap.c > >> @@ -125,7 +125,8 @@ void frontswap_init(unsigned type, unsigned long *map) > >> * p->frontswap set to something valid to work properly. > >> */ > >> frontswap_map_set(sis, map); > >> - frontswap_ops->init(type); > >> + if (frontswap_ops) > >> + frontswap_ops->init(type); > >> } > >> > >> static bool __frontswap_test(struct swap_info_struct *sis, > >> -- > >> 2.25.1 > >> > > . > > >
