Switch VM_FLUSH_RESET_PERMS to use a regular TLB flush intead of vm_unmap_aliases() and fix calculation of the direct map for the CONFIG_ARCH_HAS_SET_DIRECT_MAP case.Meelis Roos reported issues with the new VM_FLUSH_RESET_PERMS flag on a sparc machine. On investigation some issues were noticed: 1. The calculation of the direct map address range to flush was wrong. This could cause problems on x86 if a RO direct map alias ever got loaded into the TLB. This shouldn't normally happen, but it could cause the permissions to remain RO on the direct map alias, and then the page would return from the page allocator to some other component as RO and cause a crash. 2. Calling vm_unmap_alias() on vfree could potentially be a lot of work to do on a free operation. Simply flushing the TLB instead of the whole vm_unmap_alias() operation makes the frees faster and pushes the heavy work to happen on allocation where it would be more expected. In addition to the extra work, vm_unmap_alias() takes some locks including a long hold of vmap_purge_lock, which will make all other VM_FLUSH_RESET_PERMS vfrees wait while the purge operation happens. 3. page_address() can have locking on some configurations, so skip calling this when possible to further speed this up. Fixes: 868b104d7379 ("mm/vmalloc: Add flag for freeing of special permsissions") Reported-by: Meelis Roos<mr...@linux.ee> Cc: Meelis Roos<mr...@linux.ee> Cc: Peter Zijlstra<pet...@infradead.org> Cc: "David S. Miller"<da...@davemloft.net> Cc: Dave Hansen<dave.han...@intel.com> Cc: Borislav Petkov<b...@alien8.de> Cc: Andy Lutomirski<l...@kernel.org> Cc: Ingo Molnar<mi...@redhat.com> Cc: Nadav Amit<na...@vmware.com> Signed-off-by: Rick Edgecombe<rick.p.edgeco...@intel.com> --- Changes since v1: - Update commit message with more detail - Fix flush end range on !CONFIG_ARCH_HAS_SET_DIRECT_MAP case
It does not work on my V445 where the initial problem happened. [ 46.582633] systemd[1]: Detected architecture sparc64. Welcome to Debian GNU/Linux 10 (buster)! [ 46.759048] systemd[1]: Set hostname to <v445>. [ 46.831383] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid argument [ 67.989695] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [ 68.074706] rcu: 0-...!: (0 ticks this GP) idle=5c6/1/0x4000000000000000 softirq=33/33 fqs=0 [ 68.198443] rcu: 2-...!: (0 ticks this GP) idle=e7e/1/0x4000000000000000 softirq=67/67 fqs=0 [ 68.322198] (detected by 1, t=5252 jiffies, g=-939, q=108) [ 68.402204] CPU[ 0]: TSTATE[0000000080001603] TPC[000000000043f298] TNPC[000000000043f29c] TASK[systemd-debug-g:89] [ 68.556001] TPC[smp_synchronize_tick_client+0x18/0x1a0] O7[0xfff000010000691c] I7[xcall_sync_tick+0x1c/0x2c] RPC[alloc_set_pte+0xf4/0x300] [ 68.750973] CPU[ 2]: TSTATE[0000000080001600] TPC[000000000043f298] TNPC[000000000043f29c] TASK[systemd-cryptse:88] [ 68.904741] TPC[smp_synchronize_tick_client+0x18/0x1a0] O7[filemap_map_pages+0x3cc/0x3e0] I7[xcall_sync_tick+0x1c/0x2c] RPC[handle_mm_fault+0xa0/0x180] [ 69.115991] rcu: rcu_sched kthread starved for 5252 jiffies! g-939 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=3 [ 69.262239] rcu: RCU grace-period kthread stack dump: [ 69.334741] rcu_sched I 0 10 2 0x06000000 [ 69.413495] Call Trace: [ 69.448501] [000000000093325c] schedule+0x1c/0xc0 [ 69.517253] [0000000000936c74] schedule_timeout+0x154/0x260 [ 69.598514] [00000000004b65a4] rcu_gp_kthread+0x4e4/0xac0 [ 69.677261] [000000000047ecfc] kthread+0xfc/0x120 [ 69.746018] [00000000004060a4] ret_from_fork+0x1c/0x2c [ 69.821014] [0000000000000000] 0x0 and hangs here, software watchdog kicks in soon. -- Meelis Roos
