On 2025/2/22 15:33, Kairui Song wrote: > On Sat, Feb 22, 2025 at 10:56 AM Wupeng Ma <mawupeng1@xxxxxxxxxx> wrote: >> >> From: Ma Wupeng <mawupeng1@xxxxxxxxxx> >> >> During our test, infinite loop is produced during #PF will lead to infinite >> error log as follow: >> >> get_swap_device: Bad swap file entry 114000000 >> >> Digging into the source, we found that the swap entry is invalid due to >> unknown reason, and this lead to invalid swap_info_struct. Excessive log > > Hi Wupeng, > > What is the kernel version you are using? If it's another bug causing > this invalid swap entry, we should fix that bug instead, not > workaround it. > > This looks kind of similar to another PATCH & Bug report, corrupted > page table or swap entry: > https://lore.kernel.org/linux-mm/e223b0e6ba2f4924984b1917cc717bd5@xxxxxxxxx/ > > Might be the same kernel bug? Gaoxu mentioned the bug was observed on > Kernel 6.6.30 (android version), and neither of these two workarounds > will fix it completely, the invalid value could cause many other > issues too. We definitely need to find out the root cause. We are having this problem in linux-v5.10, since the log is lost and swap is not enabled in this machines, maybe memory corrupted in the pt. > >> printing can fill up the prioritized log space, leading to the purging of >> originally valid logs and hindering problem troubleshooting. To make this >> more robust, kill this task. >> >> Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> >> --- >> include/linux/swap.h | 1 + >> mm/memory.c | 9 ++++++++- >> mm/swapfile.c | 2 +- >> 3 files changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/swap.h b/include/linux/swap.h >> index b13b72645db3..0fa39cf66bc4 100644 >> --- a/include/linux/swap.h >> +++ b/include/linux/swap.h >> @@ -508,6 +508,7 @@ struct backing_dev_info; >> extern int init_swap_address_space(unsigned int type, unsigned long nr_pages); >> extern void exit_swap_address_space(unsigned int type); >> extern struct swap_info_struct *get_swap_device(swp_entry_t entry); >> +struct swap_info_struct *_swap_info_get(swp_entry_t entry); >> sector_t swap_folio_sector(struct folio *folio); >> >> static inline void put_swap_device(struct swap_info_struct *si) >> diff --git a/mm/memory.c b/mm/memory.c >> index b4d3d4893267..2d36e5a644d1 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -4365,8 +4365,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) >> >> /* Prevent swapoff from happening to us. */ >> si = get_swap_device(entry); >> - if (unlikely(!si)) >> + if (unlikely(!si)) { >> + if (unlikely(!_swap_info_get(entry))) >> + /* >> + * return VM_FAULT_SIGBUS for invalid swap entry to >> + * avoid infinite #PF. >> + */ >> + ret = VM_FAULT_SIGBUS; > > This could lead to VM_FAULT_SIGBUS on swapoff. After swapoff > get_swap_device will return NULL. If swap is off, All swap pages should be swap in as expected, so such entry can not trigger do_swap_page?
