6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> commit 9094b4a1c76cfe84b906cc152bab34d4ba26fa5c upstream. When testing shmem swapin, I encountered the warning below on my machine. The reason is that replacing an old shmem folio with a new one causes mem_cgroup_migrate() to clear the old folio's memcg data. As a result, the old folio cannot get the correct memcg's lruvec needed to remove itself from the LRU list when it is being freed. This could lead to possible serious problems, such as LRU list crashes due to holding the wrong LRU lock, and incorrect LRU statistics. To fix this issue, we can fallback to use the mem_cgroup_replace_folio() to replace the old shmem folio. [ 5241.100311] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5d9960 [ 5241.100317] head: order:4 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 5241.100319] flags: 0x17fffe0000040068(uptodate|lru|head|swapbacked|node=0|zone=2|lastcpupid=0x3ffff) [ 5241.100323] raw: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000 [ 5241.100325] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 5241.100326] head: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000 [ 5241.100327] head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 5241.100328] head: 17fffe0000000204 fffffdffd6665801 ffffffffffffffff 0000000000000000 [ 5241.100329] head: 0000000a00000010 0000000000000000 00000000ffffffff 0000000000000000 [ 5241.100330] page dumped because: VM_WARN_ON_ONCE_FOLIO(!memcg && !mem_cgroup_disabled()) [ 5241.100338] ------------[ cut here ]------------ [ 5241.100339] WARNING: CPU: 19 PID: 78402 at include/linux/memcontrol.h:775 folio_lruvec_lock_irqsave+0x140/0x150 [...] [ 5241.100374] pc : folio_lruvec_lock_irqsave+0x140/0x150 [ 5241.100375] lr : folio_lruvec_lock_irqsave+0x138/0x150 [ 5241.100376] sp : ffff80008b38b930 [...] [ 5241.100398] Call trace: [ 5241.100399] folio_lruvec_lock_irqsave+0x140/0x150 [ 5241.100401] __page_cache_release+0x90/0x300 [ 5241.100404] __folio_put+0x50/0x108 [ 5241.100406] shmem_replace_folio+0x1b4/0x240 [ 5241.100409] shmem_swapin_folio+0x314/0x528 [ 5241.100411] shmem_get_folio_gfp+0x3b4/0x930 [ 5241.100412] shmem_fault+0x74/0x160 [ 5241.100414] __do_fault+0x40/0x218 [ 5241.100417] do_shared_fault+0x34/0x1b0 [ 5241.100419] do_fault+0x40/0x168 [ 5241.100420] handle_pte_fault+0x80/0x228 [ 5241.100422] __handle_mm_fault+0x1c4/0x440 [ 5241.100424] handle_mm_fault+0x60/0x1f0 [ 5241.100426] do_page_fault+0x120/0x488 [ 5241.100429] do_translation_fault+0x4c/0x68 [ 5241.100431] do_mem_abort+0x48/0xa0 [ 5241.100434] el0_da+0x38/0xc0 [ 5241.100436] el0t_64_sync_handler+0x68/0xc0 [ 5241.100437] el0t_64_sync+0x14c/0x150 [ 5241.100439] ---[ end trace 0000000000000000 ]--- [baolin.wang@xxxxxxxxxxxxxxxxx: remove less helpful comments, per Matthew] Link: https://lkml.kernel.org/r/ccad3fe1375b468ebca3227b6b729f3eaf9d8046.1718423197.git.baolin.wang@xxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/3c11000dd6c1df83015a8321a859e9775ebbc23e.1718266112.git.baolin.wang@xxxxxxxxxxxxxxxxx Fixes: 85ce2c517ade ("memcontrol: only transfer the memcg data for migration") Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Nhat Pham <nphamcs@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 3 +-- mm/shmem.c | 2 +- 2 files changed, 2 insertions(+), 3 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7531,8 +7531,7 @@ void __mem_cgroup_uncharge_folios(struct * @new: Replacement folio. * * Charge @new as a replacement folio for @old. @old will - * be uncharged upon free. This is only used by the page cache - * (in replace_page_cache_folio()). + * be uncharged upon free. * * Both folios must be locked, @new->mapping must be set up. */ --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1786,7 +1786,7 @@ static int shmem_replace_folio(struct fo xa_lock_irq(&swap_mapping->i_pages); error = shmem_replace_entry(swap_mapping, swap_index, old, new); if (!error) { - mem_cgroup_migrate(old, new); + mem_cgroup_replace_folio(old, new); __lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1); __lruvec_stat_mod_folio(new, NR_SHMEM, 1); __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1);
