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It does this by calling set_memory_valid() -> __change_memory_common(). This being a non-sleepable context, we cannot take the init_mm mmap lock. Therefore, add PGWALK_NOLOCK to enable walk_page_range_novma() usage without locks. [1] https://lore.kernel.org/linux-arm-kernel/89d0ad18-4772-4d8f-ae8a-7c48d26a927e@arm.com/ Signed-off-by: Dev Jain --- include/linux/pagewalk.h | 2 ++ mm/pagewalk.c | 12 ++++++++---- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h index 9700a29f8afb..9bc8853ed3de 100644 --- a/include/linux/pagewalk.h +++ b/include/linux/pagewalk.h @@ -14,6 +14,8 @@ enum page_walk_lock { PGWALK_WRLOCK = 1, /* vma is expected to be already write-locked during the walk */ PGWALK_WRLOCK_VERIFY = 2, + /* no lock is needed */ + PGWALK_NOLOCK = 3, }; /** diff --git a/mm/pagewalk.c b/mm/pagewalk.c index e478777c86e1..9657cf4664b2 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -440,6 +440,8 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma, case PGWALK_RDLOCK: /* PGWALK_RDLOCK is handled by process_mm_walk_lock */ break; + default: + break; } #endif } @@ -640,10 +642,12 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start, * specified address range from being freed. The caller should take * other actions to prevent this race. */ - if (mm == &init_mm) - mmap_assert_locked(walk.mm); - else - mmap_assert_write_locked(walk.mm); + if (ops->walk_lock != PGWALK_NOLOCK) { + if (mm == &init_mm) + mmap_assert_locked(walk.mm); + else + mmap_assert_write_locked(walk.mm); + } return walk_pgd_range(start, end, &walk); } -- 2.30.2