// SPDX-License-Identifier: GPL-2.0-only
/*
 * mm/mmap.c
 *
 * Written by obz.
 *
 * Address space accounting code	<alan@lxorguk.ukuu.org.uk>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

/*
 * Official Linux v6.0: mm/mmap.c
 * https://github.com/torvalds/linux/blob/v6.0/mm/mmap.c#L3075
 * Complete upstream scope, not an elided book-code reconstruction.
 * See GPL-2.0.txt. Not a standalone translation unit.
 */

void exit_mmap(struct mm_struct *mm)
{
	struct mmu_gather tlb;
	struct vm_area_struct *vma;
	unsigned long nr_accounted = 0;

	/* mm's last user has gone, and its about to be pulled down */
	mmu_notifier_release(mm);

	if (unlikely(mm_is_oom_victim(mm))) {
		/*
		 * Manually reap the mm to free as much memory as possible.
		 * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
		 * this mm from further consideration.  Taking mm->mmap_lock for
		 * write after setting MMF_OOM_SKIP will guarantee that the oom
		 * reaper will not run on this mm again after mmap_lock is
		 * dropped.
		 *
		 * Nothing can be holding mm->mmap_lock here and the above call
		 * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
		 * __oom_reap_task_mm() will not block.
		 */
		(void)__oom_reap_task_mm(mm);
		set_bit(MMF_OOM_SKIP, &mm->flags);
	}

	mmap_write_lock(mm);
	arch_exit_mmap(mm);

	vma = mm->mmap;
	if (!vma) {
		/* Can happen if dup_mmap() received an OOM */
		mmap_write_unlock(mm);
		return;
	}

	lru_add_drain();
	flush_cache_mm(mm);
	tlb_gather_mmu_fullmm(&tlb, mm);
	/* update_hiwater_rss(mm) here? but nobody should be looking */
	/* Use -1 here to ensure all VMAs in the mm are unmapped */
	unmap_vmas(&tlb, vma, 0, -1);
	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
	tlb_finish_mmu(&tlb);

	/* Walk the list again, actually closing and freeing it. */
	while (vma) {
		if (vma->vm_flags & VM_ACCOUNT)
			nr_accounted += vma_pages(vma);
		vma = remove_vma(vma);
		cond_resched();
	}
	mm->mmap = NULL;
	mmap_write_unlock(mm);
	vm_unacct_memory(nr_accounted);
}