Commit 23010032 authored by Peter Xu's avatar Peter Xu Committed by Linus Torvalds
Browse files

mm/smaps: simplify shmem handling of pte holes 

Firstly, check_shmem_swap variable is actually not necessary, because
it's always set with pte_hole hook; checking each would work.

Meanwhile, the check within smaps_pte_entry is not easy to follow.
E.g., pte_none() check is not needed as "!pte_present && !is_swap_pte"
is the same.  Since at it, use the pte_hole() helper rather than dup the
page cache lookup.

Still keep the CONFIG_SHMEM part so the code can be optimized to nop for
!SHMEM.

There will be a very slight functional change in smaps_pte_entry(), that
for !SHMEM we'll return early for pte_none (before checking page==NULL),
but that's even nicer.

Link: https://lkml.kernel.org/r/20210917164756.8586-4-peterx@redhat.com


Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 02399c88

fs/proc/task_mmu.c

+12 −10
Original line number Diff line number Diff line
@@ -397,7 +397,6 @@ struct mem_size_stats { 
	u64 pss_shmem;

	u64 pss_locked;

	u64 swap_pss;

	bool check_shmem_swap;

};



static void smaps_page_accumulate(struct mem_size_stats *mss,
@@ -490,6 +489,16 @@ static int smaps_pte_hole(unsigned long addr, unsigned long end, 
#define smaps_pte_hole		NULL

#endif /* CONFIG_SHMEM */



static void smaps_pte_hole_lookup(unsigned long addr, struct mm_walk *walk)

{

#ifdef CONFIG_SHMEM

	if (walk->ops->pte_hole) {

		/* depth is not used */

		smaps_pte_hole(addr, addr + PAGE_SIZE, 0, walk);

	}

#endif

}



static void smaps_pte_entry(pte_t *pte, unsigned long addr,

		struct mm_walk *walk)

{
@@ -518,12 +527,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, 
			}

		} else if (is_pfn_swap_entry(swpent))

			page = pfn_swap_entry_to_page(swpent);

	} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap

							&& pte_none(*pte))) {

		page = xa_load(&vma->vm_file->f_mapping->i_pages,

						linear_page_index(vma, addr));

		if (xa_is_value(page))

			mss->swap += PAGE_SIZE;

	} else {

		smaps_pte_hole_lookup(addr, walk);

		return;

	}
@@ -737,8 +742,6 @@ static void smap_gather_stats(struct vm_area_struct *vma, 
		return;



#ifdef CONFIG_SHMEM

	/* In case of smaps_rollup, reset the value from previous vma */

	mss->check_shmem_swap = false;

	if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {

		/*

		 * For shared or readonly shmem mappings we know that all
@@ -756,7 +759,6 @@ static void smap_gather_stats(struct vm_area_struct *vma, 
					!(vma->vm_flags & VM_WRITE))) {

			mss->swap += shmem_swapped;

		} else {

			mss->check_shmem_swap = true;

			ops = &smaps_shmem_walk_ops;

		}

	}