From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
peterx@redhat.com, Matthew Wilcox <willy@infradead.org>
Subject: [PATCH 1/3] mm/smaps: Fix shmem pte hole swap calculation
Date: Fri, 17 Sep 2021 12:47:54 -0400 [thread overview]
Message-ID: <20210917164756.8586-2-peterx@redhat.com> (raw)
In-Reply-To: <20210917164756.8586-1-peterx@redhat.com>
The shmem swap calculation on the privately writable mappings are using wrong
parameters as spotted by Vlastimil. Fix them. That's introduced in commit
48131e03ca4e, when rework shmem_swap_usage to shmem_partial_swap_usage.
Test program:
==================
void main(void)
{
char *buffer, *p;
int i, fd;
fd = memfd_create("test", 0);
assert(fd > 0);
/* isize==2M*3, fill in pages, swap them out */
ftruncate(fd, SIZE_2M * 3);
buffer = mmap(NULL, SIZE_2M * 3, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
assert(buffer);
for (i = 0, p = buffer; i < SIZE_2M * 3 / 4096; i++) {
*p = 1;
p += 4096;
}
madvise(buffer, SIZE_2M * 3, MADV_PAGEOUT);
munmap(buffer, SIZE_2M * 3);
/*
* Remap with private+writtable mappings on partial of the inode (<= 2M*3),
* while the size must also be >= 2M*2 to make sure there's a none pmd so
* smaps_pte_hole will be triggered.
*/
buffer = mmap(NULL, SIZE_2M * 2, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
printf("pid=%d, buffer=%p\n", getpid(), buffer);
/* Check /proc/$PID/smap_rollup, should see 4MB swap */
sleep(1000000);
}
==================
Before the patch, smaps_rollup shows <4MB swap and the number will be random
depending on the alignment of the buffer of mmap() allocated. After this
patch, it'll show 4MB.
Fixes: 48131e03ca4e ("mm, proc: reduce cost of /proc/pid/smaps for unpopulated shmem mappings")
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
fs/proc/task_mmu.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index cf25be3e0321..2197f669e17b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -478,9 +478,11 @@ static int smaps_pte_hole(unsigned long addr, unsigned long end,
__always_unused int depth, struct mm_walk *walk)
{
struct mem_size_stats *mss = walk->private;
+ struct vm_area_struct *vma = walk->vma;
- mss->swap += shmem_partial_swap_usage(
- walk->vma->vm_file->f_mapping, addr, end);
+ mss->swap += shmem_partial_swap_usage(walk->vma->vm_file->f_mapping,
+ linear_page_index(vma, addr),
+ linear_page_index(vma, end));
return 0;
}
--
2.31.1
next prev parent reply other threads:[~2021-09-17 16:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-17 16:47 [PATCH 0/3] mm/smaps: Fixes and optimizations on shmem swap handling Peter Xu
2021-09-17 16:47 ` Peter Xu [this message]
2021-09-22 10:40 ` [PATCH 1/3] mm/smaps: Fix shmem pte hole swap calculation Vlastimil Babka
2021-09-17 16:47 ` [PATCH 2/3] mm/smaps: Use vma->vm_pgoff directly when counting partial swap Peter Xu
2021-09-22 10:41 ` Vlastimil Babka
2021-09-17 16:47 ` [PATCH 3/3] mm/smaps: Simplify shmem handling of pte holes Peter Xu
2021-10-05 11:15 ` Vlastimil Babka
2021-10-05 14:40 ` Peter Xu
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