From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/smaps: fix shmem pte hole swap calculation
Patch series "mm/smaps: Fixes and optimizations on shmem swap handling".
This patch (of 3):
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
", 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.
Link: https://lkml.kernel.org/r/20210917164756.8586-1-peterx@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210917164756.8586-2-peterx@xxxxxxxxxx
Fixes: 48131e03ca4e ("mm, proc: reduce cost of /proc/pid/smaps for unpopulated shmem mappings")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/proc/task_mmu.c~mm-smaps-fix-shmem-pte-hole-swap-calculation
+++ a/fs/proc/task_mmu.c
@@ -478,9 +478,11 @@ static int smaps_pte_hole(unsigned long
__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;
}
_
