Messages in this thread | | | Date | Thu, 6 Apr 2023 20:55:12 +0800 | Subject | Re: [PATCH v2] mm/swap: fix swap_info_struct race between swapoff and get_swap_pages() | From | Rongwei Wang <> |
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Oh, sorry, I miss this email just now, that because of I'm also replying your previous email.
On 2023/4/6 20:12, Aaron Lu wrote: > On Wed, Apr 05, 2023 at 12:08:47AM +0800, Rongwei Wang wrote: >> Hello >> >> I have fix up some stuff base on Patch v1. And in order to help all readers >> and reviewers to >> >> reproduce this bug, share a reproducer here: > I reproduced this problem under a VM this way: > > $ sudo ./stress-ng --swap 1 > // on another terminal > $ for i in `seq 8`; do ./swap & done > Looks simpler than yours :-) Cool, indeed become simpler. > (Didn't realize you have posted your reproducer here since I'm not CCed > and just found it after invented mine) > Then the warning message normally appear within a few seconds. > > Here is the code for the above swap prog: > > #include <stdio.h> > #include <stddef.h> > #include <sys/mman.h> > > #define SIZE 0x100000 > > int main(void) > { > int i, ret; > void *p; > > p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); > if (p == MAP_FAILED) { > perror("mmap"); > return -1; > } > > ret = 0; > while (1) { > for (i = 0; i < SIZE; i += 0x1000) > ((char *)p)[i] = 1; > ret = madvise(p, SIZE, MADV_PAGEOUT); > if (ret != 0) { > perror("madvise"); > break; > } > } > > return ret; > } > > Unfortunately, this test prog did not work on kernels before v5.4 because > MADV_PAGEOUT is introduced in v5.4. I tested on v5.4 and the problem is > also there.
Maybe that is this bug can not be found since now. And we found this is triggered by stress-ng-swap and stress-ng-madvise (PAGEOUT) firstly. It seems this is that reason.
It seems MADV_COLD is also introduced together with MADV_PAGEOUT. I have no idea and have to depend on you.:-)
> > Haven't found a way to trigger swap with swap device come and go on > kernels before v5.4; tried putting the test prog in a memcg with memory > limit but then the prog is easily killed due to nowhere to swap out. > Personally, I do not intend to continuing searching for the method to reproduce before v5.4. Of course, if you have idea, I can try.
Thanks:-)
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