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Date: Tue, 14 Jan 2014 21:34:35 +0100
From: Guillaume Morin <guillaume@morinfr.org>
To: linux-kernel@vger.kernel.org
Subject: BUG: Bad page state in process with linux 3.4.76
Message-ID: <20140114203434.GA22994@bender.morinfr.org>
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--azLHFNyN32YCQGCU
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Hi,

I wrote this simple program (attached) to play around with kernel AIO.
It simply does kernel AIO with O_DIRECT on a small temp file stored on
an ext4 filesystem.

When I run it with "HUGETLB_MORECORE=yes LD_PRELOAD=libhugetlbfs.so", it
triggers the kernel bug on exit every time.

Removing HUGETLB_MORECORE from the command line fixes the problem.  Note
that my kernel does not use THP, it is NOT compiled with
CONFIG_TRANSPARENT_HUGEPAGE.

I've tried it only with this 3.4.76 but I've been able to reproduce it without
any issue on multiple machines running the same kernel.

BUG: Bad page state in process aio_test  pfn:1b7a01
page:ffffea0006de8040 count:0 mapcount:1 mapping:          (null) index:0x0
page flags: 0x20000000008000(tail)
Modules linked in: nfsd exportfs nfs nfs_acl auth_rpcgss fscache lockd sunrpc
rdma_ucm rdma_cm ib_addr iw_cm ib_uverbs ib_cm ib_sa ib_mad ib_core ipmi_si
ipmi_devintf coretemp pcspkr microcode serio_raw i2c_i801 ioatdma i2c_core dca
dm_mod sg sr_mod cdrom crc32c_intel ahci libahci [last unloaded: scsi_wait_scan]
Pid: 4441, comm: aio_test Not tainted 3.4.76bug #1
Call Trace:
[<ffffffff810f3300>] ? is_free_buddy_page+0xa0/0xd0
[<ffffffff814c0791>] bad_page+0xe6/0xfc
[<ffffffff810f3dbc>] free_pages_prepare+0xfc/0x110
[<ffffffff810f3dff>] __free_pages_ok+0x2f/0xd0
[<ffffffff810f4080>] __free_pages+0x20/0x40
[<ffffffff81124737>] update_and_free_page+0x77/0x80
[<ffffffff8112633e>] free_huge_page+0x16e/0x180
[<ffffffff810f8030>] __put_compound_page+0x20/0x50
[<ffffffff810f8108>] put_compound_page+0x78/0x140
[<ffffffff810f8546>] put_page+0x36/0x40
[<ffffffff81126ede>] __unmap_hugepage_range+0x1ce/0x230
[<ffffffff81127331>] unmap_hugepage_range+0x51/0x90
[<ffffffff8110e880>] unmap_single_vma+0x730/0x740
[<ffffffff8110f05f>] unmap_vmas+0x5f/0x80
[<ffffffff8111672c>] exit_mmap+0xbc/0x130
[<ffffffff8112e170>] ? kmem_cache_free+0x20/0xe0
[<ffffffff81035155>] mmput+0x35/0xf0
[<ffffffff8103a58d>] exit_mm+0xfd/0x120
[<ffffffff8103bb6c>] do_exit+0x16c/0x8b0
[<ffffffff811540c4>] ? mntput+0x24/0x40
[<ffffffff81138962>] ? fput+0x192/0x250
[<ffffffff8103c5ff>] do_group_exit+0x3f/0xa0
[<ffffffff8103c677>] sys_exit_group+0x17/0x20
[<ffffffff814d03d2>] system_call_fastpath+0x16/0x1b


-- 
Guillaume Morin <guillaume@morinfr.org>

--azLHFNyN32YCQGCU
Content-Type: text/x-csrc; charset=us-ascii
Content-Disposition: attachment; filename="aio_test.c"

#define _GNU_SOURCE
#include <libaio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/eventfd.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>

#define FILE_SIZE 4096

int main(void)
{
    io_context_t ctx;
    int fd,fd_odirect,i,event_fd,epoll_fd;
    struct epoll_event ev;
    void *buf;
    size_t offset = 0;
    struct iocb cb;
    struct iocb * cbs[1] = { &cb };

    fd = open("/tmp/foo",O_RDWR|O_CREAT);
    if (fd == -1) {
        perror("open");
        return 1;
    }
    for (i = 0; i < FILE_SIZE; ++i) {
        char c = rand() % 255;
        write(fd, &c, 1);
    }
    close(fd);

    fd_odirect = open("/tmp/foo",O_RDONLY|O_DIRECT);
    if (fd_odirect == -1) {
        perror("open");
        return 1;
    }
    memset(&ctx, 0, sizeof(ctx));
    if (0 != io_queue_init(1, &ctx)) {
        perror("ctx");
        return 1;
    }
    event_fd = eventfd(0, EFD_CLOEXEC);
    if (event_fd == -1) {
        perror("eventfd");
        return -1;
    }

    epoll_fd = epoll_create(1);
    if (epoll_fd == -1) {
        perror("epoll_fd");
        return 1;
    }

    ev.events = EPOLLIN;

    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, event_fd, &ev) == -1) {
        perror("epoll_ctl");
        return 1;
    }

    posix_memalign(&buf, 512, 32768);

    while (1) {
        struct timespec ts = { 0, 0 };
        struct io_event ioev;
        int ret;
        long v;
        io_prep_pread(&cb, fd_odirect, buf + offset, 512, offset);
        io_set_eventfd(&cb, event_fd);
        if (1 != io_submit(ctx, 1, cbs)) {
            perror("io_submit");
            return 1;
        }

        ret = epoll_wait(epoll_fd, &ev, 1, -1);
        if (ret != 1) {
            perror("epoll_wait");
        }

        read(event_fd, &v, 8);
        
        printf("event_fd returned %ld\n", v);


        if (io_getevents(ctx, 1, 1, &ioev, &ts) != 1) {
            perror("io_getevents");
            return 1;
        }

        printf("Read 1 res %ld res2 %ld\n", ioev.res, ioev.res2);
        offset += ioev.res;

        if (ioev.res == 0) {
            break;
        } 
        if ((offset + 512) > 32768) {
            puts("ERROR - reading past buffer");
            return 1;
        }
    }

    free(buf);
    io_destroy(ctx);
    close(event_fd);
    close(epoll_fd);
    close(fd_odirect);

    return 0;
}

--azLHFNyN32YCQGCU--
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