30e235389f
Without this patch, the MAP_SYNC test case will cause a print_bad_pte
warning on arm64 as follows:
[ 25.542693] BUG: Bad page map in process mapdax333 pte:2e8000448800f53 pmd:41ff5f003
[ 25.546360] page:ffff7e0010220000 refcount:1 mapcount:-1 mapping:ffff8003e29c7440 index:0x0
[ 25.550281] ext4_dax_aops
[ 25.550282] name:"__aaabbbcccddd__"
[ 25.551553] flags: 0x3ffff0000001002(referenced|reserved)
[ 25.555802] raw: 03ffff0000001002 ffff8003dfffa908 0000000000000000 ffff8003e29c7440
[ 25.559446] raw: 0000000000000000 0000000000000000 00000001fffffffe 0000000000000000
[ 25.563075] page dumped because: bad pte
[ 25.564938] addr:0000ffffbe05b000 vm_flags:208000fb anon_vma:0000000000000000 mapping:ffff8003e29c7440 index:0
[ 25.574272] file:__aaabbbcccddd__ fault:ext4_dax_fault mmmmap:ext4_file_mmap readpage:0x0
[ 25.578799] CPU: 1 PID: 1180 Comm: mapdax333 Not tainted 5.2.0+ #21
[ 25.581702] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
[ 25.585624] Call trace:
[ 25.587008] dump_backtrace+0x0/0x178
[ 25.588799] show_stack+0x24/0x30
[ 25.590328] dump_stack+0xa8/0xcc
[ 25.591901] print_bad_pte+0x18c/0x218
[ 25.593628] unmap_page_range+0x778/0xc00
[ 25.595506] unmap_single_vma+0x94/0xe8
[ 25.597304] unmap_vmas+0x90/0x108
[ 25.598901] unmap_region+0xc0/0x128
[ 25.600566] __do_munmap+0x284/0x3f0
[ 25.602245] __vm_munmap+0x78/0xe0
[ 25.603820] __arm64_sys_munmap+0x34/0x48
[ 25.605709] el0_svc_common.constprop.0+0x78/0x168
[ 25.607956] el0_svc_handler+0x34/0x90
[ 25.609698] el0_svc+0x8/0xc
[...]
The root cause is in _vm_normal_page, without the PTE_SPECIAL bit,
the return value will be incorrectly set to pfn_to_page(pfn) instead
of NULL. Besides, this patch also rewrite the pmd_mkdevmap to avoid
setting PTE_SPECIAL for pmd
The MAP_SYNC test case is as follows(Provided by Yibo Cai)
$#include <stdio.h>
$#include <string.h>
$#include <unistd.h>
$#include <sys/file.h>
$#include <sys/mman.h>
$#ifndef MAP_SYNC
$#define MAP_SYNC 0x80000
$#endif
/* mount -o dax /dev/pmem0 /mnt */
$#define F "/mnt/__aaabbbcccddd__"
int main(void)
{
int fd;
char buf[4096];
void *addr;
if ((fd = open(F, O_CREAT|O_TRUNC|O_RDWR, 0644)) < 0) {
perror("open1");
return 1;
}
if (write(fd, buf, 4096) != 4096) {
perror("lseek");
return 1;
}
addr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_SYNC, fd, 0);
if (addr == MAP_FAILED) {
perror("mmap");
printf("did you mount with '-o dax'?\n");
return 1;
}
memset(addr, 0x55, 4096);
if (munmap(addr, 4096) == -1) {
perror("munmap");
return 1;
}
close(fd);
return 0;
}
Fixes:
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.