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: 73b20c84d42d ("arm64: mm: implement pte_devmap support") Reported-by: Yibo Cai <Yibo.Cai@arm.com> Acked-by: Will Deacon <will@kernel.org> Acked-by: Robin Murphy <Robin.Murphy@arm.com> Signed-off-by: Jia He <justin.he@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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.