On Thu, Aug 17, 2017 at 06:08:12PM +0200, Jan Kara wrote:
> Pretty crude for now...
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext4/file.c | 2 ++
> include/linux/mm.h | 1 +
> include/linux/mman.h | 3 ++-
> include/uapi/asm-generic/mman.h | 1 +
> mm/mmap.c | 5 +++++
> 5 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index f84bb29e941e..850037e140d7 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -340,6 +340,8 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
> } else {
> vma->vm_ops = &ext4_file_vm_ops;
> + if (vma->vm_flags & VM_SYNC)
> + return -EOPNOTSUPP;
> }
> return 0;
> }
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index fa036093e76c..d0fb385414a4 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -188,6 +188,7 @@ extern unsigned int kobjsize(const void *objp);
> #define VM_ACCOUNT 0x00100000 /* Is a VM accounted object */
> #define VM_NORESERVE 0x00200000 /* should the VM suppress accounting */
> #define VM_HUGETLB 0x00400000 /* Huge TLB Page VM */
> +#define VM_SYNC 0x00800000 /* Synchronous page faults */
> #define VM_ARCH_1 0x01000000 /* Architecture-specific flag */
> #define VM_ARCH_2 0x02000000
> #define VM_DONTDUMP 0x04000000 /* Do not include in the core dump */
> diff --git a/include/linux/mman.h b/include/linux/mman.h
> index c8367041fafd..c38279b651e5 100644
> --- a/include/linux/mman.h
> +++ b/include/linux/mman.h
> @@ -86,7 +86,8 @@ calc_vm_flag_bits(unsigned long flags)
> {
> return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
> _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) |
> - _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED );
> + _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
> + _calc_vm_trans(flags, MAP_SYNC, VM_SYNC );
> }
>
> unsigned long vm_commit_limit(void);
> diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
> index 7162cd4cca73..00e55627d2df 100644
> --- a/include/uapi/asm-generic/mman.h
> +++ b/include/uapi/asm-generic/mman.h
> @@ -12,6 +12,7 @@
> #define MAP_NONBLOCK 0x10000 /* do not block on IO */
> #define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */
> #define MAP_HUGETLB 0x40000 /* create a huge page mapping */
> +#define MAP_SYNC 0x80000 /* perform synchronous page faults for the mapping */
>
> /* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f19efcf75418..18453c04b09f 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1423,12 +1423,17 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> return -ENODEV;
> if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
> return -EINVAL;
> + if (!(vm_flags & VM_SHARED) && (vm_flags & VM_SYNC))
> + return -EINVAL;
I know this will be reworked with Dan's new mmap() interface, but I was
curious what the !(vm_flags & VM_SHARED) check here was for. We're in a
MAP_PRIVATE case, so is it ever possible for VM_SHARED to be set in vm_flags?
I tried to make this happen with some various test scenarios, but wasn't able.
> break;
>
> default:
> return -EINVAL;
> }
> } else {
> + if (vm_flags & VM_SYNC)
> + return -EINVAL;
> +
> switch (flags & MAP_TYPE) {
> case MAP_SHARED:
> if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
> --
> 2.12.3
>
