On Wed, Oct 11, 2017 at 1:06 PM, Jan Kara <jack@xxxxxxx> wrote:
> Now when everything is prepared, add support in ext4 to accept MAP_SYNC
> as an mmap(2) flag.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext4/file.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 61a8788168f3..f013cda84b3d 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -364,6 +364,25 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> return 0;
> }
>
> +#define EXT4_SUPPORTED_MAP_FLAGS (LEGACY_MAP_MASK | MAP_SYNC)
> +
> +static int ext4_file_mmap_validate(struct file *file,
> + struct vm_area_struct *vma,
> + unsigned long map_flags)
> +{
> + if (map_flags & ~EXT4_SUPPORTED_MAP_FLAGS)
> + return -EOPNOTSUPP;
> +
> + /*
> + * We don't support synchronous mappings for non-DAX files. At least
> + * until someone comes with a sensible use case.
> + */
> + if (!IS_DAX(file_inode(file)) && (map_flags & MAP_SYNC))
> + return -EOPNOTSUPP;
Perhaps EPERM instead to differentiate the unsupported flags case?
There's precedent for mmap returning EPERM for reasons other than
incompatible PROT flags.
