Re: [Qemu-devel] [PATCH v6 5/6] ext4: disable map_sync for async flush

[Pankaj Gupta]

> 
> On Tue 23-04-19 13:36:11, Pankaj Gupta wrote:
> > Dont support 'MAP_SYNC' with non-DAX files and DAX files
> > with asynchronous dax_device. Virtio pmem provides
> > asynchronous host page cache flush mechanism. We don't
> > support 'MAP_SYNC' with virtio pmem and ext4.
> > 
> > Signed-off-by: Pankaj Gupta <pagupta@xxxxxxxxxx>
> 
> The patch looks good to me. You can add:
> 
> Reviewed-by: Jan Kara <jack@xxxxxxx>

Thank you. Will add this.

Best regards,
Pankaj

> 
> 								Honza
> 
> 
> > ---
> >  fs/ext4/file.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> > index 69d65d49837b..4b2ccaf1932e 100644
> > --- a/fs/ext4/file.c
> > +++ b/fs/ext4/file.c
> > @@ -360,15 +360,16 @@ static const struct vm_operations_struct
> > ext4_file_vm_ops = {
> >  static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> >  {
> >  	struct inode *inode = file->f_mapping->host;
> > +	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> > +	struct dax_device *dax_dev = sbi->s_daxdev;
> >  
> > -	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
> > +	if (unlikely(ext4_forced_shutdown(sbi)))
> >  		return -EIO;
> >  
> > -	/*
> > -	 * We don't support synchronous mappings for non-DAX files. At least
> > -	 * until someone comes with a sensible use case.
> > +	/* We don't support synchronous mappings for non-DAX files and
> > +	 * for DAX files if underneath dax_device is not synchronous.
> >  	 */
> > -	if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC))
> > +	if (!daxdev_mapping_supported(vma, dax_dev))
> >  		return -EOPNOTSUPP;
> >  
> >  	file_accessed(file);
> > --
> > 2.20.1
> > 
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
> 
>