linux-ext4 - Re: [Qemu-devel] [PATCH v6 5/6] ext4: disable map

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Date:   Wed, 24 Apr 2019 01:21:44 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     cohuck@...hat.com, kvm@...r.kernel.org, mst@...hat.com,
        jasowang@...hat.com, david@...morbit.com, qemu-devel@...gnu.org,
        virtualization@...ts.linux-foundation.org,
        adilger kernel <adilger.kernel@...ger.ca>, zwisler@...nel.org,
        aarcange@...hat.com, dave jiang <dave.jiang@...el.com>,
        linux-nvdimm@...ts.01.org,
        vishal l verma <vishal.l.verma@...el.com>, david@...hat.com,
        willy@...radead.org, hch@...radead.org, linux-acpi@...r.kernel.org,
        jmoyer@...hat.com, linux-ext4@...r.kernel.org, lenb@...nel.org,
        kilobyte@...band.pl, riel@...riel.com,
        yuval shaia <yuval.shaia@...cle.com>, stefanha@...hat.com,
        pbonzini@...hat.com, dan j williams <dan.j.williams@...el.com>,
        lcapitulino@...hat.com, kwolf@...hat.com, nilal@...hat.com,
        tytso@....edu, xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
        darrick wong <darrick.wong@...cle.com>, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, imammedo@...hat.com
Subject: Re: [Qemu-devel] [PATCH v6 5/6] ext4: disable map_sync for async
 flush


> 
> 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@...hat.com>
> 
> The patch looks good to me. You can add:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>

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@...e.com>
> SUSE Labs, CR
> 
>