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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: ira.weiny@intel.com
Cc: linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed
Date: Mon, 13 Jan 2020 14:22:12 -0800
Message-ID: <20200113222212.GO8247@magnolia> (raw)
In-Reply-To: <20200110192942.25021-10-ira.weiny@intel.com>

On Fri, Jan 10, 2020 at 11:29:39AM -0800, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> Page faults need to ensure the inode mode is correct and consistent with
> the vmf information at the time of the fault.  There is no easy way to
> ensure the vmf information is correct if a mode change is in progress.
> Furthermore, there is no good use case to require a mode change while
> the file is mmap'ed.
> 
> Track mmap's of the file and fail the mode change if the file is
> mmap'ed.
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ---
>  fs/inode.c         |  2 ++
>  fs/xfs/xfs_ioctl.c |  8 ++++++++
>  include/linux/fs.h |  1 +
>  mm/mmap.c          | 19 +++++++++++++++++--
>  4 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 2b0f51161918..944711aed6f8 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -245,6 +245,8 @@ static struct inode *alloc_inode(struct super_block *sb)
>  		return NULL;
>  	}
>  
> +	atomic64_set(&inode->i_mapped, 0);
> +
>  	return inode;
>  }
>  
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index bc3654fe3b5d..1ab0906c6c7f 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1200,6 +1200,14 @@ xfs_ioctl_setattr_dax_invalidate(
>  		goto out_unlock;
>  	}
>  
> +	/*
> +	 * If there is a mapping in place we must remain in our current mode.
> +	 */
> +	if (atomic64_read(&inode->i_mapped)) {

Urk, should we really be messing around with the address space
internals?

> +		error = -EBUSY;
> +		goto out_unlock;
> +	}
> +
>  	error = filemap_write_and_wait(inode->i_mapping);
>  	if (error)
>  		goto out_unlock;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 631f11d6246e..6e7dc626b657 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -740,6 +740,7 @@ struct inode {
>  #endif
>  
>  	void			*i_private; /* fs or device private pointer */
> +	atomic64_t               i_mapped;

I would have expected to find this in struct address_space since the
mapping count is a function of the address space, right?

--D

>  } __randomize_layout;
>  
>  struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode);
> diff --git a/mm/mmap.c b/mm/mmap.c
> index dfaf1130e706..e6b68924b7ca 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -171,12 +171,17 @@ void unlink_file_vma(struct vm_area_struct *vma)
>  static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
>  {
>  	struct vm_area_struct *next = vma->vm_next;
> +	struct file *f = vma->vm_file;
>  
>  	might_sleep();
>  	if (vma->vm_ops && vma->vm_ops->close)
>  		vma->vm_ops->close(vma);
> -	if (vma->vm_file)
> -		fput(vma->vm_file);
> +	if (f) {
> +		struct inode *inode = file_inode(f);
> +		if (inode)
> +			atomic64_dec(&inode->i_mapped);
> +		fput(f);
> +	}
>  	mpol_put(vma_policy(vma));
>  	vm_area_free(vma);
>  	return next;
> @@ -1837,6 +1842,16 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  
>  	vma_set_page_prot(vma);
>  
> +	/*
> +	 * Track if there is mapping in place such that a mode change
> +	 * does not occur on a file which is mapped
> +	 */
> +	if (file) {
> +		struct inode		*inode = file_inode(file);
> +
> +		atomic64_inc(&inode->i_mapped);
> +	}
> +
>  	return addr;
>  
>  unmap_and_free_vma:
> -- 
> 2.21.0
> 

  reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 19:29 [RFC PATCH V2 00/12] Enable per-file/directory DAX operations V2 ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute ira.weiny
2020-01-15 11:37   ` Jan Kara
2020-01-15 17:38     ` Darrick J. Wong
2020-01-15 19:45       ` Ira Weiny
2020-01-15 20:10         ` Dan Williams
2020-01-15 22:38           ` Ira Weiny
2020-01-16  5:39             ` Darrick J. Wong
2020-01-16  6:05               ` Dan Williams
2020-01-16  6:18                 ` Darrick J. Wong
2020-01-16  6:25                   ` Dan Williams
2020-01-18  9:11                 ` Dave Chinner
2020-01-16 17:55               ` Ira Weiny
2020-01-16 18:04                 ` Darrick J. Wong
2020-01-16 18:52                   ` Ira Weiny
2020-01-16 22:19                     ` Darrick J. Wong
2020-01-17 11:58                     ` Jan Kara
2020-01-10 19:29 ` [RFC PATCH V2 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 04/12] fs/xfs: Clean up DAX support check ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 05/12] fs: remove unneeded IS_DAX() check ira.weiny
2020-01-16  9:38   ` Jan Kara
2020-01-16 18:47     ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 07/12] fs: Add locking for a dynamic inode 'mode' ira.weiny
2020-01-13 22:12   ` Darrick J. Wong
2020-01-14  0:20     ` Ira Weiny
2020-01-14  1:03       ` Darrick J. Wong
2020-01-15 19:08         ` Ira Weiny
2020-01-16  5:40           ` Darrick J. Wong
2020-01-16 18:54             ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs ira.weiny
2020-01-13 22:19   ` Darrick J. Wong
2020-01-14  0:35     ` Ira Weiny
2020-01-15  0:57       ` Ira Weiny
2020-01-15 23:52     ` Ira Weiny
2020-01-16  9:24   ` Jan Kara
2020-01-16 19:12     ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed ira.weiny
2020-01-13 22:22   ` Darrick J. Wong [this message]
2020-01-14  0:46     ` Ira Weiny
2020-01-14  1:30       ` Darrick J. Wong
2020-01-14 17:53         ` Ira Weiny
2020-01-15 11:34           ` Jan Kara
2020-01-15 18:24             ` Ira Weiny
2020-01-15 10:21   ` David Laight
2020-01-15 17:53     ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 10/12] fs/xfs: Fix truncate up ira.weiny
2020-01-13 22:27   ` Darrick J. Wong
2020-01-14  0:40     ` Ira Weiny
2020-01-14  1:14       ` Darrick J. Wong
2020-01-14 19:00         ` Ira Weiny
2020-01-14 19:39           ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny

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