diff mbox series

[2/9] fs/ext4: Disallow verity if inode is DAX

Message ID 20200513054324.2138483-3-ira.weiny@intel.com
State New
Headers show
Series [1/9] fs/ext4: Narrow scope of DAX check in setflags | expand

Commit Message

Ira Weiny May 13, 2020, 5:43 a.m. UTC
From: Ira Weiny <ira.weiny@intel.com>

Verity and DAX are incompatible.  Changing the DAX mode due to a verity
flag change is wrong without a corresponding address_space_operations
update.

Make the 2 options mutually exclusive by returning an error if DAX was
set first.

(Setting DAX is already disabled if Verity is set first.)

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes:
	remove WARN_ON_ONCE
	Add documentation for DAX/Verity exclusivity
---
 Documentation/filesystems/ext4/verity.rst | 7 +++++++
 fs/ext4/verity.c                          | 3 +++
 2 files changed, 10 insertions(+)

Comments

Eric Biggers May 16, 2020, 1:49 a.m. UTC | #1
On Tue, May 12, 2020 at 10:43:17PM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> Verity and DAX are incompatible.  Changing the DAX mode due to a verity
> flag change is wrong without a corresponding address_space_operations
> update.
> 
> Make the 2 options mutually exclusive by returning an error if DAX was
> set first.
> 
> (Setting DAX is already disabled if Verity is set first.)
> 
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes:
> 	remove WARN_ON_ONCE
> 	Add documentation for DAX/Verity exclusivity
> ---
>  Documentation/filesystems/ext4/verity.rst | 7 +++++++
>  fs/ext4/verity.c                          | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
> index 3e4c0ee0e068..51ab1aa17e59 100644
> --- a/Documentation/filesystems/ext4/verity.rst
> +++ b/Documentation/filesystems/ext4/verity.rst
> @@ -39,3 +39,10 @@ is encrypted as well as the data itself.
>  
>  Verity files cannot have blocks allocated past the end of the verity
>  metadata.
> +
> +Verity and DAX
> +--------------
> +
> +Verity and DAX are not compatible and attempts to set both of these flags on a
> +file will fail.
> +

If you build the documentation, this shows up as its own subsection
"2.13. Verity and DAX" alongside "2.12. Verity files", which looks odd.
I think you should delete this new subsection header so that this paragraph goes
in the existing "Verity files" subsection.

Also, Documentation/filesystems/fsverity.rst already mentions DAX (similar to
fscrypt.rst).  Is it intentional that you added this to the ext4-specific
documentation instead?

- Eric
Ira Weiny May 18, 2020, 5:32 a.m. UTC | #2
On Fri, May 15, 2020 at 06:49:16PM -0700, Eric Biggers wrote:
> On Tue, May 12, 2020 at 10:43:17PM -0700, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> > 
> > Verity and DAX are incompatible.  Changing the DAX mode due to a verity
> > flag change is wrong without a corresponding address_space_operations
> > update.
> > 
> > Make the 2 options mutually exclusive by returning an error if DAX was
> > set first.
> > 
> > (Setting DAX is already disabled if Verity is set first.)
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > 
> > ---
> > Changes:
> > 	remove WARN_ON_ONCE
> > 	Add documentation for DAX/Verity exclusivity
> > ---
> >  Documentation/filesystems/ext4/verity.rst | 7 +++++++
> >  fs/ext4/verity.c                          | 3 +++
> >  2 files changed, 10 insertions(+)
> > 
> > diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
> > index 3e4c0ee0e068..51ab1aa17e59 100644
> > --- a/Documentation/filesystems/ext4/verity.rst
> > +++ b/Documentation/filesystems/ext4/verity.rst
> > @@ -39,3 +39,10 @@ is encrypted as well as the data itself.
> >  
> >  Verity files cannot have blocks allocated past the end of the verity
> >  metadata.
> > +
> > +Verity and DAX
> > +--------------
> > +
> > +Verity and DAX are not compatible and attempts to set both of these flags on a
> > +file will fail.
> > +
> 
> If you build the documentation, this shows up as its own subsection
> "2.13. Verity and DAX" alongside "2.12. Verity files", which looks odd.
> I think you should delete this new subsection header so that this paragraph goes
> in the existing "Verity files" subsection.

Ok...  I'll fix it up...

> 
> Also, Documentation/filesystems/fsverity.rst already mentions DAX (similar to
> fscrypt.rst).  Is it intentional that you added this to the ext4-specific
> documentation instead?

I proposed this text[1] and there were no objections...  I was looking at ext4
because only ext4 supports verity and DAX.  I think having this in both the
ext4 docs and the verity docs helps.

Ira

[1] https://lore.kernel.org/lkml/20200415191451.GA2305801@iweiny-DESK2.sc.intel.com/

> 
> - Eric
diff mbox series

Patch

diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
index 3e4c0ee0e068..51ab1aa17e59 100644
--- a/Documentation/filesystems/ext4/verity.rst
+++ b/Documentation/filesystems/ext4/verity.rst
@@ -39,3 +39,10 @@  is encrypted as well as the data itself.
 
 Verity files cannot have blocks allocated past the end of the verity
 metadata.
+
+Verity and DAX
+--------------
+
+Verity and DAX are not compatible and attempts to set both of these flags on a
+file will fail.
+
diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
index dc5ec724d889..f05a09fb2ae4 100644
--- a/fs/ext4/verity.c
+++ b/fs/ext4/verity.c
@@ -113,6 +113,9 @@  static int ext4_begin_enable_verity(struct file *filp)
 	handle_t *handle;
 	int err;
 
+	if (IS_DAX(inode))
+		return -EINVAL;
+
 	if (ext4_verity_in_progress(inode))
 		return -EBUSY;