On Tue, 2018-09-11 at 11:15 -0700, Dan Williams wrote:
> On Tue, Sep 11, 2018 at 8:42 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote:
> > Sync syscall to an existing DAX file needs to flush processor cache,
> > but it does not currently. This is because 'ext4_da_aops' is set to
> > address_space_operations of existing DAX files, instead of 'ext4_dax_aops',
> > since S_DAX flag is set after ext4_set_aops() in the open path.
> >
> > New file
> > --------
> > lookup_open
> > ext4_create
> > __ext4_new_inode
> > ext4_set_inode_flags // Set S_DAX flag
> > ext4_set_aops // Set aops to ext4_dax_aops
> >
> > Existing file
> > -------------
> > lookup_open
> > ext4_lookup
> > ext4_iget
> > ext4_set_aops // Set aops to ext4_da_aops
> > ext4_set_inode_flags // Set S_DAX flag
> >
> > Change ext4_iget() to call ext4_set_inode_flags() before ext4_set_aops().
> >
> > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
>
> Same format nit:
>
> Fixes: 5f0663bb4a64 ("ext4, dax: introduce ext4_dax_aops")
> Cc: <stable@xxxxxxxxxxxxxxx>
Will do.
> > Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
> > Cc: Jan Kara <jack@xxxxxxx>
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Cc: "Theodore Ts'o" <tytso@xxxxxxx>
> > Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
> > ---
> > fs/ext4/inode.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 775cd9b4af55..93cbbb859c40 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4998,6 +4998,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
> > if (ret)
> > goto bad_inode;
> >
> > + ext4_set_inode_flags(inode);
> > +
>
> Hmm, does this have unintended behavior changes?
>
> I notice that there are some checks for flags "IS_APPEND(inode) ||
> IS_IMMUTABLE(inode)" *before* the call to ext4_set_inode_flags(). I
> didn't look too much deeper at whether those checks are bogus, but it
> would seem safer to do something like this for a lower risk fix.
>
> Thoughts?
Good catch! Agreed.
Thanks!
-Toshi
