Re: [PATCH] ovl: set overlayfs inode's a_ops->direct_IO properly

[Chengguang Xu <cgxu519@xxxxxxx>]

在 2021/9/30 14:52, Huang Jianan 写道:
> This patch can ensure that loop devices based on erofs and overlayfs 
> can't set dio through __loop_update_dio.
>
> Tested-by: Huang Jianan <huangjianan@xxxxxxxx>

HI Jianan,

Thanks for the test!



> Thanks,
> Jianan
>
> 在 2021/9/28 20:47, Chengguang Xu 写道:
> > Loop device checks the ability of DIRECT-IO by checking
> > a_ops->direct_IO of inode, in order to avoid this kind of
> > false detection we set a_ops->direct_IO for overlayfs inode
> > only when underlying inode really has DIRECT-IO ability.
> >
> > Reported-by: Huang Jianan <huangjianan@xxxxxxxx>
> > Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> > ---
> >   fs/overlayfs/dir.c       |  2 ++
> >   fs/overlayfs/inode.c     |  4 ++--
> >   fs/overlayfs/overlayfs.h |  1 +
> >   fs/overlayfs/util.c      | 14 ++++++++++++++
> >   4 files changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> > index 1fefb2b8960e..32a60f9e3f9e 100644
> > --- a/fs/overlayfs/dir.c
> > +++ b/fs/overlayfs/dir.c
> > @@ -648,6 +648,8 @@ static int ovl_create_object(struct dentry 
> > *dentry, int mode, dev_t rdev,
> >       /* Did we end up using the preallocated inode? */
> >       if (inode != d_inode(dentry))
> >           iput(inode);
> > +    else
> > +        ovl_inode_set_aops(inode);
> >     out_drop_write:
> >       ovl_drop_write(dentry);
> > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> > index 832b17589733..a7a327e4f790 100644
> > --- a/fs/overlayfs/inode.c
> > +++ b/fs/overlayfs/inode.c
> > @@ -659,7 +659,7 @@ static const struct inode_operations 
> > ovl_special_inode_operations = {
> >       .update_time    = ovl_update_time,
> >   };
> >   -static const struct address_space_operations ovl_aops = {
> > +const struct address_space_operations ovl_aops = {
> >       /* For O_DIRECT dentry_open() checks 
> > f_mapping->a_ops->direct_IO */
> >       .direct_IO        = noop_direct_IO,
> >   };
> > @@ -786,6 +786,7 @@ void ovl_inode_init(struct inode *inode, struct 
> > ovl_inode_params *oip,
> >       ovl_copyattr(realinode, inode);
> >       ovl_copyflags(realinode, inode);
> >       ovl_map_ino(inode, ino, fsid);
> > +    ovl_inode_set_aops(inode);
> >   }
> >     static void ovl_fill_inode(struct inode *inode, umode_t mode, 
> > dev_t rdev)
> > @@ -802,7 +803,6 @@ static void ovl_fill_inode(struct inode *inode, 
> > umode_t mode, dev_t rdev)
> >       case S_IFREG:
> >           inode->i_op = &ovl_file_inode_operations;
> >           inode->i_fop = &ovl_file_operations;
> > -        inode->i_mapping->a_ops = &ovl_aops;
> >           break;
> >         case S_IFDIR:
> > diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> > index 3894f3347955..976c9d634293 100644
> > --- a/fs/overlayfs/overlayfs.h
> > +++ b/fs/overlayfs/overlayfs.h
> > @@ -349,6 +349,7 @@ bool ovl_is_metacopy_dentry(struct dentry *dentry);
> >   char *ovl_get_redirect_xattr(struct ovl_fs *ofs, struct dentry 
> > *dentry,
> >                    int padding);
> >   int ovl_sync_status(struct ovl_fs *ofs);
> > +void ovl_inode_set_aops(struct inode *inode);
> >     static inline void ovl_set_flag(unsigned long flag, struct inode 
> > *inode)
> >   {
> > diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> > index f48284a2a896..33535dbee1c3 100644
> > --- a/fs/overlayfs/util.c
> > +++ b/fs/overlayfs/util.c
> > @@ -1060,3 +1060,17 @@ int ovl_sync_status(struct ovl_fs *ofs)
> >         return errseq_check(&mnt->mnt_sb->s_wb_err, ofs->errseq);
> >   }
> > +
> > +extern const struct address_space_operations ovl_aops;
> > +void ovl_inode_set_aops(struct inode *inode)
> > +{
> > +    struct inode *realinode;
> > +
> > +    if (!S_ISREG(inode->i_mode))
> > +        return;
> > +
> > +    realinode = ovl_inode_realdata(inode);
> > +    if (realinode && realinode->i_mapping && 
> > realinode->i_mapping->a_ops &&
> > +        realinode->i_mapping->a_ops->direct_IO)
> > +        inode->i_mapping->a_ops = &ovl_aops;
> > +}