Re: [PATCH] mkfs: fix symlink target if_bytes computation for protofile

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Dec 11, 2018 at 02:36:32PM -0600, Eric Sandeen wrote:
> On 12/11/18 1:02 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > When creating a local format symlink, we expect the target buffer in the
> > data fork to have enough space to contain the null, but we also expect
> > if_bytes to reflect the length of the target /not/ including the null.
> > If we don't adjust if_bytes down by one byte, we can run off into
> > uninitialized memory.  Fix this, which should clean up the spurious
> > xfs/019 failures for good.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Ugh.  Why do we even have protofiles?  I have never seen these in use
> in real life.  Can we just deprecate this half-baked crap?  :/
> 
> You suggested on IRC that we just use xfs_init_local fork; I had looked
> at that when I did the first patch and for some reason didn't use it,

Admittedly I wondered if we can leak memory that way, but AFAICT a new
inode shouldn't really have if_bytes > 0, right?

> but looking again it seems ... ok.  I hate how all of this stuff is
> re-implemented in the protofile crap code and it seems like we can't
> re-use too many of the libxfs functions directly but may as well use
> this if we can, right?

Funny you mention it, but I've been quietly refactoring the xfs_inode.c
code into libxfs as part of preparing for the metadata directory
feature, which has enabled me to cut a considerable amount of opencoded
crap out of mkfs and repair.  Granted, I still have to make sure it all
/works/, but ... yes this all should be using libxfs functions. :)

Uh, I'll give this patch a spin and see what happens.

--D

> =========
> 
> mkfs: don't open code local fork setup in protofile code
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/libxfs/libxfs_api_defs.h b/libxfs/libxfs_api_defs.h
> index ad5d65de..c3792e12 100644
> --- a/libxfs/libxfs_api_defs.h
> +++ b/libxfs/libxfs_api_defs.h
> @@ -149,5 +149,6 @@
>  #define xfs_dir_get_ops			libxfs_dir_get_ops
>  #define xfs_default_ifork_ops		libxfs_default_ifork_ops
>  #define xfs_fs_geometry			libxfs_fs_geometry
> +#define xfs_init_local_fork		libxfs_init_local_fork
>  
>  #endif /* __LIBXFS_API_DEFS_H__ */
> diff --git a/mkfs/proto.c b/mkfs/proto.c
> index 103795f1..3bba4917 100644
> --- a/mkfs/proto.c
> +++ b/mkfs/proto.c
> @@ -237,13 +237,7 @@ newfile(
>  	flags = 0;
>  	mp = ip->i_mount;
>  	if (symlink && len <= XFS_IFORK_DSIZE(ip)) {
> -		/* Copy the name's trailing NULL as well */
> -		libxfs_idata_realloc(ip, len + 1, XFS_DATA_FORK);
> -		if (buf)
> -			memmove(ip->i_df.if_u1.if_data, buf, len + 1);
> -		ip->i_d.di_size = len;
> -		ip->i_df.if_flags &= ~XFS_IFEXTENTS;
> -		ip->i_df.if_flags |= XFS_IFINLINE;
> +		libxfs_init_local_fork(ip, XFS_DATA_FORK, buf, len);
>  		ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
>  		flags = XFS_ILOG_DDATA;
>  	} else if (len > 0) {
>