[PREVIEW] [PATCH chao/erofs-dev 1/3] staging: erofs: harden inode lookup for 32-bit platforms

[Chao Yu]

On 2018-9-21 11:43, Gao Xiang wrote:
> This patch introduces inode hash function, test and set callbacks,
> and iget5_locked to find the right inode for 32-bit platforms.
> 
> Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
> ---
>  drivers/staging/erofs/inode.c    | 37 ++++++++++++++++++++++++++++++++++++-
>  drivers/staging/erofs/internal.h | 10 ++++++++++
>  2 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/erofs/inode.c b/drivers/staging/erofs/inode.c
> index da8693a..a2fa2aa 100644
> --- a/drivers/staging/erofs/inode.c
> +++ b/drivers/staging/erofs/inode.c
> @@ -232,10 +232,45 @@ static int fill_inode(struct inode *inode, int isdir)
>  	return err;
>  }
>  
> +/*
> + * erofs nid is 64bits, but i_ino is 'unsigned long', therefore
> + * we should do more for 32-bit platform to find the right inode.
> + */
> +#if BITS_PER_LONG < 64

#if BITS_PER_LOG == 32

> +static int erofs_ilookup_test_actor(struct inode *inode, void *opaque)
> +{
> +	const erofs_nid_t nid = *(erofs_nid_t *)opaque;
> +
> +	return EROFS_V(inode)->nid == nid;
> +}
> +
> +static int erofs_iget_set_actor(struct inode *inode, void *opaque)
> +{
> +	const erofs_nid_t nid = *(erofs_nid_t *)opaque;
> +
> +	inode->i_ino = erofs_inode_hash(nid);
> +	return 0;
> +}
> +#endif
> +
> +static inline struct inode *erofs_iget_locked(struct super_block *sb,
> +					      erofs_nid_t nid)
> +{
> +	const unsigned long hashval = erofs_inode_hash(nid);
> +
> +#if BITS_PER_LONG >= 64
> +	/* it is safe to use iget_locked for >= 64-bit platform */
> +	return iget_locked(sb, hashval);
> +#else
> +	return iget5_locked(sb, hashval, erofs_ilookup_test_actor,
> +		erofs_iget_set_actor, &nid);

How about just using iget5_locked? and then we can only handle 32/64-bit
platforms difference in erofs_inode_hash()?

> +#endif
> +}
> +
>  struct inode *erofs_iget(struct super_block *sb,
>  	erofs_nid_t nid, bool isdir)
>  {
> -	struct inode *inode = iget_locked(sb, nid);
> +	struct inode *inode = erofs_iget_locked(sb, nid);
>  
>  	if (unlikely(inode == NULL))
>  		return ERR_PTR(-ENOMEM);
> diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
> index c2cc4a016..823929a 100644
> --- a/drivers/staging/erofs/internal.h
> +++ b/drivers/staging/erofs/internal.h
> @@ -511,6 +511,16 @@ struct erofs_map_blocks_iter {
>  }
>  
>  /* inode.c */
> +static inline unsigned long erofs_inode_hash(erofs_nid_t nid)
> +{
> +	u64 h = nid;

unsigned long h;

> +
> +#if BITS_PER_LONG == 32
> +	h = (h >> 32) ^ (h & 0xffffffff);

h = (nid >> 32) ^ (nid & 0xffffffff);

> +#endif
> +	return (unsigned long)h;

return h;

Thanks,

> +}
> +
>  extern struct inode *erofs_iget(struct super_block *sb,
>  	erofs_nid_t nid, bool dir);
>  
>