Re: [PATCH 3/8] staging: erofs: add error handling for xattr submodule

[Chao Yu <yuchao0@huawei.com>]

On 2018/8/12 22:01, Chao Yu wrote:
> From: Gao Xiang <gaoxiang25@huawei.com>
> 
> This patch enhances the missing error handling code for
> xattr submodule, which improves the stability for the rare cases.
> 
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  drivers/staging/erofs/internal.h |   6 +-
>  drivers/staging/erofs/xattr.c    | 120 ++++++++++++++++++++-----------
>  2 files changed, 83 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
> index a756abeff7e9..8951e01216e3 100644
> --- a/drivers/staging/erofs/internal.h
> +++ b/drivers/staging/erofs/internal.h
> @@ -485,10 +485,10 @@ struct erofs_map_blocks_iter {
>  
>  
>  static inline struct page *
> -erofs_get_inline_page_nofail(struct inode *inode,
> -			     erofs_blk_t blkaddr)
> +erofs_get_inline_page(struct inode *inode,
> +		      erofs_blk_t blkaddr)
>  {
> -	return erofs_get_meta_page_nofail(inode->i_sb,
> +	return erofs_get_meta_page(inode->i_sb,
>  		blkaddr, S_ISDIR(inode->i_mode));
>  }
>  
> diff --git a/drivers/staging/erofs/xattr.c b/drivers/staging/erofs/xattr.c
> index 2593c856b079..1b5815fc70db 100644
> --- a/drivers/staging/erofs/xattr.c
> +++ b/drivers/staging/erofs/xattr.c
> @@ -24,16 +24,25 @@ struct xattr_iter {
>  
>  static inline void xattr_iter_end(struct xattr_iter *it, bool atomic)
>  {
> -	/* only init_inode_xattrs use non-atomic once */
> +	/* the only user of kunmap() is 'init_inode_xattrs' */
>  	if (unlikely(!atomic))
>  		kunmap(it->page);
>  	else
>  		kunmap_atomic(it->kaddr);
> +
>  	unlock_page(it->page);
>  	put_page(it->page);
>  }
>  
> -static void init_inode_xattrs(struct inode *inode)
> +static inline void xattr_iter_end_final(struct xattr_iter *it)
> +{
> +	if (unlikely(it->page == NULL))
> +		return;
> +
> +	xattr_iter_end(it, true);
> +}
> +
> +static int init_inode_xattrs(struct inode *inode)
>  {
>  	struct xattr_iter it;
>  	unsigned i;
> @@ -44,7 +53,7 @@ static void init_inode_xattrs(struct inode *inode)
>  	bool atomic_map;
>  
>  	if (likely(inode_has_inited_xattr(inode)))
> -		return;
> +		return 0;
>  
>  	vi = EROFS_V(inode);
>  	BUG_ON(!vi->xattr_isize);
> @@ -54,8 +63,9 @@ static void init_inode_xattrs(struct inode *inode)
>  	it.blkaddr = erofs_blknr(iloc(sbi, vi->nid) + vi->inode_isize);
>  	it.ofs = erofs_blkoff(iloc(sbi, vi->nid) + vi->inode_isize);
>  
> -	it.page = erofs_get_inline_page_nofail(inode, it.blkaddr);
> -	BUG_ON(IS_ERR(it.page));
> +	it.page = erofs_get_inline_page(inode, it.blkaddr);
> +	if (IS_ERR(it.page))
> +		return PTR_ERR(it.page);
>  
>  	/* read in shared xattr array (non-atomic, see kmalloc below) */
>  	it.kaddr = kmap(it.page);
> @@ -64,9 +74,12 @@ static void init_inode_xattrs(struct inode *inode)
>  	ih = (struct erofs_xattr_ibody_header *)(it.kaddr + it.ofs);
>  
>  	vi->xattr_shared_count = ih->h_shared_count;
> -	vi->xattr_shared_xattrs = (unsigned *)kmalloc_array(
> -		vi->xattr_shared_count, sizeof(unsigned),
> -		GFP_KERNEL | __GFP_NOFAIL);
> +	vi->xattr_shared_xattrs = kmalloc_array(vi->xattr_shared_count,
> +						sizeof(unsigned), GFP_KERNEL);
> +	if (unlikely(vi->xattr_shared_xattrs == NULL)) {
> +		xattr_iter_end(&it, atomic_map);
> +		return -ENOMEM;
> +	}
>  
>  	/* let's skip ibody header */
>  	it.ofs += sizeof(struct erofs_xattr_ibody_header);
> @@ -77,9 +90,10 @@ static void init_inode_xattrs(struct inode *inode)
>  			BUG_ON(it.ofs != EROFS_BLKSIZ);
>  			xattr_iter_end(&it, atomic_map);
>  
> -			it.page = erofs_get_meta_page_nofail(sb,
> +			it.page = erofs_get_meta_page(sb,
>  				++it.blkaddr, S_ISDIR(inode->i_mode));
> -			BUG_ON(IS_ERR(it.page));
> +			if (IS_ERR(it.page))
> +				return PTR_ERR(it.page);
>  
>  			it.kaddr = kmap_atomic(it.page);
>  			atomic_map = true;
> @@ -92,6 +106,7 @@ static void init_inode_xattrs(struct inode *inode)
>  	xattr_iter_end(&it, atomic_map);
>  
>  	inode_set_inited_xattr(inode);
> +	return 0;
>  }
>  
>  struct xattr_iter_handlers {
> @@ -101,19 +116,24 @@ struct xattr_iter_handlers {
>  	void (*value)(struct xattr_iter *, unsigned, char *, unsigned);
>  };
>  
> -static void xattr_iter_fixup(struct xattr_iter *it)
> +static inline int xattr_iter_fixup(struct xattr_iter *it)
>  {
> -	if (unlikely(it->ofs >= EROFS_BLKSIZ)) {
> -		xattr_iter_end(it, true);
> +	if (likely(it->ofs < EROFS_BLKSIZ))
> +		return 0;
>  
> -		it->blkaddr += erofs_blknr(it->ofs);
> -		it->page = erofs_get_meta_page_nofail(it->sb,
> -			it->blkaddr, false);
> -		BUG_ON(IS_ERR(it->page));
> +	xattr_iter_end(it, true);
>  
> -		it->kaddr = kmap_atomic(it->page);
> -		it->ofs = erofs_blkoff(it->ofs);
> +	it->blkaddr += erofs_blknr(it->ofs);
> +
> +	it->page = erofs_get_meta_page(it->sb, it->blkaddr, false);
> +	if (IS_ERR(it->page)) {
> +		it->page = NULL;
> +		return PTR_ERR(it->page);

As LKP reported, we need to fix this as below:

err = PTR_ERR(it->page);
it->page = NULL;
return err;

Thanks,

>  	}
> +
> +	it->kaddr = kmap_atomic(it->page);
> +	it->ofs = erofs_blkoff(it->ofs);
> +	return 0;
>  }
>  
>  static int inline_xattr_iter_begin(struct xattr_iter *it,
> @@ -134,22 +154,25 @@ static int inline_xattr_iter_begin(struct xattr_iter *it,
>  	it->blkaddr = erofs_blknr(iloc(sbi, vi->nid) + inline_xattr_ofs);
>  	it->ofs = erofs_blkoff(iloc(sbi, vi->nid) + inline_xattr_ofs);
>  
> -	it->page = erofs_get_inline_page_nofail(inode, it->blkaddr);
> -	BUG_ON(IS_ERR(it->page));
> -	it->kaddr = kmap_atomic(it->page);
> +	it->page = erofs_get_inline_page(inode, it->blkaddr);
> +	if (IS_ERR(it->page))
> +		return PTR_ERR(it->page);
>  
> +	it->kaddr = kmap_atomic(it->page);
>  	return vi->xattr_isize - xattr_header_sz;
>  }
>  
>  static int xattr_foreach(struct xattr_iter *it,
> -	struct xattr_iter_handlers *op, unsigned *tlimit)
> +	const struct xattr_iter_handlers *op, unsigned *tlimit)
>  {
>  	struct erofs_xattr_entry entry;
>  	unsigned value_sz, processed, slice;
>  	int err;
>  
>  	/* 0. fixup blkaddr, ofs, ipage */
> -	xattr_iter_fixup(it);
> +	err = xattr_iter_fixup(it);
> +	if (unlikely(err))
> +		return err;
>  
>  	/*
>  	 * 1. read xattr entry to the memory,
> @@ -181,7 +204,9 @@ static int xattr_foreach(struct xattr_iter *it,
>  		if (it->ofs >= EROFS_BLKSIZ) {
>  			BUG_ON(it->ofs > EROFS_BLKSIZ);
>  
> -			xattr_iter_fixup(it);
> +			err = xattr_iter_fixup(it);
> +			if (unlikely(err))
> +				goto out;
>  			it->ofs = 0;
>  		}
>  
> @@ -213,7 +238,10 @@ static int xattr_foreach(struct xattr_iter *it,
>  	while (processed < value_sz) {
>  		if (it->ofs >= EROFS_BLKSIZ) {
>  			BUG_ON(it->ofs > EROFS_BLKSIZ);
> -			xattr_iter_fixup(it);
> +
> +			err = xattr_iter_fixup(it);
> +			if (unlikely(err))
> +				goto out;
>  			it->ofs = 0;
>  		}
>  
> @@ -273,7 +301,7 @@ static void xattr_copyvalue(struct xattr_iter *_it,
>  	memcpy(it->buffer + processed, buf, len);
>  }
>  
> -static struct xattr_iter_handlers find_xattr_handlers = {
> +static const struct xattr_iter_handlers find_xattr_handlers = {
>  	.entry = xattr_entrymatch,
>  	.name = xattr_namematch,
>  	.alloc_buffer = xattr_checkbuffer,
> @@ -294,8 +322,11 @@ static int inline_getxattr(struct inode *inode, struct getxattr_iter *it)
>  		ret = xattr_foreach(&it->it, &find_xattr_handlers, &remaining);
>  		if (ret >= 0)
>  			break;
> +
> +		if (unlikely(ret != -ENOATTR))	/* -ENOMEM, -EIO, etc. */
> +			break;
>  	}
> -	xattr_iter_end(&it->it, true);
> +	xattr_iter_end_final(&it->it);
>  
>  	return ret < 0 ? ret : it->buffer_size;
>  }
> @@ -318,9 +349,10 @@ static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
>  			if (i)
>  				xattr_iter_end(&it->it, true);
>  
> -			it->it.page = erofs_get_meta_page_nofail(sb,
> -				blkaddr, false);
> -			BUG_ON(IS_ERR(it->it.page));
> +			it->it.page = erofs_get_meta_page(sb, blkaddr, false);
> +			if (IS_ERR(it->it.page))
> +				return PTR_ERR(it->it.page);
> +
>  			it->it.kaddr = kmap_atomic(it->it.page);
>  			it->it.blkaddr = blkaddr;
>  		}
> @@ -328,9 +360,12 @@ static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
>  		ret = xattr_foreach(&it->it, &find_xattr_handlers, NULL);
>  		if (ret >= 0)
>  			break;
> +
> +		if (unlikely(ret != -ENOATTR))	/* -ENOMEM, -EIO, etc. */
> +			break;
>  	}
>  	if (vi->xattr_shared_count)
> -		xattr_iter_end(&it->it, true);
> +		xattr_iter_end_final(&it->it);
>  
>  	return ret < 0 ? ret : it->buffer_size;
>  }
> @@ -355,7 +390,9 @@ int erofs_getxattr(struct inode *inode, int index,
>  	if (unlikely(name == NULL))
>  		return -EINVAL;
>  
> -	init_inode_xattrs(inode);
> +	ret = init_inode_xattrs(inode);
> +	if (unlikely(ret < 0))
> +		return ret;
>  
>  	it.index = index;
>  
> @@ -498,7 +535,7 @@ static int xattr_skipvalue(struct xattr_iter *_it,
>  	return 1;
>  }
>  
> -static struct xattr_iter_handlers list_xattr_handlers = {
> +static const struct xattr_iter_handlers list_xattr_handlers = {
>  	.entry = xattr_entrylist,
>  	.name = xattr_namelist,
>  	.alloc_buffer = xattr_skipvalue,
> @@ -520,7 +557,7 @@ static int inline_listxattr(struct listxattr_iter *it)
>  		if (ret < 0)
>  			break;
>  	}
> -	xattr_iter_end(&it->it, true);
> +	xattr_iter_end_final(&it->it);
>  	return ret < 0 ? ret : it->buffer_ofs;
>  }
>  
> @@ -542,9 +579,10 @@ static int shared_listxattr(struct listxattr_iter *it)
>  			if (i)
>  				xattr_iter_end(&it->it, true);
>  
> -			it->it.page = erofs_get_meta_page_nofail(sb,
> -				blkaddr, false);
> -			BUG_ON(IS_ERR(it->it.page));
> +			it->it.page = erofs_get_meta_page(sb, blkaddr, false);
> +			if (IS_ERR(it->it.page))
> +				return PTR_ERR(it->it.page);
> +
>  			it->it.kaddr = kmap_atomic(it->it.page);
>  			it->it.blkaddr = blkaddr;
>  		}
> @@ -554,7 +592,7 @@ static int shared_listxattr(struct listxattr_iter *it)
>  			break;
>  	}
>  	if (vi->xattr_shared_count)
> -		xattr_iter_end(&it->it, true);
> +		xattr_iter_end_final(&it->it);
>  
>  	return ret < 0 ? ret : it->buffer_ofs;
>  }
> @@ -565,7 +603,9 @@ ssize_t erofs_listxattr(struct dentry *dentry,
>  	int ret;
>  	struct listxattr_iter it;
>  
> -	init_inode_xattrs(d_inode(dentry));
> +	ret = init_inode_xattrs(d_inode(dentry));
> +	if (unlikely(ret < 0))
> +		return ret;
>  
>  	it.dentry = dentry;
>  	it.buffer = buffer;
>