[lustre-devel] [PATCH] fscrypt: allow alternative bounce buffers

[Sebastien Buisson]

This looks good to me, thanks James.
I have updated Lustre patch https://review.whamcloud.com/47149 to integrate this change.

> Le 28 avr. 2022 à 19:23, James Simmons <jsimmons at infradead.org> a écrit :
> 
> Currently fscrypt offers two options. One option is to use the
> internal bounce buffer allocated or perform inline encrpytion.
> Add the option to use an external bounce buffer. This change can
> be used useful for example for a network file systems which can
> pass in a page from the page cache and place the encrypted data
> into a page for a network packet to be sent. Another potential
> use is the use of GPU pages with RDMA being the final destination
> for the encrypted data.
> 
> Signed-off-By: James Simmons <jsimmons at infradead.org>
> ---
> fs/crypto/crypto.c      | 34 +++++++++++++++++++---------------
> include/linux/fscrypt.h | 34 ++++++++++++++++++++++++++++------
> 2 files changed, 47 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
> index e78be66..f241c69 100644
> --- a/fs/crypto/crypto.c
> +++ b/fs/crypto/crypto.c
> @@ -210,9 +210,10 @@ struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
> EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
> 
> /**
> - * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
> + * fscrypt_encrypt_page() - Cache an encrypt filesystem block in a page
>  * @inode:     The inode to which this block belongs
> - * @page:      The page containing the block to encrypt
> + * @src:       The page containing the block to encrypt
> + * @dst:       The page which will contain the encrypted data
>  * @len:       Size of block to encrypt.  This must be a multiple of
>  *		FSCRYPT_CONTENTS_ALIGNMENT.
>  * @offs:      Byte offset within @page at which the block to encrypt begins
> @@ -223,17 +224,18 @@ struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
>  * Encrypt a possibly-compressed filesystem block that is located in an
>  * arbitrary page, not necessarily in the original pagecache page.  The @inode
>  * and @lblk_num must be specified, as they can't be determined from @page.
> + * The decrypted data will be stored in @dst.
>  *
>  * Return: 0 on success; -errno on failure
>  */
> -int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
> -				  unsigned int len, unsigned int offs,
> -				  u64 lblk_num, gfp_t gfp_flags)
> +int fscrypt_encrypt_page(const struct inode *inode, struct page *src,
> +			 struct page *dst, unsigned int len, unsigned int offs,
> +			 u64 lblk_num, gfp_t gfp_flags)
> {
> -	return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
> +	return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, src, dst,
> 				   len, offs, gfp_flags);
> }
> -EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
> +EXPORT_SYMBOL(fscrypt_encrypt_page);
> 
> /**
>  * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a
> @@ -280,9 +282,10 @@ int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
> EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
> 
> /**
> - * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
> + * fscrypt_decrypt_page() - Cache a decrypt a filesystem block in a page
>  * @inode:     The inode to which this block belongs
> - * @page:      The page containing the block to decrypt
> + * @src:       The page containing the block to decrypt
> + * @dst:       The page which will contain the plain data
>  * @len:       Size of block to decrypt.  This must be a multiple of
>  *		FSCRYPT_CONTENTS_ALIGNMENT.
>  * @offs:      Byte offset within @page at which the block to decrypt begins
> @@ -292,17 +295,18 @@ int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
>  * Decrypt a possibly-compressed filesystem block that is located in an
>  * arbitrary page, not necessarily in the original pagecache page.  The @inode
>  * and @lblk_num must be specified, as they can't be determined from @page.
> + * The encrypted data will be stored in @dst.
>  *
>  * Return: 0 on success; -errno on failure
>  */
> -int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
> -				  unsigned int len, unsigned int offs,
> -				  u64 lblk_num)
> +int fscrypt_decrypt_page(const struct inode *inode, struct page *src,
> +			 struct page *dst, unsigned int len, unsigned int offs,
> +			 u64 lblk_num, gfp_t gfp_flags)
> {
> -	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
> -				   len, offs, GFP_NOFS);
> +	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, src, dst,
> +				   len, offs, gfp_flags);
> }
> -EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
> +EXPORT_SYMBOL(fscrypt_decrypt_page);
> 
> /**
>  * fscrypt_initialize() - allocate major buffers for fs encryption.
> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index efc7f96..c2b67d1 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -255,15 +255,37 @@ struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
> 					      unsigned int len,
> 					      unsigned int offs,
> 					      gfp_t gfp_flags);
> -int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
> -				  unsigned int len, unsigned int offs,
> -				  u64 lblk_num, gfp_t gfp_flags);
> +int fscrypt_encrypt_page(const struct inode *inode, struct page *src,
> +			 struct page *dst, unsigned int len,
> +			 unsigned int offs, u64 lblk_num, gfp_t gfp_flags);
> +
> +static inline int fscrypt_encrypt_block_inplace(const struct inode *inode,
> +						struct page *page,
> +						unsigned int len,
> +						unsigned int offs,
> +						u64 lblk_num,
> +						gfp_t gfp_flags)
> +{
> +	return fscrypt_encrypt_page(inode, page, page, len, offs, lblk_num,
> +				    gfp_flags);
> +}
> 
> int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
> 				     unsigned int offs);
> -int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
> -				  unsigned int len, unsigned int offs,
> -				  u64 lblk_num);
> +
> +int fscrypt_decrypt_page(const struct inode *inode, struct page *src,
> +			 struct page *dst, unsigned int len,
> +			 unsigned int offs, u64 lblk_num, gfp_t gfp_flags);
> +
> +static inline int fscrypt_decrypt_block_inplace(const struct inode *inode,
> +						struct page *page,
> +						unsigned int len,
> +						unsigned int offs,
> +						u64 lblk_num)
> +{
> +	return fscrypt_decrypt_page(inode, page, page, len, offs, lblk_num,
> +				    GFP_NOFS);
> +}
> 
> static inline bool fscrypt_is_bounce_page(struct page *page)
> {
> -- 
> 1.8.3.1
>