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fscrypt: introduce fscrypt_encrypt_block_inplace()

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fscrypt_encrypt_page() behaves very differently depending on whether the
filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations.  This makes
the function difficult to understand and document.  It also makes it so
that all callers have to provide inode and lblk_num, when fscrypt could
determine these itself for pagecache pages.

Therefore, move the FS_CFLG_OWN_PAGES behavior into a new function
fscrypt_encrypt_block_inplace().

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
2019-05-20 09:29:43 -07:00
parent eeacfdc68a
commit 03569f2fb8
3 changed files with 50 additions and 25 deletions
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50
fs/crypto/crypto.c
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@@ -200,8 +200,7 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
/**
* fscypt_encrypt_page() - Encrypts a page
* @inode: The inode for which the encryption should take place
* @page: The page to encrypt. Must be locked for bounce-page
* encryption.
* @page: The page to encrypt. Must be locked.
* @len: Length of data to encrypt in @page and encrypted
* data in returned page.
* @offs: Offset of data within @page and returned
@@ -211,10 +210,9 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
* previously written data.
* @gfp_flags: The gfp flag for memory allocation
*
* Encrypts @page. If the filesystem set FS_CFLG_OWN_PAGES, then the data is
* encrypted in-place and @page is returned. Else, a bounce page is allocated,
* the data is encrypted into the bounce page, and the bounce page is returned.
* The caller is responsible for calling fscrypt_free_bounce_page().
* Encrypts @page. A bounce page is allocated, the data is encrypted into the
* bounce page, and the bounce page is returned. The caller is responsible for
* calling fscrypt_free_bounce_page().
*
* Return: A page containing the encrypted data on success, else an ERR_PTR()
*/
@@ -225,24 +223,12 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
u64 lblk_num, gfp_t gfp_flags)
{
struct page *ciphertext_page = page;
struct page *ciphertext_page;
int err;
if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
/* with inplace-encryption we just encrypt the page */
err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page,
ciphertext_page, len, offs,
gfp_flags);
if (err)
return ERR_PTR(err);
return ciphertext_page;
}
if (WARN_ON_ONCE(!PageLocked(page)))
return ERR_PTR(-EINVAL);
/* The encryption operation will require a bounce page. */
ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
if (!ciphertext_page)
return ERR_PTR(-ENOMEM);
@@ -259,6 +245,32 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
}
EXPORT_SYMBOL(fscrypt_encrypt_page);
/**
* fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
* @inode: The inode to which this block belongs
* @page: The page containing the block to encrypt
* @len: Size of block to encrypt. Doesn't need to be a multiple of the
* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
* @offs: Byte offset within @page at which the block to encrypt begins
* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
* number of the block within the file
* @gfp_flags: Memory allocation flags
*
* 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.
*
* 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)
{
return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
len, offs, gfp_flags);
}
EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
/**
* fscrypt_decrypt_page() - Decrypts a page in-place
* @inode: The corresponding inode for the page to decrypt.