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Commit 1c7dcf69 authored by David Gstir's avatar David Gstir Committed by Theodore Ts'o
Browse files

fscrypt: Add in-place encryption mode 



ext4 and f2fs require a bounce page when encrypting pages. However, not
all filesystems will need that (eg. UBIFS). This is handled via a
flag on fscrypt_operations where a fs implementation can select in-place
encryption over using a bounce page (which is the default).

Signed-off-by: default avatarDavid Gstir <david@sigma-star.at>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent bc33b0ca

fs/crypto/crypto.c

+15 −10
Original line number Diff line number Diff line
@@ -217,8 +217,9 @@ static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags) 
 * @plaintext_page: The page to encrypt. Must be locked.

 * @gfp_flags:      The gfp flag for memory allocation

 *

 * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx

 * encryption context.

 * Encrypts plaintext_page using the ctx encryption context. If

 * the filesystem supports it, encryption is performed in-place, otherwise a

 * new ciphertext_page is allocated and returned.

 *

 * Called on the page write path.  The caller must call

 * fscrypt_restore_control_page() on the returned ciphertext page to
@@ -231,7 +232,7 @@ struct page *fscrypt_encrypt_page(struct inode *inode, 
				struct page *plaintext_page, gfp_t gfp_flags)

{

	struct fscrypt_ctx *ctx;

	struct page *ciphertext_page = NULL;

	struct page *ciphertext_page = plaintext_page;

	int err;



	BUG_ON(!PageLocked(plaintext_page));
@@ -240,10 +241,12 @@ struct page *fscrypt_encrypt_page(struct inode *inode, 
	if (IS_ERR(ctx))

		return (struct page *)ctx;



	if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {

		/* The encryption operation will require a bounce page. */

		ciphertext_page = alloc_bounce_page(ctx, gfp_flags);

		if (IS_ERR(ciphertext_page))

			goto errout;

	}



	ctx->w.control_page = plaintext_page;

	err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index,
@@ -253,9 +256,11 @@ struct page *fscrypt_encrypt_page(struct inode *inode, 
		ciphertext_page = ERR_PTR(err);

		goto errout;

	}

	if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {

		SetPagePrivate(ciphertext_page);

		set_page_private(ciphertext_page, (unsigned long)ctx);

		lock_page(ciphertext_page);

	}

	return ciphertext_page;



errout:

include/linux/fscrypto.h

+6 −0
Original line number Diff line number Diff line
@@ -153,10 +153,16 @@ struct fscrypt_name { 
#define fname_name(p)		((p)->disk_name.name)

#define fname_len(p)		((p)->disk_name.len)



/*

 * fscrypt superblock flags

 */

#define FS_CFLG_INPLACE_ENCRYPTION (1U << 1)



/*

 * crypto opertions for filesystems

 */

struct fscrypt_operations {

	unsigned int flags;

	int (*get_context)(struct inode *, void *, size_t);

	int (*key_prefix)(struct inode *, u8 **);

	int (*prepare_context)(struct inode *);