fs/crypto/crypto.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * This contains encryption functions for per-file encryption.
  *
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility
  *
  * Written by Michael Halcrow, 2014.
  *
  * Filename encryption additions
  *	Uday Savagaonkar, 2014
  * Encryption policy handling additions
  *	Ildar Muslukhov, 2014
  * Add fscrypt_pullback_bio_page()
  *	Jaegeuk Kim, 2015.
  *
  * This has not yet undergone a rigorous security audit.
  *
  * The usage of AES-XTS should conform to recommendations in NIST
  * Special Publication 800-38E and IEEE P1619/D16.
  */

 #include <linux/pagemap.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
 #include <crypto/skcipher.h>
 #include "fscrypt_private.h"

 static unsigned int num_prealloc_crypto_pages = 32;

 module_param(num_prealloc_crypto_pages, uint, 0444);
 MODULE_PARM_DESC(num_prealloc_crypto_pages,
 		"Number of crypto pages to preallocate");

 static mempool_t *fscrypt_bounce_page_pool = NULL;

 static struct workqueue_struct *fscrypt_read_workqueue;
 static DEFINE_MUTEX(fscrypt_init_mutex);

 struct kmem_cache *fscrypt_info_cachep;

 void fscrypt_enqueue_decrypt_work(struct work_struct *work)
 {
 	queue_work(fscrypt_read_workqueue, work);
 }
 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);

 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
 {
 	return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
 }

 /**
  * fscrypt_free_bounce_page() - free a ciphertext bounce page
  *
  * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
  * or by fscrypt_alloc_bounce_page() directly.
  */
 void fscrypt_free_bounce_page(struct page *bounce_page)
 {
 	if (!bounce_page)
 		return;
 	set_page_private(bounce_page, (unsigned long)NULL);
 	ClearPagePrivate(bounce_page);
 	mempool_free(bounce_page, fscrypt_bounce_page_pool);
 }
 EXPORT_SYMBOL(fscrypt_free_bounce_page);

 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 			 const struct fscrypt_info *ci)
 {
 	u8 flags = fscrypt_policy_flags(&ci->ci_policy);

 	memset(iv, 0, ci->ci_mode->ivsize);

 	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
 		WARN_ON_ONCE((u32)lblk_num != lblk_num);
 		lblk_num |= (u64)ci->ci_inode->i_ino << 32;
 	} else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
 		memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 	}
 	iv->lblk_num = cpu_to_le64(lblk_num);
 }

 /* Encrypt or decrypt a single filesystem block of file contents */
 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
 			u64 lblk_num, struct page *src_page,
 			struct page *dest_page, unsigned int len,
 			unsigned int offs, gfp_t gfp_flags)
 {
 	union fscrypt_iv iv;
 	struct skcipher_request *req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist dst, src;
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	struct crypto_skcipher *tfm = ci->ci_ctfm;
 	int res = 0;

 	if (WARN_ON_ONCE(len <= 0))
 		return -EINVAL;
 	if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
 		return -EINVAL;

 	fscrypt_generate_iv(&iv, lblk_num, ci);

 	req = skcipher_request_alloc(tfm, gfp_flags);
 	if (!req)
 		return -ENOMEM;

 	skcipher_request_set_callback(
 		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		crypto_req_done, &wait);

 	sg_init_table(&dst, 1);
 	sg_set_page(&dst, dest_page, len, offs);
 	sg_init_table(&src, 1);
 	sg_set_page(&src, src_page, len, offs);
 	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
 	if (rw == FS_DECRYPT)
 		res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
 	else
 		res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 	skcipher_request_free(req);
 	if (res) {
 		fscrypt_err(inode, "%scryption failed for block %llu: %d",
 			    (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
 		return res;
 	}
 	return 0;
 }

 /**
  * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
  * @page:      The locked pagecache page containing the block(s) to encrypt
  * @len:       Total size of the block(s) to encrypt.  Must be a nonzero
  *		multiple of the filesystem's block size.
  * @offs:      Byte offset within @page of the first block to encrypt.  Must be
  *		a multiple of the filesystem's block size.
  * @gfp_flags: Memory allocation flags.  See details below.
  *
  * A new bounce page is allocated, and the specified block(s) are encrypted into
  * it.  In the bounce page, the ciphertext block(s) will be located at the same
  * offsets at which the plaintext block(s) were located in the source page; any
  * other parts of the bounce page will be left uninitialized.  However, normally
  * blocksize == PAGE_SIZE and the whole page is encrypted at once.
  *
  * This is for use by the filesystem's ->writepages() method.
  *
  * The bounce page allocation is mempool-backed, so it will always succeed when
  * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS.  However,
  * only the first page of each bio can be allocated this way.  To prevent
  * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
  *
  * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
  */
 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
 					      unsigned int len,
 					      unsigned int offs,
 					      gfp_t gfp_flags)

 {
 	const struct inode *inode = page->mapping->host;
 	const unsigned int blockbits = inode->i_blkbits;
 	const unsigned int blocksize = 1 << blockbits;
 	struct page *ciphertext_page;
 	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 		       (offs >> blockbits);
 	unsigned int i;
 	int err;

 	if (WARN_ON_ONCE(!PageLocked(page)))
 		return ERR_PTR(-EINVAL);

 	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 		return ERR_PTR(-EINVAL);

 	ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
 	if (!ciphertext_page)
 		return ERR_PTR(-ENOMEM);

 	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 		err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
 					  page, ciphertext_page,
 					  blocksize, i, gfp_flags);
 		if (err) {
 			fscrypt_free_bounce_page(ciphertext_page);
 			return ERR_PTR(err);
 		}
 	}
 	SetPagePrivate(ciphertext_page);
 	set_page_private(ciphertext_page, (unsigned long)page);
 	return ciphertext_page;
 }
 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);

 /**
  * 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_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
  * @page:      The locked pagecache page containing the block(s) to decrypt
  * @len:       Total size of the block(s) to decrypt.  Must be a nonzero
  *		multiple of the filesystem's block size.
  * @offs:      Byte offset within @page of the first block to decrypt.  Must be
  *		a multiple of the filesystem's block size.
  *
  * The specified block(s) are decrypted in-place within the pagecache page,
  * which must still be locked and not uptodate.  Normally, blocksize ==
  * PAGE_SIZE and the whole page is decrypted at once.
  *
  * This is for use by the filesystem's ->readpages() method.
  *
  * Return: 0 on success; -errno on failure
  */
 int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
 				     unsigned int offs)
 {
 	const struct inode *inode = page->mapping->host;
 	const unsigned int blockbits = inode->i_blkbits;
 	const unsigned int blocksize = 1 << blockbits;
 	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 		       (offs >> blockbits);
 	unsigned int i;
 	int err;

 	if (WARN_ON_ONCE(!PageLocked(page)))
 		return -EINVAL;

 	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 		return -EINVAL;

 	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 		err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
 					  page, blocksize, i, GFP_NOFS);
 		if (err)
 			return err;
 	}
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);

 /**
  * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
  * @inode:     The inode to which this block belongs
  * @page:      The page containing the block to decrypt
  * @len:       Size of block to decrypt.  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 decrypt begins
  * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
  *		number of the block within the file
  *
  * 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.
  *
  * 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)
 {
 	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
 				   len, offs, GFP_NOFS);
 }
 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);

 /**
  * fscrypt_initialize() - allocate major buffers for fs encryption.
  * @cop_flags:  fscrypt operations flags
  *
  * We only call this when we start accessing encrypted files, since it
  * results in memory getting allocated that wouldn't otherwise be used.
  *
  * Return: 0 on success; -errno on failure
  */
 int fscrypt_initialize(unsigned int cop_flags)
 {
 	int err = 0;

 	/* No need to allocate a bounce page pool if this FS won't use it. */
 	if (cop_flags & FS_CFLG_OWN_PAGES)
 		return 0;

 	mutex_lock(&fscrypt_init_mutex);
 	if (fscrypt_bounce_page_pool)
 		goto out_unlock;

 	err = -ENOMEM;
 	fscrypt_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 	if (!fscrypt_bounce_page_pool)
 		goto out_unlock;

 	err = 0;
 out_unlock:
 	mutex_unlock(&fscrypt_init_mutex);
 	return err;
 }

 void fscrypt_msg(const struct inode *inode, const char *level,
 		 const char *fmt, ...)
 {
 	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
 				      DEFAULT_RATELIMIT_BURST);
 	struct va_format vaf;
 	va_list args;

 	if (!__ratelimit(&rs))
 		return;

 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
 	if (inode)
 		printk("%sfscrypt (%s, inode %lu): %pV\n",
 		       level, inode->i_sb->s_id, inode->i_ino, &vaf);
 	else
 		printk("%sfscrypt: %pV\n", level, &vaf);
 	va_end(args);
 }

 /**
  * fscrypt_init() - Set up for fs encryption.
  */
 static int __init fscrypt_init(void)
 {
 	int err = -ENOMEM;

 	/*
 	 * Use an unbound workqueue to allow bios to be decrypted in parallel
 	 * even when they happen to complete on the same CPU.  This sacrifices
 	 * locality, but it's worthwhile since decryption is CPU-intensive.
 	 *
 	 * Also use a high-priority workqueue to prioritize decryption work,
 	 * which blocks reads from completing, over regular application tasks.
 	 */
 	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
 						 WQ_UNBOUND | WQ_HIGHPRI,
 						 num_online_cpus());
 	if (!fscrypt_read_workqueue)
 		goto fail;

 	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
 	if (!fscrypt_info_cachep)
 		goto fail_free_queue;

 	err = fscrypt_init_keyring();
 	if (err)
 		goto fail_free_info;

 	return 0;

 fail_free_info:
 	kmem_cache_destroy(fscrypt_info_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:
 	return err;
 }
 late_initcall(fscrypt_init)
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* This contains encryption functions for per-file encryption.
	*
	* Copyright (C) 2015, Google, Inc.
	* Copyright (C) 2015, Motorola Mobility
	*
	* Written by Michael Halcrow, 2014.
	*
	* Filename encryption additions
	* Uday Savagaonkar, 2014
	* Encryption policy handling additions
	* Ildar Muslukhov, 2014
	* Add fscrypt_pullback_bio_page()
	* Jaegeuk Kim, 2015.
	*
	* This has not yet undergone a rigorous security audit.
	*
	* The usage of AES-XTS should conform to recommendations in NIST
	* Special Publication 800-38E and IEEE P1619/D16.
	*/

	#include <linux/pagemap.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/scatterlist.h>
	#include <linux/ratelimit.h>
	#include <crypto/skcipher.h>
	#include "fscrypt_private.h"

	static unsigned int num_prealloc_crypto_pages = 32;

	module_param(num_prealloc_crypto_pages, uint, 0444);
	MODULE_PARM_DESC(num_prealloc_crypto_pages,
	"Number of crypto pages to preallocate");

	static mempool_t *fscrypt_bounce_page_pool = NULL;

	static struct workqueue_struct *fscrypt_read_workqueue;
	static DEFINE_MUTEX(fscrypt_init_mutex);

	struct kmem_cache *fscrypt_info_cachep;

	void fscrypt_enqueue_decrypt_work(struct work_struct *work)
	{
	queue_work(fscrypt_read_workqueue, work);
	}
	EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);

	struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
	{
	return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
	}

	/**
	* fscrypt_free_bounce_page() - free a ciphertext bounce page
	*
	* Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
	* or by fscrypt_alloc_bounce_page() directly.
	*/
	void fscrypt_free_bounce_page(struct page *bounce_page)
	{
	if (!bounce_page)
	return;
	set_page_private(bounce_page, (unsigned long)NULL);
	ClearPagePrivate(bounce_page);
	mempool_free(bounce_page, fscrypt_bounce_page_pool);
	}
	EXPORT_SYMBOL(fscrypt_free_bounce_page);

	void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
	const struct fscrypt_info *ci)
	{
	u8 flags = fscrypt_policy_flags(&ci->ci_policy);

	memset(iv, 0, ci->ci_mode->ivsize);

	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
	WARN_ON_ONCE((u32)lblk_num != lblk_num);
	lblk_num \|= (u64)ci->ci_inode->i_ino << 32;
	} else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
	memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
	}
	iv->lblk_num = cpu_to_le64(lblk_num);
	}

	/* Encrypt or decrypt a single filesystem block of file contents */
	int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
	u64 lblk_num, struct page *src_page,
	struct page *dest_page, unsigned int len,
	unsigned int offs, gfp_t gfp_flags)
	{
	union fscrypt_iv iv;
	struct skcipher_request *req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	struct scatterlist dst, src;
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_skcipher *tfm = ci->ci_ctfm;
	int res = 0;

	if (WARN_ON_ONCE(len <= 0))
	return -EINVAL;
	if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
	return -EINVAL;

	fscrypt_generate_iv(&iv, lblk_num, ci);

	req = skcipher_request_alloc(tfm, gfp_flags);
	if (!req)
	return -ENOMEM;

	skcipher_request_set_callback(
	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	crypto_req_done, &wait);

	sg_init_table(&dst, 1);
	sg_set_page(&dst, dest_page, len, offs);
	sg_init_table(&src, 1);
	sg_set_page(&src, src_page, len, offs);
	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
	if (rw == FS_DECRYPT)
	res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
	else
	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
	skcipher_request_free(req);
	if (res) {
	fscrypt_err(inode, "%scryption failed for block %llu: %d",
	(rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
	return res;
	}
	return 0;
	}

	/**
	* fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
	* @page: The locked pagecache page containing the block(s) to encrypt
	* @len: Total size of the block(s) to encrypt. Must be a nonzero
	* multiple of the filesystem's block size.
	* @offs: Byte offset within @page of the first block to encrypt. Must be
	* a multiple of the filesystem's block size.
	* @gfp_flags: Memory allocation flags. See details below.
	*
	* A new bounce page is allocated, and the specified block(s) are encrypted into
	* it. In the bounce page, the ciphertext block(s) will be located at the same
	* offsets at which the plaintext block(s) were located in the source page; any
	* other parts of the bounce page will be left uninitialized. However, normally
	* blocksize == PAGE_SIZE and the whole page is encrypted at once.
	*
	* This is for use by the filesystem's ->writepages() method.
	*
	* The bounce page allocation is mempool-backed, so it will always succeed when
	* @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However,
	* only the first page of each bio can be allocated this way. To prevent
	* deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
	*
	* Return: the new encrypted bounce page on success; an ERR_PTR() on failure
	*/
	struct page fscrypt_encrypt_pagecache_blocks(struct page page,
	unsigned int len,
	unsigned int offs,
	gfp_t gfp_flags)

	{
	const struct inode *inode = page->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	struct page *ciphertext_page;
	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
	(offs >> blockbits);
	unsigned int i;
	int err;

	if (WARN_ON_ONCE(!PageLocked(page)))
	return ERR_PTR(-EINVAL);

	if (WARN_ON_ONCE(len <= 0 \|\| !IS_ALIGNED(len \| offs, blocksize)))
	return ERR_PTR(-EINVAL);

	ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
	if (!ciphertext_page)
	return ERR_PTR(-ENOMEM);

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
	err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
	page, ciphertext_page,
	blocksize, i, gfp_flags);
	if (err) {
	fscrypt_free_bounce_page(ciphertext_page);
	return ERR_PTR(err);
	}
	}
	SetPagePrivate(ciphertext_page);
	set_page_private(ciphertext_page, (unsigned long)page);
	return ciphertext_page;
	}
	EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);

	/**
	* 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_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
	* @page: The locked pagecache page containing the block(s) to decrypt
	* @len: Total size of the block(s) to decrypt. Must be a nonzero
	* multiple of the filesystem's block size.
	* @offs: Byte offset within @page of the first block to decrypt. Must be
	* a multiple of the filesystem's block size.
	*
	* The specified block(s) are decrypted in-place within the pagecache page,
	* which must still be locked and not uptodate. Normally, blocksize ==
	* PAGE_SIZE and the whole page is decrypted at once.
	*
	* This is for use by the filesystem's ->readpages() method.
	*
	* Return: 0 on success; -errno on failure
	*/
	int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
	unsigned int offs)
	{
	const struct inode *inode = page->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
	(offs >> blockbits);
	unsigned int i;
	int err;

	if (WARN_ON_ONCE(!PageLocked(page)))
	return -EINVAL;

	if (WARN_ON_ONCE(len <= 0 \|\| !IS_ALIGNED(len \| offs, blocksize)))
	return -EINVAL;

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
	err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
	page, blocksize, i, GFP_NOFS);
	if (err)
	return err;
	}
	return 0;
	}
	EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);

	/**
	* fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
	* @inode: The inode to which this block belongs
	* @page: The page containing the block to decrypt
	* @len: Size of block to decrypt. 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 decrypt begins
	* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
	* number of the block within the file
	*
	* 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.
	*
	* 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)
	{
	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
	len, offs, GFP_NOFS);
	}
	EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);

	/**
	* fscrypt_initialize() - allocate major buffers for fs encryption.
	* @cop_flags: fscrypt operations flags
	*
	* We only call this when we start accessing encrypted files, since it
	* results in memory getting allocated that wouldn't otherwise be used.
	*
	* Return: 0 on success; -errno on failure
	*/
	int fscrypt_initialize(unsigned int cop_flags)
	{
	int err = 0;

	/* No need to allocate a bounce page pool if this FS won't use it. */
	if (cop_flags & FS_CFLG_OWN_PAGES)
	return 0;

	mutex_lock(&fscrypt_init_mutex);
	if (fscrypt_bounce_page_pool)
	goto out_unlock;

	err = -ENOMEM;
	fscrypt_bounce_page_pool =
	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!fscrypt_bounce_page_pool)
	goto out_unlock;

	err = 0;
	out_unlock:
	mutex_unlock(&fscrypt_init_mutex);
	return err;
	}

	void fscrypt_msg(const struct inode inode, const char level,
	const char *fmt, ...)
	{
	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
	DEFAULT_RATELIMIT_BURST);
	struct va_format vaf;
	va_list args;

	if (!__ratelimit(&rs))
	return;

	va_start(args, fmt);
	vaf.fmt = fmt;
	vaf.va = &args;
	if (inode)
	printk("%sfscrypt (%s, inode %lu): %pV\n",
	level, inode->i_sb->s_id, inode->i_ino, &vaf);
	else
	printk("%sfscrypt: %pV\n", level, &vaf);
	va_end(args);
	}

	/**
	* fscrypt_init() - Set up for fs encryption.
	*/
	static int __init fscrypt_init(void)
	{
	int err = -ENOMEM;

	/*
	* Use an unbound workqueue to allow bios to be decrypted in parallel
	* even when they happen to complete on the same CPU. This sacrifices
	* locality, but it's worthwhile since decryption is CPU-intensive.
	*
	* Also use a high-priority workqueue to prioritize decryption work,
	* which blocks reads from completing, over regular application tasks.
	*/
	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
	WQ_UNBOUND \| WQ_HIGHPRI,
	num_online_cpus());
	if (!fscrypt_read_workqueue)
	goto fail;

	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_info_cachep)
	goto fail_free_queue;

	err = fscrypt_init_keyring();
	if (err)
	goto fail_free_info;

	return 0;

	fail_free_info:
	kmem_cache_destroy(fscrypt_info_cachep);
	fail_free_queue:
	destroy_workqueue(fscrypt_read_workqueue);
	fail:
	return err;
	}
	late_initcall(fscrypt_init)