linux/include/crypto/acompress.h
Eric Biggers 29ce50e078 crypto: remove CONFIG_CRYPTO_STATS
Remove support for the "Crypto usage statistics" feature
(CONFIG_CRYPTO_STATS).  This feature does not appear to have ever been
used, and it is harmful because it significantly reduces performance and
is a large maintenance burden.

Covering each of these points in detail:

1. Feature is not being used

Since these generic crypto statistics are only readable using netlink,
it's fairly straightforward to look for programs that use them.  I'm
unable to find any evidence that any such programs exist.  For example,
Debian Code Search returns no hits except the kernel header and kernel
code itself and translations of the kernel header:
https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1

The patch series that added this feature in 2018
(https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/)
said "The goal is to have an ifconfig for crypto device."  This doesn't
appear to have happened.

It's not clear that there is real demand for crypto statistics.  Just
because the kernel provides other types of statistics such as I/O and
networking statistics and some people find those useful does not mean
that crypto statistics are useful too.

Further evidence that programs are not using CONFIG_CRYPTO_STATS is that
it was able to be disabled in RHEL and Fedora as a bug fix
(https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947).

Even further evidence comes from the fact that there are and have been
bugs in how the stats work, but they were never reported.  For example,
before Linux v6.7 hash stats were double-counted in most cases.

There has also never been any documentation for this feature, so it
might be hard to use even if someone wanted to.

2. CONFIG_CRYPTO_STATS significantly reduces performance

Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of
the crypto API, even if no program ever retrieves the statistics.  This
primarily affects systems with a large number of CPUs.  For example,
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported
that Lustre client encryption performance improved from 21.7GB/s to
48.2GB/s by disabling CONFIG_CRYPTO_STATS.

It can be argued that this means that CONFIG_CRYPTO_STATS should be
optimized with per-cpu counters similar to many of the networking
counters.  But no one has done this in 5+ years.  This is consistent
with the fact that the feature appears to be unused, so there seems to
be little interest in improving it as opposed to just disabling it.

It can be argued that because CONFIG_CRYPTO_STATS is off by default,
performance doesn't matter.  But Linux distros tend to error on the side
of enabling options.  The option is enabled in Ubuntu and Arch Linux,
and until recently was enabled in RHEL and Fedora (see above).  So, even
just having the option available is harmful to users.

3. CONFIG_CRYPTO_STATS is a large maintenance burden

There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS,
spread among 32 files.  It significantly complicates much of the
implementation of the crypto API.  After the initial submission, many
fixes and refactorings have consumed effort of multiple people to keep
this feature "working".  We should be spending this effort elsewhere.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2024-04-02 10:49:38 +08:00

269 lines
7.7 KiB
C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Asynchronous Compression operations
*
* Copyright (c) 2016, Intel Corporation
* Authors: Weigang Li <weigang.li@intel.com>
* Giovanni Cabiddu <giovanni.cabiddu@intel.com>
*/
#ifndef _CRYPTO_ACOMP_H
#define _CRYPTO_ACOMP_H
#include <linux/atomic.h>
#include <linux/container_of.h>
#include <linux/crypto.h>
#define CRYPTO_ACOMP_ALLOC_OUTPUT 0x00000001
#define CRYPTO_ACOMP_DST_MAX 131072
/**
* struct acomp_req - asynchronous (de)compression request
*
* @base: Common attributes for asynchronous crypto requests
* @src: Source Data
* @dst: Destination data
* @slen: Size of the input buffer
* @dlen: Size of the output buffer and number of bytes produced
* @flags: Internal flags
* @__ctx: Start of private context data
*/
struct acomp_req {
struct crypto_async_request base;
struct scatterlist *src;
struct scatterlist *dst;
unsigned int slen;
unsigned int dlen;
u32 flags;
void *__ctx[] CRYPTO_MINALIGN_ATTR;
};
/**
* struct crypto_acomp - user-instantiated objects which encapsulate
* algorithms and core processing logic
*
* @compress: Function performs a compress operation
* @decompress: Function performs a de-compress operation
* @dst_free: Frees destination buffer if allocated inside the
* algorithm
* @reqsize: Context size for (de)compression requests
* @base: Common crypto API algorithm data structure
*/
struct crypto_acomp {
int (*compress)(struct acomp_req *req);
int (*decompress)(struct acomp_req *req);
void (*dst_free)(struct scatterlist *dst);
unsigned int reqsize;
struct crypto_tfm base;
};
#define COMP_ALG_COMMON { \
struct crypto_alg base; \
}
struct comp_alg_common COMP_ALG_COMMON;
/**
* DOC: Asynchronous Compression API
*
* The Asynchronous Compression API is used with the algorithms of type
* CRYPTO_ALG_TYPE_ACOMPRESS (listed as type "acomp" in /proc/crypto)
*/
/**
* crypto_alloc_acomp() -- allocate ACOMPRESS tfm handle
* @alg_name: is the cra_name / name or cra_driver_name / driver name of the
* compression algorithm e.g. "deflate"
* @type: specifies the type of the algorithm
* @mask: specifies the mask for the algorithm
*
* Allocate a handle for a compression algorithm. The returned struct
* crypto_acomp is the handle that is required for any subsequent
* API invocation for the compression operations.
*
* Return: allocated handle in case of success; IS_ERR() is true in case
* of an error, PTR_ERR() returns the error code.
*/
struct crypto_acomp *crypto_alloc_acomp(const char *alg_name, u32 type,
u32 mask);
/**
* crypto_alloc_acomp_node() -- allocate ACOMPRESS tfm handle with desired NUMA node
* @alg_name: is the cra_name / name or cra_driver_name / driver name of the
* compression algorithm e.g. "deflate"
* @type: specifies the type of the algorithm
* @mask: specifies the mask for the algorithm
* @node: specifies the NUMA node the ZIP hardware belongs to
*
* Allocate a handle for a compression algorithm. Drivers should try to use
* (de)compressors on the specified NUMA node.
* The returned struct crypto_acomp is the handle that is required for any
* subsequent API invocation for the compression operations.
*
* Return: allocated handle in case of success; IS_ERR() is true in case
* of an error, PTR_ERR() returns the error code.
*/
struct crypto_acomp *crypto_alloc_acomp_node(const char *alg_name, u32 type,
u32 mask, int node);
static inline struct crypto_tfm *crypto_acomp_tfm(struct crypto_acomp *tfm)
{
return &tfm->base;
}
static inline struct comp_alg_common *__crypto_comp_alg_common(
struct crypto_alg *alg)
{
return container_of(alg, struct comp_alg_common, base);
}
static inline struct crypto_acomp *__crypto_acomp_tfm(struct crypto_tfm *tfm)
{
return container_of(tfm, struct crypto_acomp, base);
}
static inline struct comp_alg_common *crypto_comp_alg_common(
struct crypto_acomp *tfm)
{
return __crypto_comp_alg_common(crypto_acomp_tfm(tfm)->__crt_alg);
}
static inline unsigned int crypto_acomp_reqsize(struct crypto_acomp *tfm)
{
return tfm->reqsize;
}
static inline void acomp_request_set_tfm(struct acomp_req *req,
struct crypto_acomp *tfm)
{
req->base.tfm = crypto_acomp_tfm(tfm);
}
static inline bool acomp_is_async(struct crypto_acomp *tfm)
{
return crypto_comp_alg_common(tfm)->base.cra_flags &
CRYPTO_ALG_ASYNC;
}
static inline struct crypto_acomp *crypto_acomp_reqtfm(struct acomp_req *req)
{
return __crypto_acomp_tfm(req->base.tfm);
}
/**
* crypto_free_acomp() -- free ACOMPRESS tfm handle
*
* @tfm: ACOMPRESS tfm handle allocated with crypto_alloc_acomp()
*
* If @tfm is a NULL or error pointer, this function does nothing.
*/
static inline void crypto_free_acomp(struct crypto_acomp *tfm)
{
crypto_destroy_tfm(tfm, crypto_acomp_tfm(tfm));
}
static inline int crypto_has_acomp(const char *alg_name, u32 type, u32 mask)
{
type &= ~CRYPTO_ALG_TYPE_MASK;
type |= CRYPTO_ALG_TYPE_ACOMPRESS;
mask |= CRYPTO_ALG_TYPE_ACOMPRESS_MASK;
return crypto_has_alg(alg_name, type, mask);
}
/**
* acomp_request_alloc() -- allocates asynchronous (de)compression request
*
* @tfm: ACOMPRESS tfm handle allocated with crypto_alloc_acomp()
*
* Return: allocated handle in case of success or NULL in case of an error
*/
struct acomp_req *acomp_request_alloc(struct crypto_acomp *tfm);
/**
* acomp_request_free() -- zeroize and free asynchronous (de)compression
* request as well as the output buffer if allocated
* inside the algorithm
*
* @req: request to free
*/
void acomp_request_free(struct acomp_req *req);
/**
* acomp_request_set_callback() -- Sets an asynchronous callback
*
* Callback will be called when an asynchronous operation on a given
* request is finished.
*
* @req: request that the callback will be set for
* @flgs: specify for instance if the operation may backlog
* @cmlp: callback which will be called
* @data: private data used by the caller
*/
static inline void acomp_request_set_callback(struct acomp_req *req,
u32 flgs,
crypto_completion_t cmpl,
void *data)
{
req->base.complete = cmpl;
req->base.data = data;
req->base.flags &= CRYPTO_ACOMP_ALLOC_OUTPUT;
req->base.flags |= flgs & ~CRYPTO_ACOMP_ALLOC_OUTPUT;
}
/**
* acomp_request_set_params() -- Sets request parameters
*
* Sets parameters required by an acomp operation
*
* @req: asynchronous compress request
* @src: pointer to input buffer scatterlist
* @dst: pointer to output buffer scatterlist. If this is NULL, the
* acomp layer will allocate the output memory
* @slen: size of the input buffer
* @dlen: size of the output buffer. If dst is NULL, this can be used by
* the user to specify the maximum amount of memory to allocate
*/
static inline void acomp_request_set_params(struct acomp_req *req,
struct scatterlist *src,
struct scatterlist *dst,
unsigned int slen,
unsigned int dlen)
{
req->src = src;
req->dst = dst;
req->slen = slen;
req->dlen = dlen;
req->flags &= ~CRYPTO_ACOMP_ALLOC_OUTPUT;
if (!req->dst)
req->flags |= CRYPTO_ACOMP_ALLOC_OUTPUT;
}
/**
* crypto_acomp_compress() -- Invoke asynchronous compress operation
*
* Function invokes the asynchronous compress operation
*
* @req: asynchronous compress request
*
* Return: zero on success; error code in case of error
*/
static inline int crypto_acomp_compress(struct acomp_req *req)
{
return crypto_acomp_reqtfm(req)->compress(req);
}
/**
* crypto_acomp_decompress() -- Invoke asynchronous decompress operation
*
* Function invokes the asynchronous decompress operation
*
* @req: asynchronous compress request
*
* Return: zero on success; error code in case of error
*/
static inline int crypto_acomp_decompress(struct acomp_req *req)
{
return crypto_acomp_reqtfm(req)->decompress(req);
}
#endif