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crypto: scompress - Use per-CPU struct instead multiple variables
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Two per-CPU variables are allocated as pointer to per-CPU memory which
then are used as scratch buffers.
We could be smart about this and use instead a per-CPU struct which
contains the pointers already and then we need to allocate just the
scratch buffers.
Add a lock to the struct. By doing so we can avoid the get_cpu()
statement and gain lockdep coverage (if enabled) to ensure that the lock
is always acquired in the right context. On non-preemptible kernels the
lock vanishes.
It is okay to use raw_cpu_ptr() in order to get a pointer to the struct
since it is protected by the spinlock.

The diffstat of this is negative and according to size scompress.o:
   text    data     bss     dec     hex filename
   1847     160      24    2031     7ef dbg_before.o
   1754     232       4    1990     7c6 dbg_after.o
   1799      64      24    1887     75f no_dbg-before.o
   1703      88       4    1795     703 no_dbg-after.o

The overall size increase difference is also negative. The increase in
the data section is only four bytes without lockdep.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Sebastian Andrzej Siewior authored and Herbert Xu committed Apr 8, 2019
1 parent 6a4d1b1 commit 71052dc
Showing 1 changed file with 54 additions and 71 deletions.
125 changes: 54 additions & 71 deletions crypto/scompress.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,17 @@
#include <crypto/internal/scompress.h>
#include "internal.h"

struct scomp_scratch {
spinlock_t lock;
void *src;
void *dst;
};

static DEFINE_PER_CPU(struct scomp_scratch, scomp_scratch) = {
.lock = __SPIN_LOCK_UNLOCKED(scomp_scratch.lock),
};

static const struct crypto_type crypto_scomp_type;
static void * __percpu *scomp_src_scratches;
static void * __percpu *scomp_dst_scratches;
static int scomp_scratch_users;
static DEFINE_MUTEX(scomp_lock);

Expand Down Expand Up @@ -62,76 +70,53 @@ static void crypto_scomp_show(struct seq_file *m, struct crypto_alg *alg)
seq_puts(m, "type : scomp\n");
}

static void crypto_scomp_free_scratches(void * __percpu *scratches)
static void crypto_scomp_free_scratches(void)
{
struct scomp_scratch *scratch;
int i;

if (!scratches)
return;

for_each_possible_cpu(i)
vfree(*per_cpu_ptr(scratches, i));
for_each_possible_cpu(i) {
scratch = raw_cpu_ptr(&scomp_scratch);

free_percpu(scratches);
vfree(scratch->src);
vfree(scratch->dst);
scratch->src = NULL;
scratch->dst = NULL;
}
}

static void * __percpu *crypto_scomp_alloc_scratches(void)
static int crypto_scomp_alloc_scratches(void)
{
void * __percpu *scratches;
struct scomp_scratch *scratch;
int i;

scratches = alloc_percpu(void *);
if (!scratches)
return NULL;

for_each_possible_cpu(i) {
void *scratch;

scratch = vmalloc_node(SCOMP_SCRATCH_SIZE, cpu_to_node(i));
if (!scratch)
goto error;
*per_cpu_ptr(scratches, i) = scratch;
}

return scratches;

error:
crypto_scomp_free_scratches(scratches);
return NULL;
}
void *mem;

static void crypto_scomp_free_all_scratches(void)
{
if (!--scomp_scratch_users) {
crypto_scomp_free_scratches(scomp_src_scratches);
crypto_scomp_free_scratches(scomp_dst_scratches);
scomp_src_scratches = NULL;
scomp_dst_scratches = NULL;
}
}
scratch = raw_cpu_ptr(&scomp_scratch);

static int crypto_scomp_alloc_all_scratches(void)
{
if (!scomp_scratch_users++) {
scomp_src_scratches = crypto_scomp_alloc_scratches();
if (!scomp_src_scratches)
return -ENOMEM;
scomp_dst_scratches = crypto_scomp_alloc_scratches();
if (!scomp_dst_scratches) {
crypto_scomp_free_scratches(scomp_src_scratches);
scomp_src_scratches = NULL;
return -ENOMEM;
}
mem = vmalloc_node(SCOMP_SCRATCH_SIZE, cpu_to_node(i));
if (!mem)
goto error;
scratch->src = mem;
mem = vmalloc_node(SCOMP_SCRATCH_SIZE, cpu_to_node(i));
if (!mem)
goto error;
scratch->dst = mem;
}
return 0;
error:
crypto_scomp_free_scratches();
return -ENOMEM;
}

static int crypto_scomp_init_tfm(struct crypto_tfm *tfm)
{
int ret;
int ret = 0;

mutex_lock(&scomp_lock);
ret = crypto_scomp_alloc_all_scratches();
if (!scomp_scratch_users++)
ret = crypto_scomp_alloc_scratches();
mutex_unlock(&scomp_lock);

return ret;
Expand All @@ -143,31 +128,28 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
void **tfm_ctx = acomp_tfm_ctx(tfm);
struct crypto_scomp *scomp = *tfm_ctx;
void **ctx = acomp_request_ctx(req);
const int cpu = get_cpu();
u8 *scratch_src = *per_cpu_ptr(scomp_src_scratches, cpu);
u8 *scratch_dst = *per_cpu_ptr(scomp_dst_scratches, cpu);
struct scomp_scratch *scratch;
int ret;

if (!req->src || !req->slen || req->slen > SCOMP_SCRATCH_SIZE) {
ret = -EINVAL;
goto out;
}
if (!req->src || !req->slen || req->slen > SCOMP_SCRATCH_SIZE)
return -EINVAL;

if (req->dst && !req->dlen) {
ret = -EINVAL;
goto out;
}
if (req->dst && !req->dlen)
return -EINVAL;

if (!req->dlen || req->dlen > SCOMP_SCRATCH_SIZE)
req->dlen = SCOMP_SCRATCH_SIZE;

scatterwalk_map_and_copy(scratch_src, req->src, 0, req->slen, 0);
scratch = raw_cpu_ptr(&scomp_scratch);
spin_lock(&scratch->lock);

scatterwalk_map_and_copy(scratch->src, req->src, 0, req->slen, 0);
if (dir)
ret = crypto_scomp_compress(scomp, scratch_src, req->slen,
scratch_dst, &req->dlen, *ctx);
ret = crypto_scomp_compress(scomp, scratch->src, req->slen,
scratch->dst, &req->dlen, *ctx);
else
ret = crypto_scomp_decompress(scomp, scratch_src, req->slen,
scratch_dst, &req->dlen, *ctx);
ret = crypto_scomp_decompress(scomp, scratch->src, req->slen,
scratch->dst, &req->dlen, *ctx);
if (!ret) {
if (!req->dst) {
req->dst = sgl_alloc(req->dlen, GFP_ATOMIC, NULL);
Expand All @@ -176,11 +158,11 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
goto out;
}
}
scatterwalk_map_and_copy(scratch_dst, req->dst, 0, req->dlen,
scatterwalk_map_and_copy(scratch->dst, req->dst, 0, req->dlen,
1);
}
out:
put_cpu();
spin_unlock(&scratch->lock);
return ret;
}

Expand All @@ -201,7 +183,8 @@ static void crypto_exit_scomp_ops_async(struct crypto_tfm *tfm)
crypto_free_scomp(*ctx);

mutex_lock(&scomp_lock);
crypto_scomp_free_all_scratches();
if (!--scomp_scratch_users)
crypto_scomp_free_scratches();
mutex_unlock(&scomp_lock);
}

Expand Down

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