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Subject[PATCH v3 6/7] zram: Allocate struct zcomp_strm as per-CPU memory
Date
zcomp::stream is a per-CPU pointer, pointing to struct zcomp_strm
which contains two pointers. Having struct zcomp_strm allocated
directly as per-CPU memory would avoid one additional memory
allocation and a pointer dereference. This also simplifies the
addition of a local_lock to struct zcomp_strm.

Allocate zcomp::stream directly as per-CPU memory.

Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/block/zram/zcomp.c | 41 +++++++++++++++-----------------------
drivers/block/zram/zcomp.h | 2 +-
2 files changed, 17 insertions(+), 26 deletions(-)

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 1a8564a79d8dc..912e3e63d8a09 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -37,19 +37,16 @@ static void zcomp_strm_free(struct zcomp_strm *zstrm)
if (!IS_ERR_OR_NULL(zstrm->tfm))
crypto_free_comp(zstrm->tfm);
free_pages((unsigned long)zstrm->buffer, 1);
- kfree(zstrm);
+ zstrm->tfm = NULL;
+ zstrm->buffer = NULL;
}

/*
- * allocate new zcomp_strm structure with ->tfm initialized by
- * backend, return NULL on error
+ * Initialize zcomp_strm structure with ->tfm initialized by backend, and
+ * ->buffer. Return a negative value on error.
*/
-static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
+static int zcomp_strm_init(struct zcomp_strm *zstrm, struct zcomp *comp)
{
- struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_KERNEL);
- if (!zstrm)
- return NULL;
-
zstrm->tfm = crypto_alloc_comp(comp->name, 0, 0);
/*
* allocate 2 pages. 1 for compressed data, plus 1 extra for the
@@ -58,9 +55,9 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
if (IS_ERR_OR_NULL(zstrm->tfm) || !zstrm->buffer) {
zcomp_strm_free(zstrm);
- zstrm = NULL;
+ return -ENOMEM;
}
- return zstrm;
+ return 0;
}

bool zcomp_available_algorithm(const char *comp)
@@ -113,7 +110,7 @@ ssize_t zcomp_available_show(const char *comp, char *buf)

struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
{
- return *get_cpu_ptr(comp->stream);
+ return get_cpu_ptr(comp->stream);
}

void zcomp_stream_put(struct zcomp *comp)
@@ -159,17 +156,13 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
{
struct zcomp *comp = hlist_entry(node, struct zcomp, node);
struct zcomp_strm *zstrm;
+ int ret;

- if (WARN_ON(*per_cpu_ptr(comp->stream, cpu)))
- return 0;
-
- zstrm = zcomp_strm_alloc(comp);
- if (IS_ERR_OR_NULL(zstrm)) {
+ zstrm = per_cpu_ptr(comp->stream, cpu);
+ ret = zcomp_strm_init(zstrm, comp);
+ if (ret)
pr_err("Can't allocate a compression stream\n");
- return -ENOMEM;
- }
- *per_cpu_ptr(comp->stream, cpu) = zstrm;
- return 0;
+ return ret;
}

int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node)
@@ -177,10 +170,8 @@ int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node)
struct zcomp *comp = hlist_entry(node, struct zcomp, node);
struct zcomp_strm *zstrm;

- zstrm = *per_cpu_ptr(comp->stream, cpu);
- if (!IS_ERR_OR_NULL(zstrm))
- zcomp_strm_free(zstrm);
- *per_cpu_ptr(comp->stream, cpu) = NULL;
+ zstrm = per_cpu_ptr(comp->stream, cpu);
+ zcomp_strm_free(zstrm);
return 0;
}

@@ -188,7 +179,7 @@ static int zcomp_init(struct zcomp *comp)
{
int ret;

- comp->stream = alloc_percpu(struct zcomp_strm *);
+ comp->stream = alloc_percpu(struct zcomp_strm);
if (!comp->stream)
return -ENOMEM;

diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 1806475b919df..72c2ee4d843ed 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -14,7 +14,7 @@ struct zcomp_strm {

/* dynamic per-device compression frontend */
struct zcomp {
- struct zcomp_strm * __percpu *stream;
+ struct zcomp_strm __percpu *stream;
const char *name;
struct hlist_node node;
};
--
2.27.0.rc0
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