[PATCH] zram: multi stream compressing backend abstraction

[Sergey Senozhatsky]

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
 drivers/block/zram/zcomp.c     | 174 +++++++++++++++++++++++++++++++++++++++++
 drivers/block/zram/zcomp.h     |  58 ++++++++++++++
 drivers/block/zram/zcomp_lzo.c |  48 ++++++++++++
 3 files changed, 280 insertions(+)
 create mode 100644 drivers/block/zram/zcomp.c
 create mode 100644 drivers/block/zram/zcomp.h
 create mode 100644 drivers/block/zram/zcomp_lzo.c

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
new file mode 100644
index 0000000..6bf49fc
--- /dev/null
+++ b/drivers/block/zram/zcomp.c
@@ -0,0 +1,174 @@
+/*
+ * Copyright (C) 2014 Sergey Senozhatsky.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+
+#include "zcomp.h"
+
+extern struct zcomp_backend zcomp_lzo;
+
+static struct zcomp_backend *find_backend(const char *compress)
+{
+	if (strncmp(compress, "lzo", 3) == 0)
+		return &zcomp_lzo;
+	return NULL;
+}
+
+static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
+{
+	if (zstrm->private)
+		comp->backend->destroy(zstrm->private);
+	free_pages((unsigned long)zstrm->buffer, 1);
+	kfree(zstrm);
+}
+
+/*
+ * allocate new zcomp_strm structure with ->private initialized by
+ * backend, return NULL on error
+ */
+static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
+{
+	struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_KERNEL);
+	if (!zstrm)
+		return NULL;
+
+	zstrm->private = comp->backend->create();
+	/*
+	 * allocate 2 pages. 1 for compressed data, plus 1 extra for the
+	 * case when compressed size is larger than the original one
+	 */
+	zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
+	if (!zstrm->private || !zstrm->buffer) {
+		zcomp_strm_free(comp, zstrm);
+		zstrm = NULL;
+	}
+	return zstrm;
+}
+
+/*
+ * get available idle stream or allocate a new one
+ */
+struct zcomp_strm *zcomp_strm_get(struct zcomp *comp)
+{
+	struct zcomp_strm *zstrm;
+
+	while (1) {
+		spin_lock(&comp->strm_lock);
+		if (!list_empty(&comp->idle_strm)) {
+			zstrm = list_entry(comp->idle_strm.next,
+					struct zcomp_strm, list);
+			list_del(&zstrm->list);
+			spin_unlock(&comp->strm_lock);
+			return zstrm;
+		}
+
+		if (atomic_read(&comp->num_strm) >= num_online_cpus()) {
+			spin_unlock(&comp->strm_lock);
+			wait_event(comp->strm_wait,
+					!list_empty(&comp->idle_strm));
+			continue;
+		}
+
+		atomic_inc(&comp->num_strm);
+		spin_unlock(&comp->strm_lock);
+
+		zstrm = zcomp_strm_alloc(comp);
+		if (!zstrm) {
+			atomic_dec(&comp->num_strm);
+			wait_event(comp->strm_wait,
+					!list_empty(&comp->idle_strm));
+			continue;
+		}
+		break;
+	}
+	return zstrm;
+}
+
+/*
+ * put zstrm back to idle list and wake up waiters or free it if
+ * current number of streams is above the limit
+ */
+void zcomp_strm_put(struct zcomp *comp, struct zcomp_strm *zstrm)
+{
+	spin_lock(&comp->strm_lock);
+	if (atomic_read(&comp->num_strm) <= num_online_cpus()) {
+		list_add(&zstrm->list, &comp->idle_strm);
+		spin_unlock(&comp->strm_lock);
+	} else {
+		atomic_dec(&comp->num_strm);
+		spin_unlock(&comp->strm_lock);
+		zcomp_strm_free(comp, zstrm);
+	}
+
+	wake_up(&comp->strm_wait);
+}
+
+int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
+		const unsigned char *src, size_t *dst_len)
+{
+	return comp->backend->compress(src, zstrm->buffer, dst_len,
+			zstrm->private);
+}
+
+int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
+		size_t src_len, unsigned char *dst)
+{
+	return comp->backend->decompress(src, src_len, dst);
+}
+
+void zcomp_destroy(struct zcomp *comp)
+{
+	struct zcomp_strm *zstrm;
+	while (!list_empty(&comp->idle_strm)) {
+		zstrm = list_entry(comp->idle_strm.next,
+				struct zcomp_strm, list);
+		list_del(&zstrm->list);
+		zcomp_strm_free(comp, zstrm);
+	}
+	kfree(comp);
+}
+
+/*
+ * search available compressors for requested algorithm.
+ * allocate new zcomp and initialize it. return NULL
+ * if requested algorithm is not supported or in case
+ * of init error
+ */
+struct zcomp *zcomp_create(const char *compress)
+{
+	struct zcomp *comp;
+	struct zcomp_backend *backend;
+	struct zcomp_strm *zstrm;
+
+	backend = find_backend(compress);
+	if (!backend)
+		return NULL;
+
+	comp = kmalloc(sizeof(struct zcomp), GFP_KERNEL);
+	if (!comp)
+		return NULL;
+
+	comp->backend = backend;
+	spin_lock_init(&comp->strm_lock);
+	INIT_LIST_HEAD(&comp->idle_strm);
+	init_waitqueue_head(&comp->strm_wait);
+	atomic_set(&comp->num_strm, 1);
+
+	zstrm = zcomp_strm_alloc(comp);
+	if (!zstrm) {
+		zcomp_destroy(comp);
+		return NULL;
+	}
+	list_add(&zstrm->list, &comp->idle_strm);
+	return comp;
+}
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
new file mode 100644
index 0000000..fd3871d
--- /dev/null
+++ b/drivers/block/zram/zcomp.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2014 Sergey Senozhatsky.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _ZCOMP_H_
+#define _ZCOMP_H_
+
+#include <linux/spinlock.h>
+
+struct zcomp_strm {
+	void *buffer;     /* compression/decompression buffer */
+	void *private;
+	struct list_head list;
+};
+
+/* static compression backend */
+struct zcomp_backend {
+	int (*compress)(const unsigned char *src, unsigned char *dst,
+			size_t *dst_len, void *private);
+
+	int (*decompress)(const unsigned char *src, size_t src_len,
+			unsigned char *dst);
+
+	void * (*create)(void);
+	void (*destroy)(void *private);
+
+	const char *name;
+};
+
+/* dynamic per-device compression frontend */
+struct zcomp {
+	/* protect strm list */
+	spinlock_t strm_lock;
+	/* list of available strms */
+	struct list_head idle_strm;
+	wait_queue_head_t strm_wait;
+	/* number of allocated strms */
+	atomic_t num_strm;
+	struct zcomp_backend *backend;
+};
+
+struct zcomp *zcomp_create(const char *comp);
+void zcomp_destroy(struct zcomp *comp);
+
+struct zcomp_strm *zcomp_strm_get(struct zcomp *comp);
+void zcomp_strm_put(struct zcomp *comp, struct zcomp_strm *zstrm);
+
+int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
+		const unsigned char *src, size_t *dst_len);
+
+int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
+		size_t src_len, unsigned char *dst);
+#endif /* _ZCOMP_H_ */
diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
new file mode 100644
index 0000000..b7722a2
--- /dev/null
+++ b/drivers/block/zram/zcomp_lzo.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2014 Sergey Senozhatsky.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/lzo.h>
+
+#include "zcomp.h"
+
+static void *lzo_create(void)
+{
+	return kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
+}
+
+static void lzo_destroy(void *private)
+{
+	kfree(private);
+}
+
+static int lzo_compress(const unsigned char *src, unsigned char *dst,
+		size_t *dst_len, void *private)
+{
+	int ret = lzo1x_1_compress(src, PAGE_SIZE, dst, dst_len, private);
+	return ret == LZO_E_OK ? 0 : ret;
+}
+
+static int lzo_decompress(const unsigned char *src, size_t src_len,
+		unsigned char *dst)
+{
+	size_t dst_len = PAGE_SIZE;
+	int ret = lzo1x_decompress_safe(src, src_len, dst, &dst_len);
+	return ret == LZO_E_OK ? 0 : ret;
+}
+
+extern struct zcomp_backend zcomp_lzo;
+struct zcomp_backend zcomp_lzo = {
+	.compress = lzo_compress,
+	.decompress = lzo_decompress,
+	.create = lzo_create,
+	.destroy = lzo_destroy,
+	.name = "lzo",
+};
-- 
1.9.0.279.gdc9e3eb

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