[Qemu-devel] [PATCH 2/9] Add API to manipulate cache_data

[Qiao Nuohan <qiaonuohan@cn.fujitsu.com>]

Struct dump_bitmap is associated with a tmp file, and the tmp file can be used
to save data of page desc and page data in kdump-compressed format temporarily.
The following patch will use these function to get the data of page desc and
page data and cache them in tmp files.

Signed-off-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Reviewed-by: Zhang Xiaohe <zhangxh@cn.fujitsu.com>
---
 Makefile.target      |    2 +-
 cache_data.c         |  114 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/cache_data.h |   52 +++++++++++++++++++++++
 3 files changed, 167 insertions(+), 1 deletions(-)
 create mode 100644 cache_data.c
 create mode 100644 include/cache_data.h

diff --git a/Makefile.target b/Makefile.target
index 00d4f13..b579aff 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -112,7 +112,7 @@ obj-$(CONFIG_FDT) += device_tree.o
 obj-$(CONFIG_KVM) += kvm-all.o
 obj-y += memory.o savevm.o cputlb.o
 obj-$(CONFIG_HAVE_GET_MEMORY_MAPPING) += memory_mapping.o
-obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o dump_bitmap.o
+obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o dump_bitmap.o cache_data.o
 obj-$(CONFIG_NO_GET_MEMORY_MAPPING) += memory_mapping-stub.o
 obj-$(CONFIG_NO_CORE_DUMP) += dump-stub.o
 LIBS+=$(libs_softmmu)
diff --git a/cache_data.c b/cache_data.c
new file mode 100644
index 0000000..8602ef9
--- /dev/null
+++ b/cache_data.c
@@ -0,0 +1,114 @@
+/*
+ * QEMU cache data
+ *
+ * Copyright Fujitsu, Corp. 2013
+ *
+ * Authors:
+ *     Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "cache_data.h"
+
+int init_cache_data(struct cache_data *cd, const char *filename)
+{
+    int fd;
+    char tmpdir[] = TMP_DIR;
+    char *tmpname;
+
+    /* init the tmp file */
+    tmpname = getenv("TMPDIR");
+    if (!tmpname)
+        tmpname = tmpdir;
+
+    cd->file_name = (char *)g_malloc(strlen(filename) + strlen(tmpname) + 1);
+
+    strcpy(cd->file_name, tmpname);
+    strcat(cd->file_name, "/");
+    strcat(cd->file_name, filename);
+
+    if ((fd = mkstemp(cd->file_name)) < 0)
+        return -1;
+
+    cd->fd = fd;
+    unlink(cd->file_name);
+
+    /* init buf */
+    cd->buf_size= BUFSIZE_CACHE_DATA;
+    cd->cache_size= 0;
+    cd->buf = g_malloc0(BUFSIZE_CACHE_DATA);
+
+    cd->offset = 0;
+
+    return 0;
+}
+
+int write_cache(struct cache_data *cd, void *buf, size_t size)
+{
+    /*
+     * check if the space is enough to cache data, if not write cached
+     * data to the tmp file
+     */
+    if (cd->cache_size + size > cd->buf_size) {
+        if (lseek(cd->fd, cd->offset, SEEK_SET) < 0)
+            return -1;
+
+        if (write(cd->fd, cd->buf, cd->cache_size) != cd->cache_size)
+            return -1;
+
+        cd->offset += cd->cache_size;
+        cd->cache_size = 0;
+    }
+
+    memcpy(cd->buf + cd->cache_size, buf, size);
+    cd->cache_size += size;
+
+    return 0;
+}
+
+int sync_cache(struct cache_data *cd)
+{
+    /* no data is cached in cache_data */
+    if (cd->cache_size == 0)
+        return 0;
+
+    if (lseek(cd->fd, cd->offset, SEEK_SET) < 0)
+        return -1;
+
+    if (write(cd->fd, cd->buf, cd->cache_size) != cd->cache_size)
+        return -1;
+
+    cd->offset += cd->cache_size;
+
+    return 0;
+}
+
+int read_cache(struct cache_data *cd)
+{
+    if (lseek(cd->fd, cd->offset, SEEK_SET) < 0)
+        return -1;
+
+    if (read(cd->fd, cd->buf, cd->cache_size) != cd->cache_size)
+        return -1;
+
+    cd->offset += cd->cache_size;
+
+    return 0;
+}
+
+void free_cache_data(struct cache_data *cd)
+{
+    if (cd) {
+        if (cd->file_name)
+            g_free(cd->file_name);
+
+        if (cd->buf)
+            g_free(cd->buf);
+
+        g_free(cd);
+    }
+}
diff --git a/include/cache_data.h b/include/cache_data.h
new file mode 100644
index 0000000..4d6656f
--- /dev/null
+++ b/include/cache_data.h
@@ -0,0 +1,52 @@
+/*
+ * QEMU cache data
+ *
+ * Copyright Fujitsu, Corp. 2013
+ *
+ * Authors:
+ *     Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#define TMP_DIR                     "/tmp"
+#define BUFSIZE_CACHE_DATA          (4096 * 4)
+
+struct cache_data {
+    int fd;             /* fd of the tmp file used to store cache data */
+    char *file_name;    /* name of the tmp file */
+    char *buf;          /* used to cache data */
+    size_t buf_size;    /* size of the buf */
+    size_t cache_size;  /* size of cached data in buf */
+    off_t offset;       /* offset of the tmp file */
+};
+
+/*
+ * create a tmp file used to store cache data, then init the buf
+ */
+int init_cache_data(struct cache_data *cd, const char *filename);
+
+/*
+ * write data to the tmp file, the data may first be cached in the buf of
+ * cache_data
+ */
+int write_cache(struct cache_data *cd, void *buf, size_t size);
+
+/*
+ * when cache_data is caching data in the buf, sync_cache is needed to write the
+ * data back to tmp file
+ */
+int sync_cache(struct cache_data *cd);
+
+/*  read data from the tmp file to the buf of 'cd', the start place is set by
+ *  cd->offset, and the size is set by cd->cache_size.
+ *  cd->offset is changed automaticlly according to the size of data read this time.
+ */
+int read_cache(struct cache_data *cd);
+
+/*
+ * free the space used by cache_data
+ */
+void free_cache_data(struct cache_data *cd);
-- 
1.7.1