[Qemu-devel] [PATCH v8 10/13] dump: add APIs to operate DataCache

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

DataCache is used to store data temporarily, then the data will be written to
vmcore. These functions will be called later when writing data of page to
vmcore.

Signed-off-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---
 dump.c                |   47 +++++++++++++++++++++++++++++++++++++++++++++++
 include/sysemu/dump.h |    9 +++++++++
 2 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/dump.c b/dump.c
index 5755534..a7a85d3 100644
--- a/dump.c
+++ b/dump.c
@@ -1165,6 +1165,53 @@ out:
     return ret;
 }
 
+static void prepare_data_cache(DataCache *data_cache, DumpState *s,
+                               off_t offset)
+{
+    data_cache->fd = s->fd;
+    data_cache->data_size = 0;
+    data_cache->buf_size = BUFSIZE_DATA_CACHE;
+    data_cache->buf = g_malloc0(BUFSIZE_DATA_CACHE);
+    data_cache->offset = offset;
+}
+
+static int write_cache(DataCache *dc, const void *buf, size_t size,
+                       bool flag_sync)
+{
+    /*
+     * dc->buf_size should not be less than size, otherwise dc will never be
+     * enough
+     */
+    assert(size <= dc->buf_size);
+
+    /*
+     * if flag_sync is set, synchronize data in dc->buf into vmcore.
+     * otherwise check if the space is enough for caching data in buf, if not,
+     * write the data in dc->buf to dc->fd and reset dc->buf
+     */
+    if ((!flag_sync && dc->data_size + size > dc->buf_size) ||
+        (flag_sync && dc->data_size > 0)) {
+        if (write_buffer(dc->fd, dc->offset, dc->buf, dc->data_size) < 0) {
+            return -1;
+        }
+
+        dc->offset += dc->data_size;
+        dc->data_size = 0;
+    }
+
+    if (!flag_sync) {
+        memcpy(dc->buf + dc->data_size, buf, size);
+        dc->data_size += size;
+    }
+
+    return 0;
+}
+
+static void free_data_cache(DataCache *data_cache)
+{
+    g_free(data_cache->buf);
+}
+
 static ram_addr_t get_start_block(DumpState *s)
 {
     GuestPhysBlock *block;
diff --git a/include/sysemu/dump.h b/include/sysemu/dump.h
index 6d4d0bc..92a95e4 100644
--- a/include/sysemu/dump.h
+++ b/include/sysemu/dump.h
@@ -41,6 +41,7 @@
 #define DISKDUMP_HEADER_BLOCKS      (1)
 #define BUFSIZE_BITMAP              (TARGET_PAGE_SIZE)
 #define PFN_BUFBITMAP               (CHAR_BIT * BUFSIZE_BITMAP)
+#define BUFSIZE_DATA_CACHE          (TARGET_PAGE_SIZE * 4)
 
 typedef struct ArchDumpInfo {
     int d_machine;  /* Architecture */
@@ -142,6 +143,14 @@ typedef struct QEMU_PACKED KdumpSubHeader64 {
     uint64_t max_mapnr_64;          /* header_version 6 and later */
 } KdumpSubHeader64;
 
+typedef struct DataCache {
+    int fd;             /* fd of the file where to write the cached data */
+    uint8_t *buf;       /* buffer for cached data */
+    size_t buf_size;    /* size of the buf */
+    size_t data_size;   /* size of cached data in buf */
+    off_t offset;       /* offset of the file */
+} DataCache;
+
 struct GuestPhysBlockList; /* memory_mapping.h */
 int cpu_get_dump_info(ArchDumpInfo *info,
                       const struct GuestPhysBlockList *guest_phys_blocks);
-- 
1.7.1