[Qemu-devel] [PATCH 1/9 v3] Add API to manipulate dump_bitmap

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

Struct dump_bitmap is associated with a tmp file which is used to store bitmap
in kdump-compressed format temporarily. The following patch will use these
functions to gather data of bitmap and cache them into tmp files.

Signed-off-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Reviewed-by: Zhang Xiaohe <zhangxh@cn.fujitsu.com>
---
 Makefile.target       |    2 +-
 dump_bitmap.c         |  171 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/dump_bitmap.h |   60 +++++++++++++++++
 3 files changed, 232 insertions(+), 1 deletions(-)
 create mode 100644 dump_bitmap.c
 create mode 100644 include/dump_bitmap.h

diff --git a/Makefile.target b/Makefile.target
index ce4391f..00d4f13 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
+obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o dump_bitmap.o
 obj-$(CONFIG_NO_GET_MEMORY_MAPPING) += memory_mapping-stub.o
 obj-$(CONFIG_NO_CORE_DUMP) += dump-stub.o
 LIBS+=$(libs_softmmu)
diff --git a/dump_bitmap.c b/dump_bitmap.c
new file mode 100644
index 0000000..f35f39d
--- /dev/null
+++ b/dump_bitmap.c
@@ -0,0 +1,171 @@
+/*
+ * QEMU dump bitmap
+ *
+ * Copyright (C) 2013 FUJITSU LIMITED
+ *
+ * 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 "dump_bitmap.h"
+
+int init_dump_bitmap(struct dump_bitmap *db, const char *filename)
+{
+    int fd;
+    char *tmpname;
+
+    /* init the tmp file */
+    tmpname = getenv("TMPDIR");
+    if (!tmpname) {
+        tmpname = (char *)P_tmpdir;
+    }
+
+    db->file_name = (char *)g_strdup_printf("%s/%s", tmpname, filename);
+
+    fd = mkstemp(db->file_name);
+    if (fd < 0) {
+        return -1;
+    }
+
+    db->fd = fd;
+    unlink(db->file_name);
+
+    /* num_block should be set to -1, for nothing is store in buf now */
+    db->num_block = -1;
+    memset(db->buf, 0, BUFSIZE_BITMAP);
+    /* the tmp file starts to write at the very beginning */
+    db->offset = 0;
+
+    return 0;
+}
+
+int clear_dump_bitmap(struct dump_bitmap *db, size_t len_db)
+{
+    int ret;
+    char buf[BUFSIZE_BITMAP];
+    off_t offset_bit;
+
+    /* use buf to clear the tmp file block by block */
+    memset(buf, 0, sizeof(buf));
+
+    ret = lseek(db->fd, db->offset, SEEK_SET);
+    if (ret < 0) {
+        return -1;
+    }
+
+    offset_bit = 0;
+    while (offset_bit < len_db) {
+        if (write(db->fd, buf, BUFSIZE_BITMAP) != BUFSIZE_BITMAP) {
+            return -1;
+        }
+
+        offset_bit += BUFSIZE_BITMAP;
+    }
+
+    return 0;
+}
+
+int set_dump_bitmap(struct dump_bitmap *db, unsigned long long pfn, int val)
+{
+    int byte, bit;
+    off_t old_offset, new_offset;
+    old_offset = db->offset + BUFSIZE_BITMAP * db->num_block;
+    new_offset = db->offset + BUFSIZE_BITMAP * (pfn / PFN_BUFBITMAP);
+
+    /*
+     * if the block needed to be set is not same as the one cached in buf,
+     * write the block back to the tmp file, then cache new block to the buf
+     */
+    if (0 <= db->num_block && old_offset != new_offset) {
+        if (lseek(db->fd, old_offset, SEEK_SET) < 0) {
+            return -1;
+        }
+
+        if (write(db->fd, db->buf, BUFSIZE_BITMAP) != BUFSIZE_BITMAP) {
+            return -1;
+        }
+    }
+
+    if (old_offset != new_offset) {
+        if (lseek(db->fd, new_offset, SEEK_SET) < 0) {
+            return -1;
+        }
+
+        if (read(db->fd, db->buf, BUFSIZE_BITMAP) != BUFSIZE_BITMAP) {
+            return -1;
+        }
+
+        db->num_block = pfn / PFN_BUFBITMAP;
+    }
+
+    /* get the exact place of the bit in the buf, set it */
+    byte = (pfn % PFN_BUFBITMAP) >> 3;
+    bit  = (pfn % PFN_BUFBITMAP) & 7;
+    if (val) {
+        db->buf[byte] |= 1<<bit;
+    } else {
+        db->buf[byte] &= ~(1<<bit);
+    }
+
+    return 0;
+}
+
+int sync_dump_bitmap(struct dump_bitmap *db)
+{
+    off_t offset;
+    offset = db->offset + BUFSIZE_BITMAP * db->num_block;
+
+    /* db has not been used yet */
+    if (db->num_block < 0) {
+        return 0;
+    }
+
+    if (lseek(db->fd, offset, SEEK_SET) < 0) {
+        return -1;
+    }
+
+    if (write(db->fd, db->buf, BUFSIZE_BITMAP) != BUFSIZE_BITMAP) {
+        return -1;
+    }
+
+    return 0;
+}
+
+/*
+ * check if the bit is set to 1
+ */
+static inline int is_on(char *bitmap, int i)
+{
+    return bitmap[i>>3] & (1 << (i & 7));
+}
+
+int is_bit_set(struct dump_bitmap *db, unsigned long long pfn)
+{
+    off_t offset;
+
+    /* cache the block pfn belongs to, then check the block */
+    if (pfn == 0 || db->num_block != pfn/PFN_BUFBITMAP) {
+        offset = db->offset + BUFSIZE_BITMAP * (pfn/PFN_BUFBITMAP);
+        lseek(db->fd, offset, SEEK_SET);
+        read(db->fd, db->buf, BUFSIZE_BITMAP);
+        db->num_block = pfn/PFN_BUFBITMAP;
+    }
+
+    return is_on(db->buf, pfn%PFN_BUFBITMAP);
+}
+
+void free_dump_bitmap(struct dump_bitmap *db)
+{
+    if (db) {
+        if (db->file_name) {
+            g_free(db->file_name);
+        }
+
+        g_free(db);
+    }
+}
diff --git a/include/dump_bitmap.h b/include/dump_bitmap.h
new file mode 100644
index 0000000..f81106c
--- /dev/null
+++ b/include/dump_bitmap.h
@@ -0,0 +1,60 @@
+/*
+ * QEMU dump bitmap
+ *
+ * Copyright (C) 2013 FUJITSU LIMITED
+ *
+ * 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.
+ *
+ */
+
+#ifndef DUMP_BITMAP_H
+#define DUMP_BITMAP_H
+
+#define BUFSIZE_BITMAP              (4096)
+#define PFN_BUFBITMAP               (CHAR_BIT * BUFSIZE_BITMAP)
+
+struct dump_bitmap {
+    int fd;                     /* fd of the tmp file */
+    int num_block;              /* number of blocks cached in buf */
+    char *file_name;            /* name of the tmp file */
+    char buf[BUFSIZE_BITMAP];   /* used to cache blocks */
+    off_t offset;               /* offset of the tmp file */
+};
+
+/*
+ * create a tmp file used to store dump bitmap, then init buf of dump_bitmap
+ */
+int init_dump_bitmap(struct dump_bitmap *db, const char *filename);
+
+/*
+ * clear the content of the tmp file with all bits set to 0
+ */
+int clear_dump_bitmap(struct dump_bitmap *db, size_t len_db);
+
+/*
+ * 'pfn' is the number of bit needed to be set, use buf to cache the block which
+ * 'pfn' belongs to, then set 'val' to the bit
+ */
+int set_dump_bitmap(struct dump_bitmap *db, unsigned long long pfn, int val);
+
+/*
+ * when buf is caching a block, sync_dump_bitmap is needed to write the cached
+ * block to the tmp file
+ */
+int sync_dump_bitmap(struct dump_bitmap *db);
+
+/*
+ * check whether 'pfn' is set
+ */
+int is_bit_set(struct dump_bitmap *db, unsigned long long pfn);
+
+/*
+ * free the space used by dump_bitmap
+ */
+void free_dump_bitmap(struct dump_bitmap *db);
+
+#endif
-- 
1.7.1