[Qemu-devel] [v2 Patch 1/9]block: Framework for reopening image files safely

[Supriya Kannery]

Struct BDRVReopenState along with three reopen related functions
introduced for handling reopening of images safely. This can be
extended by each of the block drivers to reopen respective
image files.

Signed-off-by: Supriya Kannery <address@hidden>

---
Index: qemu/block.c
===================================================================
--- qemu.orig/block.c
+++ qemu/block.c
@@ -859,6 +859,60 @@ unlink_and_fail:
     return ret;
 }
 
+int bdrv_reopen_prepare(BlockDriverState *bs, BDRVReopenState **prs, int flags)
+{
+     BlockDriver *drv = bs->drv;
+
+     return drv->bdrv_reopen_prepare(bs, prs, flags);
+}
+
+void bdrv_reopen_commit(BlockDriverState *bs, BDRVReopenState *rs)
+{
+    BlockDriver *drv = bs->drv;
+
+    drv->bdrv_reopen_commit(bs, rs);
+}
+
+void bdrv_reopen_abort(BlockDriverState *bs, BDRVReopenState *rs)
+{
+    BlockDriver *drv = bs->drv;
+
+    drv->bdrv_reopen_abort(bs, rs);
+}
+
+void bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp)
+{
+    BlockDriver *drv = bs->drv;
+    int ret = 0;
+    BDRVReopenState *reopen_state = NULL;
+
+    /* Quiesce IO for the given block device */
+    bdrv_drain_all();
+    ret = bdrv_flush(bs);
+    if (ret != 0) {
+        error_set(errp, QERR_IO_ERROR);
+        return;
+    }
+
+    /* Use driver specific reopen() if available */
+    if (drv->bdrv_reopen_prepare) {
+        ret = bdrv_reopen_prepare(bs, &reopen_state, bdrv_flags);
+         if (ret < 0) {
+            bdrv_reopen_abort(bs, reopen_state);
+            error_set(errp, QERR_OPEN_FILE_FAILED, bs->filename);
+            return;
+        }
+
+        bdrv_reopen_commit(bs, reopen_state);
+        bs->open_flags = bdrv_flags;
+    } else {
+        error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
+                  drv->format_name, bs->device_name,
+                  "reopening of file");
+        return;
+    }
+}
+
 void bdrv_close(BlockDriverState *bs)
 {
     bdrv_flush(bs);
Index: qemu/block_int.h
===================================================================
--- qemu.orig/block_int.h
+++ qemu/block_int.h
@@ -136,6 +136,14 @@ struct BlockDriver {
     int instance_size;
     int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
     int (*bdrv_probe_device)(const char *filename);
+
+    /* For handling image reopen for split or non-split files */
+    int (*bdrv_reopen_prepare)(BlockDriverState *bs,
+                               BDRVReopenState **prs,
+                               int flags);
+    void (*bdrv_reopen_commit)(BlockDriverState *bs, BDRVReopenState *rs);
+    void (*bdrv_reopen_abort)(BlockDriverState *bs, BDRVReopenState *rs);
+
     int (*bdrv_open)(BlockDriverState *bs, int flags);
     int (*bdrv_file_open)(BlockDriverState *bs, const char *filename, int 
flags);
     int (*bdrv_read)(BlockDriverState *bs, int64_t sector_num,
@@ -335,6 +343,10 @@ struct BlockDriverState {
     BlockJob *job;
 };
 
+struct BDRVReopenState {
+    BlockDriverState *bs;
+};
+
 int get_tmp_filename(char *filename, int size);
 
 void bdrv_set_io_limits(BlockDriverState *bs,
Index: qemu/block.h
===================================================================
--- qemu.orig/block.h
+++ qemu/block.h
@@ -129,6 +129,10 @@ int bdrv_parse_cache_flags(const char *m
 int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);
 int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
               BlockDriver *drv);
+void bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp);
+int bdrv_reopen_prepare(BlockDriverState *bs, BDRVReopenState **prs, int 
flags);
+void bdrv_reopen_commit(BlockDriverState *bs, BDRVReopenState *rs);
+void bdrv_reopen_abort(BlockDriverState *bs, BDRVReopenState *rs);
 void bdrv_close(BlockDriverState *bs);
 int bdrv_attach_dev(BlockDriverState *bs, void *dev);
 void bdrv_attach_dev_nofail(BlockDriverState *bs, void *dev);
Index: qemu/qemu-common.h
===================================================================
--- qemu.orig/qemu-common.h
+++ qemu/qemu-common.h
@@ -223,6 +223,7 @@ typedef struct NICInfo NICInfo;
 typedef struct HCIInfo HCIInfo;
 typedef struct AudioState AudioState;
 typedef struct BlockDriverState BlockDriverState;
+typedef struct BDRVReopenState BDRVReopenState;
 typedef struct DriveInfo DriveInfo;
 typedef struct DisplayState DisplayState;
 typedef struct DisplayChangeListener DisplayChangeListener;