[Qemu-devel] [v7 Patch 5/5]Qemu: New struct 'BDRVReopenState' for image files reopen

[Supriya Kannery]

Struct BDRVReopenState introduced for handling reopen state of images. 
This can be  extended by each of the block drivers to reopen respective
image files. Implementation for raw-posix is done here.

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

---
 block.c           |   46 ++++++++++++++++++++++++++++++++--------
 block/raw-posix.c |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 block_int.h       |   15 +++++++++++++
 3 files changed, 114 insertions(+), 9 deletions(-)

Index: qemu/block/raw-posix.c
===================================================================
--- qemu.orig/block/raw-posix.c
+++ qemu/block/raw-posix.c
@@ -279,6 +279,66 @@ static int raw_open(BlockDriverState *bs
     return raw_open_common(bs, filename, flags, 0);
 }
 
+static int raw_reopen_prepare(BlockDriverState *bs, BDRVReopenState **rs,
+                              int flags)
+{
+    BDRVReopenState *raw_rs = g_malloc0(sizeof(BDRVReopenState));
+    BDRVRawState *s = bs->opaque;
+
+    raw_rs->bs = bs;
+    raw_rs->reopen_flags = flags;
+    raw_rs->reopen_fd = -1;
+
+    /* If only O_DIRECT to be toggled, use fcntl */
+    if (!((bs->open_flags & ~BDRV_O_NOCACHE) ^
+            (flags & ~BDRV_O_NOCACHE))) {
+        raw_rs->reopen_fd = dup(s->fd);
+        if (raw_rs->reopen_fd <= 0) {
+            return -1;
+        }
+    }
+
+    /* TBD: Handle O_DSYNC and other flags */
+    *rs = raw_rs;
+    return 0;
+}
+
+static int raw_reopen_commit(BDRVReopenState *rs)
+{
+    BlockDriverState *bs = rs->bs;
+    BDRVRawState *s = bs->opaque;
+
+    if (!rs->reopen_fd) {
+        return -1;
+    }
+
+    int ret = fcntl_setfl(rs->reopen_fd, rs->reopen_flags);
+    if (ret < 0) {
+        return ret;
+    }
+
+    /* Set new flags, so replace old fd with new one */
+    close(s->fd);
+    s->fd = rs->reopen_fd;
+    s->open_flags = bs->open_flags = rs->reopen_flags;
+    g_free(rs);
+    rs = NULL;
+
+    return 0;
+}
+
+static int raw_reopen_abort(BDRVReopenState *rs)
+{
+    if (rs->reopen_fd != -1) {
+        close(rs->reopen_fd);
+        rs->reopen_fd = -1;
+        rs->reopen_flags = 0;
+    }
+    g_free(rs);
+    rs = NULL;
+    return 0;
+}
+
 /* XXX: use host sector size if necessary with:
 #ifdef DIOCGSECTORSIZE
         {
@@ -896,6 +956,9 @@ static BlockDriver bdrv_file = {
     .instance_size = sizeof(BDRVRawState),
     .bdrv_probe = NULL, /* no probe for protocols */
     .bdrv_file_open = raw_open,
+    .bdrv_reopen_prepare = raw_reopen_prepare,
+    .bdrv_reopen_commit = raw_reopen_commit,
+    .bdrv_reopen_abort = raw_reopen_abort,
     .bdrv_read = raw_read,
     .bdrv_write = raw_write,
     .bdrv_close = raw_close,
@@ -1166,6 +1229,10 @@ static BlockDriver bdrv_host_device = {
     .instance_size      = sizeof(BDRVRawState),
     .bdrv_probe_device  = hdev_probe_device,
     .bdrv_file_open     = hdev_open,
+    .bdrv_reopen_prepare
+                        = raw_reopen_prepare,
+    .bdrv_reopen_commit = raw_reopen_commit,
+    .bdrv_reopen_abort  = raw_reopen_abort,
     .bdrv_close         = raw_close,
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
Index: qemu/block.c
===================================================================
--- qemu.orig/block.c
+++ qemu/block.c
@@ -706,6 +706,7 @@ int bdrv_reopen(BlockDriverState *bs, in
 {
     BlockDriver *drv = bs->drv;
     int ret = 0, open_flags;
+    BDRVReopenState *rs;
 
     /* Quiesce IO for the given block device */
     qemu_aio_flush();
@@ -713,20 +714,48 @@ int bdrv_reopen(BlockDriverState *bs, in
         qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);
         return ret;
     }
-    open_flags = bs->open_flags;
-    bdrv_close(bs);
 
-    ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
-    if (ret < 0) {
-        /* Reopen failed. Try to open with original flags */
-        qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
-        ret = bdrv_open(bs, bs->filename, open_flags, drv);
+    /* Use driver specific reopen() if available */
+    if (drv->bdrv_reopen_prepare) {
+        ret = drv->bdrv_reopen_prepare(bs, &rs, bdrv_flags);
         if (ret < 0) {
-            /* Reopen failed with orig and modified flags */
-            abort();
+            goto fail;
         }
-    }
+        if (drv->bdrv_reopen_commit) {
+            ret = drv->bdrv_reopen_commit(rs);
+            if (ret < 0) {
+                goto fail;
+            }
+            return 0;
+        }
+fail:
+        if (drv->bdrv_reopen_abort) {
+            ret = drv->bdrv_reopen_abort(rs);
+            qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
+            return ret;
+        }
+
+    } else {
+
+        /* Use reopen procedure common for all drivers */
+        open_flags = bs->open_flags;
+        bdrv_close(bs);
 
+        ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
+        if (ret < 0) {
+            /*
+             * Reopen failed. Try to open with original flags
+            */
+            qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
+            ret = bdrv_open(bs, bs->filename, open_flags, drv);
+            if (ret < 0) {
+                /*
+                 * Reopen with orig and modified flags failed
+                 */
+                abort();
+            }
+        }
+    }
     return ret;
 }
 
Index: qemu/block_int.h
===================================================================
--- qemu.orig/block_int.h
+++ qemu/block_int.h
@@ -55,6 +55,13 @@ struct BlockDriver {
     int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
     int (*bdrv_probe_device)(const char *filename);
     int (*bdrv_open)(BlockDriverState *bs, int flags);
+
+    /* For handling image reopen for split or non-split files */
+    int (*bdrv_reopen_prepare)(BlockDriverState *bs, BDRVReopenState **rs,
+          int flags);
+    int (*bdrv_reopen_commit)(BDRVReopenState *rs);
+    int (*bdrv_reopen_abort)(BDRVReopenState *rs);
+
     int (*bdrv_file_open)(BlockDriverState *bs, const char *filename, int 
flags);
     int (*bdrv_read)(BlockDriverState *bs, int64_t sector_num,
                      uint8_t *buf, int nb_sectors);
@@ -207,6 +214,14 @@ struct BlockDriverState {
     void *private;
 };
 
+struct BDRVReopenState {
+    BlockDriverState *bs;
+    int reopen_flags;
+
+    /* For raw-posix */
+    int reopen_fd;
+};
+
 struct BlockDriverAIOCB {
     AIOPool *pool;
     BlockDriverState *bs;
Index: qemu/qemu-common.h
===================================================================
--- qemu.orig/qemu-common.h
+++ qemu/qemu-common.h
@@ -228,6 +228,7 @@ 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;
Index: qemu/block/raw.c
===================================================================
--- qemu.orig/block/raw.c
+++ qemu/block/raw.c
@@ -9,6 +9,15 @@ static int raw_open(BlockDriverState *bs
     return 0;
 }
 
+static int raw_reopen(BlockDriverState *bs, BDRVReopenState **prs, int flags)
+{
+    int ret = bdrv_reopen(bs->file, flags);
+    if (!ret) {
+        bs->open_flags = bs->file->open_flags;
+    }
+    return ret;
+}
+
 static int raw_read(BlockDriverState *bs, int64_t sector_num,
                     uint8_t *buf, int nb_sectors)
 {
@@ -128,6 +137,8 @@ static BlockDriver bdrv_raw = {
     .instance_size      = 1,
 
     .bdrv_open          = raw_open,
+    .bdrv_reopen_prepare
+                        = raw_reopen,
     .bdrv_close         = raw_close,
     .bdrv_read          = raw_read,
     .bdrv_write         = raw_write,