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authorJeff Cody <jcody@redhat.com>2012-09-20 15:13:19 -0400
committerKevin Wolf <kwolf@redhat.com>2012-09-24 15:15:11 +0200
commite971aa12739f269d6fbfaeabdd4acaeb0f15960b (patch)
tree051780d65892511c8d4c5ba00e610ea967453843
parent55b110f24ec765a09cfb7f4c013fcd90dd807628 (diff)
downloadqemu-arm-e971aa12739f269d6fbfaeabdd4acaeb0f15960b.tar.gz
block: Framework for reopening files safely
This is based on Supriya Kannery's bdrv_reopen() patch series. This provides a transactional method to reopen multiple images files safely. Image files are queue for reopen via bdrv_reopen_queue(), and the reopen occurs when bdrv_reopen_multiple() is called. Changes are staged in bdrv_reopen_prepare() and in the equivalent driver level functions. If any of the staged images fails a prepare, then all of the images left untouched, and the staged changes for each image abandoned. Block drivers are passed a reopen state structure, that contains: * BDS to reopen * flags for the reopen * opaque pointer for any driver-specific data that needs to be persistent from _prepare to _commit/_abort * reopen queue pointer, if the driver needs to queue additional BDS for a reopen Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block.c232
-rw-r--r--block.h17
-rw-r--r--block_int.h8
3 files changed, 257 insertions, 0 deletions
diff --git a/block.c b/block.c
index 458bcc9b13..c7c1a3bd33 100644
--- a/block.c
+++ b/block.c
@@ -863,6 +863,238 @@ unlink_and_fail:
return ret;
}
+typedef struct BlockReopenQueueEntry {
+ bool prepared;
+ BDRVReopenState state;
+ QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry;
+} BlockReopenQueueEntry;
+
+/*
+ * Adds a BlockDriverState to a simple queue for an atomic, transactional
+ * reopen of multiple devices.
+ *
+ * bs_queue can either be an existing BlockReopenQueue that has had QSIMPLE_INIT
+ * already performed, or alternatively may be NULL a new BlockReopenQueue will
+ * be created and initialized. This newly created BlockReopenQueue should be
+ * passed back in for subsequent calls that are intended to be of the same
+ * atomic 'set'.
+ *
+ * bs is the BlockDriverState to add to the reopen queue.
+ *
+ * flags contains the open flags for the associated bs
+ *
+ * returns a pointer to bs_queue, which is either the newly allocated
+ * bs_queue, or the existing bs_queue being used.
+ *
+ */
+BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
+ BlockDriverState *bs, int flags)
+{
+ assert(bs != NULL);
+
+ BlockReopenQueueEntry *bs_entry;
+ if (bs_queue == NULL) {
+ bs_queue = g_new0(BlockReopenQueue, 1);
+ QSIMPLEQ_INIT(bs_queue);
+ }
+
+ if (bs->file) {
+ bdrv_reopen_queue(bs_queue, bs->file, flags);
+ }
+
+ bs_entry = g_new0(BlockReopenQueueEntry, 1);
+ QSIMPLEQ_INSERT_TAIL(bs_queue, bs_entry, entry);
+
+ bs_entry->state.bs = bs;
+ bs_entry->state.flags = flags;
+
+ return bs_queue;
+}
+
+/*
+ * Reopen multiple BlockDriverStates atomically & transactionally.
+ *
+ * The queue passed in (bs_queue) must have been built up previous
+ * via bdrv_reopen_queue().
+ *
+ * Reopens all BDS specified in the queue, with the appropriate
+ * flags. All devices are prepared for reopen, and failure of any
+ * device will cause all device changes to be abandonded, and intermediate
+ * data cleaned up.
+ *
+ * If all devices prepare successfully, then the changes are committed
+ * to all devices.
+ *
+ */
+int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
+{
+ int ret = -1;
+ BlockReopenQueueEntry *bs_entry, *next;
+ Error *local_err = NULL;
+
+ assert(bs_queue != NULL);
+
+ bdrv_drain_all();
+
+ QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+ if (bdrv_reopen_prepare(&bs_entry->state, bs_queue, &local_err)) {
+ error_propagate(errp, local_err);
+ goto cleanup;
+ }
+ bs_entry->prepared = true;
+ }
+
+ /* If we reach this point, we have success and just need to apply the
+ * changes
+ */
+ QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+ bdrv_reopen_commit(&bs_entry->state);
+ }
+
+ ret = 0;
+
+cleanup:
+ QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
+ if (ret && bs_entry->prepared) {
+ bdrv_reopen_abort(&bs_entry->state);
+ }
+ g_free(bs_entry);
+ }
+ g_free(bs_queue);
+ return ret;
+}
+
+
+/* Reopen a single BlockDriverState with the specified flags. */
+int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp)
+{
+ int ret = -1;
+ Error *local_err = NULL;
+ BlockReopenQueue *queue = bdrv_reopen_queue(NULL, bs, bdrv_flags);
+
+ ret = bdrv_reopen_multiple(queue, &local_err);
+ if (local_err != NULL) {
+ error_propagate(errp, local_err);
+ }
+ return ret;
+}
+
+
+/*
+ * Prepares a BlockDriverState for reopen. All changes are staged in the
+ * 'opaque' field of the BDRVReopenState, which is used and allocated by
+ * the block driver layer .bdrv_reopen_prepare()
+ *
+ * bs is the BlockDriverState to reopen
+ * flags are the new open flags
+ * queue is the reopen queue
+ *
+ * Returns 0 on success, non-zero on error. On error errp will be set
+ * as well.
+ *
+ * On failure, bdrv_reopen_abort() will be called to clean up any data.
+ * It is the responsibility of the caller to then call the abort() or
+ * commit() for any other BDS that have been left in a prepare() state
+ *
+ */
+int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
+ Error **errp)
+{
+ int ret = -1;
+ Error *local_err = NULL;
+ BlockDriver *drv;
+
+ assert(reopen_state != NULL);
+ assert(reopen_state->bs->drv != NULL);
+ drv = reopen_state->bs->drv;
+
+ /* if we are to stay read-only, do not allow permission change
+ * to r/w */
+ if (!(reopen_state->bs->open_flags & BDRV_O_ALLOW_RDWR) &&
+ reopen_state->flags & BDRV_O_RDWR) {
+ error_set(errp, QERR_DEVICE_IS_READ_ONLY,
+ reopen_state->bs->device_name);
+ goto error;
+ }
+
+
+ ret = bdrv_flush(reopen_state->bs);
+ if (ret) {
+ error_set(errp, ERROR_CLASS_GENERIC_ERROR, "Error (%s) flushing drive",
+ strerror(-ret));
+ goto error;
+ }
+
+ if (drv->bdrv_reopen_prepare) {
+ ret = drv->bdrv_reopen_prepare(reopen_state, queue, &local_err);
+ if (ret) {
+ if (local_err != NULL) {
+ error_propagate(errp, local_err);
+ } else {
+ error_set(errp, QERR_OPEN_FILE_FAILED,
+ reopen_state->bs->filename);
+ }
+ goto error;
+ }
+ } else {
+ /* It is currently mandatory to have a bdrv_reopen_prepare()
+ * handler for each supported drv. */
+ error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
+ drv->format_name, reopen_state->bs->device_name,
+ "reopening of file");
+ ret = -1;
+ goto error;
+ }
+
+ ret = 0;
+
+error:
+ return ret;
+}
+
+/*
+ * Takes the staged changes for the reopen from bdrv_reopen_prepare(), and
+ * makes them final by swapping the staging BlockDriverState contents into
+ * the active BlockDriverState contents.
+ */
+void bdrv_reopen_commit(BDRVReopenState *reopen_state)
+{
+ BlockDriver *drv;
+
+ assert(reopen_state != NULL);
+ drv = reopen_state->bs->drv;
+ assert(drv != NULL);
+
+ /* If there are any driver level actions to take */
+ if (drv->bdrv_reopen_commit) {
+ drv->bdrv_reopen_commit(reopen_state);
+ }
+
+ /* set BDS specific flags now */
+ reopen_state->bs->open_flags = reopen_state->flags;
+ reopen_state->bs->enable_write_cache = !!(reopen_state->flags &
+ BDRV_O_CACHE_WB);
+ reopen_state->bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
+}
+
+/*
+ * Abort the reopen, and delete and free the staged changes in
+ * reopen_state
+ */
+void bdrv_reopen_abort(BDRVReopenState *reopen_state)
+{
+ BlockDriver *drv;
+
+ assert(reopen_state != NULL);
+ drv = reopen_state->bs->drv;
+ assert(drv != NULL);
+
+ if (drv->bdrv_reopen_abort) {
+ drv->bdrv_reopen_abort(reopen_state);
+ }
+}
+
+
void bdrv_close(BlockDriverState *bs)
{
bdrv_flush(bs);
diff --git a/block.h b/block.h
index 4d919c249f..b1095d8599 100644
--- a/block.h
+++ b/block.h
@@ -97,6 +97,15 @@ typedef enum {
BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
} BlockQMPEventAction;
+typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;
+
+typedef struct BDRVReopenState {
+ BlockDriverState *bs;
+ int flags;
+ void *opaque;
+} BDRVReopenState;
+
+
void bdrv_iostatus_enable(BlockDriverState *bs);
void bdrv_iostatus_reset(BlockDriverState *bs);
void bdrv_iostatus_disable(BlockDriverState *bs);
@@ -131,6 +140,14 @@ int bdrv_parse_cache_flags(const char *mode, int *flags);
int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);
int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
BlockDriver *drv);
+BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
+ BlockDriverState *bs, int flags);
+int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp);
+int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp);
+int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
+ BlockReopenQueue *queue, Error **errp);
+void bdrv_reopen_commit(BDRVReopenState *reopen_state);
+void bdrv_reopen_abort(BDRVReopenState *reopen_state);
void bdrv_close(BlockDriverState *bs);
int bdrv_attach_dev(BlockDriverState *bs, void *dev);
void bdrv_attach_dev_nofail(BlockDriverState *bs, void *dev);
diff --git a/block_int.h b/block_int.h
index 4452f6f398..22b3d93d19 100644
--- a/block_int.h
+++ b/block_int.h
@@ -139,6 +139,13 @@ 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)(BDRVReopenState *reopen_state,
+ BlockReopenQueue *queue, Error **errp);
+ void (*bdrv_reopen_commit)(BDRVReopenState *reopen_state);
+ void (*bdrv_reopen_abort)(BDRVReopenState *reopen_state);
+
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,
@@ -336,6 +343,7 @@ struct BlockDriverState {
/* long-running background operation */
BlockJob *job;
+
};
int get_tmp_filename(char *filename, int size);