From be28aed80a705810be0f712a9f2474778a24c36a Mon Sep 17 00:00:00 2001 Message-Id: In-Reply-To: References: From: Jeffrey Cody Date: Wed, 17 Oct 2012 05:59:25 +0200 Subject: [PATCH 12/35] block: Framework for reopening files safely RH-Author: Jeffrey Cody Message-id: Patchwork-id: 43270 O-Subject: [RHEL6.4 qemu-kvm PATCH v4 12/35] block: Framework for reopening files safely Bugzilla: 767233 RH-Acked-by: Eric Blake RH-Acked-by: Paolo Bonzini RH-Acked-by: Kevin Wolf 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 Signed-off-by: Kevin Wolf (cherry picked from commit e971aa12739f269d6fbfaeabdd4acaeb0f15960b) Conflicts: block.h RHEL6 note: added "" to the QERR_OPEN_FILE_FAILED for commit a02a5946 --- block.c | 229 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ block.h | 18 +++++ block_int.h | 8 +++ 3 files changed, 255 insertions(+) Signed-off-by: Michal Novotny --- block.c | 229 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ block.h | 18 +++++ block_int.h | 8 +++ 3 files changed, 255 insertions(+) diff --git a/block.c b/block.c index e0edad5..5c4b2bd 100644 --- a/block.c +++ b/block.c @@ -705,6 +705,235 @@ 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, QERR_IO_ERROR); + 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_NOT_SUPPORTED); + 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) { if (bs->drv) { diff --git a/block.h b/block.h index 8e4485c..17fbd79 100644 --- a/block.h +++ b/block.h @@ -6,6 +6,7 @@ #include "qemu-option.h" #include "qemu-coroutine.h" #include "qobject.h" +#include "error.h" /* block.c */ typedef struct BlockDriverInfo { @@ -93,6 +94,15 @@ typedef enum { BDRV_IOS_MAX } BlockIOStatus; +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); @@ -124,6 +134,14 @@ void bdrv_delete(BlockDriverState *bs); 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 d0b4f7c..883fd5f 100644 --- a/block_int.h +++ b/block_int.h @@ -108,6 +108,13 @@ 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, @@ -284,6 +291,7 @@ struct BlockDriverState { /* long-running background operation */ BlockJob *job; + }; struct BlockDriverAIOCB { -- 1.7.11.7