qemu

block_int-common.h (49691B)

---

 /*
  * QEMU System Emulator block driver
  *
  * Copyright (c) 2003 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 #ifndef BLOCK_INT_COMMON_H
 #define BLOCK_INT_COMMON_H
 
 #include "block/accounting.h"
 #include "block/block.h"
 #include "block/aio-wait.h"
 #include "qemu/queue.h"
 #include "qemu/coroutine.h"
 #include "qemu/stats64.h"
 #include "qemu/timer.h"
 #include "qemu/hbitmap.h"
 #include "block/snapshot.h"
 #include "qemu/throttle.h"
 #include "qemu/rcu.h"
 
 #define BLOCK_FLAG_LAZY_REFCOUNTS   8
 
 #define BLOCK_OPT_SIZE              "size"
 #define BLOCK_OPT_ENCRYPT           "encryption"
 #define BLOCK_OPT_ENCRYPT_FORMAT    "encrypt.format"
 #define BLOCK_OPT_COMPAT6           "compat6"
 #define BLOCK_OPT_HWVERSION         "hwversion"
 #define BLOCK_OPT_BACKING_FILE      "backing_file"
 #define BLOCK_OPT_BACKING_FMT       "backing_fmt"
 #define BLOCK_OPT_CLUSTER_SIZE      "cluster_size"
 #define BLOCK_OPT_TABLE_SIZE        "table_size"
 #define BLOCK_OPT_PREALLOC          "preallocation"
 #define BLOCK_OPT_SUBFMT            "subformat"
 #define BLOCK_OPT_COMPAT_LEVEL      "compat"
 #define BLOCK_OPT_LAZY_REFCOUNTS    "lazy_refcounts"
 #define BLOCK_OPT_ADAPTER_TYPE      "adapter_type"
 #define BLOCK_OPT_REDUNDANCY        "redundancy"
 #define BLOCK_OPT_NOCOW             "nocow"
 #define BLOCK_OPT_EXTENT_SIZE_HINT  "extent_size_hint"
 #define BLOCK_OPT_OBJECT_SIZE       "object_size"
 #define BLOCK_OPT_REFCOUNT_BITS     "refcount_bits"
 #define BLOCK_OPT_DATA_FILE         "data_file"
 #define BLOCK_OPT_DATA_FILE_RAW     "data_file_raw"
 #define BLOCK_OPT_COMPRESSION_TYPE  "compression_type"
 #define BLOCK_OPT_EXTL2             "extended_l2"
 
 #define BLOCK_PROBE_BUF_SIZE        512
 
 enum BdrvTrackedRequestType {
     BDRV_TRACKED_READ,
     BDRV_TRACKED_WRITE,
     BDRV_TRACKED_DISCARD,
     BDRV_TRACKED_TRUNCATE,
 };
 
 /*
  * That is not quite good that BdrvTrackedRequest structure is public,
  * as block/io.c is very careful about incoming offset/bytes being
  * correct. Be sure to assert bdrv_check_request() succeeded after any
  * modification of BdrvTrackedRequest object out of block/io.c
  */
 typedef struct BdrvTrackedRequest {
     BlockDriverState *bs;
     int64_t offset;
     int64_t bytes;
     enum BdrvTrackedRequestType type;
 
     bool serialising;
     int64_t overlap_offset;
     int64_t overlap_bytes;
 
     QLIST_ENTRY(BdrvTrackedRequest) list;
     Coroutine *co; /* owner, used for deadlock detection */
     CoQueue wait_queue; /* coroutines blocked on this request */
 
     struct BdrvTrackedRequest *waiting_for;
 } BdrvTrackedRequest;
 
 
 struct BlockDriver {
     /*
      * These fields are initialized when this object is created,
      * and are never changed afterwards.
      */
 
     const char *format_name;
     int instance_size;
 
     /*
      * Set to true if the BlockDriver is a block filter. Block filters pass
      * certain callbacks that refer to data (see block.c) to their bs->file
      * or bs->backing (whichever one exists) if the driver doesn't implement
      * them. Drivers that do not wish to forward must implement them and return
      * -ENOTSUP.
      * Note that filters are not allowed to modify data.
      *
      * Filters generally cannot have more than a single filtered child,
      * because the data they present must at all times be the same as
      * that on their filtered child.  That would be impossible to
      * achieve for multiple filtered children.
      * (And this filtered child must then be bs->file or bs->backing.)
      */
     bool is_filter;
     /*
      * Only make sense for filter drivers, for others must be false.
      * If true, filtered child is bs->backing. Otherwise it's bs->file.
      * Two internal filters use bs->backing as filtered child and has this
      * field set to true: mirror_top and commit_top. There also two such test
      * filters in tests/unit/test-bdrv-graph-mod.c.
      *
      * Never create any more such filters!
      *
      * TODO: imagine how to deprecate this behavior and make all filters work
      * similarly using bs->file as filtered child.
      */
     bool filtered_child_is_backing;
 
     /*
      * Set to true if the BlockDriver is a format driver.  Format nodes
      * generally do not expect their children to be other format nodes
      * (except for backing files), and so format probing is disabled
      * on those children.
      */
     bool is_format;
 
     /*
      * Drivers not implementing bdrv_parse_filename nor bdrv_open should have
      * this field set to true, except ones that are defined only by their
      * child's bs.
      * An example of the last type will be the quorum block driver.
      */
     bool bdrv_needs_filename;
 
     /*
      * Set if a driver can support backing files. This also implies the
      * following semantics:
      *
      *  - Return status 0 of .bdrv_co_block_status means that corresponding
      *    blocks are not allocated in this layer of backing-chain
      *  - For such (unallocated) blocks, read will:
      *    - fill buffer with zeros if there is no backing file
      *    - read from the backing file otherwise, where the block layer
      *      takes care of reading zeros beyond EOF if backing file is short
      */
     bool supports_backing;
 
     bool has_variable_length;
 
     /*
      * Drivers setting this field must be able to work with just a plain
      * filename with '<protocol_name>:' as a prefix, and no other options.
      * Options may be extracted from the filename by implementing
      * bdrv_parse_filename.
      */
     const char *protocol_name;
 
     /* List of options for creating images, terminated by name == NULL */
     QemuOptsList *create_opts;
 
     /* List of options for image amend */
     QemuOptsList *amend_opts;
 
     /*
      * If this driver supports reopening images this contains a
      * NULL-terminated list of the runtime options that can be
      * modified. If an option in this list is unspecified during
      * reopen then it _must_ be reset to its default value or return
      * an error.
      */
     const char *const *mutable_opts;
 
     /*
      * Pointer to a NULL-terminated array of names of strong options
      * that can be specified for bdrv_open(). A strong option is one
      * that changes the data of a BDS.
      * If this pointer is NULL, the array is considered empty.
      * "filename" and "driver" are always considered strong.
      */
     const char *const *strong_runtime_opts;
 
 
     /*
      * Global state (GS) API. These functions run under the BQL.
      *
      * See include/block/block-global-state.h for more information about
      * the GS API.
      */
 
     /*
      * This function is invoked under BQL before .bdrv_co_amend()
      * (which in contrast does not necessarily run under the BQL)
      * to allow driver-specific initialization code that requires
      * the BQL, like setting up specific permission flags.
      */
     int (*bdrv_amend_pre_run)(BlockDriverState *bs, Error **errp);
     /*
      * This function is invoked under BQL after .bdrv_co_amend()
      * to allow cleaning up what was done in .bdrv_amend_pre_run().
      */
     void (*bdrv_amend_clean)(BlockDriverState *bs);
 
     /*
      * Return true if @to_replace can be replaced by a BDS with the
      * same data as @bs without it affecting @bs's behavior (that is,
      * without it being visible to @bs's parents).
      */
     bool (*bdrv_recurse_can_replace)(BlockDriverState *bs,
                                      BlockDriverState *to_replace);
 
     int (*bdrv_probe_device)(const char *filename);
 
     /*
      * Any driver implementing this callback is expected to be able to handle
      * NULL file names in its .bdrv_open() implementation.
      */
     void (*bdrv_parse_filename)(const char *filename, QDict *options,
                                 Error **errp);
 
     /* 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_commit_post)(BDRVReopenState *reopen_state);
     void (*bdrv_reopen_abort)(BDRVReopenState *reopen_state);
     void (*bdrv_join_options)(QDict *options, QDict *old_options);
 
     int (*bdrv_open)(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp);
 
     /* Protocol drivers should implement this instead of bdrv_open */
     int (*bdrv_file_open)(BlockDriverState *bs, QDict *options, int flags,
                           Error **errp);
     void (*bdrv_close)(BlockDriverState *bs);
 
     int coroutine_fn (*bdrv_co_create)(BlockdevCreateOptions *opts,
                                        Error **errp);
     int coroutine_fn (*bdrv_co_create_opts)(BlockDriver *drv,
                                             const char *filename,
                                             QemuOpts *opts,
                                             Error **errp);
 
     int (*bdrv_amend_options)(BlockDriverState *bs,
                               QemuOpts *opts,
                               BlockDriverAmendStatusCB *status_cb,
                               void *cb_opaque,
                               bool force,
                               Error **errp);
 
     int (*bdrv_make_empty)(BlockDriverState *bs);
 
     /*
      * Refreshes the bs->exact_filename field. If that is impossible,
      * bs->exact_filename has to be left empty.
      */
     void (*bdrv_refresh_filename)(BlockDriverState *bs);
 
     /*
      * Gathers the open options for all children into @target.
      * A simple format driver (without backing file support) might
      * implement this function like this:
      *
      *     QINCREF(bs->file->bs->full_open_options);
      *     qdict_put(target, "file", bs->file->bs->full_open_options);
      *
      * If not specified, the generic implementation will simply put
      * all children's options under their respective name.
      *
      * @backing_overridden is true when bs->backing seems not to be
      * the child that would result from opening bs->backing_file.
      * Therefore, if it is true, the backing child's options should be
      * gathered; otherwise, there is no need since the backing child
      * is the one implied by the image header.
      *
      * Note that ideally this function would not be needed.  Every
      * block driver which implements it is probably doing something
      * shady regarding its runtime option structure.
      */
     void (*bdrv_gather_child_options)(BlockDriverState *bs, QDict *target,
                                       bool backing_overridden);
 
     /*
      * Returns an allocated string which is the directory name of this BDS: It
      * will be used to make relative filenames absolute by prepending this
      * function's return value to them.
      */
     char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);
 
     /*
      * This informs the driver that we are no longer interested in the result
      * of in-flight requests, so don't waste the time if possible.
      *
      * One example usage is to avoid waiting for an nbd target node reconnect
      * timeout during job-cancel with force=true.
      */
     void (*bdrv_cancel_in_flight)(BlockDriverState *bs);
 
     int (*bdrv_inactivate)(BlockDriverState *bs);
 
     int (*bdrv_snapshot_create)(BlockDriverState *bs,
                                 QEMUSnapshotInfo *sn_info);
     int (*bdrv_snapshot_goto)(BlockDriverState *bs,
                               const char *snapshot_id);
     int (*bdrv_snapshot_delete)(BlockDriverState *bs,
                                 const char *snapshot_id,
                                 const char *name,
                                 Error **errp);
     int (*bdrv_snapshot_list)(BlockDriverState *bs,
                               QEMUSnapshotInfo **psn_info);
     int (*bdrv_snapshot_load_tmp)(BlockDriverState *bs,
                                   const char *snapshot_id,
                                   const char *name,
                                   Error **errp);
 
     int (*bdrv_change_backing_file)(BlockDriverState *bs,
         const char *backing_file, const char *backing_fmt);
 
     /* TODO Better pass a option string/QDict/QemuOpts to add any rule? */
     int (*bdrv_debug_breakpoint)(BlockDriverState *bs, const char *event,
         const char *tag);
     int (*bdrv_debug_remove_breakpoint)(BlockDriverState *bs,
         const char *tag);
     int (*bdrv_debug_resume)(BlockDriverState *bs, const char *tag);
     bool (*bdrv_debug_is_suspended)(BlockDriverState *bs, const char *tag);
 
     void (*bdrv_refresh_limits)(BlockDriverState *bs, Error **errp);
 
     /*
      * Returns 1 if newly created images are guaranteed to contain only
      * zeros, 0 otherwise.
      */
     int (*bdrv_has_zero_init)(BlockDriverState *bs);
 
     /*
      * Remove fd handlers, timers, and other event loop callbacks so the event
      * loop is no longer in use.  Called with no in-flight requests and in
      * depth-first traversal order with parents before child nodes.
      */
     void (*bdrv_detach_aio_context)(BlockDriverState *bs);
 
     /*
      * Add fd handlers, timers, and other event loop callbacks so I/O requests
      * can be processed again.  Called with no in-flight requests and in
      * depth-first traversal order with child nodes before parent nodes.
      */
     void (*bdrv_attach_aio_context)(BlockDriverState *bs,
                                     AioContext *new_context);
 
     /**
      * Try to get @bs's logical and physical block size.
      * On success, store them in @bsz and return zero.
      * On failure, return negative errno.
      */
     int (*bdrv_probe_blocksizes)(BlockDriverState *bs, BlockSizes *bsz);
     /**
      * Try to get @bs's geometry (cyls, heads, sectors)
      * On success, store them in @geo and return 0.
      * On failure return -errno.
      * Only drivers that want to override guest geometry implement this
      * callback; see hd_geometry_guess().
      */
     int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo);
 
     void (*bdrv_add_child)(BlockDriverState *parent, BlockDriverState *child,
                            Error **errp);
     void (*bdrv_del_child)(BlockDriverState *parent, BdrvChild *child,
                            Error **errp);
 
     /**
      * Informs the block driver that a permission change is intended. The
      * driver checks whether the change is permissible and may take other
      * preparations for the change (e.g. get file system locks). This operation
      * is always followed either by a call to either .bdrv_set_perm or
      * .bdrv_abort_perm_update.
      *
      * Checks whether the requested set of cumulative permissions in @perm
      * can be granted for accessing @bs and whether no other users are using
      * permissions other than those given in @shared (both arguments take
      * BLK_PERM_* bitmasks).
      *
      * If both conditions are met, 0 is returned. Otherwise, -errno is returned
      * and errp is set to an error describing the conflict.
      */
     int (*bdrv_check_perm)(BlockDriverState *bs, uint64_t perm,
                            uint64_t shared, Error **errp);
 
     /**
      * Called to inform the driver that the set of cumulative set of used
      * permissions for @bs has changed to @perm, and the set of sharable
      * permission to @shared. The driver can use this to propagate changes to
      * its children (i.e. request permissions only if a parent actually needs
      * them).
      *
      * This function is only invoked after bdrv_check_perm(), so block drivers
      * may rely on preparations made in their .bdrv_check_perm implementation.
      */
     void (*bdrv_set_perm)(BlockDriverState *bs, uint64_t perm, uint64_t shared);
 
     /*
      * Called to inform the driver that after a previous bdrv_check_perm()
      * call, the permission update is not performed and any preparations made
      * for it (e.g. taken file locks) need to be undone.
      *
      * This function can be called even for nodes that never saw a
      * bdrv_check_perm() call. It is a no-op then.
      */
     void (*bdrv_abort_perm_update)(BlockDriverState *bs);
 
     /**
      * Returns in @nperm and @nshared the permissions that the driver for @bs
      * needs on its child @c, based on the cumulative permissions requested by
      * the parents in @parent_perm and @parent_shared.
      *
      * If @c is NULL, return the permissions for attaching a new child for the
      * given @child_class and @role.
      *
      * If @reopen_queue is non-NULL, don't return the currently needed
      * permissions, but those that will be needed after applying the
      * @reopen_queue.
      */
      void (*bdrv_child_perm)(BlockDriverState *bs, BdrvChild *c,
                              BdrvChildRole role,
                              BlockReopenQueue *reopen_queue,
                              uint64_t parent_perm, uint64_t parent_shared,
                              uint64_t *nperm, uint64_t *nshared);
 
     /**
      * Register/unregister a buffer for I/O. For example, when the driver is
      * interested to know the memory areas that will later be used in iovs, so
      * that it can do IOMMU mapping with VFIO etc., in order to get better
      * performance. In the case of VFIO drivers, this callback is used to do
      * DMA mapping for hot buffers.
      *
      * Returns: true on success, false on failure
      */
     bool (*bdrv_register_buf)(BlockDriverState *bs, void *host, size_t size,
                               Error **errp);
     void (*bdrv_unregister_buf)(BlockDriverState *bs, void *host, size_t size);
 
     /*
      * This field is modified only under the BQL, and is part of
      * the global state.
      */
     QLIST_ENTRY(BlockDriver) list;
 
     /*
      * I/O API functions. These functions are thread-safe.
      *
      * See include/block/block-io.h for more information about
      * the I/O API.
      */
 
     int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
 
     int coroutine_fn (*bdrv_co_amend)(BlockDriverState *bs,
                                       BlockdevAmendOptions *opts,
                                       bool force,
                                       Error **errp);
 
     /* aio */
     BlockAIOCB *(*bdrv_aio_preadv)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
     BlockAIOCB *(*bdrv_aio_pwritev)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
     BlockAIOCB *(*bdrv_aio_flush)(BlockDriverState *bs,
         BlockCompletionFunc *cb, void *opaque);
     BlockAIOCB *(*bdrv_aio_pdiscard)(BlockDriverState *bs,
         int64_t offset, int bytes,
         BlockCompletionFunc *cb, void *opaque);
 
     int coroutine_fn (*bdrv_co_readv)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
 
     /**
      * @offset: position in bytes to read at
      * @bytes: number of bytes to read
      * @qiov: the buffers to fill with read data
      * @flags: currently unused, always 0
      *
      * @offset and @bytes will be a multiple of 'request_alignment',
      * but the length of individual @qiov elements does not have to
      * be a multiple.
      *
      * @bytes will always equal the total size of @qiov, and will be
      * no larger than 'max_transfer'.
      *
      * The buffer in @qiov may point directly to guest memory.
      */
     int coroutine_fn (*bdrv_co_preadv)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags);
 
     int coroutine_fn (*bdrv_co_preadv_part)(BlockDriverState *bs,
         int64_t offset, int64_t bytes,
         QEMUIOVector *qiov, size_t qiov_offset,
         BdrvRequestFlags flags);
 
     int coroutine_fn (*bdrv_co_writev)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
         int flags);
     /**
      * @offset: position in bytes to write at
      * @bytes: number of bytes to write
      * @qiov: the buffers containing data to write
      * @flags: zero or more bits allowed by 'supported_write_flags'
      *
      * @offset and @bytes will be a multiple of 'request_alignment',
      * but the length of individual @qiov elements does not have to
      * be a multiple.
      *
      * @bytes will always equal the total size of @qiov, and will be
      * no larger than 'max_transfer'.
      *
      * The buffer in @qiov may point directly to guest memory.
      */
     int coroutine_fn (*bdrv_co_pwritev)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags);
     int coroutine_fn (*bdrv_co_pwritev_part)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset,
         BdrvRequestFlags flags);
 
     /*
      * Efficiently zero a region of the disk image.  Typically an image format
      * would use a compact metadata representation to implement this.  This
      * function pointer may be NULL or return -ENOSUP and .bdrv_co_writev()
      * will be called instead.
      */
     int coroutine_fn (*bdrv_co_pwrite_zeroes)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, BdrvRequestFlags flags);
     int coroutine_fn (*bdrv_co_pdiscard)(BlockDriverState *bs,
         int64_t offset, int64_t bytes);
 
     /*
      * Map [offset, offset + nbytes) range onto a child of @bs to copy from,
      * and invoke bdrv_co_copy_range_from(child, ...), or invoke
      * bdrv_co_copy_range_to() if @bs is the leaf child to copy data from.
      *
      * See the comment of bdrv_co_copy_range for the parameter and return value
      * semantics.
      */
     int coroutine_fn (*bdrv_co_copy_range_from)(BlockDriverState *bs,
                                                 BdrvChild *src,
                                                 int64_t offset,
                                                 BdrvChild *dst,
                                                 int64_t dst_offset,
                                                 int64_t bytes,
                                                 BdrvRequestFlags read_flags,
                                                 BdrvRequestFlags write_flags);
 
     /*
      * Map [offset, offset + nbytes) range onto a child of bs to copy data to,
      * and invoke bdrv_co_copy_range_to(child, src, ...), or perform the copy
      * operation if @bs is the leaf and @src has the same BlockDriver.  Return
      * -ENOTSUP if @bs is the leaf but @src has a different BlockDriver.
      *
      * See the comment of bdrv_co_copy_range for the parameter and return value
      * semantics.
      */
     int coroutine_fn (*bdrv_co_copy_range_to)(BlockDriverState *bs,
                                               BdrvChild *src,
                                               int64_t src_offset,
                                               BdrvChild *dst,
                                               int64_t dst_offset,
                                               int64_t bytes,
                                               BdrvRequestFlags read_flags,
                                               BdrvRequestFlags write_flags);
 
     /*
      * Building block for bdrv_block_status[_above] and
      * bdrv_is_allocated[_above].  The driver should answer only
      * according to the current layer, and should only need to set
      * BDRV_BLOCK_DATA, BDRV_BLOCK_ZERO, BDRV_BLOCK_OFFSET_VALID,
      * and/or BDRV_BLOCK_RAW; if the current layer defers to a backing
      * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  See
      * block.h for the overall meaning of the bits.  As a hint, the
      * flag want_zero is true if the caller cares more about precise
      * mappings (favor accurate _OFFSET_VALID/_ZERO) or false for
      * overall allocation (favor larger *pnum, perhaps by reporting
      * _DATA instead of _ZERO).  The block layer guarantees input
      * clamped to bdrv_getlength() and aligned to request_alignment,
      * as well as non-NULL pnum, map, and file; in turn, the driver
      * must return an error or set pnum to an aligned non-zero value.
      *
      * Note that @bytes is just a hint on how big of a region the
      * caller wants to inspect.  It is not a limit on *pnum.
      * Implementations are free to return larger values of *pnum if
      * doing so does not incur a performance penalty.
      *
      * block/io.c's bdrv_co_block_status() will utilize an unclamped
      * *pnum value for the block-status cache on protocol nodes, prior
      * to clamping *pnum for return to its caller.
      */
     int coroutine_fn (*bdrv_co_block_status)(BlockDriverState *bs,
         bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
         int64_t *map, BlockDriverState **file);
 
     /*
      * Snapshot-access API.
      *
      * Block-driver may provide snapshot-access API: special functions to access
      * some internal "snapshot". The functions are similar with normal
      * read/block_status/discard handler, but don't have any specific handling
      * in generic block-layer: no serializing, no alignment, no tracked
      * requests. So, block-driver that realizes these APIs is fully responsible
      * for synchronization between snapshot-access API and normal IO requests.
      *
      * TODO: To be able to support qcow2's internal snapshots, this API will
      * need to be extended to:
      * - be able to select a specific snapshot
      * - receive the snapshot's actual length (which may differ from bs's
      *   length)
      */
     int coroutine_fn (*bdrv_co_preadv_snapshot)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset);
     int coroutine_fn (*bdrv_co_snapshot_block_status)(BlockDriverState *bs,
         bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
         int64_t *map, BlockDriverState **file);
     int coroutine_fn (*bdrv_co_pdiscard_snapshot)(BlockDriverState *bs,
         int64_t offset, int64_t bytes);
 
     /*
      * Invalidate any cached meta-data.
      */
     void coroutine_fn (*bdrv_co_invalidate_cache)(BlockDriverState *bs,
                                                   Error **errp);
 
     /*
      * Flushes all data for all layers by calling bdrv_co_flush for underlying
      * layers, if needed. This function is needed for deterministic
      * synchronization of the flush finishing callback.
      */
     int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs);
 
     /* Delete a created file. */
     int coroutine_fn (*bdrv_co_delete_file)(BlockDriverState *bs,
                                             Error **errp);
 
     /*
      * Flushes all data that was already written to the OS all the way down to
      * the disk (for example file-posix.c calls fsync()).
      */
     int coroutine_fn (*bdrv_co_flush_to_disk)(BlockDriverState *bs);
 
     /*
      * Flushes all internal caches to the OS. The data may still sit in a
      * writeback cache of the host OS, but it will survive a crash of the qemu
      * process.
      */
     int coroutine_fn (*bdrv_co_flush_to_os)(BlockDriverState *bs);
 
     /*
      * Truncate @bs to @offset bytes using the given @prealloc mode
      * when growing.  Modes other than PREALLOC_MODE_OFF should be
      * rejected when shrinking @bs.
      *
      * If @exact is true, @bs must be resized to exactly @offset.
      * Otherwise, it is sufficient for @bs (if it is a host block
      * device and thus there is no way to resize it) to be at least
      * @offset bytes in length.
      *
      * If @exact is true and this function fails but would succeed
      * with @exact = false, it should return -ENOTSUP.
      */
     int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
                                          bool exact, PreallocMode prealloc,
                                          BdrvRequestFlags flags, Error **errp);
     int64_t (*bdrv_getlength)(BlockDriverState *bs);
     int64_t (*bdrv_get_allocated_file_size)(BlockDriverState *bs);
     BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
                                       Error **errp);
 
     int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov);
     int coroutine_fn (*bdrv_co_pwritev_compressed_part)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         size_t qiov_offset);
 
     int (*bdrv_get_info)(BlockDriverState *bs, BlockDriverInfo *bdi);
 
     ImageInfoSpecific *(*bdrv_get_specific_info)(BlockDriverState *bs,
                                                  Error **errp);
     BlockStatsSpecific *(*bdrv_get_specific_stats)(BlockDriverState *bs);
 
     int coroutine_fn (*bdrv_save_vmstate)(BlockDriverState *bs,
                                           QEMUIOVector *qiov,
                                           int64_t pos);
     int coroutine_fn (*bdrv_load_vmstate)(BlockDriverState *bs,
                                           QEMUIOVector *qiov,
                                           int64_t pos);
 
     /* removable device specific */
     bool (*bdrv_is_inserted)(BlockDriverState *bs);
     void (*bdrv_eject)(BlockDriverState *bs, bool eject_flag);
     void (*bdrv_lock_medium)(BlockDriverState *bs, bool locked);
 
     /* to control generic scsi devices */
     BlockAIOCB *(*bdrv_aio_ioctl)(BlockDriverState *bs,
         unsigned long int req, void *buf,
         BlockCompletionFunc *cb, void *opaque);
     int coroutine_fn (*bdrv_co_ioctl)(BlockDriverState *bs,
                                       unsigned long int req, void *buf);
 
     /*
      * Returns 0 for completed check, -errno for internal errors.
      * The check results are stored in result.
      */
     int coroutine_fn (*bdrv_co_check)(BlockDriverState *bs,
                                       BdrvCheckResult *result,
                                       BdrvCheckMode fix);
 
     void (*bdrv_debug_event)(BlockDriverState *bs, BlkdebugEvent event);
 
     /* io queue for linux-aio */
     void (*bdrv_io_plug)(BlockDriverState *bs);
     void (*bdrv_io_unplug)(BlockDriverState *bs);
 
     /**
      * bdrv_co_drain_begin is called if implemented in the beginning of a
      * drain operation to drain and stop any internal sources of requests in
      * the driver.
      * bdrv_co_drain_end is called if implemented at the end of the drain.
      *
      * They should be used by the driver to e.g. manage scheduled I/O
      * requests, or toggle an internal state. After the end of the drain new
      * requests will continue normally.
      */
     void coroutine_fn (*bdrv_co_drain_begin)(BlockDriverState *bs);
     void coroutine_fn (*bdrv_co_drain_end)(BlockDriverState *bs);
 
     bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
     bool coroutine_fn (*bdrv_co_can_store_new_dirty_bitmap)(
         BlockDriverState *bs, const char *name, uint32_t granularity,
         Error **errp);
     int coroutine_fn (*bdrv_co_remove_persistent_dirty_bitmap)(
         BlockDriverState *bs, const char *name, Error **errp);
 };
 
 static inline bool block_driver_can_compress(BlockDriver *drv)
 {
     return drv->bdrv_co_pwritev_compressed ||
            drv->bdrv_co_pwritev_compressed_part;
 }
 
 typedef struct BlockLimits {
     /*
      * Alignment requirement, in bytes, for offset/length of I/O
      * requests. Must be a power of 2 less than INT_MAX; defaults to
      * 1 for drivers with modern byte interfaces, and to 512
      * otherwise.
      */
     uint32_t request_alignment;
 
     /*
      * Maximum number of bytes that can be discarded at once. Must be multiple
      * of pdiscard_alignment, but need not be power of 2. May be 0 if no
      * inherent 64-bit limit.
      */
     int64_t max_pdiscard;
 
     /*
      * Optimal alignment for discard requests in bytes. A power of 2
      * is best but not mandatory.  Must be a multiple of
      * bl.request_alignment, and must be less than max_pdiscard if
      * that is set. May be 0 if bl.request_alignment is good enough
      */
     uint32_t pdiscard_alignment;
 
     /*
      * Maximum number of bytes that can zeroized at once. Must be multiple of
      * pwrite_zeroes_alignment. 0 means no limit.
      */
     int64_t max_pwrite_zeroes;
 
     /*
      * Optimal alignment for write zeroes requests in bytes. A power
      * of 2 is best but not mandatory.  Must be a multiple of
      * bl.request_alignment, and must be less than max_pwrite_zeroes
      * if that is set. May be 0 if bl.request_alignment is good
      * enough
      */
     uint32_t pwrite_zeroes_alignment;
 
     /*
      * Optimal transfer length in bytes.  A power of 2 is best but not
      * mandatory.  Must be a multiple of bl.request_alignment, or 0 if
      * no preferred size
      */
     uint32_t opt_transfer;
 
     /*
      * Maximal transfer length in bytes.  Need not be power of 2, but
      * must be multiple of opt_transfer and bl.request_alignment, or 0
      * for no 32-bit limit.  For now, anything larger than INT_MAX is
      * clamped down.
      */
     uint32_t max_transfer;
 
     /*
      * Maximal hardware transfer length in bytes.  Applies whenever
      * transfers to the device bypass the kernel I/O scheduler, for
      * example with SG_IO.  If larger than max_transfer or if zero,
      * blk_get_max_hw_transfer will fall back to max_transfer.
      */
     uint64_t max_hw_transfer;
 
     /*
      * Maximal number of scatter/gather elements allowed by the hardware.
      * Applies whenever transfers to the device bypass the kernel I/O
      * scheduler, for example with SG_IO.  If larger than max_iov
      * or if zero, blk_get_max_hw_iov will fall back to max_iov.
      */
     int max_hw_iov;
 
 
     /* memory alignment, in bytes so that no bounce buffer is needed */
     size_t min_mem_alignment;
 
     /* memory alignment, in bytes, for bounce buffer */
     size_t opt_mem_alignment;
 
     /* maximum number of iovec elements */
     int max_iov;
 } BlockLimits;
 
 typedef struct BdrvOpBlocker BdrvOpBlocker;
 
 typedef struct BdrvAioNotifier {
     void (*attached_aio_context)(AioContext *new_context, void *opaque);
     void (*detach_aio_context)(void *opaque);
 
     void *opaque;
     bool deleted;
 
     QLIST_ENTRY(BdrvAioNotifier) list;
 } BdrvAioNotifier;
 
 struct BdrvChildClass {
     /*
      * If true, bdrv_replace_node() doesn't change the node this BdrvChild
      * points to.
      */
     bool stay_at_node;
 
     /*
      * If true, the parent is a BlockDriverState and bdrv_next_all_states()
      * will return it. This information is used for drain_all, where every node
      * will be drained separately, so the drain only needs to be propagated to
      * non-BDS parents.
      */
     bool parent_is_bds;
 
     /*
      * Global state (GS) API. These functions run under the BQL.
      *
      * See include/block/block-global-state.h for more information about
      * the GS API.
      */
     void (*inherit_options)(BdrvChildRole role, bool parent_is_format,
                             int *child_flags, QDict *child_options,
                             int parent_flags, QDict *parent_options);
     void (*change_media)(BdrvChild *child, bool load);
 
     /*
      * Returns a malloced string that describes the parent of the child for a
      * human reader. This could be a node-name, BlockBackend name, qdev ID or
      * QOM path of the device owning the BlockBackend, job type and ID etc. The
      * caller is responsible for freeing the memory.
      */
     char *(*get_parent_desc)(BdrvChild *child);
 
     /*
      * Notifies the parent that the child has been activated/inactivated (e.g.
      * when migration is completing) and it can start/stop requesting
      * permissions and doing I/O on it.
      */
     void (*activate)(BdrvChild *child, Error **errp);
     int (*inactivate)(BdrvChild *child);
 
     void (*attach)(BdrvChild *child);
     void (*detach)(BdrvChild *child);
 
     /*
      * Notifies the parent that the filename of its child has changed (e.g.
      * because the direct child was removed from the backing chain), so that it
      * can update its reference.
      */
     int (*update_filename)(BdrvChild *child, BlockDriverState *new_base,
                            const char *filename, Error **errp);
 
     bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx,
                            GHashTable *visited, Transaction *tran,
                            Error **errp);
 
     /*
      * I/O API functions. These functions are thread-safe.
      *
      * See include/block/block-io.h for more information about
      * the I/O API.
      */
 
     void (*resize)(BdrvChild *child);
 
     /*
      * Returns a name that is supposedly more useful for human users than the
      * node name for identifying the node in question (in particular, a BB
      * name), or NULL if the parent can't provide a better name.
      */
     const char *(*get_name)(BdrvChild *child);
 
     AioContext *(*get_parent_aio_context)(BdrvChild *child);
 
     /*
      * If this pair of functions is implemented, the parent doesn't issue new
      * requests after returning from .drained_begin() until .drained_end() is
      * called.
      *
      * These functions must not change the graph (and therefore also must not
      * call aio_poll(), which could change the graph indirectly).
      *
      * If drained_end() schedules background operations, it must atomically
      * increment *drained_end_counter for each such operation and atomically
      * decrement it once the operation has settled.
      *
      * Note that this can be nested. If drained_begin() was called twice, new
      * I/O is allowed only after drained_end() was called twice, too.
      */
     void (*drained_begin)(BdrvChild *child);
     void (*drained_end)(BdrvChild *child, int *drained_end_counter);
 
     /*
      * Returns whether the parent has pending requests for the child. This
      * callback is polled after .drained_begin() has been called until all
      * activity on the child has stopped.
      */
     bool (*drained_poll)(BdrvChild *child);
 };
 
 extern const BdrvChildClass child_of_bds;
 
 struct BdrvChild {
     BlockDriverState *bs;
     char *name;
     const BdrvChildClass *klass;
     BdrvChildRole role;
     void *opaque;
 
     /**
      * Granted permissions for operating on this BdrvChild (BLK_PERM_* bitmask)
      */
     uint64_t perm;
 
     /**
      * Permissions that can still be granted to other users of @bs while this
      * BdrvChild is still attached to it. (BLK_PERM_* bitmask)
      */
     uint64_t shared_perm;
 
     /*
      * This link is frozen: the child can neither be replaced nor
      * detached from the parent.
      */
     bool frozen;
 
     /*
      * How many times the parent of this child has been drained
      * (through klass->drained_*).
      * Usually, this is equal to bs->quiesce_counter (potentially
      * reduced by bdrv_drain_all_count).  It may differ while the
      * child is entering or leaving a drained section.
      */
     int parent_quiesce_counter;
 
     QLIST_ENTRY(BdrvChild) next;
     QLIST_ENTRY(BdrvChild) next_parent;
 };
 
 /*
  * Allows bdrv_co_block_status() to cache one data region for a
  * protocol node.
  *
  * @valid: Whether the cache is valid (should be accessed with atomic
  *         functions so this can be reset by RCU readers)
  * @data_start: Offset where we know (or strongly assume) is data
  * @data_end: Offset where the data region ends (which is not necessarily
  *            the start of a zeroed region)
  */
 typedef struct BdrvBlockStatusCache {
     struct rcu_head rcu;
 
     bool valid;
     int64_t data_start;
     int64_t data_end;
 } BdrvBlockStatusCache;
 
 struct BlockDriverState {
     /*
      * Protected by big QEMU lock or read-only after opening.  No special
      * locking needed during I/O...
      */
     int open_flags; /* flags used to open the file, re-used for re-open */
     bool encrypted; /* if true, the media is encrypted */
     bool sg;        /* if true, the device is a /dev/sg* */
     bool probed;    /* if true, format was probed rather than specified */
     bool force_share; /* if true, always allow all shared permissions */
     bool implicit;  /* if true, this filter node was automatically inserted */
 
     BlockDriver *drv; /* NULL means no media */
     void *opaque;
 
     AioContext *aio_context; /* event loop used for fd handlers, timers, etc */
     /*
      * long-running tasks intended to always use the same AioContext as this
      * BDS may register themselves in this list to be notified of changes
      * regarding this BDS's context
      */
     QLIST_HEAD(, BdrvAioNotifier) aio_notifiers;
     bool walking_aio_notifiers; /* to make removal during iteration safe */
 
     char filename[PATH_MAX];
     /*
      * If not empty, this image is a diff in relation to backing_file.
      * Note that this is the name given in the image header and
      * therefore may or may not be equal to .backing->bs->filename.
      * If this field contains a relative path, it is to be resolved
      * relatively to the overlay's location.
      */
     char backing_file[PATH_MAX];
     /*
      * The backing filename indicated by the image header.  Contrary
      * to backing_file, if we ever open this file, auto_backing_file
      * is replaced by the resulting BDS's filename (i.e. after a
      * bdrv_refresh_filename() run).
      */
     char auto_backing_file[PATH_MAX];
     char backing_format[16]; /* if non-zero and backing_file exists */
 
     QDict *full_open_options;
     char exact_filename[PATH_MAX];
 
     /* I/O Limits */
     BlockLimits bl;
 
     /*
      * Flags honored during pread
      */
     BdrvRequestFlags supported_read_flags;
     /*
      * Flags honored during pwrite (so far: BDRV_REQ_FUA,
      * BDRV_REQ_WRITE_UNCHANGED).
      * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those
      * writes will be issued as normal writes without the flag set.
      * This is important to note for drivers that do not explicitly
      * request a WRITE permission for their children and instead take
      * the same permissions as their parent did (this is commonly what
      * block filters do).  Such drivers have to be aware that the
      * parent may have taken a WRITE_UNCHANGED permission only and is
      * issuing such requests.  Drivers either must make sure that
      * these requests do not result in plain WRITE accesses (usually
      * by supporting BDRV_REQ_WRITE_UNCHANGED, and then forwarding
      * every incoming write request as-is, including potentially that
      * flag), or they have to explicitly take the WRITE permission for
      * their children.
      */
     BdrvRequestFlags supported_write_flags;
     /*
      * Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
      * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED)
      */
     BdrvRequestFlags supported_zero_flags;
     /*
      * Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
      *
      * If BDRV_REQ_ZERO_WRITE is given, the truncate operation must make sure
      * that any added space reads as all zeros. If this can't be guaranteed,
      * the operation must fail.
      */
     BdrvRequestFlags supported_truncate_flags;
 
     /* the following member gives a name to every node on the bs graph. */
     char node_name[32];
     /* element of the list of named nodes building the graph */
     QTAILQ_ENTRY(BlockDriverState) node_list;
     /* element of the list of all BlockDriverStates (all_bdrv_states) */
     QTAILQ_ENTRY(BlockDriverState) bs_list;
     /* element of the list of monitor-owned BDS */
     QTAILQ_ENTRY(BlockDriverState) monitor_list;
     int refcnt;
 
     /* operation blockers. Protected by BQL. */
     QLIST_HEAD(, BdrvOpBlocker) op_blockers[BLOCK_OP_TYPE_MAX];
 
     /*
      * The node that this node inherited default options from (and a reopen on
      * which can affect this node by changing these defaults). This is always a
      * parent node of this node.
      */
     BlockDriverState *inherits_from;
 
     /*
      * @backing and @file are some of @children or NULL. All these three fields
      * (@file, @backing and @children) are modified only in
      * bdrv_child_cb_attach() and bdrv_child_cb_detach().
      *
      * See also comment in include/block/block.h, to learn how backing and file
      * are connected with BdrvChildRole.
      */
     QLIST_HEAD(, BdrvChild) children;
     BdrvChild *backing;
     BdrvChild *file;
 
     QLIST_HEAD(, BdrvChild) parents;
 
     QDict *options;
     QDict *explicit_options;
     BlockdevDetectZeroesOptions detect_zeroes;
 
     /* The error object in use for blocking operations on backing_hd */
     Error *backing_blocker;
 
     /* Protected by AioContext lock */
 
     /*
      * If we are reading a disk image, give its size in sectors.
      * Generally read-only; it is written to by load_snapshot and
      * save_snaphost, but the block layer is quiescent during those.
      */
     int64_t total_sectors;
 
     /* threshold limit for writes, in bytes. "High water mark". */
     uint64_t write_threshold_offset;
 
     /*
      * Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
      * Reading from the list can be done with either the BQL or the
      * dirty_bitmap_mutex.  Modifying a bitmap only requires
      * dirty_bitmap_mutex.
      */
     QemuMutex dirty_bitmap_mutex;
     QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
 
     /* Offset after the highest byte written to */
     Stat64 wr_highest_offset;
 
     /*
      * If true, copy read backing sectors into image.  Can be >1 if more
      * than one client has requested copy-on-read.  Accessed with atomic
      * ops.
      */
     int copy_on_read;
 
     /*
      * number of in-flight requests; overall and serialising.
      * Accessed with atomic ops.
      */
     unsigned int in_flight;
     unsigned int serialising_in_flight;
 
     /*
      * counter for nested bdrv_io_plug.
      * Accessed with atomic ops.
      */
     unsigned io_plugged;
 
     /* do we need to tell the quest if we have a volatile write cache? */
     int enable_write_cache;
 
     /* Accessed with atomic ops.  */
     int quiesce_counter;
     int recursive_quiesce_counter;
 
     unsigned int write_gen;               /* Current data generation */
 
     /* Protected by reqs_lock.  */
     CoMutex reqs_lock;
     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
     CoQueue flush_queue;                  /* Serializing flush queue */
     bool active_flush_req;                /* Flush request in flight? */
 
     /* Only read/written by whoever has set active_flush_req to true.  */
     unsigned int flushed_gen;             /* Flushed write generation */
 
     /* BdrvChild links to this node may never be frozen */
     bool never_freeze;
 
     /* Lock for block-status cache RCU writers */
     CoMutex bsc_modify_lock;
     /* Always non-NULL, but must only be dereferenced under an RCU read guard */
     BdrvBlockStatusCache *block_status_cache;
 };
 
 struct BlockBackendRootState {
     int open_flags;
     BlockdevDetectZeroesOptions detect_zeroes;
 };
 
 typedef enum BlockMirrorBackingMode {
     /*
      * Reuse the existing backing chain from the source for the target.
      * - sync=full: Set backing BDS to NULL.
      * - sync=top:  Use source's backing BDS.
      * - sync=none: Use source as the backing BDS.
      */
     MIRROR_SOURCE_BACKING_CHAIN,
 
     /* Open the target's backing chain completely anew */
     MIRROR_OPEN_BACKING_CHAIN,
 
     /* Do not change the target's backing BDS after job completion */
     MIRROR_LEAVE_BACKING_CHAIN,
 } BlockMirrorBackingMode;
 
 
 /*
  * Essential block drivers which must always be statically linked into qemu, and
  * which therefore can be accessed without using bdrv_find_format()
  */
 extern BlockDriver bdrv_file;
 extern BlockDriver bdrv_raw;
 extern BlockDriver bdrv_qcow2;
 
 extern unsigned int bdrv_drain_all_count;
 extern QemuOptsList bdrv_create_opts_simple;
 
 /*
  * Common functions that are neither I/O nor Global State.
  *
  * See include/block/block-commmon.h for more information about
  * the Common API.
  */
 
 static inline BlockDriverState *child_bs(BdrvChild *child)
 {
     return child ? child->bs : NULL;
 }
 
 int bdrv_check_request(int64_t offset, int64_t bytes, Error **errp);
 char *create_tmp_file(Error **errp);
 void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
                                       QDict *options);
 
 
 int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
                             QEMUIOVector *qiov, size_t qiov_offset,
                             Error **errp);
 
 #ifdef _WIN32
 int is_windows_drive(const char *filename);
 #endif
 
 #endif /* BLOCK_INT_COMMON_H */