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b94a261057
The block layer generally keeps the size of an image cached in bs->total_sectors so that it doesn't have to perform expensive operations to get the size whenever it needs it. This doesn't work however when using a backend that can change its size without qemu being aware of it, i.e. passthrough of removable media like CD-ROMs or floppy disks. For this reason, the caching is disabled when a removable device is used. It is obvious that checking whether the _guest_ device has removable media isn't the right thing to do when we want to know whether the size of the host backend can change. To make things worse, non-top-level BlockDriverStates never have any device attached, which makes qemu assume they are removable, so drv->bdrv_getlength() is always called on the protocol layer. In the case of raw-posix, this causes unnecessary lseek() system calls, which turned out to be rather expensive. This patch completely changes the logic and disables bs->total_sectors caching only for certain block driver types, for which a size change is expected: host_cdrom and host_floppy on POSIX, host_device on win32; also the raw format in case it sits on top of one of these protocols, but in the common case the nested bdrv_getlength() call on the protocol driver will use the cache again and avoid an expensive drv->bdrv_getlength() call. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
199 lines
6.0 KiB
C
199 lines
6.0 KiB
C
/* BlockDriver implementation for "raw"
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*
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* Copyright (C) 2010, 2013, Red Hat, Inc.
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* Copyright (C) 2010, Blue Swirl <blauwirbel@gmail.com>
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* Copyright (C) 2009, Anthony Liguori <aliguori@us.ibm.com>
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*
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* Author:
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* Laszlo Ersek <lersek@redhat.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include "block/block_int.h"
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#include "qemu/option.h"
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static QEMUOptionParameter raw_create_options[] = {
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{
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.name = BLOCK_OPT_SIZE,
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.type = OPT_SIZE,
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.help = "Virtual disk size"
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},
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{ 0 }
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};
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static int raw_reopen_prepare(BDRVReopenState *reopen_state,
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BlockReopenQueue *queue, Error **errp)
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{
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return 0;
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}
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static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
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int nb_sectors, QEMUIOVector *qiov)
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{
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BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
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return bdrv_co_readv(bs->file, sector_num, nb_sectors, qiov);
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}
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static int coroutine_fn raw_co_writev(BlockDriverState *bs, int64_t sector_num,
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int nb_sectors, QEMUIOVector *qiov)
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{
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BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
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return bdrv_co_writev(bs->file, sector_num, nb_sectors, qiov);
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}
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static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
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int64_t sector_num,
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int nb_sectors, int *pnum)
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{
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*pnum = nb_sectors;
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return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA |
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(sector_num << BDRV_SECTOR_BITS);
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}
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static int coroutine_fn raw_co_write_zeroes(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors)
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{
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return bdrv_co_write_zeroes(bs->file, sector_num, nb_sectors);
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}
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static int coroutine_fn raw_co_discard(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors)
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{
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return bdrv_co_discard(bs->file, sector_num, nb_sectors);
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}
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static int64_t raw_getlength(BlockDriverState *bs)
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{
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return bdrv_getlength(bs->file);
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}
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static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
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{
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return bdrv_get_info(bs->file, bdi);
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}
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static int raw_truncate(BlockDriverState *bs, int64_t offset)
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{
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return bdrv_truncate(bs->file, offset);
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}
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static int raw_is_inserted(BlockDriverState *bs)
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{
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return bdrv_is_inserted(bs->file);
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}
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static int raw_media_changed(BlockDriverState *bs)
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{
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return bdrv_media_changed(bs->file);
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}
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static void raw_eject(BlockDriverState *bs, bool eject_flag)
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{
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bdrv_eject(bs->file, eject_flag);
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}
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static void raw_lock_medium(BlockDriverState *bs, bool locked)
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{
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bdrv_lock_medium(bs->file, locked);
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}
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static int raw_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
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{
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return bdrv_ioctl(bs->file, req, buf);
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}
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static BlockDriverAIOCB *raw_aio_ioctl(BlockDriverState *bs,
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unsigned long int req, void *buf,
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BlockDriverCompletionFunc *cb,
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void *opaque)
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{
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return bdrv_aio_ioctl(bs->file, req, buf, cb, opaque);
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}
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static int raw_has_zero_init(BlockDriverState *bs)
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{
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return bdrv_has_zero_init(bs->file);
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}
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static int raw_create(const char *filename, QEMUOptionParameter *options,
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Error **errp)
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{
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Error *local_err = NULL;
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int ret;
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ret = bdrv_create_file(filename, options, &local_err);
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if (error_is_set(&local_err)) {
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error_propagate(errp, local_err);
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}
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return ret;
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}
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static int raw_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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bs->sg = bs->file->sg;
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return 0;
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}
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static void raw_close(BlockDriverState *bs)
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{
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}
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static int raw_probe(const uint8_t *buf, int buf_size, const char *filename)
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{
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/* smallest possible positive score so that raw is used if and only if no
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* other block driver works
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*/
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return 1;
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}
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static BlockDriver bdrv_raw = {
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.format_name = "raw",
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.bdrv_probe = &raw_probe,
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.bdrv_reopen_prepare = &raw_reopen_prepare,
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.bdrv_open = &raw_open,
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.bdrv_close = &raw_close,
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.bdrv_create = &raw_create,
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.bdrv_co_readv = &raw_co_readv,
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.bdrv_co_writev = &raw_co_writev,
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.bdrv_co_write_zeroes = &raw_co_write_zeroes,
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.bdrv_co_discard = &raw_co_discard,
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.bdrv_co_get_block_status = &raw_co_get_block_status,
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.bdrv_truncate = &raw_truncate,
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.bdrv_getlength = &raw_getlength,
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.has_variable_length = true,
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.bdrv_get_info = &raw_get_info,
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.bdrv_is_inserted = &raw_is_inserted,
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.bdrv_media_changed = &raw_media_changed,
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.bdrv_eject = &raw_eject,
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.bdrv_lock_medium = &raw_lock_medium,
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.bdrv_ioctl = &raw_ioctl,
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.bdrv_aio_ioctl = &raw_aio_ioctl,
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.create_options = &raw_create_options[0],
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.bdrv_has_zero_init = &raw_has_zero_init
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};
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static void bdrv_raw_init(void)
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{
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bdrv_register(&bdrv_raw);
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}
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block_init(bdrv_raw_init);
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