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https://gitlab.com/qemu-project/qemu
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a4b740db5e
Most implementations of .bdrv_open first open their file child (which is an operation that internally takes the write lock and therefore we shouldn't hold the graph lock while calling it), and afterwards many operations that require holding the graph lock, e.g. for accessing bs->file. This changes block drivers that follow this pattern to take the graph lock after opening the child node. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-ID: <20231027155333.420094-24-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
136 lines
4.2 KiB
C
136 lines
4.2 KiB
C
/*
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* snapshot_access block driver
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*
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* Copyright (c) 2022 Virtuozzo International GmbH.
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*
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* Author:
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* Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "qemu/osdep.h"
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#include "sysemu/block-backend.h"
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#include "qemu/cutils.h"
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#include "block/block_int.h"
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static int coroutine_fn GRAPH_RDLOCK
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snapshot_access_co_preadv_part(BlockDriverState *bs,
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int64_t offset, int64_t bytes,
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QEMUIOVector *qiov, size_t qiov_offset,
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BdrvRequestFlags flags)
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{
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if (flags) {
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return -ENOTSUP;
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}
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return bdrv_co_preadv_snapshot(bs->file, offset, bytes, qiov, qiov_offset);
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}
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static int coroutine_fn GRAPH_RDLOCK
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snapshot_access_co_block_status(BlockDriverState *bs,
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bool want_zero, int64_t offset,
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int64_t bytes, int64_t *pnum,
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int64_t *map, BlockDriverState **file)
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{
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return bdrv_co_snapshot_block_status(bs->file->bs, want_zero, offset,
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bytes, pnum, map, file);
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}
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static int coroutine_fn GRAPH_RDLOCK
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snapshot_access_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
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{
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return bdrv_co_pdiscard_snapshot(bs->file->bs, offset, bytes);
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}
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static int coroutine_fn
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snapshot_access_co_pwrite_zeroes(BlockDriverState *bs,
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int64_t offset, int64_t bytes,
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BdrvRequestFlags flags)
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{
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return -ENOTSUP;
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}
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static coroutine_fn int
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snapshot_access_co_pwritev_part(BlockDriverState *bs,
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int64_t offset, int64_t bytes,
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QEMUIOVector *qiov, size_t qiov_offset,
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BdrvRequestFlags flags)
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{
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return -ENOTSUP;
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}
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static void GRAPH_RDLOCK snapshot_access_refresh_filename(BlockDriverState *bs)
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{
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pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
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bs->file->bs->filename);
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}
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static int snapshot_access_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
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BDRV_CHILD_DATA | BDRV_CHILD_PRIMARY,
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false, errp);
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GRAPH_RDLOCK_GUARD_MAINLOOP();
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if (!bs->file) {
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return -EINVAL;
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}
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bs->total_sectors = bs->file->bs->total_sectors;
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return 0;
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}
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static void snapshot_access_child_perm(BlockDriverState *bs, BdrvChild *c,
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BdrvChildRole role,
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BlockReopenQueue *reopen_queue,
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uint64_t perm, uint64_t shared,
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uint64_t *nperm, uint64_t *nshared)
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{
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/*
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* Currently, we don't need any permissions. If bs->file provides
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* snapshot-access API, we can use it.
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*/
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*nperm = 0;
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*nshared = BLK_PERM_ALL;
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}
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static BlockDriver bdrv_snapshot_access_drv = {
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.format_name = "snapshot-access",
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.bdrv_open = snapshot_access_open,
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.bdrv_co_preadv_part = snapshot_access_co_preadv_part,
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.bdrv_co_pwritev_part = snapshot_access_co_pwritev_part,
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.bdrv_co_pwrite_zeroes = snapshot_access_co_pwrite_zeroes,
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.bdrv_co_pdiscard = snapshot_access_co_pdiscard,
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.bdrv_co_block_status = snapshot_access_co_block_status,
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.bdrv_refresh_filename = snapshot_access_refresh_filename,
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.bdrv_child_perm = snapshot_access_child_perm,
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};
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static void snapshot_access_init(void)
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{
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bdrv_register(&bdrv_snapshot_access_drv);
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}
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block_init(snapshot_access_init);
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