b3af2af43b
Note that some filters have secondary children, namely blkverify (the
image to be verified) and blklogwrites (the log). This patch does not
touch those children.
Note that for blkverify, the filtered child should not be format-probed.
While there is nothing enforcing this here, in practice, it will not be:
blkverify implements .bdrv_file_open. The block layer ensures (and in
fact, asserts) that BDRV_O_PROTOCOL is set for every BDS whose driver
implements .bdrv_file_open. This flag will then be bequeathed to
blkverify's children, and they will thus (by default) not be probed
either.
("By default" refers to the fact that blkverify's other child (the
non-filtered one) will have BDRV_O_PROTOCOL force-unset, because that is
what happens for all non-filtered children of non-format drivers.)
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200513110544.176672-27-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
151 lines
4.6 KiB
C
151 lines
4.6 KiB
C
/*
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* Copy-on-read filter block driver
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*
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* Copyright (c) 2018 Red Hat, Inc.
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*
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* Author:
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* Max Reitz <mreitz@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 or
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* (at your option) version 3 of the License.
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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 "block/block_int.h"
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#include "qemu/module.h"
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static int cor_open(BlockDriverState *bs, QDict *options, int flags,
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Error **errp)
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{
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bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
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BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
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false, errp);
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if (!bs->file) {
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return -EINVAL;
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}
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bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
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(BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
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bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
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((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
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bs->file->bs->supported_zero_flags);
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return 0;
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}
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#define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \
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| BLK_PERM_WRITE \
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| BLK_PERM_RESIZE)
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#define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH)
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static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
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const BdrvChildClass *child_class,
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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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*nperm = perm & PERM_PASSTHROUGH;
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*nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
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/* We must not request write permissions for an inactive node, the child
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* cannot provide it. */
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if (!(bs->open_flags & BDRV_O_INACTIVE)) {
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*nperm |= BLK_PERM_WRITE_UNCHANGED;
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}
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}
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static int64_t cor_getlength(BlockDriverState *bs)
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{
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return bdrv_getlength(bs->file->bs);
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}
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static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
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uint64_t offset, uint64_t bytes,
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QEMUIOVector *qiov, int flags)
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{
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return bdrv_co_preadv(bs->file, offset, bytes, qiov,
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flags | BDRV_REQ_COPY_ON_READ);
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}
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static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
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uint64_t offset, uint64_t bytes,
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QEMUIOVector *qiov, int flags)
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{
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return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
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}
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static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
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int64_t offset, int bytes,
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BdrvRequestFlags flags)
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{
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return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
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}
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static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs,
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int64_t offset, int bytes)
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{
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return bdrv_co_pdiscard(bs->file, offset, bytes);
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}
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static void cor_eject(BlockDriverState *bs, bool eject_flag)
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{
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bdrv_eject(bs->file->bs, eject_flag);
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}
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static void cor_lock_medium(BlockDriverState *bs, bool locked)
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{
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bdrv_lock_medium(bs->file->bs, locked);
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}
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static BlockDriver bdrv_copy_on_read = {
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.format_name = "copy-on-read",
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.bdrv_open = cor_open,
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.bdrv_child_perm = cor_child_perm,
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.bdrv_getlength = cor_getlength,
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.bdrv_co_preadv = cor_co_preadv,
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.bdrv_co_pwritev = cor_co_pwritev,
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.bdrv_co_pwrite_zeroes = cor_co_pwrite_zeroes,
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.bdrv_co_pdiscard = cor_co_pdiscard,
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.bdrv_eject = cor_eject,
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.bdrv_lock_medium = cor_lock_medium,
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.bdrv_co_block_status = bdrv_co_block_status_from_file,
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.has_variable_length = true,
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.is_filter = true,
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};
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static void bdrv_copy_on_read_init(void)
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{
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bdrv_register(&bdrv_copy_on_read);
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}
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block_init(bdrv_copy_on_read_init);
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