From e4c8fddde79d45b061d29e69bb564ea73d027a7a Mon Sep 17 00:00:00 2001 From: Andrey Shinkevich Date: Wed, 16 Dec 2020 09:16:55 +0300 Subject: [PATCH] qapi: copy-on-read filter: add 'bottom' option Add an option to limit copy-on-read operations to specified sub-chain of backing-chain, to make copy-on-read filter useful for block-stream job. Suggested-by: Max Reitz Suggested-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Andrey Shinkevich Signed-off-by: Vladimir Sementsov-Ogievskiy [vsementsov: change subject, modified to freeze the chain, do some fixes] Message-Id: <20201216061703.70908-6-vsementsov@virtuozzo.com> Signed-off-by: Max Reitz --- block/copy-on-read.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++-- qapi/block-core.json | 20 ++++++++++- 2 files changed, 115 insertions(+), 3 deletions(-) diff --git a/block/copy-on-read.c b/block/copy-on-read.c index 618c4c4f43..71560984f6 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -24,18 +24,24 @@ #include "block/block_int.h" #include "qemu/module.h" #include "qapi/error.h" +#include "qapi/qmp/qdict.h" #include "block/copy-on-read.h" typedef struct BDRVStateCOR { bool active; + BlockDriverState *bottom_bs; + bool chain_frozen; } BDRVStateCOR; static int cor_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { + BlockDriverState *bottom_bs = NULL; BDRVStateCOR *state = bs->opaque; + /* Find a bottom node name, if any */ + const char *bottom_node = qdict_get_try_str(options, "bottom"); bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds, BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, @@ -51,7 +57,38 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags, ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) & bs->file->bs->supported_zero_flags); + if (bottom_node) { + bottom_bs = bdrv_find_node(bottom_node); + if (!bottom_bs) { + error_setg(errp, "Bottom node '%s' not found", bottom_node); + qdict_del(options, "bottom"); + return -EINVAL; + } + qdict_del(options, "bottom"); + + if (!bottom_bs->drv) { + error_setg(errp, "Bottom node '%s' not opened", bottom_node); + return -EINVAL; + } + + if (bottom_bs->drv->is_filter) { + error_setg(errp, "Bottom node '%s' is a filter", bottom_node); + return -EINVAL; + } + + if (bdrv_freeze_backing_chain(bs, bottom_bs, errp) < 0) { + return -EINVAL; + } + state->chain_frozen = true; + + /* + * We do freeze the chain, so it shouldn't be removed. Still, storing a + * pointer worth bdrv_ref(). + */ + bdrv_ref(bottom_bs); + } state->active = true; + state->bottom_bs = bottom_bs; /* * We don't need to call bdrv_child_refresh_perms() now as the permissions @@ -107,8 +144,46 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, size_t qiov_offset, int flags) { - return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset, - flags | BDRV_REQ_COPY_ON_READ); + int64_t n; + int local_flags; + int ret; + BDRVStateCOR *state = bs->opaque; + + if (!state->bottom_bs) { + return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset, + flags | BDRV_REQ_COPY_ON_READ); + } + + while (bytes) { + local_flags = flags; + + /* In case of failure, try to copy-on-read anyway */ + ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n); + if (ret <= 0) { + ret = bdrv_is_allocated_above(bdrv_backing_chain_next(bs->file->bs), + state->bottom_bs, true, offset, + n, &n); + if (ret > 0 || ret < 0) { + local_flags |= BDRV_REQ_COPY_ON_READ; + } + /* Finish earlier if the end of a backing file has been reached */ + if (n == 0) { + break; + } + } + + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, + local_flags); + if (ret < 0) { + return ret; + } + + offset += n; + qiov_offset += n; + bytes -= n; + } + + return 0; } @@ -160,11 +235,25 @@ static void cor_lock_medium(BlockDriverState *bs, bool locked) } +static void cor_close(BlockDriverState *bs) +{ + BDRVStateCOR *s = bs->opaque; + + if (s->chain_frozen) { + s->chain_frozen = false; + bdrv_unfreeze_backing_chain(bs, s->bottom_bs); + } + + bdrv_unref(s->bottom_bs); +} + + static BlockDriver bdrv_copy_on_read = { .format_name = "copy-on-read", .instance_size = sizeof(BDRVStateCOR), .bdrv_open = cor_open, + .bdrv_close = cor_close, .bdrv_child_perm = cor_child_perm, .bdrv_getlength = cor_getlength, @@ -201,6 +290,11 @@ void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs) bdrv_drained_begin(bs); /* Drop permissions before the graph change. */ s->active = false; + /* unfreeze, as otherwise bdrv_replace_node() will fail */ + if (s->chain_frozen) { + s->chain_frozen = false; + bdrv_unfreeze_backing_chain(cor_filter_bs, s->bottom_bs); + } bdrv_child_refresh_perms(cor_filter_bs, child, &error_abort); bdrv_replace_node(cor_filter_bs, bs, &error_abort); diff --git a/qapi/block-core.json b/qapi/block-core.json index b55732d802..65167ebf56 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3959,6 +3959,24 @@ 'data': { 'throttle-group': 'str', 'file' : 'BlockdevRef' } } + +## +# @BlockdevOptionsCor: +# +# Driver specific block device options for the copy-on-read driver. +# +# @bottom: The name of a non-filter node (allocation-bearing layer) that +# limits the COR operations in the backing chain (inclusive), so +# that no data below this node will be copied by this filter. +# If option is absent, the limit is not applied, so that data +# from all backing layers may be copied. +# +# Since: 6.0 +## +{ 'struct': 'BlockdevOptionsCor', + 'base': 'BlockdevOptionsGenericFormat', + 'data': { '*bottom': 'str' } } + ## # @BlockdevOptions: # @@ -4011,7 +4029,7 @@ 'bochs': 'BlockdevOptionsGenericFormat', 'cloop': 'BlockdevOptionsGenericFormat', 'compress': 'BlockdevOptionsGenericFormat', - 'copy-on-read':'BlockdevOptionsGenericFormat', + 'copy-on-read':'BlockdevOptionsCor', 'dmg': 'BlockdevOptionsGenericFormat', 'file': 'BlockdevOptionsFile', 'ftp': 'BlockdevOptionsCurlFtp', -- 2.11.4.GIT