| Message ID | 1598633579-221780-5-git-send-email-andrey.shinkevich@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Apply COR-filter to the block-stream permanently | expand |
On 28.08.20 18:52, Andrey Shinkevich wrote: > To limit the guest's COR operations by the base node in the backing > chain during stream job, pass the base file name to the copy-on-read Does it have to be a filename? That sounds really bad to me. > driver. The rest of the functionality will be implemented in the patch > that follows. > > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> > --- > block/copy-on-read.c | 41 ++++++++++++++++++++++++++++++++++++++++- > block/copy-on-read.h | 1 + > 2 files changed, 41 insertions(+), 1 deletion(-) Furthermore, I believe that this option should become an externally visible option for the copy-on-read filter (i.e., part of its BlockdevOptions) – but that definitely won’t be viable if @base contains a filename. Can’t we let the stream job invoke bdrv_find_backing_image() to translate a filename into a node name that’s then passed to the COR filter? > diff --git a/block/copy-on-read.c b/block/copy-on-read.c > index 0ede7aa..1f858bb 100644 > --- a/block/copy-on-read.c > +++ b/block/copy-on-read.c > @@ -24,19 +24,45 @@ > #include "block/block_int.h" > #include "qemu/module.h" > #include "qapi/error.h" > +#include "qapi/qmp/qerror.h" > #include "qapi/qmp/qdict.h" > #include "block/copy-on-read.h" > > > typedef struct BDRVStateCOR { > bool active; > + BlockDriverState *base_bs; > } BDRVStateCOR; > > +/* > + * Non-zero pointers are the caller's responsibility. > + */ > +static BlockDriverState *get_base_by_name(BlockDriverState *bs, > + const char *base_name, Error **errp) > +{ > + BlockDriverState *base_bs = NULL; > + AioContext *aio_context; > + > + base_bs = bdrv_find_backing_image(bs, base_name); > + if (base_bs == NULL) { > + error_setg(errp, QERR_BASE_NOT_FOUND, base_name); > + return NULL; > + } > + > + aio_context = bdrv_get_aio_context(bs); > + aio_context_acquire(aio_context); > + assert(bdrv_get_aio_context(base_bs) == aio_context); > + aio_context_release(aio_context); Er. OK. But why? Isn’t this just guaranteed by the block layer? I don’t think we need an explicit assertion for this, especially if it means having to acquire an AioContext. Furthermore, I don’t even know why we’d need the AioContext. On one hand, we don’t need to acquire a context just to get it or compare it; on the other, this I would have thought that .bdrv_open() runs in the BDS’s AioContext anyway (or the caller already has it acquired at least). Max
04.09.2020 15:17, Max Reitz wrote: > On 28.08.20 18:52, Andrey Shinkevich wrote: >> To limit the guest's COR operations by the base node in the backing >> chain during stream job, pass the base file name to the copy-on-read > > Does it have to be a filename? That sounds really bad to me. Agree, it should be node-name. Filename-based interfaces is a headache. > >> driver. The rest of the functionality will be implemented in the patch >> that follows. >> >> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> >> --- >> block/copy-on-read.c | 41 ++++++++++++++++++++++++++++++++++++++++- >> block/copy-on-read.h | 1 + >> 2 files changed, 41 insertions(+), 1 deletion(-) > > Furthermore, I believe that this option should become an externally > visible option for the copy-on-read filter (i.e., part of its > BlockdevOptions) – but that definitely won’t be viable if @base contains > a filename. > > Can’t we let the stream job invoke bdrv_find_backing_image() to > translate a filename into a node name that’s then passed to the COR filter? > >> diff --git a/block/copy-on-read.c b/block/copy-on-read.c >> index 0ede7aa..1f858bb 100644 >> --- a/block/copy-on-read.c >> +++ b/block/copy-on-read.c >> @@ -24,19 +24,45 @@ >> #include "block/block_int.h" >> #include "qemu/module.h" >> #include "qapi/error.h" >> +#include "qapi/qmp/qerror.h" >> #include "qapi/qmp/qdict.h" >> #include "block/copy-on-read.h" >> >> >> typedef struct BDRVStateCOR { >> bool active; >> + BlockDriverState *base_bs; >> } BDRVStateCOR; >> >> +/* >> + * Non-zero pointers are the caller's responsibility. >> + */ >> +static BlockDriverState *get_base_by_name(BlockDriverState *bs, >> + const char *base_name, Error **errp) >> +{ >> + BlockDriverState *base_bs = NULL; >> + AioContext *aio_context; >> + >> + base_bs = bdrv_find_backing_image(bs, base_name); >> + if (base_bs == NULL) { >> + error_setg(errp, QERR_BASE_NOT_FOUND, base_name); >> + return NULL; >> + } >> + >> + aio_context = bdrv_get_aio_context(bs); >> + aio_context_acquire(aio_context); >> + assert(bdrv_get_aio_context(base_bs) == aio_context); >> + aio_context_release(aio_context); > > Er. OK. But why? Isn’t this just guaranteed by the block layer? I > don’t think we need an explicit assertion for this, especially if it > means having to acquire an AioContext. > > Furthermore, I don’t even know why we’d need the AioContext. On one > hand, we don’t need to acquire a context just to get it or compare it; > on the other, this I would have thought that .bdrv_open() runs in the > BDS’s AioContext anyway (or the caller already has it acquired at least). > > Max >
diff --git a/block/copy-on-read.c b/block/copy-on-read.c index 0ede7aa..1f858bb 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -24,19 +24,45 @@ #include "block/block_int.h" #include "qemu/module.h" #include "qapi/error.h" +#include "qapi/qmp/qerror.h" #include "qapi/qmp/qdict.h" #include "block/copy-on-read.h" typedef struct BDRVStateCOR { bool active; + BlockDriverState *base_bs; } BDRVStateCOR; +/* + * Non-zero pointers are the caller's responsibility. + */ +static BlockDriverState *get_base_by_name(BlockDriverState *bs, + const char *base_name, Error **errp) +{ + BlockDriverState *base_bs = NULL; + AioContext *aio_context; + + base_bs = bdrv_find_backing_image(bs, base_name); + if (base_bs == NULL) { + error_setg(errp, QERR_BASE_NOT_FOUND, base_name); + return NULL; + } + + aio_context = bdrv_get_aio_context(bs); + aio_context_acquire(aio_context); + assert(bdrv_get_aio_context(base_bs) == aio_context); + aio_context_release(aio_context); + + return base_bs; +} static int cor_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { + BlockDriverState *base_bs = NULL; BDRVStateCOR *state = bs->opaque; + const char *base_name = qdict_get_try_str(options, "base"); bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds, BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, @@ -52,7 +78,15 @@ 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 (base_name) { + qdict_del(options, "base"); + base_bs = get_base_by_name(bs, base_name, errp); + if (!base_bs) { + return -EINVAL; + } + } state->active = true; + state->base_bs = base_bs; /* * We don't need to call bdrv_child_refresh_perms() now as the permissions @@ -190,6 +224,7 @@ static void bdrv_copy_on_read_init(void) static BlockDriverState *create_filter_node(BlockDriverState *bs, + const char *base_name, const char *filter_node_name, Error **errp) { @@ -197,6 +232,9 @@ static BlockDriverState *create_filter_node(BlockDriverState *bs, qdict_put_str(opts, "driver", "copy-on-read"); qdict_put_str(opts, "file", bdrv_get_node_name(bs)); + if (base_name) { + qdict_put_str(opts, "base", base_name); + } if (filter_node_name) { qdict_put_str(opts, "node-name", filter_node_name); } @@ -206,13 +244,14 @@ static BlockDriverState *create_filter_node(BlockDriverState *bs, BlockDriverState *bdrv_cor_filter_append(BlockDriverState *bs, + const char *base_name, const char *filter_node_name, Error **errp) { BlockDriverState *cor_filter_bs; Error *local_err = NULL; - cor_filter_bs = create_filter_node(bs, filter_node_name, errp); + cor_filter_bs = create_filter_node(bs, base_name, filter_node_name, errp); if (cor_filter_bs == NULL) { error_prepend(errp, "Could not create filter node: "); return NULL; diff --git a/block/copy-on-read.h b/block/copy-on-read.h index 1686e4e..6a7c8bb 100644 --- a/block/copy-on-read.h +++ b/block/copy-on-read.h @@ -28,6 +28,7 @@ #include "block/block_int.h" BlockDriverState *bdrv_cor_filter_append(BlockDriverState *bs, + const char *base_name, const char *filter_node_name, Error **errp); void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs);
To limit the guest's COR operations by the base node in the backing chain during stream job, pass the base file name to the copy-on-read driver. The rest of the functionality will be implemented in the patch that follows. Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> --- block/copy-on-read.c | 41 ++++++++++++++++++++++++++++++++++++++++- block/copy-on-read.h | 1 + 2 files changed, 41 insertions(+), 1 deletion(-)