| Message ID | 20170922093926.9723-3-pbutsykin@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/22/2017 05:39 AM, Pavel Butsykin wrote: > Now after shrinking the image, at the end of the image file, there might be a > tail that probably will never be used. So we can find the last used cluster and > cut the tail. > > Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> Reviewed-by: John Snow <jsnow@redhat.com>
On 2017-09-22 11:39, Pavel Butsykin wrote: > Now after shrinking the image, at the end of the image file, there might be a > tail that probably will never be used. So we can find the last used cluster and > cut the tail. > > Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> > --- > block/qcow2-refcount.c | 22 ++++++++++++++++++++++ > block/qcow2.c | 23 +++++++++++++++++++++++ > block/qcow2.h | 1 + > 3 files changed, 46 insertions(+) > > diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c > index 88d5a3f1ad..aa3fd6cf17 100644 > --- a/block/qcow2-refcount.c > +++ b/block/qcow2-refcount.c > @@ -3181,3 +3181,25 @@ out: > g_free(reftable_tmp); > return ret; > } > + > +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size) > +{ > + BDRVQcow2State *s = bs->opaque; > + int64_t i; > + > + for (i = size_to_clusters(s, size) - 1; i >= 0; i--) { > + uint64_t refcount; > + int ret = qcow2_get_refcount(bs, i, &refcount); > + if (ret < 0) { > + fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", > + i, strerror(-ret)); > + return ret; > + } > + if (refcount > 0) { > + return i; > + } > + } > + qcow2_signal_corruption(bs, true, -1, -1, > + "There are no references in the refcount table."); > + return -EIO; > +} > diff --git a/block/qcow2.c b/block/qcow2.c > index 8a4311d338..8dfb5393a7 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, > new_l1_size = size_to_l1(s, offset); > > if (offset < old_length) { > + int64_t last_cluster, old_file_size; > if (prealloc != PREALLOC_MODE_OFF) { > error_setg(errp, > "Preallocation can't be used for shrinking an image"); > @@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, > "Failed to discard unused refblocks"); > return ret; > } > + > + old_file_size = bdrv_getlength(bs->file->bs); > + if (old_file_size < 0) { > + error_setg_errno(errp, -old_file_size, > + "Failed to inquire current file length"); > + return old_file_size; > + } > + last_cluster = qcow2_get_last_cluster(bs, old_file_size); > + if (last_cluster < 0) { > + error_setg_errno(errp, -last_cluster, > + "Failed to find the last cluster"); > + return last_cluster; > + } My idea was rather that you just wouldn't truncate the image file if something fails here. So in any of these new cases where you currently just report the whole truncate operation as having failed, you could just emit a warning and not do the truncation of bs->file. I can live with the current version, though, so: Reviewed-by: Max Reitz <mreitz@redhat.com> But I'll wait for a response from you before merging this series. Max > + if ((last_cluster + 1) * s->cluster_size < old_file_size) { > + ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size, > + PREALLOC_MODE_OFF, NULL); > + if (ret < 0) { > + error_setg_errno(errp, -ret, > + "Failed to truncate the tail of the image"); > + return ret; > + } > + } > } else { > ret = qcow2_grow_l1_table(bs, new_l1_size, true); > if (ret < 0) { > diff --git a/block/qcow2.h b/block/qcow2.h > index 5a289a81e2..782a206ecb 100644 > --- a/block/qcow2.h > +++ b/block/qcow2.h > @@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order, > BlockDriverAmendStatusCB *status_cb, > void *cb_opaque, Error **errp); > int qcow2_shrink_reftable(BlockDriverState *bs); > +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size); > > /* qcow2-cluster.c functions */ > int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, >
On 27.09.2017 19:00, Max Reitz wrote: > On 2017-09-22 11:39, Pavel Butsykin wrote: >> Now after shrinking the image, at the end of the image file, there might be a >> tail that probably will never be used. So we can find the last used cluster and >> cut the tail. >> >> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> >> --- >> block/qcow2-refcount.c | 22 ++++++++++++++++++++++ >> block/qcow2.c | 23 +++++++++++++++++++++++ >> block/qcow2.h | 1 + >> 3 files changed, 46 insertions(+) >> >> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >> index 88d5a3f1ad..aa3fd6cf17 100644 >> --- a/block/qcow2-refcount.c >> +++ b/block/qcow2-refcount.c >> @@ -3181,3 +3181,25 @@ out: >> g_free(reftable_tmp); >> return ret; >> } >> + >> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size) >> +{ >> + BDRVQcow2State *s = bs->opaque; >> + int64_t i; >> + >> + for (i = size_to_clusters(s, size) - 1; i >= 0; i--) { >> + uint64_t refcount; >> + int ret = qcow2_get_refcount(bs, i, &refcount); >> + if (ret < 0) { >> + fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", >> + i, strerror(-ret)); >> + return ret; >> + } >> + if (refcount > 0) { >> + return i; >> + } >> + } >> + qcow2_signal_corruption(bs, true, -1, -1, >> + "There are no references in the refcount table."); >> + return -EIO; >> +} >> diff --git a/block/qcow2.c b/block/qcow2.c >> index 8a4311d338..8dfb5393a7 100644 >> --- a/block/qcow2.c >> +++ b/block/qcow2.c >> @@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, >> new_l1_size = size_to_l1(s, offset); >> >> if (offset < old_length) { >> + int64_t last_cluster, old_file_size; >> if (prealloc != PREALLOC_MODE_OFF) { >> error_setg(errp, >> "Preallocation can't be used for shrinking an image"); >> @@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, >> "Failed to discard unused refblocks"); >> return ret; >> } >> + >> + old_file_size = bdrv_getlength(bs->file->bs); >> + if (old_file_size < 0) { >> + error_setg_errno(errp, -old_file_size, >> + "Failed to inquire current file length"); >> + return old_file_size; >> + } >> + last_cluster = qcow2_get_last_cluster(bs, old_file_size); >> + if (last_cluster < 0) { >> + error_setg_errno(errp, -last_cluster, >> + "Failed to find the last cluster"); >> + return last_cluster; >> + } > > My idea was rather that you just wouldn't truncate the image file if > something fails here. So in any of these new cases where you currently > just report the whole truncate operation as having failed, you could > just emit a warning and not do the truncation of bs->file. I'm not sure that's right. If the qcow2_get_last_cluster() returned an error, probably with the image was a problem.. can we continue to work with the image without risking to damage it even more? if something bad happened with the reftable we usually mark the image as corrupted, it's the same thing. Although if the shrink is almost complete, the truncation of bs->file isn't so important thing and we could update qcow2 header. > I can live with the current version, though, so: > > Reviewed-by: Max Reitz <mreitz@redhat.com> > > But I'll wait for a response from you before merging this series. > > Max > >> + if ((last_cluster + 1) * s->cluster_size < old_file_size) { >> + ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size, >> + PREALLOC_MODE_OFF, NULL); >> + if (ret < 0) { >> + error_setg_errno(errp, -ret, >> + "Failed to truncate the tail of the image"); >> + return ret; >> + } >> + } >> } else { >> ret = qcow2_grow_l1_table(bs, new_l1_size, true); >> if (ret < 0) { >> diff --git a/block/qcow2.h b/block/qcow2.h >> index 5a289a81e2..782a206ecb 100644 >> --- a/block/qcow2.h >> +++ b/block/qcow2.h >> @@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order, >> BlockDriverAmendStatusCB *status_cb, >> void *cb_opaque, Error **errp); >> int qcow2_shrink_reftable(BlockDriverState *bs); >> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size); >> >> /* qcow2-cluster.c functions */ >> int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, >> > >
On 2017-09-27 18:27, Pavel Butsykin wrote: > On 27.09.2017 19:00, Max Reitz wrote: >> On 2017-09-22 11:39, Pavel Butsykin wrote: >>> Now after shrinking the image, at the end of the image file, there >>> might be a >>> tail that probably will never be used. So we can find the last used >>> cluster and >>> cut the tail. >>> >>> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> >>> --- >>> block/qcow2-refcount.c | 22 ++++++++++++++++++++++ >>> block/qcow2.c | 23 +++++++++++++++++++++++ >>> block/qcow2.h | 1 + >>> 3 files changed, 46 insertions(+) >>> >>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >>> index 88d5a3f1ad..aa3fd6cf17 100644 >>> --- a/block/qcow2-refcount.c >>> +++ b/block/qcow2-refcount.c >>> @@ -3181,3 +3181,25 @@ out: >>> g_free(reftable_tmp); >>> return ret; >>> } >>> + >>> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size) >>> +{ >>> + BDRVQcow2State *s = bs->opaque; >>> + int64_t i; >>> + >>> + for (i = size_to_clusters(s, size) - 1; i >= 0; i--) { >>> + uint64_t refcount; >>> + int ret = qcow2_get_refcount(bs, i, &refcount); >>> + if (ret < 0) { >>> + fprintf(stderr, "Can't get refcount for cluster %" >>> PRId64 ": %s\n", >>> + i, strerror(-ret)); >>> + return ret; >>> + } >>> + if (refcount > 0) { >>> + return i; >>> + } >>> + } >>> + qcow2_signal_corruption(bs, true, -1, -1, >>> + "There are no references in the refcount >>> table."); >>> + return -EIO; >>> +} >>> diff --git a/block/qcow2.c b/block/qcow2.c >>> index 8a4311d338..8dfb5393a7 100644 >>> --- a/block/qcow2.c >>> +++ b/block/qcow2.c >>> @@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, >>> int64_t offset, >>> new_l1_size = size_to_l1(s, offset); >>> if (offset < old_length) { >>> + int64_t last_cluster, old_file_size; >>> if (prealloc != PREALLOC_MODE_OFF) { >>> error_setg(errp, >>> "Preallocation can't be used for shrinking >>> an image"); >>> @@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState >>> *bs, int64_t offset, >>> "Failed to discard unused refblocks"); >>> return ret; >>> } >>> + >>> + old_file_size = bdrv_getlength(bs->file->bs); >>> + if (old_file_size < 0) { >>> + error_setg_errno(errp, -old_file_size, >>> + "Failed to inquire current file length"); >>> + return old_file_size; >>> + } >>> + last_cluster = qcow2_get_last_cluster(bs, old_file_size); >>> + if (last_cluster < 0) { >>> + error_setg_errno(errp, -last_cluster, >>> + "Failed to find the last cluster"); >>> + return last_cluster; >>> + } >> >> My idea was rather that you just wouldn't truncate the image file if >> something fails here. So in any of these new cases where you currently >> just report the whole truncate operation as having failed, you could >> just emit a warning and not do the truncation of bs->file. > > I'm not sure that's right. If the qcow2_get_last_cluster() returned an > error, probably with the image was a problem.. can we continue to work > with the image without risking to damage it even more? if something bad > happened with the reftable we usually mark the image as corrupted, it's > the same thing. Well, the only thing that's left to do is to write the new size into the image header, so I think that should work just fine... I won't disagree that bdrv_getlength() or qcow2_get_last_cluster() failing may be reasons to stop truncation (although I don't think they necessarily are at this point). But I could well imagine that the below bdrv_truncate() of bs->file fails for benign reasons, e.g. because the underlying protocol does not support shrinking of images or something. Then we probably should carry on. Max > Although if the shrink is almost complete, the truncation of bs->file > isn't so important thing and we could update qcow2 header. > >> I can live with the current version, though, so: >> >> Reviewed-by: Max Reitz <mreitz@redhat.com> >> >> But I'll wait for a response from you before merging this series. >> >> Max >> >>> + if ((last_cluster + 1) * s->cluster_size < old_file_size) { >>> + ret = bdrv_truncate(bs->file, (last_cluster + 1) * >>> s->cluster_size, >>> + PREALLOC_MODE_OFF, NULL); >>> + if (ret < 0) { >>> + error_setg_errno(errp, -ret, >>> + "Failed to truncate the tail of the >>> image"); >>> + return ret; >>> + } >>> + } >>> } else { >>> ret = qcow2_grow_l1_table(bs, new_l1_size, true); >>> if (ret < 0) { >>> diff --git a/block/qcow2.h b/block/qcow2.h >>> index 5a289a81e2..782a206ecb 100644 >>> --- a/block/qcow2.h >>> +++ b/block/qcow2.h >>> @@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState >>> *bs, int refcount_order, >>> BlockDriverAmendStatusCB *status_cb, >>> void *cb_opaque, Error **errp); >>> int qcow2_shrink_reftable(BlockDriverState *bs); >>> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size); >>> /* qcow2-cluster.c functions */ >>> int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, >>> >> >>
On 27.09.2017 19:36, Max Reitz wrote: > On 2017-09-27 18:27, Pavel Butsykin wrote: >> On 27.09.2017 19:00, Max Reitz wrote: >>> On 2017-09-22 11:39, Pavel Butsykin wrote: >>>> Now after shrinking the image, at the end of the image file, there >>>> might be a >>>> tail that probably will never be used. So we can find the last used >>>> cluster and >>>> cut the tail. >>>> >>>> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> >>>> --- >>>> block/qcow2-refcount.c | 22 ++++++++++++++++++++++ >>>> block/qcow2.c | 23 +++++++++++++++++++++++ >>>> block/qcow2.h | 1 + >>>> 3 files changed, 46 insertions(+) >>>> >>>> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c >>>> index 88d5a3f1ad..aa3fd6cf17 100644 >>>> --- a/block/qcow2-refcount.c >>>> +++ b/block/qcow2-refcount.c >>>> @@ -3181,3 +3181,25 @@ out: >>>> g_free(reftable_tmp); >>>> return ret; >>>> } >>>> + >>>> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size) >>>> +{ >>>> + BDRVQcow2State *s = bs->opaque; >>>> + int64_t i; >>>> + >>>> + for (i = size_to_clusters(s, size) - 1; i >= 0; i--) { >>>> + uint64_t refcount; >>>> + int ret = qcow2_get_refcount(bs, i, &refcount); >>>> + if (ret < 0) { >>>> + fprintf(stderr, "Can't get refcount for cluster %" >>>> PRId64 ": %s\n", >>>> + i, strerror(-ret)); >>>> + return ret; >>>> + } >>>> + if (refcount > 0) { >>>> + return i; >>>> + } >>>> + } >>>> + qcow2_signal_corruption(bs, true, -1, -1, >>>> + "There are no references in the refcount >>>> table."); >>>> + return -EIO; >>>> +} >>>> diff --git a/block/qcow2.c b/block/qcow2.c >>>> index 8a4311d338..8dfb5393a7 100644 >>>> --- a/block/qcow2.c >>>> +++ b/block/qcow2.c >>>> @@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, >>>> int64_t offset, >>>> new_l1_size = size_to_l1(s, offset); >>>> if (offset < old_length) { >>>> + int64_t last_cluster, old_file_size; >>>> if (prealloc != PREALLOC_MODE_OFF) { >>>> error_setg(errp, >>>> "Preallocation can't be used for shrinking >>>> an image"); >>>> @@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState >>>> *bs, int64_t offset, >>>> "Failed to discard unused refblocks"); >>>> return ret; >>>> } >>>> + >>>> + old_file_size = bdrv_getlength(bs->file->bs); >>>> + if (old_file_size < 0) { >>>> + error_setg_errno(errp, -old_file_size, >>>> + "Failed to inquire current file length"); >>>> + return old_file_size; >>>> + } >>>> + last_cluster = qcow2_get_last_cluster(bs, old_file_size); >>>> + if (last_cluster < 0) { >>>> + error_setg_errno(errp, -last_cluster, >>>> + "Failed to find the last cluster"); >>>> + return last_cluster; >>>> + } >>> >>> My idea was rather that you just wouldn't truncate the image file if >>> something fails here. So in any of these new cases where you currently >>> just report the whole truncate operation as having failed, you could >>> just emit a warning and not do the truncation of bs->file. >> >> I'm not sure that's right. If the qcow2_get_last_cluster() returned an >> error, probably with the image was a problem.. can we continue to work >> with the image without risking to damage it even more? if something bad >> happened with the reftable we usually mark the image as corrupted, it's >> the same thing. > > Well, the only thing that's left to do is to write the new size into the > image header, so I think that should work just fine... Yes, but what difference will update the size in the header or not, if the reftable was corrupted. A much more important point here is that the qcow2_truncate() should return an error and the caller must stop the work. > I won't disagree that bdrv_getlength() or qcow2_get_last_cluster() > failing may be reasons to stop truncation (although I don't think they > necessarily are at this point). > > But I could well imagine that the below bdrv_truncate() of bs->file > fails for benign reasons, e.g. because the underlying protocol does not > support shrinking of images or something. Then we probably should carry on. Yes, I agree here. If the bdrv_truncate() of bs->file failed, we can print just a warning :) So, I'll send new version of the patch with this change. > Max > >> Although if the shrink is almost complete, the truncation of bs->file >> isn't so important thing and we could update qcow2 header. >> >>> I can live with the current version, though, so: >>> >>> Reviewed-by: Max Reitz <mreitz@redhat.com> >>> >>> But I'll wait for a response from you before merging this series. >>> >>> Max >>> >>>> + if ((last_cluster + 1) * s->cluster_size < old_file_size) { >>>> + ret = bdrv_truncate(bs->file, (last_cluster + 1) * >>>> s->cluster_size, >>>> + PREALLOC_MODE_OFF, NULL); >>>> + if (ret < 0) { >>>> + error_setg_errno(errp, -ret, >>>> + "Failed to truncate the tail of the >>>> image"); >>>> + return ret; >>>> + } >>>> + } >>>> } else { >>>> ret = qcow2_grow_l1_table(bs, new_l1_size, true); >>>> if (ret < 0) { >>>> diff --git a/block/qcow2.h b/block/qcow2.h >>>> index 5a289a81e2..782a206ecb 100644 >>>> --- a/block/qcow2.h >>>> +++ b/block/qcow2.h >>>> @@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState >>>> *bs, int refcount_order, >>>> BlockDriverAmendStatusCB *status_cb, >>>> void *cb_opaque, Error **errp); >>>> int qcow2_shrink_reftable(BlockDriverState *bs); >>>> +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size); >>>> /* qcow2-cluster.c functions */ >>>> int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, >>>> >>> >>> > >
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 88d5a3f1ad..aa3fd6cf17 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -3181,3 +3181,25 @@ out: g_free(reftable_tmp); return ret; } + +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size) +{ + BDRVQcow2State *s = bs->opaque; + int64_t i; + + for (i = size_to_clusters(s, size) - 1; i >= 0; i--) { + uint64_t refcount; + int ret = qcow2_get_refcount(bs, i, &refcount); + if (ret < 0) { + fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n", + i, strerror(-ret)); + return ret; + } + if (refcount > 0) { + return i; + } + } + qcow2_signal_corruption(bs, true, -1, -1, + "There are no references in the refcount table."); + return -EIO; +} diff --git a/block/qcow2.c b/block/qcow2.c index 8a4311d338..8dfb5393a7 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -3106,6 +3106,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, new_l1_size = size_to_l1(s, offset); if (offset < old_length) { + int64_t last_cluster, old_file_size; if (prealloc != PREALLOC_MODE_OFF) { error_setg(errp, "Preallocation can't be used for shrinking an image"); @@ -3134,6 +3135,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, "Failed to discard unused refblocks"); return ret; } + + old_file_size = bdrv_getlength(bs->file->bs); + if (old_file_size < 0) { + error_setg_errno(errp, -old_file_size, + "Failed to inquire current file length"); + return old_file_size; + } + last_cluster = qcow2_get_last_cluster(bs, old_file_size); + if (last_cluster < 0) { + error_setg_errno(errp, -last_cluster, + "Failed to find the last cluster"); + return last_cluster; + } + if ((last_cluster + 1) * s->cluster_size < old_file_size) { + ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size, + PREALLOC_MODE_OFF, NULL); + if (ret < 0) { + error_setg_errno(errp, -ret, + "Failed to truncate the tail of the image"); + return ret; + } + } } else { ret = qcow2_grow_l1_table(bs, new_l1_size, true); if (ret < 0) { diff --git a/block/qcow2.h b/block/qcow2.h index 5a289a81e2..782a206ecb 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order, BlockDriverAmendStatusCB *status_cb, void *cb_opaque, Error **errp); int qcow2_shrink_reftable(BlockDriverState *bs); +int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size); /* qcow2-cluster.c functions */ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
Now after shrinking the image, at the end of the image file, there might be a tail that probably will never be used. So we can find the last used cluster and cut the tail. Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> --- block/qcow2-refcount.c | 22 ++++++++++++++++++++++ block/qcow2.c | 23 +++++++++++++++++++++++ block/qcow2.h | 1 + 3 files changed, 46 insertions(+)