From nobody Mon Feb 9 23:40:32 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1543568457611470.1774045750668; Fri, 30 Nov 2018 01:00:57 -0800 (PST) Received: from localhost ([::1]:58810 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSefQ-0006dQ-81 for importer@patchew.org; Fri, 30 Nov 2018 04:00:56 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55173) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSeaJ-0001dS-Rk for qemu-devel@nongnu.org; Fri, 30 Nov 2018 03:55:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gSeaE-0000Tq-Qy for qemu-devel@nongnu.org; Fri, 30 Nov 2018 03:55:38 -0500 Received: from relay.sw.ru ([185.231.240.75]:41910) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gSeaE-0000RW-5U; Fri, 30 Nov 2018 03:55:34 -0500 Received: from [172.16.25.136] (helo=localhost.sw.ru) by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1gSea7-0004HZ-B4; Fri, 30 Nov 2018 11:55:27 +0300 From: Andrey Shinkevich To: qemu-devel@nongnu.org, qemu-block@nongnu.org Date: Fri, 30 Nov 2018 11:55:22 +0300 Message-Id: <1543568126-727235-2-git-send-email-andrey.shinkevich@virtuozzo.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1543568126-727235-1-git-send-email-andrey.shinkevich@virtuozzo.com> References: <1543568126-727235-1-git-send-email-andrey.shinkevich@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v4 1/5] Discard blocks while copy-on-read X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, armbru@redhat.com, mreitz@redhat.com, andrey.shinkevich@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Discards the block duplicated in an intermediate backing file after the block have been copied into the active layer during QMP block-stream operation. It saves the disk space while merging external snapshots. Signed-off-by: Andrey Shinkevich --- block/stream.c | 428 +++++++++++++++++++++++++++++++++++++++++++++++++++++= ++-- 1 file changed, 413 insertions(+), 15 deletions(-) diff --git a/block/stream.c b/block/stream.c index 81a7ec8..9e85954 100644 --- a/block/stream.c +++ b/block/stream.c @@ -12,6 +12,7 @@ */ =20 #include "qemu/osdep.h" +#include "qemu/cutils.h" #include "trace.h" #include "block/block_int.h" #include "block/blockjob_int.h" @@ -35,9 +36,62 @@ typedef struct StreamBlockJob { BlockdevOnError on_error; char *backing_file_str; int bs_flags; + bool discard; + BlockDriverState *stream_top_bs; + GSList *im_nodes; } StreamBlockJob; =20 -static int coroutine_fn stream_populate(BlockBackend *blk, +typedef struct IntermediateNode { + BlockBackend *blk; + int flags; +} IntermediateNode; + +static inline void restore_all_im_nodes(StreamBlockJob *s) +{ + GSList *l; + BlockDriverState *bs_active; + BlockDriverState *bs_im; + IntermediateNode *im_node; + BlockReopenQueue *queue =3D NULL; + Error *local_err =3D NULL; + + assert(s->stream_top_bs && s->stream_top_bs->backing && + s->stream_top_bs->backing->bs); + bs_active =3D backing_bs(s->stream_top_bs); + assert(backing_bs(bs_active)); + + bdrv_subtree_drained_begin(backing_bs(bs_active)); + + for (l =3D s->im_nodes; l; l =3D l->next) { + im_node =3D l->data; + if (im_node->blk) { + bs_im =3D blk_bs(im_node->blk); + + if (im_node->flags !=3D bdrv_get_flags(bs_im) && bs_im) { + queue =3D bdrv_reopen_queue(queue, bs_im, NULL, im_node->f= lags); + } + /* Give up write permissions before making it read-only */ + blk_set_perm(im_node->blk, 0, BLK_PERM_ALL, &error_abort); + blk_unref(im_node->blk); + bdrv_unref(bs_im); + } + g_free(im_node); + } + g_slist_free(s->im_nodes); + s->im_nodes =3D NULL; + + if (queue) { + bdrv_reopen_multiple(bdrv_get_aio_context(bs_active), queue, + &local_err); + if (local_err !=3D NULL) { + error_report_err(local_err); + } + } + + bdrv_subtree_drained_end(backing_bs(bs_active)); +} + +static int coroutine_fn stream_populate(const StreamBlockJob *s, int64_t offset, uint64_t bytes, void *buf) { @@ -46,19 +100,33 @@ static int coroutine_fn stream_populate(BlockBackend *= blk, .iov_len =3D bytes, }; QEMUIOVector qiov; + GSList *l; + IntermediateNode *im_node; + int ret; =20 + assert(s); assert(bytes < SIZE_MAX); qemu_iovec_init_external(&qiov, &iov, 1); =20 /* Copy-on-read the unallocated clusters */ - return blk_co_preadv(blk, offset, qiov.size, &qiov, BDRV_REQ_COPY_ON_R= EAD); + ret =3D blk_co_preadv(s->common.blk, offset, qiov.size, &qiov, + BDRV_REQ_COPY_ON_READ); + + if (ret < 0 || !s->discard) { + return ret; + } + + for (l =3D s->im_nodes; l; l =3D l->next) { + im_node =3D l->data; + blk_co_pdiscard(im_node->blk, offset, bytes); + } + + return ret; } =20 -static int stream_prepare(Job *job) +static int stream_change_backing_file(StreamBlockJob *s, + BlockDriverState *bs) { - StreamBlockJob *s =3D container_of(job, StreamBlockJob, common.job); - BlockJob *bjob =3D &s->common; - BlockDriverState *bs =3D blk_bs(bjob->blk); BlockDriverState *base =3D s->base; Error *local_err =3D NULL; int ret =3D 0; @@ -82,6 +150,68 @@ static int stream_prepare(Job *job) return ret; } =20 +static int stream_exit_discard(StreamBlockJob *s, bool abort) +{ + BlockJob *bjob =3D &s->common; + BlockDriverState *bs_active =3D backing_bs(s->stream_top_bs); + int ret =3D 0; + + /* Make sure that the BDS doesn't go away during bdrv_replace_node, + * before we can call bdrv_drained_end */ + bdrv_ref(s->stream_top_bs); + /* Reopen intermediate images back in read-only mode */ + restore_all_im_nodes(s); + /* Hold a guest back from writing until we remove the filter */ + bdrv_drained_begin(bs_active); + /* Dropping WRITE is required before changing the backing file. */ + bdrv_child_try_set_perm(s->stream_top_bs->backing, 0, BLK_PERM_ALL, + &error_abort); + if (abort =3D=3D false) { + ret =3D stream_change_backing_file(s, bs_active); + } + /* Remove the filter driver from the graph. Before this, get rid of + * the blockers on the intermediate nodes so that the resulting state = is + * valid. Also give up permissions on stream_top_bs->backing, which mi= ght + * block the removal. */ + block_job_remove_all_bdrv(bjob); + bdrv_child_try_set_perm(s->stream_top_bs->backing, 0, BLK_PERM_ALL, + &error_abort); + bdrv_replace_node(s->stream_top_bs, bs_active, &error_abort); + /* We just changed the BDS the job BB refers to (with either or both o= f the + * bdrv_replace_node() calls), so switch the BB back so the cleanup do= es + * the right thing. We don't need any permissions any more now. */ + blk_remove_bs(bjob->blk); + blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort); + blk_insert_bs(bjob->blk, s->stream_top_bs, &error_abort); + + bdrv_drained_end(bs_active); + bdrv_unref(s->stream_top_bs); + + return ret; +} + +static int stream_prepare(Job *job) +{ + StreamBlockJob *s =3D container_of(job, StreamBlockJob, common.job); + BlockJob *bjob =3D &s->common; + BlockDriverState *bs =3D blk_bs(bjob->blk); + + if (s->discard) { + return stream_exit_discard(s, false); + } + + return stream_change_backing_file(s, bs); +} + +static void stream_abort(Job *job) +{ + StreamBlockJob *s =3D container_of(job, StreamBlockJob, common.job); + + if (s->discard) { + stream_exit_discard(s, job->ret < 0); + } +} + static void stream_clean(Job *job) { StreamBlockJob *s =3D container_of(job, StreamBlockJob, common.job); @@ -102,7 +232,7 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) { StreamBlockJob *s =3D container_of(job, StreamBlockJob, common.job); BlockBackend *blk =3D s->common.blk; - BlockDriverState *bs =3D blk_bs(blk); + BlockDriverState *bs; BlockDriverState *base =3D s->base; int64_t len; int64_t offset =3D 0; @@ -112,6 +242,12 @@ static int coroutine_fn stream_run(Job *job, Error **e= rrp) int64_t n =3D 0; /* bytes */ void *buf; =20 + if (s->discard) { + bs =3D backing_bs(s->stream_top_bs); + } else { + bs =3D blk_bs(blk); + } + if (!bs->backing) { goto out; } @@ -165,7 +301,7 @@ static int coroutine_fn stream_run(Job *job, Error **er= rp) } trace_stream_one_iteration(s, offset, n, ret); if (copy) { - ret =3D stream_populate(blk, offset, n, buf); + ret =3D stream_populate(s, offset, n, buf); } if (ret < 0) { BlockErrorAction action =3D @@ -206,6 +342,232 @@ out: return ret; } =20 +static int coroutine_fn bdrv_stream_top_preadv(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) +{ + return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags); +} + +static int coroutine_fn bdrv_stream_top_pwritev(BlockDriverState *bs, + uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) +{ + /* TODO: A temporary hack to pass the QEMU test suite and + * to allow writing through a backing child of the filter as + * the WRITE operation is delegated to blk_co_preadv() via + * job BlockBackend in stream_populate(). + * bs->backing->perm |=3D BLK_PERM_WRITE; */ + + return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags); +} + +static int coroutine_fn bdrv_stream_top_flush(BlockDriverState *bs) +{ + if (bs->backing =3D=3D NULL) { + /* we can be here after failed bdrv_append in stream_start */ + return 0; + } + return bdrv_co_flush(bs->backing->bs); +} + +static int coroutine_fn bdrv_stream_top_pwrite_zeroes(BlockDriverState *bs, + int64_t offset, int bytes, BdrvRequestFlags flags) +{ + return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags); +} + +static int coroutine_fn bdrv_stream_top_pdiscard(BlockDriverState *bs, + int64_t offset, int bytes) +{ + return bdrv_co_pdiscard(bs->backing, offset, bytes); +} + +static int bdrv_stream_top_get_info(BlockDriverState *bs, BlockDriverInfo = *bdi) +{ + return bdrv_get_info(bs->backing->bs, bdi); +} + +static void bdrv_stream_top_refresh_filename(BlockDriverState *bs, QDict *= opts) +{ + if (bs->backing =3D=3D NULL) { + /* we can be here after failed bdrv_attach_child in + * bdrv_set_backing_hd */ + return; + } + bdrv_refresh_filename(bs->backing->bs); + pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), + bs->backing->bs->filename); +} + +static void bdrv_stream_top_child_perm(BlockDriverState *bs, BdrvChild *c, + const BdrvChildRole *role, + BlockReopenQueue *reopen_queue, + uint64_t perm, uint64_t shared, + uint64_t *nperm, uint64_t *nshared) +{ + /* Must be able to forward guest writes to the real image */ + *nperm =3D 0; + if (perm & BLK_PERM_WRITE) { + *nperm |=3D BLK_PERM_WRITE; + } + + *nshared =3D BLK_PERM_ALL; +} + +/* Dummy node that provides consistent read to its users without requiring= it + * from its backing file and that allows writes on the backing file chain.= */ +static BlockDriver bdrv_stream_top =3D { + .format_name =3D "stream_top", + .bdrv_co_preadv =3D bdrv_stream_top_preadv, + .bdrv_co_pwritev =3D bdrv_stream_top_pwritev, + .bdrv_co_pwrite_zeroes =3D bdrv_stream_top_pwrite_zeroes, + .bdrv_co_pdiscard =3D bdrv_stream_top_pdiscard, + .bdrv_get_info =3D bdrv_stream_top_get_info, + .bdrv_co_flush =3D bdrv_stream_top_flush, + .bdrv_co_block_status =3D bdrv_co_block_status_from_backing, + .bdrv_refresh_filename =3D bdrv_stream_top_refresh_filename, + .bdrv_child_perm =3D bdrv_stream_top_child_perm, +}; + +static void remove_filter(BlockDriverState *stream_top_bs, + BlockDriverState *bs) { + bdrv_drained_begin(bs); + bdrv_child_try_set_perm(stream_top_bs->backing, 0, BLK_PERM_ALL, + &error_abort); + bdrv_replace_node(stream_top_bs, backing_bs(stream_top_bs), + &error_abort); + bdrv_drained_end(bs); + bdrv_unref(stream_top_bs); +} + +/* In the case of block discard, add a dummy driver + * to make the backing chain writable. */ +static BlockDriverState *insert_filter(BlockDriverState *bs, Error **errp) +{ + const char *filter_node_name =3D NULL; + BlockDriverState *stream_top_bs; + Error *local_err =3D NULL; + + stream_top_bs =3D bdrv_new_open_driver(&bdrv_stream_top, filter_node_n= ame, + BDRV_O_RDWR, errp); + if (stream_top_bs =3D=3D NULL) { + return NULL; + } + if (!filter_node_name) { + stream_top_bs->implicit =3D true; + } + + stream_top_bs->total_sectors =3D bs->total_sectors; + stream_top_bs->supported_write_flags =3D BDRV_REQ_WRITE_UNCHANGED; + stream_top_bs->supported_zero_flags =3D BDRV_REQ_WRITE_UNCHANGED; + bdrv_set_aio_context(stream_top_bs, bdrv_get_aio_context(bs)); + + /* bdrv_append takes ownership of the stream_top_bs reference, need to= keep + * it alive until block_job_create() succeeds even if bs has no parent= . */ + bdrv_ref(stream_top_bs); + bdrv_drained_begin(bs); + bdrv_append(stream_top_bs, bs, &local_err); + bdrv_drained_end(bs); + + if (local_err) { + bdrv_unref(stream_top_bs); + error_propagate(errp, local_err); + return NULL; + } + + if ((stream_top_bs->backing->perm & BLK_PERM_WRITE) =3D=3D 0) { + remove_filter(stream_top_bs, bs); + error_setg(errp, "There is no write permission."); + return NULL; + } + + return stream_top_bs; +} + +/* Makes intermediate block chain writable */ +static int init_intermediate_nodes(StreamBlockJob *s, + BlockDriverState *bs, + BlockDriverState *base, Error **errp) +{ + BlockDriverState *iter; + int backing_bs_flags; + IntermediateNode *im_node; + BlockBackend *blk; + BlockReopenQueue *queue =3D NULL; + Error *local_err =3D NULL; + int ret; + + /* Sanity check */ + if (!backing_bs(bs)) { + error_setg(errp, "Top BDS does not have a backing file."); + return -EINVAL; + } + if (base && !bdrv_chain_contains(bs, base)) { + error_setg(errp, "The backing chain does not contain the base file= ."); + return -EINVAL; + } + + /* Reopen intermediate images in read-write mode */ + bdrv_subtree_drained_begin(backing_bs(bs)); + + for (iter =3D backing_bs(bs); iter && iter !=3D base; iter =3D backing= _bs(iter)) { + /* Keep the intermediate backing chain with BDRV original flags */ + backing_bs_flags =3D bdrv_get_flags(iter); + im_node =3D g_new0(IntermediateNode, 1); + im_node->blk =3D NULL; + im_node->flags =3D backing_bs_flags; + bdrv_ref(iter); + s->im_nodes =3D g_slist_prepend(s->im_nodes, im_node); + + if ((backing_bs_flags & BDRV_O_RDWR) =3D=3D 0) { + queue =3D bdrv_reopen_queue(queue, iter, NULL, + backing_bs_flags | BDRV_O_RDWR); + } + } + + if (queue) { + ret =3D bdrv_reopen_multiple(bdrv_get_aio_context(bs), queue, &loc= al_err); + if (local_err !=3D NULL) { + error_propagate(errp, local_err); + bdrv_subtree_drained_end(backing_bs(bs)); + restore_all_im_nodes(s); + return -1; + } + } + + bdrv_subtree_drained_end(backing_bs(bs)); + + s->im_nodes =3D g_slist_reverse(s->im_nodes); + GSList *l =3D s->im_nodes; + + for (iter =3D backing_bs(bs); iter && iter !=3D base; iter =3D backing= _bs(iter)) { + blk =3D blk_new(BLK_PERM_WRITE, BLK_PERM_CONSISTENT_READ | + BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED | + BLK_PERM_GRAPH_MOD); + if (!blk) { + error_setg(errp, + "Block Stream: failed to create new Block Backend."= ); + goto fail; + } + + ret =3D blk_insert_bs(blk, iter, errp); + if (ret < 0) { + goto fail; + } + + assert(l); + im_node =3D l->data; + im_node->blk =3D blk; + l =3D l->next; + } + + return 0; + +fail: + restore_all_im_nodes(s); + + return -1; +} + static const BlockJobDriver stream_job_driver =3D { .job_driver =3D { .instance_size =3D sizeof(StreamBlockJob), @@ -213,6 +575,7 @@ static const BlockJobDriver stream_job_driver =3D { .free =3D block_job_free, .run =3D stream_run, .prepare =3D stream_prepare, + .abort =3D stream_abort, .clean =3D stream_clean, .user_resume =3D block_job_user_resume, .drain =3D block_job_drain, @@ -224,9 +587,13 @@ void stream_start(const char *job_id, BlockDriverState= *bs, int creation_flags, int64_t speed, BlockdevOnError on_error, Error **errp) { - StreamBlockJob *s; + const bool discard =3D false; + StreamBlockJob *s =3D NULL; BlockDriverState *iter; int orig_bs_flags; + BlockDriverState *stream_top_bs; + int node_shared_flags =3D BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UN= CHANGED; + int ret; =20 /* Make sure that the image is opened in read-write mode */ orig_bs_flags =3D bdrv_get_flags(bs); @@ -236,10 +603,19 @@ void stream_start(const char *job_id, BlockDriverStat= e *bs, } } =20 + if (discard) { + node_shared_flags |=3D BLK_PERM_WRITE; + stream_top_bs =3D insert_filter(bs, errp); + if (stream_top_bs =3D=3D NULL) { + goto fail; + } + } else { + stream_top_bs =3D bs; + } /* Prevent concurrent jobs trying to modify the graph structure here, = we * already have our own plans. Also don't allow resize as the image si= ze is * queried only at the job start and then cached. */ - s =3D block_job_create(job_id, &stream_job_driver, NULL, bs, + s =3D block_job_create(job_id, &stream_job_driver, NULL, stream_top_bs, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANG= ED | BLK_PERM_GRAPH_MOD, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANG= ED | @@ -251,18 +627,28 @@ void stream_start(const char *job_id, BlockDriverStat= e *bs, =20 /* Block all intermediate nodes between bs and base, because they will * disappear from the chain after this operation. The streaming job re= ads - * every block only once, assuming that it doesn't change, so block wr= ites - * and resizes. */ + * every block only once, assuming that it doesn't change, so forbid w= rites + * and resizes. Allow writing in case of discard. */ for (iter =3D backing_bs(bs); iter && iter !=3D base; iter =3D backing= _bs(iter)) { block_job_add_bdrv(&s->common, "intermediate node", iter, 0, - BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHA= NGED, - &error_abort); + node_shared_flags, &error_abort); + } + + if (discard) { + s->stream_top_bs =3D stream_top_bs; + /* The block job now has a reference to this node */ + bdrv_unref(stream_top_bs); + + ret =3D init_intermediate_nodes(s, bs, base, errp); + if (ret < 0) { + goto fail; + } } =20 s->base =3D base; s->backing_file_str =3D g_strdup(backing_file_str); s->bs_flags =3D orig_bs_flags; - + s->discard =3D discard; s->on_error =3D on_error; trace_stream_start(bs, base, s); job_start(&s->common.job); @@ -272,4 +658,16 @@ fail: if (orig_bs_flags !=3D bdrv_get_flags(bs)) { bdrv_reopen(bs, orig_bs_flags, NULL); } + if (!discard) { + return; + } + if (s) { + /* Make sure this BDS does not go away until we have completed the= graph + * changes below */ + bdrv_ref(stream_top_bs); + job_early_fail(&s->common.job); + } + if (stream_top_bs) { + remove_filter(stream_top_bs, bs); + } } --=20 1.8.3.1