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Re: [Qemu-devel] [PATCH v4 2/2] block/quorum: add simple read pattern su
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From: |
Liu Yuan |
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Subject: |
Re: [Qemu-devel] [PATCH v4 2/2] block/quorum: add simple read pattern support |
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Date: |
Thu, 14 Aug 2014 15:01:04 +0800 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Aug 12, 2014 at 10:41:28AM +0800, Liu Yuan wrote:
> On Mon, Aug 11, 2014 at 02:31:43PM +0200, Benoît Canet wrote:
> > The Thursday 17 Jul 2014 à 13:18:56 (+0800), Liu Yuan wrote :
> > > This patch adds single read pattern to quorum driver and quorum vote is
> > > default
> > > pattern.
> > >
> > > For now we do a quorum vote on all the reads, it is designed for
> > > unreliable
> > > underlying storage such as non-redundant NFS to make sure data integrity
> > > at the
> > > cost of the read performance.
> > >
> > > For some use cases as following:
> > >
> > > VM
> > > --------------
> > > | |
> > > v v
> > > A B
> > >
> > > Both A and B has hardware raid storage to justify the data integrity on
> > > its own.
> > > So it would help performance if we do a single read instead of on all the
> > > nodes.
> > > Further, if we run VM on either of the storage node, we can make a local
> > > read
> > > request for better performance.
> > >
> > > This patch generalize the above 2 nodes case in the N nodes. That is,
> > >
> > > vm -> write to all the N nodes, read just one of them. If single read
> > > fails, we
> > > try to read next node in FIFO order specified by the startup command.
> > >
> > > The 2 nodes case is very similar to DRBD[1] though lack of auto-sync
> > > functionality in the single device/node failure for now. But compared
> > > with DRBD
> > > we still have some advantages over it:
> > >
> > > - Suppose we have 20 VMs running on one(assume A) of 2 nodes' DRBD backed
> > > storage. And if A crashes, we need to restart all the VMs on node B. But
> > > for
> > > practice case, we can't because B might not have enough resources to
> > > setup 20 VMs
> > > at once. So if we run our 20 VMs with quorum driver, and scatter the
> > > replicated
> > > images over the data center, we can very likely restart 20 VMs without any
> > > resource problem.
> > >
> > > After all, I think we can build a more powerful replicated image
> > > functionality
> > > on quorum and block jobs(block mirror) to meet various High Availibility
> > > needs.
> > >
> > > E.g, Enable single read pattern on 2 children,
> > >
> > > -drive driver=quorum,children.0.file.filename=0.qcow2,\
> > > children.1.file.filename=1.qcow2,read-pattern=fifo,vote-threshold=1
> > >
> > > [1] http://en.wikipedia.org/wiki/Distributed_Replicated_Block_Device
> > >
> > > Cc: Benoit Canet <address@hidden>
> > > Cc: Eric Blake <address@hidden>
> > > Cc: Kevin Wolf <address@hidden>
> > > Cc: Stefan Hajnoczi <address@hidden>
> > > Signed-off-by: Liu Yuan <address@hidden>
> > > ---
> > > block/quorum.c | 179
> > > +++++++++++++++++++++++++++++++++++++++++----------------
> > > 1 file changed, 131 insertions(+), 48 deletions(-)
> > >
> > > diff --git a/block/quorum.c b/block/quorum.c
> > > index d5ee9c0..ebf5c71 100644
> > > --- a/block/quorum.c
> > > +++ b/block/quorum.c
> > > @@ -24,6 +24,7 @@
> > > #define QUORUM_OPT_VOTE_THRESHOLD "vote-threshold"
> > > #define QUORUM_OPT_BLKVERIFY "blkverify"
> > > #define QUORUM_OPT_REWRITE "rewrite-corrupted"
> > > +#define QUORUM_OPT_READ_PATTERN "read-pattern"
> > >
> > > /* This union holds a vote hash value */
> > > typedef union QuorumVoteValue {
> > > @@ -74,6 +75,8 @@ typedef struct BDRVQuorumState {
> > > bool rewrite_corrupted;/* true if the driver must rewrite-on-read
> > > corrupted
> > > * block if Quorum is reached.
> > > */
> > > +
> > > + QuorumReadPattern read_pattern;
> > > } BDRVQuorumState;
> > >
> > > typedef struct QuorumAIOCB QuorumAIOCB;
> > > @@ -117,6 +120,7 @@ struct QuorumAIOCB {
> > >
> > > bool is_read;
> > > int vote_ret;
> > > + int child_iter; /* which child to read in fifo pattern */
> > > };
> > >
> > > static bool quorum_vote(QuorumAIOCB *acb);
> > > @@ -154,8 +158,10 @@ static void quorum_aio_finalize(QuorumAIOCB *acb)
> > >
> > > if (acb->is_read) {
> > > for (i = 0; i < s->num_children; i++) {
> > > - qemu_vfree(acb->qcrs[i].buf);
> > > - qemu_iovec_destroy(&acb->qcrs[i].qiov);
> > > + if (i <= acb->child_iter) {
> > > + qemu_vfree(acb->qcrs[i].buf);
> > > + qemu_iovec_destroy(&acb->qcrs[i].qiov);
> > > + }
> > > }
> > > }
> > >
> > > @@ -256,6 +262,21 @@ static void quorum_rewrite_aio_cb(void *opaque, int
> > > ret)
> > > quorum_aio_finalize(acb);
> > > }
> > >
> > > +static BlockDriverAIOCB *read_fifo_child(QuorumAIOCB *acb);
> > > +
> > > +static void quorum_copy_qiov(QEMUIOVector *dest, QEMUIOVector *source)
> > > +{
> > > + int i;
> > > + assert(dest->niov == source->niov);
> > > + assert(dest->size == source->size);
> > > + for (i = 0; i < source->niov; i++) {
> > > + assert(dest->iov[i].iov_len == source->iov[i].iov_len);
> > > + memcpy(dest->iov[i].iov_base,
> > > + source->iov[i].iov_base,
> > > + source->iov[i].iov_len);
> > > + }
> > > +}
> > > +
> > > static void quorum_aio_cb(void *opaque, int ret)
> > > {
> > > QuorumChildRequest *sacb = opaque;
> > > @@ -263,6 +284,21 @@ static void quorum_aio_cb(void *opaque, int ret)
> > > BDRVQuorumState *s = acb->common.bs->opaque;
> > > bool rewrite = false;
> > >
> > > + if (acb->is_read && s->read_pattern == QUORUM_READ_PATTERN_FIFO) {
> > > + /* We try to read next child in FIFO order if we fail to read */
> > > + if (ret < 0 && ++acb->child_iter < s->num_children) {
> > > + read_fifo_child(acb);
> > > + return;
> > > + }
> > > +
> > > + if (ret == 0) {
> > > + quorum_copy_qiov(acb->qiov,
> > > &acb->qcrs[acb->child_iter].qiov);
> > > + }
> > > + acb->vote_ret = ret;
> > > + quorum_aio_finalize(acb);
> > > + return;
> > > + }
> > > +
> > > sacb->ret = ret;
> > > acb->count++;
> > > if (ret == 0) {
> > > @@ -343,19 +379,6 @@ static bool
> > > quorum_rewrite_bad_versions(BDRVQuorumState *s, QuorumAIOCB *acb,
> > > return count;
> > > }
> > >
> > > -static void quorum_copy_qiov(QEMUIOVector *dest, QEMUIOVector *source)
> > > -{
> > > - int i;
> > > - assert(dest->niov == source->niov);
> > > - assert(dest->size == source->size);
> > > - for (i = 0; i < source->niov; i++) {
> > > - assert(dest->iov[i].iov_len == source->iov[i].iov_len);
> > > - memcpy(dest->iov[i].iov_base,
> > > - source->iov[i].iov_base,
> > > - source->iov[i].iov_len);
> > > - }
> > > -}
> > > -
> > > static void quorum_count_vote(QuorumVotes *votes,
> > > QuorumVoteValue *value,
> > > int index)
> > > @@ -615,34 +638,62 @@ free_exit:
> > > return rewrite;
> > > }
> > >
> > > -static BlockDriverAIOCB *quorum_aio_readv(BlockDriverState *bs,
> > > - int64_t sector_num,
> > > - QEMUIOVector *qiov,
> > > - int nb_sectors,
> > > - BlockDriverCompletionFunc *cb,
> > > - void *opaque)
> > > +static BlockDriverAIOCB *read_quorum_children(QuorumAIOCB *acb)
> > > {
> > > - BDRVQuorumState *s = bs->opaque;
> > > - QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num,
> > > - nb_sectors, cb, opaque);
> > > + BDRVQuorumState *s = acb->common.bs->opaque;
> > > int i;
> > >
> > > - acb->is_read = true;
> > > -
> > > for (i = 0; i < s->num_children; i++) {
> > > - acb->qcrs[i].buf = qemu_blockalign(s->bs[i], qiov->size);
> > > - qemu_iovec_init(&acb->qcrs[i].qiov, qiov->niov);
> > > - qemu_iovec_clone(&acb->qcrs[i].qiov, qiov, acb->qcrs[i].buf);
> > > + acb->qcrs[i].buf = qemu_blockalign(s->bs[i], acb->qiov->size);
> > > + qemu_iovec_init(&acb->qcrs[i].qiov, acb->qiov->niov);
> > > + qemu_iovec_clone(&acb->qcrs[i].qiov, acb->qiov,
> > > acb->qcrs[i].buf);
> > > }
> > >
> > > for (i = 0; i < s->num_children; i++) {
> > > - bdrv_aio_readv(s->bs[i], sector_num, &acb->qcrs[i].qiov,
> > > nb_sectors,
> > > - quorum_aio_cb, &acb->qcrs[i]);
> > > + bdrv_aio_readv(s->bs[i], acb->sector_num, &acb->qcrs[i].qiov,
> > > + acb->nb_sectors, quorum_aio_cb, &acb->qcrs[i]);
> > > }
> > >
> > > return &acb->common;
> > > }
> > >
> > > +static BlockDriverAIOCB *read_fifo_child(QuorumAIOCB *acb)
> > > +{
> > > + BDRVQuorumState *s = acb->common.bs->opaque;
> > > +
> > > + acb->qcrs[acb->child_iter].buf =
> > > qemu_blockalign(s->bs[acb->child_iter],
> > > + acb->qiov->size);
> > > + qemu_iovec_init(&acb->qcrs[acb->child_iter].qiov, acb->qiov->niov);
> > > + qemu_iovec_clone(&acb->qcrs[acb->child_iter].qiov, acb->qiov,
> > > + acb->qcrs[acb->child_iter].buf);
> > > + bdrv_aio_readv(s->bs[acb->child_iter], acb->sector_num,
> > > + &acb->qcrs[acb->child_iter].qiov, acb->nb_sectors,
> > > + quorum_aio_cb, &acb->qcrs[acb->child_iter]);
> > > +
> > > + return &acb->common;
> > > +}
> > > +
> > > +static BlockDriverAIOCB *quorum_aio_readv(BlockDriverState *bs,
> > > + int64_t sector_num,
> > > + QEMUIOVector *qiov,
> > > + int nb_sectors,
> > > + BlockDriverCompletionFunc *cb,
> > > + void *opaque)
> > > +{
> > > + BDRVQuorumState *s = bs->opaque;
> > > + QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num,
> > > + nb_sectors, cb, opaque);
> > > + acb->is_read = true;
> > > +
> > > + if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
> > > + acb->child_iter = s->num_children - 1;
> > > + return read_quorum_children(acb);
> > > + }
> > > +
> > > + acb->child_iter = 0;
> > > + return read_fifo_child(acb);
> > > +}
> > > +
> > > static BlockDriverAIOCB *quorum_aio_writev(BlockDriverState *bs,
> > > int64_t sector_num,
> > > QEMUIOVector *qiov,
> > > @@ -782,10 +833,33 @@ static QemuOptsList quorum_runtime_opts = {
> > > .type = QEMU_OPT_BOOL,
> > > .help = "Rewrite corrupted block on read quorum",
> > > },
> > > + {
> > > + .name = QUORUM_OPT_READ_PATTERN,
> > > + .type = QEMU_OPT_STRING,
> > > + .help = "Allowed pattern: quorum, fifo. Quorum is default",
> > > + },
> > > { /* end of list */ }
> > > },
> > > };
> > >
> > > +static int parse_read_pattern(const char *opt)
> > > +{
> > > + int i;
> > > +
> > > + if (!opt) {
> > > + /* Set quorum as default */
> > > + return QUORUM_READ_PATTERN_QUORUM;
> > > + }
> > > +
> > > + for (i = 0; i < QUORUM_READ_PATTERN_MAX; i++) {
> > > + if (!strcmp(opt, QuorumReadPattern_lookup[i])) {
> > > + return i;
> > > + }
> > > + }
> > > +
> > > + return -EINVAL;
> > > +}
> > > +
> > > static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
> > > Error **errp)
> > > {
> > > @@ -827,28 +901,37 @@ static int quorum_open(BlockDriverState *bs, QDict
> > > *options, int flags,
> > > }
> > >
> > > s->threshold = qemu_opt_get_number(opts, QUORUM_OPT_VOTE_THRESHOLD,
> > > 0);
> > > -
> > > - /* and validate it against s->num_children */
> > > - ret = quorum_valid_threshold(s->threshold, s->num_children,
> > > &local_err);
> > > + ret = parse_read_pattern(qemu_opt_get(opts,
> > > QUORUM_OPT_READ_PATTERN));
> > > if (ret < 0) {
> > > + error_setg(&local_err, "Please set read-pattern as fifo or
> > > quorum\n");
> > > goto exit;
> > > }
> > > + s->read_pattern = ret;
> > >
> > > - /* is the driver in blkverify mode */
> > > - if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false) &&
> > > - s->num_children == 2 && s->threshold == 2) {
> > > - s->is_blkverify = true;
> > > - } else if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false)) {
> > > - fprintf(stderr, "blkverify mode is set by setting blkverify=on "
> > > - "and using two files with vote_threshold=2\n");
> > > - }
> > > + if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
> > > + /* and validate it against s->num_children */
> > > + ret = quorum_valid_threshold(s->threshold, s->num_children,
> > > &local_err);
> > > + if (ret < 0) {
> > > + goto exit;
> > > + }
> > >
> > > - s->rewrite_corrupted = qemu_opt_get_bool(opts, QUORUM_OPT_REWRITE,
> > > false);
> > > - if (s->rewrite_corrupted && s->is_blkverify) {
> > > - error_setg(&local_err,
> > > - "rewrite-corrupted=on cannot be used with
> > > blkverify=on");
> > > - ret = -EINVAL;
> > > - goto exit;
> > > + /* is the driver in blkverify mode */
> > > + if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false) &&
> > > + s->num_children == 2 && s->threshold == 2) {
> > > + s->is_blkverify = true;
> > > + } else if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false))
> > > {
> > > + fprintf(stderr, "blkverify mode is set by setting
> > > blkverify=on "
> > > + "and using two files with vote_threshold=2\n");
> > > + }
> > > +
> > > + s->rewrite_corrupted = qemu_opt_get_bool(opts,
> > > QUORUM_OPT_REWRITE,
> > > + false);
> > > + if (s->rewrite_corrupted && s->is_blkverify) {
> > > + error_setg(&local_err,
> > > + "rewrite-corrupted=on cannot be used with
> > > blkverify=on");
> > > + ret = -EINVAL;
> > > + goto exit;
> > > + }
> > > }
> > >
> > > /* allocate the children BlockDriverState array */
> > > --
> > > 1.9.1
> > >
> >
> > I think I responded you with comments signaling a potential memory leak but
> > you missed it.
> >
>
> Hi Benoit,
>
> Thanks for your time.
>
> I in fact responded you in
>
> http://lists.gnu.org/archive/html/qemu-devel/2014-07/msg02103.html
>
> For v4 I think there isn't memory leak problem since quorum_aio_finalize()
> will
> be called in any case finally and will free the resrouces allocated by
> all the read_fifo_child().
>
> Or am I missing something?
>
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