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Fri, 28 Jun 2019 12:21:25 +0200 (CEST) Received: from kaod.org (lns-bzn-46-82-253-208-248.adsl.proxad.net [82.253.208.248]) (Authenticated sender: groug@kaod.org) by player771.ha.ovh.net (Postfix) with ESMTPSA id 8DF9775A1071; Fri, 28 Jun 2019 10:21:21 +0000 (UTC) Date: Fri, 28 Jun 2019 12:21:20 +0200 From: Greg Kurz To: Christian Schoenebeck via Qemu-devel Message-ID: <20190628122120.60a1ec0b@bahia.lan> In-Reply-To: References: X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Ovh-Tracer-Id: 16871610105681975616 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgeduvddrvddtgdeftdcutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 46.105.63.230 Subject: Re: [Qemu-devel] [PATCH v4 4/5] 9p: stat_to_qid: implement slow path X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" , Christian Schoenebeck , Antonios Motakis Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 26 Jun 2019 20:46:24 +0200 Christian Schoenebeck via Qemu-devel wrote: > stat_to_qid attempts via qid_path_prefixmap to map unique files (which are > identified by 64 bit inode nr and 32 bit device id) to a 64 QID path value. > However this implementation makes some assumptions about inode number > generation on the host. > > If qid_path_prefixmap fails, we still have 48 bits available in the QID > path to fall back to a less memory efficient full mapping. > > Signed-off-by: Antonios Motakis > Signed-off-by: Christian Schoenebeck > --- > hw/9pfs/9p.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----- > hw/9pfs/9p.h | 9 +++++++++ > 2 files changed, 67 insertions(+), 5 deletions(-) > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > index 7ccc68a829..e6e410972f 100644 > --- a/hw/9pfs/9p.c > +++ b/hw/9pfs/9p.c > @@ -579,23 +579,69 @@ static uint32_t qpp_hash(QppEntry e) > return qemu_xxhash7(e.ino_prefix, e.dev, 0, 0, 0); > } > > +static uint32_t qpf_hash(QpfEntry e) > +{ > + return qemu_xxhash7(e.ino, e.dev, 0, 0, 0); > +} > + > static bool qpp_lookup_func(const void *obj, const void *userp) > { > const QppEntry *e1 = obj, *e2 = userp; > return e1->dev == e2->dev && e1->ino_prefix == e2->ino_prefix; > } > > -static void qpp_table_remove(void *p, uint32_t h, void *up) > +static bool qpf_lookup_func(const void *obj, const void *userp) > +{ > + const QpfEntry *e1 = obj, *e2 = userp; > + return e1->dev == e2->dev && e1->ino == e2->ino; > +} > + > +static void qp_table_remove(void *p, uint32_t h, void *up) > { > g_free(p); > } > > -static void qpp_table_destroy(struct qht *ht) > +static void qp_table_destroy(struct qht *ht) > { > - qht_iter(ht, qpp_table_remove, NULL); > + qht_iter(ht, qp_table_remove, NULL); > qht_destroy(ht); > } > > +static int qid_path_fullmap(V9fsPDU *pdu, const struct stat *stbuf, > + uint64_t *path) > +{ > + QpfEntry lookup = { > + .dev = stbuf->st_dev, > + .ino = stbuf->st_ino > + }, *val; > + uint32_t hash = qpf_hash(lookup); > + > + /* most users won't need the fullmap, so init the table lazily */ > + if (!pdu->s->qpf_table.map) { > + qht_init(&pdu->s->qpf_table, qpf_lookup_func, 1 << 16, QHT_MODE_AUTO_RESIZE); > + } > + > + val = qht_lookup(&pdu->s->qpf_table, &lookup, hash); > + > + if (!val) { > + if (pdu->s->qp_fullpath_next == 0) { > + /* no more files can be mapped :'( */ This would be the place to put the error_report_once() suggested in the previous patch actually. > + return -ENFILE; > + } > + > + val = g_malloc0(sizeof(QppEntry)); > + *val = lookup; > + > + /* new unique inode and device combo */ > + val->path = pdu->s->qp_fullpath_next++; > + pdu->s->qp_fullpath_next &= QPATH_INO_MASK; > + qht_insert(&pdu->s->qpf_table, val, hash, NULL); > + } > + > + *path = val->path; > + return 0; > +} > + > /* stat_to_qid needs to map inode number (64 bits) and device id (32 bits) > * to a unique QID path (64 bits). To avoid having to map and keep track > * of up to 2^64 objects, we map only the 16 highest bits of the inode plus > @@ -642,6 +688,10 @@ static int stat_to_qid(V9fsPDU *pdu, const struct stat *stbuf, V9fsQID *qidp) > if (pdu->s->ctx.export_flags & V9FS_REMAP_INODES) { > /* map inode+device to qid path (fast path) */ > err = qid_path_prefixmap(pdu, stbuf, &qidp->path); > + if (err == -ENFILE) { > + /* fast path didn't work, fall back to full map */ > + err = qid_path_fullmap(pdu, stbuf, &qidp->path); > + } > if (err) { > return err; > } > @@ -3752,6 +3802,7 @@ int v9fs_device_realize_common(V9fsState *s, const V9fsTransport *t, > /* QID path hash table. 1 entry ought to be enough for anybody ;) */ > qht_init(&s->qpp_table, qpp_lookup_func, 1, QHT_MODE_AUTO_RESIZE); > s->qp_prefix_next = 1; /* reserve 0 to detect overflow */ > + s->qp_fullpath_next = 1; > > s->ctx.fst = &fse->fst; > fsdev_throttle_init(s->ctx.fst); > @@ -3766,7 +3817,8 @@ out: > } > g_free(s->tag); > g_free(s->ctx.fs_root); > - qpp_table_destroy(&s->qpp_table); > + qp_table_destroy(&s->qpp_table); > + qp_table_destroy(&s->qpf_table); > v9fs_path_free(&path); > } > return rc; > @@ -3779,7 +3831,8 @@ void v9fs_device_unrealize_common(V9fsState *s, Error **errp) > } > fsdev_throttle_cleanup(s->ctx.fst); > g_free(s->tag); > - qpp_table_destroy(&s->qpp_table); > + qp_table_destroy(&s->qpp_table); > + qp_table_destroy(&s->qpf_table); I'm starting to think v9fs_device_unrealize_common() should be made idempotent, so that it can be used to handle rollback of a partially realized device, and thus avoid the code duplication. But this is out-of-scope for this series. LGTM. > g_free(s->ctx.fs_root); > } > > diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h > index 0200e04176..2b74561030 100644 > --- a/hw/9pfs/9p.h > +++ b/hw/9pfs/9p.h > @@ -245,6 +245,13 @@ typedef struct { > uint16_t qp_prefix; > } QppEntry; > > +/* QID path full entry, as above */ > +typedef struct { > + dev_t dev; > + ino_t ino; > + uint64_t path; > +} QpfEntry; > + > struct V9fsState > { > QLIST_HEAD(, V9fsPDU) free_list; > @@ -268,7 +275,9 @@ struct V9fsState > V9fsQID root_qid; > dev_t dev_id; > struct qht qpp_table; > + struct qht qpf_table; > uint16_t qp_prefix_next; > + uint64_t qp_fullpath_next; > }; > > /* 9p2000.L open flags */