From f3fe4a2d92bb4ee5b599b8b1eb781b2ae68af36c Mon Sep 17 00:00:00 2001 From: Antonios Motakis Date: Mon, 7 Oct 2019 17:02:45 +0200 Subject: [PATCH] 9p: stat_to_qid: implement slow path 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 [CS: - Rebased to https://github.com/gkurz/qemu/commits/9p-next (SHA1 7fc4c49e91). - Updated hash calls to new xxhash API. - Removed unnecessary parantheses in qpf_lookup_func(). - Removed unnecessary g_malloc0() result checks. - Log error message when running out of prefixes in qid_path_fullmap(). - Log warning message about potential degraded performance in qid_path_prefixmap(). - Wrapped qpf_table initialization to dedicated qpf_table_init() function. - Fixed typo in comment. ] Signed-off-by: Christian Schoenebeck Signed-off-by: Greg Kurz --- hw/9pfs/9p.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++----- hw/9pfs/9p.h | 9 +++++++ 2 files changed, 76 insertions(+), 7 deletions(-) diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 8eb89c5c7d..d9be2d45d3 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -579,23 +579,34 @@ 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) { if (!ht || !ht->map) { return; } - qht_iter(ht, qpp_table_remove, NULL); + qht_iter(ht, qp_table_remove, NULL); qht_destroy(ht); } @@ -604,6 +615,50 @@ static void qpp_table_init(struct qht *ht) qht_init(ht, qpp_lookup_func, 1, QHT_MODE_AUTO_RESIZE); } +static void qpf_table_init(struct qht *ht) +{ + qht_init(ht, qpf_lookup_func, 1 << 16, QHT_MODE_AUTO_RESIZE); +} + +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) { + qpf_table_init(&pdu->s->qpf_table); + } + + val = qht_lookup(&pdu->s->qpf_table, &lookup, hash); + + if (!val) { + if (pdu->s->qp_fullpath_next == 0) { + /* no more files can be mapped :'( */ + error_report_once( + "9p: No more prefixes available for remapping inodes from " + "host to guest." + ); + 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 @@ -629,9 +684,8 @@ static int qid_path_prefixmap(V9fsPDU *pdu, const struct stat *stbuf, if (!val) { if (pdu->s->qp_prefix_next == 0) { /* we ran out of prefixes */ - error_report_once( - "9p: No more prefixes available for remapping inodes from " - "host to guest." + warn_report_once( + "9p: Potential degraded performance of inode remapping" ); return -ENFILE; } @@ -656,6 +710,10 @@ 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; } @@ -3820,6 +3878,7 @@ int v9fs_device_realize_common(V9fsState *s, const V9fsTransport *t, qpp_table_init(&s->qpp_table); 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); @@ -3842,7 +3901,8 @@ 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); g_free(s->ctx.fs_root); } diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h index 7262fe80aa..35a362c0d7 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 */