On Thu, 8 Feb 2018 19:00:19 +0100
wrote:
> From: Antonios Motakis
>
> stat_to_qid attempts via qid_path_prefixmap to map unique files
> (which are identified by 64bt 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 48bits available in
> the QID path to fall back to a less memory efficient full mapping.
>
> Signed-off-by: Antonios Motakis
> ---
> hw/9pfs/9p.c | 66
> +++-
> hw/9pfs/9p.h | 9 +
> 2 files changed, 70 insertions(+), 5 deletions(-)
>
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index f434f05..ae7845d 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -581,23 +581,72 @@ static uint32_t qpp_hash(QppEntry e)
> return tb_hash_func7(e.ino_prefix, e.dev, 0, 0, 0);
> }
>
> +static uint32_t qpf_hash(QpfEntry e)
> +{
> +return tb_hash_func7(e.ino, e.dev, 0, 0, 0);
Same remark as with previous patch, obviously :)
> +}
> +
> 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);
Parenthesitis ? ;)
> }
>
> -static void qpp_table_remove(struct qht *ht, 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);
Parenthesitis ? ;)
> +}
> +
> +static void qp_table_remove(struct qht *ht, 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(>s->qpf_table, 1 << 16, QHT_MODE_AUTO_RESIZE);
> +}
> +
> +val = qht_lookup(>s->qpf_table, qpf_lookup_func, , hash);
> +
> +if (!val) {
> +if (pdu->s->qp_fullpath_next == 0) {
> +/* no more files can be mapped :'( */
> +return -ENFILE;
> +}
> +
> +val = g_malloc0(sizeof(QppEntry));
> +if (!val) {
> +return -ENOMEM;
> +}
> +*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(>s->qpf_table, val, hash);
> +}
> +
> +*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
> @@ -646,6 +695,10 @@ static int stat_to_qid(V9fsPDU *pdu, const struct stat
> *stbuf, V9fsQID *qidp)
>
> /* map inode+device to qid path (fast path) */
> err = qid_path_prefixmap(pdu, stbuf, >path);
> +if (err == -ENFILE) {
> +/* fast path didn't work, fal back to full map */
> +err = qid_path_fullmap(pdu, stbuf, >path);
Hmm... if we have already generate QIDs with fast path, how
can we be sure we won't collide with the ones from the full
map ?
IIRC, Emilio had suggested to use bit 63 to distinguish between
fast and slow path.
> +}
> if (err) {
> return err;
> }
> @@ -3693,6 +3746,7 @@ int v9fs_device_realize_common(V9fsState *s, const
> V9fsTransport *t,
> /* QID path hash table. 1 entry ought to be enough for anybody ;) */
> qht_init(>qpp_table, 1, QHT_MODE_AUTO_RESIZE);
> s->qp_prefix_next = 1; /* reserve 0 to detect overflow */
> +s->qp_fullpath_next = 1;
>
> s->ctx.fst = >fst;
> fsdev_throttle_init(s->ctx.fst);
> @@ -3707,7 +3761,8 @@ out:
> }
> g_free(s->tag);
> g_free(s->ctx.fs_root);
> -qpp_table_destroy(>qpp_table);
> +qp_table_destroy(>qpp_table);
> +qp_table_destroy(>qpf_table);
> v9fs_path_free();
> }
> return rc;
> @@ -3720,7 +3775,8 @@ void v9fs_device_unrealize_common(V9fsState *s, Error
> **errp)
> }
> fsdev_throttle_cleanup(s->ctx.fst);
> g_free(s->tag);
> -qpp_table_destroy(>qpp_table);
> +qp_table_destroy(>qpp_table);
> +qp_table_destroy(>qpf_table);
> g_free(s->ctx.fs_root);
> }
>
> diff --git