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[PULL v2 6/8] 9p: stat_to_qid: implement slow path
From: |
Greg Kurz |
Subject: |
[PULL v2 6/8] 9p: stat_to_qid: implement slow path |
Date: |
Thu, 10 Oct 2019 15:18:07 +0200 |
From: Antonios Motakis <address@hidden>
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 <address@hidden>
[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 <address@hidden>
Signed-off-by: Greg Kurz <address@hidden>
---
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 8eb89c5c7d3f..d9be2d45d3e4 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 7262fe80aa02..35a362c0d797 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 */
--
2.21.0
- [PULL v2 0/8] 9p patches 2019-10-10, Greg Kurz, 2019/10/10
- [PULL v2 1/8] 9p: unsigned type for type, version, path, Greg Kurz, 2019/10/10
- [PULL v2 6/8] 9p: stat_to_qid: implement slow path,
Greg Kurz <=
- [PULL v2 3/8] fsdev: Add return value to fsdev_throttle_parse_opts(), Greg Kurz, 2019/10/10
- [PULL v2 5/8] 9p: Added virtfs option 'multidevs=remap|forbid|warn', Greg Kurz, 2019/10/10
- [PULL v2 8/8] MAINTAINERS: Downgrade status of virtio-9p to "Odd Fixes", Greg Kurz, 2019/10/10
- [PULL v2 2/8] 9p: Simplify error path of v9fs_device_realize_common(), Greg Kurz, 2019/10/10
- [PULL v2 4/8] 9p: Treat multiple devices on one export as an error, Greg Kurz, 2019/10/10
- [PULL v2 7/8] 9p: Use variable length suffixes for inode remapping, Greg Kurz, 2019/10/10
- Re: [PULL v2 0/8] 9p patches 2019-10-10, Peter Maydell, 2019/10/14