Merge remote-tracking branch 'remotes/gkurz/tags/9p-next-2019-10-10' into staging

The most notable change is that we now detect cross-device setups in the
host since it may cause inode number collision and mayhem in the guest.
A new fsdev property is added for the user to choose the appropriate
policy to handle that: either remap all inode numbers or fail I/Os to
another host device or just print out a warning (default behaviour).

This is also my last PR as _active_ maintainer of 9pfs.

# gpg: Signature made Thu 10 Oct 2019 12:14:07 BST
# gpg:                using RSA key B4828BAF943140CEF2A3491071D4D5E5822F73D6
# gpg: Good signature from "Greg Kurz <groug@kaod.org>" [full]
# gpg:                 aka "Gregory Kurz <gregory.kurz@free.fr>" [full]
# gpg:                 aka "[jpeg image of size 3330]" [full]
# Primary key fingerprint: B482 8BAF 9431 40CE F2A3  4910 71D4 D5E5 822F 73D6

* remotes/gkurz/tags/9p-next-2019-10-10:
  MAINTAINERS: Downgrade status of virtio-9p to "Odd Fixes"
  9p: Use variable length suffixes for inode remapping
  9p: stat_to_qid: implement slow path
  9p: Added virtfs option 'multidevs=remap|forbid|warn'
  9p: Treat multiple devices on one export as an error
  fsdev: Add return value to fsdev_throttle_parse_opts()
  9p: Simplify error path of v9fs_device_realize_common()
  9p: unsigned type for type, version, path

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 8883761b2c..3904f82901 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -8,6 +8,7 @@
 #include "fsdev/9p-iov-marshal.h"
 #include "qemu/thread.h"
 #include "qemu/coroutine.h"
+#include "qemu/qht.h"
 
 enum {
     P9_TLERROR = 6,
@@ -235,6 +236,58 @@ struct V9fsFidState
     V9fsFidState *rclm_lst;
 };
 
+typedef enum AffixType_t {
+    AffixType_Prefix,
+    AffixType_Suffix, /* A.k.a. postfix. */
+} AffixType_t;
+
+/**
+ * @brief Unique affix of variable length.
+ *
+ * An affix is (currently) either a suffix or a prefix, which is either
+ * going to be prepended (prefix) or appended (suffix) with some other
+ * number for the goal to generate unique numbers. Accordingly the
+ * suffixes (or prefixes) we generate @b must all have the mathematical
+ * property of being suffix-free (or prefix-free in case of prefixes)
+ * so that no matter what number we concatenate the affix with, that we
+ * always reliably get unique numbers as result after concatenation.
+ */
+typedef struct VariLenAffix {
+    AffixType_t type; /* Whether this affix is a suffix or a prefix. */
+    uint64_t value; /* Actual numerical value of this affix. */
+    /*
+     * Lenght of the affix, that is how many (of the lowest) bits of @c value
+     * must be used for appending/prepending this affix to its final resulting,
+     * unique number.
+     */
+    int bits;
+} VariLenAffix;
+
+/* See qid_inode_prefix_hash_bits(). */
+typedef struct {
+    dev_t dev; /* FS device on host. */
+    /*
+     * How many (high) bits of the original inode number shall be used for
+     * hashing.
+     */
+    int prefix_bits;
+} QpdEntry;
+
+/* QID path prefix entry, see stat_to_qid */
+typedef struct {
+    dev_t dev;
+    uint16_t ino_prefix;
+    uint32_t qp_affix_index;
+    VariLenAffix qp_affix;
+} 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;
@@ -256,6 +309,13 @@ struct V9fsState
     Error *migration_blocker;
     V9fsConf fsconf;
     V9fsQID root_qid;
+    dev_t dev_id;
+    struct qht qpd_table;
+    struct qht qpp_table;
+    struct qht qpf_table;
+    uint64_t qp_ndevices; /* Amount of entries in qpd_table. */
+    uint16_t qp_affix_next;
+    uint64_t qp_fullpath_next;
 };
 
 /* 9p2000.L open flags */