refactor(tvix/store/fuse): Switch from fuser to fuse-backend-rs r/6621

This switches the FUSE implementation from fuser to fuse-backend-rs.
fuse-backend-rs is designed to work with both FUSE and virtiofs.
Virtiofs support will make it possible to plug the tvix-store into a
microvm and have `/nix/store` access without having to setup FUSE inside
the guest.

Additionally fuse-backend-rs has nice support for running multiple FUSE
threads and has some async support.

The goal of this commit is to mechanically switch over to
fuse-backend-rs with minimal changes. I did have to add some locks here
and there because fuse-backend-rs uses `&self` on all methods whereas
fuser uses `&mut self`. `&self` is required for concurrent access to the
FUSE server, so this makes sense.

We can consider switching to concurrent maps and use some other
techniques to reduce lock contention and critical section size.

Issue: https://b.tvl.fyi/issues/305

Change-Id: Icde5a58c6eef98f8984c1e04e980b756dfb76b47
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9341
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 110 insertions, 61 deletions

diff --git a/tvix/Cargo.lock b/tvix/Cargo.lock
index f0a73f3a3f51..02726751705c 100644
--- a/tvix/Cargo.lock
+++ b/tvix/Cargo.lock
@@ -88,6 +88,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
 
 [[package]]
+name = "arc-swap"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bddcadddf5e9015d310179a59bb28c4d4b9920ad0f11e8e14dbadf654890c9a6"
+
+[[package]]
 name = "arrayref"
 version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -332,6 +338,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "89b2fd2a0dcf38d7971e2194b6b6eebab45ae01067456a7fd93d5547a61b70be"
 
 [[package]]
+name = "caps"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "190baaad529bcfbde9e1a19022c42781bdb6ff9de25721abdb8fd98c0807730b"
+dependencies = [
+ "libc",
+ "thiserror",
+]
+
+[[package]]
 name = "cast"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -477,12 +493,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
 
 [[package]]
+name = "const-zero"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3c6565524986fe3225da0beb9b4aa55ebc73cd57ff8cb4ccf016ca4c8d006af"
+
+[[package]]
 name = "constant_time_eq"
 version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "13418e745008f7349ec7e449155f419a61b92b58a99cc3616942b926825ec76b"
 
 [[package]]
+name = "core-foundation-sys"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e496a50fda8aacccc86d7529e2c1e0892dbd0f898a6b5645b5561b89c3210efa"
+
+[[package]]
 name = "count-write"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -578,7 +606,7 @@ dependencies = [
  "autocfg",
  "cfg-if",
  "crossbeam-utils",
- "memoffset",
+ "memoffset 0.8.0",
  "scopeguard",
 ]
 
@@ -791,19 +819,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 
 [[package]]
-name = "fuser"
-version = "0.12.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5910691a0ececcc6eba8bb14029025c2d123e96a53db1533f6a4602861a5aaf7"
+name = "fuse-backend-rs"
+version = "0.10.5"
+source = "git+https://github.com/cbrewster/fuse-backend-rs.git?branch=optional-allow_other#b553ce526a7267578ae5af4f4cbba717932518ac"
 dependencies = [
+ "arc-swap",
+ "bitflags",
+ "caps",
+ "core-foundation-sys",
+ "lazy_static",
  "libc",
  "log",
- "memchr",
- "page_size",
- "pkg-config",
- "smallvec",
- "users",
- "zerocopy",
+ "mio",
+ "nix 0.24.3",
+ "vm-memory",
+ "vmm-sys-util",
 ]
 
 [[package]]
@@ -1328,6 +1358,15 @@ checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 
 [[package]]
 name = "memoffset"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aa361d4faea93603064a027415f07bd8e1d5c88c9fbf68bf56a285428fd79ce"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "memoffset"
 version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d61c719bcfbcf5d62b3a09efa6088de8c54bc0bfcd3ea7ae39fcc186108b8de1"
@@ -1379,6 +1418,18 @@ dependencies = [
 
 [[package]]
 name = "nix"
+version = "0.24.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa52e972a9a719cecb6864fb88568781eb706bac2cd1d4f04a648542dbf78069"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "libc",
+ "memoffset 0.6.5",
+]
+
+[[package]]
+name = "nix"
 version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f346ff70e7dbfd675fe90590b92d59ef2de15a8779ae305ebcbfd3f0caf59be4"
@@ -1501,24 +1552,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
 
 [[package]]
-name = "page_size"
-version = "0.4.2"
+name = "parking_lot"
+version = "0.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eebde548fbbf1ea81a99b128872779c437752fb99f217c45245e1a61dcd9edcd"
+checksum = "7d17b78036a60663b797adeaee46f5c9dfebb86948d1255007a1d6be0271ff99"
 dependencies = [
- "libc",
- "winapi",
+ "instant",
+ "lock_api",
+ "parking_lot_core 0.8.6",
 ]
 
 [[package]]
 name = "parking_lot"
-version = "0.11.2"
+version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7d17b78036a60663b797adeaee46f5c9dfebb86948d1255007a1d6be0271ff99"
+checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
 dependencies = [
- "instant",
  "lock_api",
- "parking_lot_core",
+ "parking_lot_core 0.9.8",
 ]
 
 [[package]]
@@ -1536,6 +1587,19 @@ dependencies = [
 ]
 
 [[package]]
+name = "parking_lot_core"
+version = "0.9.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93f00c865fe7cabf650081affecd3871070f26767e7b2070a3ffae14c654b447"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "redox_syscall 0.3.5",
+ "smallvec",
+ "windows-targets 0.48.0",
+]
+
+[[package]]
 name = "path-clean"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1590,12 +1654,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
-name = "pkg-config"
-version = "0.3.27"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26072860ba924cbfa98ea39c8c19b4dd6a4a25423dbdf219c1eca91aa0cf6964"
-
-[[package]]
 name = "plotters"
 version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1999,7 +2057,7 @@ checksum = "64449cfef9483a475ed56ae30e2da5ee96448789fb2aa240a04beb6a055078bf"
 dependencies = [
  "countme",
  "hashbrown",
- "memoffset",
+ "memoffset 0.8.0",
  "rustc-hash",
  "text-size",
 ]
@@ -2062,7 +2120,7 @@ dependencies = [
  "libc",
  "log",
  "memchr",
- "nix",
+ "nix 0.25.1",
  "radix_trie",
  "scopeguard",
  "unicode-segmentation",
@@ -2207,7 +2265,7 @@ dependencies = [
  "fxhash",
  "libc",
  "log",
- "parking_lot",
+ "parking_lot 0.11.2",
  "zstd",
 ]
 
@@ -2869,13 +2927,15 @@ dependencies = [
  "blake3",
  "bytes",
  "clap 4.2.7",
+ "const-zero",
  "count-write",
  "data-encoding",
- "fuser",
+ "fuse-backend-rs",
  "futures",
  "lazy_static",
  "libc",
  "nix-compat",
+ "parking_lot 0.12.1",
  "pin-project-lite",
  "prost",
  "prost-build",
@@ -2964,16 +3024,6 @@ dependencies = [
 ]
 
 [[package]]
-name = "users"
-version = "0.11.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "24cc0f6d6f267b73e5a2cadf007ba8f9bc39c6a6f9666f8cf25ea809a153b032"
-dependencies = [
- "libc",
- "log",
-]
-
-[[package]]
 name = "utf8parse"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -2992,6 +3042,26 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
 [[package]]
+name = "vm-memory"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "688a70366615b45575a424d9c665561c1b5ab2224d494f706b6a6812911a827c"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
+[[package]]
+name = "vmm-sys-util"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd64fe09d8e880e600c324e7d664760a17f56e9672b7495a86381b49e4f72f46"
+dependencies = [
+ "bitflags",
+ "libc",
+]
+
+[[package]]
 name = "wait-timeout"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -3282,27 +3352,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09041cd90cf85f7f8b2df60c646f853b7f535ce68f85244eb6731cf89fa498ec"
 
 [[package]]
-name = "zerocopy"
-version = "0.6.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "332f188cc1bcf1fe1064b8c58d150f497e697f49774aa846f2dc949d9a25f236"
-dependencies = [
- "byteorder",
- "zerocopy-derive",
-]
-
-[[package]]
-name = "zerocopy-derive"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6505e6815af7de1746a08f69c69606bb45695a17149517680f3b2149713b19a3"
-dependencies = [
- "proc-macro2 1.0.56",
- "quote 1.0.26",
- "syn 1.0.109",
-]
-
-[[package]]
 name = "zstd"
 version = "0.9.2+zstd.1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"