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Merge pull request #170 from mtelvers/xfs
XFS aka reflink store
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,155 @@ | ||
| (* This store will work with any file system which supports reflinks. *) | ||
| open Lwt.Infix | ||
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| type cache = { | ||
| lock : Lwt_mutex.t; | ||
| mutable gen : int; | ||
| } | ||
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| type t = { | ||
| path : string; | ||
| caches : (string, cache) Hashtbl.t; | ||
| mutable next : int; | ||
| } | ||
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| let ( / ) = Filename.concat | ||
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| module Xfs = struct | ||
| let create dir = Lwt.return @@ Os.ensure_dir dir | ||
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| let delete dir = | ||
| Os.sudo [ "rm"; "-r"; dir ] | ||
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| let cp ~src ~dst = | ||
| Os.sudo [ "cp"; "-pRduT"; "--reflink=always"; src; dst ] | ||
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| let rename ~src ~dst = | ||
| Os.sudo [ "mv"; src; dst ] | ||
| end | ||
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| module Path = struct | ||
| let state_dirname = "state" | ||
| let cache_dirname = "cache" | ||
| let cache_tmp_dirname = "cache-tmp" | ||
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| let result_dirname = "result" | ||
| let result_tmp_dirname = "result-tmp" | ||
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| let dirs root = | ||
| List.map ((/) root) | ||
| [ state_dirname; cache_dirname; cache_tmp_dirname; result_dirname; result_tmp_dirname ] | ||
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| let result t id = t.path / result_dirname / id | ||
| let cache t id = t.path / cache_dirname / id | ||
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| let cache_tmp t n id = t.path / cache_tmp_dirname / Printf.sprintf "%i-%s" n id | ||
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| let result_tmp t id = t.path / result_tmp_dirname / id | ||
| end | ||
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| let root t = t.path | ||
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| let df t = Lwt.return (Os.free_space_percent t.path) | ||
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| let create ~path = | ||
| Xfs.create path >>= fun () -> | ||
| Lwt_list.iter_s Xfs.create (Path.dirs path) >|= fun () -> | ||
| { path; caches = Hashtbl.create 10; next = 0 } | ||
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| let build t ?base ~id fn = | ||
| Log.debug (fun f -> f "xfs: build %S" id); | ||
| let result = Path.result t id in | ||
| let result_tmp = Path.result_tmp t id in | ||
| let base = Option.map (Path.result t) base in | ||
| begin match base with | ||
| | None -> Xfs.create result_tmp | ||
| | Some src -> Xfs.cp ~src ~dst:result_tmp | ||
| end | ||
| >>= fun () -> | ||
| Lwt.try_bind | ||
| (fun () -> fn result_tmp) | ||
| (fun r -> | ||
| begin match r with | ||
| | Ok () -> Xfs.rename ~src:result_tmp ~dst:result | ||
| | Error _ -> Xfs.delete result_tmp | ||
| end >>= fun () -> | ||
| Lwt.return r | ||
| ) | ||
| (fun ex -> | ||
| Log.warn (fun f -> f "Uncaught exception from %S build function: %a" id Fmt.exn ex); | ||
| Xfs.delete result_tmp >>= fun () -> | ||
| Lwt.fail ex | ||
| ) | ||
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| let delete t id = | ||
| let path = Path.result t id in | ||
| match Os.check_dir path with | ||
| | `Present -> Xfs.delete path | ||
| | `Missing -> Lwt.return_unit | ||
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| let result t id = | ||
| let dir = Path.result t id in | ||
| match Os.check_dir dir with | ||
| | `Present -> Lwt.return_some dir | ||
| | `Missing -> Lwt.return_none | ||
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| let log_file t id = | ||
| result t id >|= function | ||
| | Some dir -> dir / "log" | ||
| | None -> (Path.result_tmp t id) / "log" | ||
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| let state_dir t = t.path / Path.state_dirname | ||
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| let get_cache t name = | ||
| match Hashtbl.find_opt t.caches name with | ||
| | Some c -> c | ||
| | None -> | ||
| let c = { lock = Lwt_mutex.create (); gen = 0 } in | ||
| Hashtbl.add t.caches name c; | ||
| c | ||
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| let cache ~user t name = | ||
| let cache = get_cache t name in | ||
| Lwt_mutex.with_lock cache.lock @@ fun () -> | ||
| let tmp = Path.cache_tmp t t.next name in | ||
| t.next <- t.next + 1; | ||
| let snapshot = Path.cache t name in | ||
| (* Create cache if it doesn't already exist. *) | ||
| begin match Os.check_dir snapshot with | ||
| | `Missing -> Xfs.create snapshot >>= fun () -> | ||
| let { Obuilder_spec.uid; gid } = match user with | ||
| | `Unix user -> user | ||
| | `Windows _ -> assert false (* xfs not supported on Windows *) | ||
| in | ||
| Os.sudo [ "chown"; Printf.sprintf "%d:%d" uid gid; snapshot ] | ||
| | `Present -> Lwt.return_unit | ||
| end >>= fun () -> | ||
| (* Create writeable clone. *) | ||
| let gen = cache.gen in | ||
| Xfs.cp ~src:snapshot ~dst:tmp >>= fun () -> | ||
| let release () = | ||
| Lwt_mutex.with_lock cache.lock @@ fun () -> | ||
| begin | ||
| if cache.gen = gen then ( | ||
| (* The cache hasn't changed since we cloned it. Update it. *) | ||
| (* todo: check if it has actually changed. *) | ||
| cache.gen <- cache.gen + 1; | ||
| Xfs.delete snapshot >>= fun () -> | ||
| Xfs.rename ~src:tmp ~dst:snapshot | ||
| ) else | ||
| Xfs.delete tmp | ||
| end | ||
| in | ||
| Lwt.return (tmp, release) | ||
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| let delete_cache t name = | ||
| let cache = get_cache t name in | ||
| Lwt_mutex.with_lock cache.lock @@ fun () -> | ||
| cache.gen <- cache.gen + 1; (* Ensures in-progress writes will be discarded *) | ||
| let snapshot = Path.cache t name in | ||
| if Sys.file_exists snapshot then ( | ||
| Xfs.delete snapshot >>= fun () -> | ||
| Lwt_result.return () | ||
| ) else Lwt_result.return () | ||
|
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| let complete_deletes _t = Lwt.return_unit |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,11 @@ | ||
| (** Store builds results using {b XFS} with the reflink feature. | ||
| XFS is intended to behave consistently as it scales to large storage and many files, modern-day XFS was originally from SGI Irix. This store uses the {b reflink} feature in XFS to share blocks between files, to support fast snapshots of directory trees and deduplicate file data for more efficient use of storage hardware. | ||
| For more details on the XFS implementation see {{: https://blogs.oracle.com/linux/post/xfs-data-block-sharing-reflink} XFS - Data Block Sharing (Reflink)} and {{: https://blogs.oracle.com/linux/post/upcoming-xfs-work-in-linux-v48-v49-and-v410-by-darrick-wong} Upcoming XFS Work in Linux v4.8 v4.9 and v4.10+}. *) | ||
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| include S.STORE | ||
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| val create : path:string -> t Lwt.t | ||
| (** [create ~path] creates a new XFS store where everything will | ||
| be stored under [path]. *) |