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guix/gnu/build/file-systems.scm
Guillaume Le Vaillant 0dc5c85638
file-systems: Add support for 'strict-atime' and 'lazy-time' flags. 
* guix/build/syscalls.scm (MS_LAZYTIME): New variable.
* gnu/build/file-systems.scm (mount-flags->bit-mask): Add match rules for
  'strict-atime' and 'lazy-time'.
* doc/guix.texi (File Systems): Add 'strict-atime' and 'lazy-time' to the list
  of supported flags.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2019-12-07 01:00:24 +01:00

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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016, 2017 David Craven <david@craven.ch>
;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2019 Guillaume Le Vaillant <glv@posteo.net>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu build file-systems)
#:use-module (gnu system uuid)
#:use-module (gnu system file-systems)
#:use-module (guix build utils)
#:use-module (guix build bournish)
#:use-module ((guix build syscalls)
#:hide (file-system-type))
#:use-module (rnrs io ports)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 match)
#:use-module (ice-9 rdelim)
#:use-module (system foreign)
#:autoload (system repl repl) (start-repl)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:export (disk-partitions
partition-label-predicate
partition-uuid-predicate
partition-luks-uuid-predicate
find-partition-by-label
find-partition-by-uuid
find-partition-by-luks-uuid
canonicalize-device-spec
read-partition-label
read-partition-uuid
read-luks-partition-uuid
bind-mount
mount-flags->bit-mask
check-file-system
mount-file-system))
;;; Commentary:
;;;
;;; This modules provides tools to deal with disk partitions, and to mount and
;;; check file systems.
;;;
;;; Code:
(define (bind-mount source target)
"Bind-mount SOURCE at TARGET."
(mount source target "" MS_BIND))
(define (seek* fd/port offset whence)
"Like 'seek' but return -1 instead of throwing to 'system-error' upon
EINVAL. This makes it easier to catch cases like OFFSET being too large for
FD/PORT."
(catch 'system-error
(lambda ()
(seek fd/port offset whence))
(lambda args
(if (= EINVAL (system-error-errno args))
-1
(apply throw args)))))
(define (read-superblock device offset size magic?)
"Read a superblock of SIZE from OFFSET and DEVICE. Return the raw
superblock on success, and #f if no valid superblock was found. MAGIC?
takes a bytevector and returns #t when it's a valid superblock."
(call-with-input-file device
(lambda (port)
(and (= offset (seek* port offset SEEK_SET))
(let ((block (make-bytevector size)))
(match (get-bytevector-n! port block 0 (bytevector-length block))
((? eof-object?)
#f)
((? number? len)
(and (= len (bytevector-length block))
(and (magic? block)
block)))))))))
(define null-terminated-latin1->string
(cut latin1->string <> zero?))
;;;
;;; Ext2 file systems.
;;;
;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>.
;; TODO: Use "packed structs" from Guile-OpenGL or similar.
(define-syntax %ext2-endianness
;; Endianness of ext2 file systems.
(identifier-syntax (endianness little)))
(define (ext2-superblock? sblock)
"Return #t when SBLOCK is an ext2 superblock."
(let ((magic (bytevector-u16-ref sblock 56 %ext2-endianness)))
(= magic #xef53)))
(define (read-ext2-superblock device)
"Return the raw contents of DEVICE's ext2 superblock as a bytevector, or #f
if DEVICE does not contain an ext2 file system."
(read-superblock device 1024 264 ext2-superblock?))
(define (ext2-superblock-uuid sblock)
"Return the UUID of ext2 superblock SBLOCK as a 16-byte bytevector."
(sub-bytevector sblock 104 16))
(define (ext2-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string of at most 16 characters, or
#f if SBLOCK has no volume name."
(null-terminated-latin1->string (sub-bytevector sblock 120 16)))
(define (check-ext2-file-system device)
"Return the health of an ext2 file system on DEVICE."
(match (status:exit-val
(system* "e2fsck" "-v" "-p" "-C" "0" device))
(0 'pass)
(1 'errors-corrected)
(2 'reboot-required)
(_ 'fatal-error)))
;;;
;;; Btrfs file systems.
;;;
;; <https://btrfs.wiki.kernel.org/index.php/On-disk_Format#Superblock>.
(define-syntax %btrfs-endianness
;; Endianness of btrfs file systems.
(identifier-syntax (endianness little)))
(define (btrfs-superblock? sblock)
"Return #t when SBLOCK is a btrfs superblock."
(bytevector=? (sub-bytevector sblock 64 8)
(string->utf8 "_BHRfS_M")))
(define (read-btrfs-superblock device)
"Return the raw contents of DEVICE's btrfs superblock as a bytevector, or #f
if DEVICE does not contain a btrfs file system."
(read-superblock device 65536 4096 btrfs-superblock?))
(define (btrfs-superblock-uuid sblock)
"Return the UUID of a btrfs superblock SBLOCK as a 16-byte bytevector."
(sub-bytevector sblock 32 16))
(define (btrfs-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string of at most 256 characters, or
#f if SBLOCK has no volume name."
(null-terminated-latin1->string (sub-bytevector sblock 299 256)))
(define (check-btrfs-file-system device)
"Return the health of a btrfs file system on DEVICE."
(match (status:exit-val
(system* "btrfs" "device" "scan"))
(0 'pass)
(_ 'fatal-error)))
;;;
;;; FAT32 file systems.
;;;
;; <http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-107.pdf>.
(define (fat32-superblock? sblock)
"Return #t when SBLOCK is a fat32 superblock."
(bytevector=? (sub-bytevector sblock 82 8)
(string->utf8 "FAT32 ")))
(define (read-fat32-superblock device)
"Return the raw contents of DEVICE's fat32 superblock as a bytevector, or
#f if DEVICE does not contain a fat32 file system."
(read-superblock device 0 90 fat32-superblock?))
(define (fat32-superblock-uuid sblock)
"Return the Volume ID of a fat superblock SBLOCK as a 4-byte bytevector."
(sub-bytevector sblock 67 4))
(define (fat32-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string of at most 11 characters, or
#f if SBLOCK has no volume name. The volume name is a latin1 string.
Trailing spaces are trimmed."
(string-trim-right (latin1->string (sub-bytevector sblock 71 11) (lambda (c) #f)) #\space))
(define (check-fat-file-system device)
"Return the health of a fat file system on DEVICE."
(match (status:exit-val
(system* "fsck.vfat" "-v" "-a" device))
(0 'pass)
(1 'errors-corrected)
(_ 'fatal-error)))
;;;
;;; FAT16 file systems.
;;;
(define (fat16-superblock? sblock)
"Return #t when SBLOCK is a fat16 boot record."
(bytevector=? (sub-bytevector sblock 54 8)
(string->utf8 "FAT16 ")))
(define (read-fat16-superblock device)
"Return the raw contents of DEVICE's fat16 superblock as a bytevector, or
#f if DEVICE does not contain a fat16 file system."
(read-superblock device 0 62 fat16-superblock?))
(define (fat16-superblock-uuid sblock)
"Return the Volume ID of a fat superblock SBLOCK as a 4-byte bytevector."
(sub-bytevector sblock 39 4))
(define (fat16-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string of at most 11 characters, or
#f if SBLOCK has no volume name. The volume name is a latin1 string.
Trailing spaces are trimmed."
(string-trim-right (latin1->string (sub-bytevector sblock 43 11)
(lambda (c) #f))
#\space))
;;;
;;; ISO9660 file systems.
;;;
;; <http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-119.pdf>.
(define (iso9660-superblock? sblock)
"Return #t when SBLOCK is an iso9660 volume descriptor."
(bytevector=? (sub-bytevector sblock 1 6)
;; Note: "\x01" is the volume descriptor format version
(string->utf8 "CD001\x01")))
(define (read-iso9660-primary-volume-descriptor device offset)
"Find and read the first primary volume descriptor, starting at OFFSET.
Return #f if not found."
(let* ((sblock (read-superblock device offset 2048 iso9660-superblock?))
(type-code (if sblock
(bytevector-u8-ref sblock 0)
(error (format #f
"Could not read ISO9660 primary
volume descriptor from ~s"
device)))))
(match type-code
(255 #f) ; Volume Descriptor Set Terminator.
(1 sblock) ; Primary Volume Descriptor
(_ (read-iso9660-primary-volume-descriptor device (+ offset 2048))))))
(define (read-iso9660-superblock device)
"Return the raw contents of DEVICE's iso9660 primary volume descriptor
as a bytevector, or #f if DEVICE does not contain an iso9660 file system."
;; Start reading at sector 16.
;; Since we are not sure that the device contains an ISO9660 file system,
;; we have to find that out first.
(if (read-superblock device (* 2048 16) 2048 iso9660-superblock?)
(read-iso9660-primary-volume-descriptor device (* 2048 16))
#f)) ; Device does not contain an iso9660 file system.
(define (iso9660-superblock-uuid sblock)
"Return the modification time of an iso9660 primary volume descriptor
SBLOCK as a bytevector. If that's not set, returns the creation time."
;; Drops GMT offset for compatibility with Grub, blkid and /dev/disk/by-uuid.
;; Compare Grub: "2014-12-02-19-30-23-00".
;; Compare blkid result: "2014-12-02-19-30-23-00".
;; Compare /dev/disk/by-uuid entry: "2014-12-02-19-30-23-00".
(let* ((creation-time (sub-bytevector sblock 813 17))
(modification-time (sub-bytevector sblock 830 17))
(unset-time (make-bytevector 17 0))
(time (if (bytevector=? unset-time modification-time)
creation-time
modification-time)))
(sub-bytevector time 0 16))) ; strips GMT offset.
(define (iso9660-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string. The volume name is an ASCII
string. Trailing spaces are trimmed."
;; Note: Valid characters are of the set "[0-9][A-Z]_" (ECMA-119 Appendix A)
(string-trim-right (latin1->string (sub-bytevector sblock 40 32)
(lambda (c) #f)) #\space))
;;;
;;; LUKS encrypted devices.
;;;
;; The LUKS header format is described in "LUKS On-Disk Format Specification":
;; <https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification>. We follow
;; version 1.2.1 of this document.
(define-syntax %luks-endianness
;; Endianness of LUKS headers.
(identifier-syntax (endianness big)))
(define (luks-superblock? sblock)
"Return #t when SBLOCK is a luks superblock."
(define %luks-magic
;; The 'LUKS_MAGIC' constant.
(u8-list->bytevector (append (map char->integer (string->list "LUKS"))
(list #xba #xbe))))
(let ((magic (sub-bytevector sblock 0 6))
(version (bytevector-u16-ref sblock 6 %luks-endianness)))
(and (bytevector=? magic %luks-magic)
(= version 1))))
(define (read-luks-header file)
"Read a LUKS header from FILE. Return the raw header on success, and #f if
not valid header was found."
;; Size in bytes of the LUKS header, including key slots.
(read-superblock file 0 592 luks-superblock?))
(define (luks-header-uuid header)
"Return the LUKS UUID from HEADER, as a 16-byte bytevector."
;; 40 bytes are reserved for the UUID, but in practice, it contains the 36
;; bytes of its ASCII representation.
(let ((uuid (sub-bytevector header 168 36)))
(string->uuid (utf8->string uuid))))
;;;
;;; Partition lookup.
;;;
(define (disk-partitions)
"Return the list of device names corresponding to valid disk partitions."
(define (partition? name major minor)
;; grub-mkrescue does some funny things for EFI support which
;; makes it a lot more difficult than one would expect to support
;; booting an ISO-9660 image from an USB flash drive.
;; For example there's a buggy (too small) hidden partition in it
;; which Linux mounts and then proceeds to fail while trying to
;; fall off the edge.
;; In any case, partition tables are supposed to be optional so
;; here we allow checking entire disks for file systems, too.
(> major 2)) ;ignore RAM disks and floppy disks
(call-with-input-file "/proc/partitions"
(lambda (port)
;; Skip the two header lines.
(read-line port)
(read-line port)
;; Read each subsequent line, and extract the last space-separated
;; field.
(let loop ((parts '()))
(let ((line (read-line port)))
(if (eof-object? line)
(reverse parts)
(match (string-tokenize line)
(((= string->number major) (= string->number minor)
blocks name)
(if (partition? name major minor)
(loop (cons name parts))
(loop parts))))))))))
(define (ENOENT-safe proc)
"Wrap the one-argument PROC such that ENOENT errors are caught and lead to a
warning and #f as the result."
(lambda (device)
(catch 'system-error
(lambda ()
(proc device))
(lambda args
;; When running on the hand-made /dev,
;; 'disk-partitions' could return partitions for which
;; we have no /dev node. Handle that gracefully.
(let ((errno (system-error-errno args)))
(cond ((= ENOENT errno)
(format (current-error-port)
"warning: device '~a' not found~%" device)
#f)
((= ENOMEDIUM errno) ;for removable media
#f)
((= EIO errno) ;unreadable hardware like audio CDs
(format (current-error-port)
"warning: failed to read from device '~a'~%" device)
#f)
(else
(apply throw args))))))))
(define (partition-field-reader read field)
"Return a procedure that takes a device and returns the value of a FIELD in
the partition superblock or #f."
(let ((read (ENOENT-safe read)))
(lambda (device)
(let ((sblock (read device)))
(and sblock
(field sblock))))))
(define (read-partition-field device partition-field-readers)
"Returns the value of a FIELD in the partition superblock of DEVICE or #f. It
takes a list of PARTITION-FIELD-READERS and returns the result of the first
partition field reader that returned a value."
(match (filter-map (cut apply <> (list device)) partition-field-readers)
((field . _) field)
(_ #f)))
(define %partition-label-readers
(list (partition-field-reader read-iso9660-superblock
iso9660-superblock-volume-name)
(partition-field-reader read-ext2-superblock
ext2-superblock-volume-name)
(partition-field-reader read-btrfs-superblock
btrfs-superblock-volume-name)
(partition-field-reader read-fat32-superblock
fat32-superblock-volume-name)
(partition-field-reader read-fat16-superblock
fat16-superblock-volume-name)))
(define %partition-uuid-readers
(list (partition-field-reader read-iso9660-superblock
iso9660-superblock-uuid)
(partition-field-reader read-ext2-superblock
ext2-superblock-uuid)
(partition-field-reader read-btrfs-superblock
btrfs-superblock-uuid)
(partition-field-reader read-fat32-superblock
fat32-superblock-uuid)
(partition-field-reader read-fat16-superblock
fat16-superblock-uuid)))
(define read-partition-label
(cut read-partition-field <> %partition-label-readers))
(define read-partition-uuid
(cut read-partition-field <> %partition-uuid-readers))
(define luks-partition-field-reader
(partition-field-reader read-luks-header luks-header-uuid))
(define read-luks-partition-uuid
(cut read-partition-field <> (list luks-partition-field-reader)))
(define (partition-predicate reader =)
"Return a predicate that returns true if the FIELD of partition header that
was READ is = to the given value."
(lambda (expected)
(lambda (device)
(let ((actual (reader device)))
(and actual
(= actual expected))))))
(define partition-label-predicate
(partition-predicate read-partition-label string=?))
(define partition-uuid-predicate
(partition-predicate read-partition-uuid uuid=?))
(define luks-partition-uuid-predicate
(partition-predicate luks-partition-field-reader uuid=?))
(define (find-partition predicate)
"Return the first partition found that matches PREDICATE, or #f if none
were found."
(lambda (expected)
(find (predicate expected)
(map (cut string-append "/dev/" <>)
(disk-partitions)))))
(define find-partition-by-label
(find-partition partition-label-predicate))
(define find-partition-by-uuid
(find-partition partition-uuid-predicate))
(define find-partition-by-luks-uuid
(find-partition luks-partition-uuid-predicate))
(define (canonicalize-device-spec spec)
"Return the device name corresponding to SPEC, which can be a <uuid>, a
<file-system-label>, or a string (typically a /dev file name)."
(define max-trials
;; Number of times we retry partition label resolution, 1 second per
;; trial. Note: somebody reported a delay of 16 seconds (!) before their
;; USB key would be detected by the kernel, so we must wait for at least
;; this long.
20)
(define (resolve find-partition spec fmt)
(let loop ((count 0))
(let ((device (find-partition spec)))
(or device
;; Some devices take a bit of time to appear, most notably USB
;; storage devices. Thus, wait for the device to appear.
(if (> count max-trials)
(error "failed to resolve partition" (fmt spec))
(begin
(format #t "waiting for partition '~a' to appear...~%"
(fmt spec))
(sleep 1)
(loop (+ 1 count))))))))
(match spec
((? string?)
;; Nothing to do, but wait until SPEC shows up.
(resolve identity spec identity))
((? file-system-label?)
;; Resolve the label.
(resolve find-partition-by-label
(file-system-label->string spec)
identity))
((? uuid?)
(resolve find-partition-by-uuid
(uuid-bytevector spec)
uuid->string))))
(define (check-file-system device type)
"Run a file system check of TYPE on DEVICE."
(define check-procedure
(cond
((string-prefix? "ext" type) check-ext2-file-system)
((string-prefix? "btrfs" type) check-btrfs-file-system)
((string-suffix? "fat" type) check-fat-file-system)
(else #f)))
(if check-procedure
(match (check-procedure device)
('pass
#t)
('errors-corrected
(format (current-error-port)
"File system check corrected errors on ~a; continuing~%"
device))
('reboot-required
(format (current-error-port)
"File system check corrected errors on ~a; rebooting~%"
device)
(sleep 3)
(reboot))
('fatal-error
(format (current-error-port) "File system check on ~a failed~%"
device)
;; Spawn a REPL only if someone would be able to interact with it.
(when (isatty? (current-input-port))
(format (current-error-port) "Spawning Bourne-like REPL.~%")
;; 'current-output-port' is typically connected to /dev/klog (in
;; PID 1), but here we want to make sure we talk directly to the
;; user.
(with-output-to-file "/dev/console"
(lambda ()
(start-repl %bournish-language))))))
(format (current-error-port)
"No file system check procedure for ~a; skipping~%"
device)))
(define (mount-flags->bit-mask flags)
"Return the number suitable for the 'flags' argument of 'mount' that
corresponds to the symbols listed in FLAGS."
(let loop ((flags flags))
(match flags
(('read-only rest ...)
(logior MS_RDONLY (loop rest)))
(('bind-mount rest ...)
(logior MS_BIND (loop rest)))
(('no-suid rest ...)
(logior MS_NOSUID (loop rest)))
(('no-dev rest ...)
(logior MS_NODEV (loop rest)))
(('no-exec rest ...)
(logior MS_NOEXEC (loop rest)))
(('no-atime rest ...)
(logior MS_NOATIME (loop rest)))
(('strict-atime rest ...)
(logior MS_STRICTATIME (loop rest)))
(('lazy-time rest ...)
(logior MS_LAZYTIME (loop rest)))
(()
0))))
(define* (mount-file-system fs #:key (root "/root"))
"Mount the file system described by FS, a <file-system> object, under ROOT."
(define (mount-nfs source mount-point type flags options)
(let* ((idx (string-rindex source #\:))
(host-part (string-take source idx))
;; Strip [] from around host if present
(host (match (string-split host-part (string->char-set "[]"))
(("" h "") h)
((h) h)))
(aa (match (getaddrinfo host "nfs") ((x . _) x)))
(sa (addrinfo:addr aa))
(inet-addr (inet-ntop (sockaddr:fam sa)
(sockaddr:addr sa))))
;; Mounting an NFS file system requires passing the address
;; of the server in the addr= option
(mount source mount-point type flags
(string-append "addr="
inet-addr
(if options
(string-append "," options)
"")))))
(let ((type (file-system-type fs))
(options (file-system-options fs))
(source (canonicalize-device-spec (file-system-device fs)))
(mount-point (string-append root "/"
(file-system-mount-point fs)))
(flags (mount-flags->bit-mask (file-system-flags fs))))
(when (file-system-check? fs)
(check-file-system source type))
;; Create the mount point. Most of the time this is a directory, but
;; in the case of a bind mount, a regular file or socket may be needed.
(if (and (= MS_BIND (logand flags MS_BIND))
(not (file-is-directory? source)))
(unless (file-exists? mount-point)
(mkdir-p (dirname mount-point))
(call-with-output-file mount-point (const #t)))
(mkdir-p mount-point))
(cond
((string-prefix? "nfs" type)
(mount-nfs source mount-point type flags options))
(else
(mount source mount-point type flags options)))
;; For read-only bind mounts, an extra remount is needed, as per
;; <http://lwn.net/Articles/281157/>, which still applies to Linux 4.0.
(when (and (= MS_BIND (logand flags MS_BIND))
(= MS_RDONLY (logand flags MS_RDONLY)))
(let ((flags (logior MS_BIND MS_REMOUNT MS_RDONLY)))
(mount source mount-point type flags #f)))))
;;; file-systems.scm ends here
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