Re: [PATCH] build: file-systems: Allow for bind mounting regular files.

["Thompson, David" <dthompson2@worcester.edu>]

[-- Attachment #1: Type: text/plain, Size: 767 bytes --]

On Sun, Aug 2, 2015 at 8:10 AM, Alex Kost <alezost@gmail.com> wrote:
> David Thompson (2015-08-01 22:17 +0300) wrote:
>
>> diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
>> index c58d23c..f0d6f70 100644
>> --- a/gnu/build/file-systems.scm
>> +++ b/gnu/build/file-systems.scm
>> @@ -305,6 +305,10 @@ the following:
>>                 fsck code device)
>>         (start-repl)))))
>>
>> +(define (regular-file? file-name)
>> +  "Return #t if FILE-NAME is a regular file."
>> +  (eq? (stat:type (stat file-name)) 'regular))
>
> There are similar procedures in (guix build utils): 'directory-exists?',
> 'executable-file?' and 'symbolic-link?'.  So I think it is better to put
> 'regular-file?' there.  WDYT?

Sure, that makes sense.  Done.

- Dave

[-- Attachment #2: 0001-build-file-systems-Allow-for-bind-mounting-regular-f.patch --]
[-- Type: text/x-patch, Size: 2283 bytes --]

From 1b2413bd06b1e769edfbe4d170de41398015a67d Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sat, 1 Aug 2015 13:43:33 -0400
Subject: [PATCH] build: file-systems: Allow for bind mounting regular files.

* guix/build/utils.scm (regular-file?): New procedure.
* gnu/build/file-systems.scm (mount-file-system): Create a regular file
  instead of a directory when bind mounting a regular file.
---
 gnu/build/file-systems.scm | 11 ++++++++++-
 guix/build/utils.scm       |  5 +++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index c58d23c..f0b4b79 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -339,7 +339,16 @@ run a file system check."
            (flags       (mount-flags->bit-mask flags)))
        (when check?
          (check-file-system source type))
-       (mkdir-p mount-point)
+
+       ;; Create the mount point.  Most of the time this is a directory, but
+       ;; in the case of a bind mount, a regular file may be needed.
+       (if (and (= MS_BIND (logand flags MS_BIND))
+                (regular-file? source))
+           (begin
+             (mkdir-p (dirname mount-point))
+             (call-with-output-file mount-point (const #t)))
+           (mkdir-p mount-point))
+
        (mount source mount-point type flags options)
 
        ;; For read-only bind mounts, an extra remount is needed, as per
diff --git a/guix/build/utils.scm b/guix/build/utils.scm
index 676a012..b9543ed 100644
--- a/guix/build/utils.scm
+++ b/guix/build/utils.scm
@@ -38,6 +38,7 @@
             directory-exists?
             executable-file?
             symbolic-link?
+            regular-file?
             call-with-ascii-input-file
             elf-file?
             ar-file?
@@ -110,6 +111,10 @@
   "Return #t if FILE is a symbolic link (aka. \"symlink\".)"
   (eq? (stat:type (lstat file)) 'symlink))
 
+(define (regular-file? file-name)
+  "Return #t if FILE-NAME is a regular file."
+  (eq? (stat:type (stat file-name)) 'regular))
+
 (define (call-with-ascii-input-file file proc)
   "Open FILE as an ASCII or binary file, and pass the resulting port to
 PROC.  FILE is closed when PROC's dynamic extent is left.  Return the
-- 
2.4.3