bug#47007: dcb640f02b broke guix environment --container

[Ludovic Courtès]

Here’s a more sensible patch for you to try.  This time it should
correctly determine the necessary mount flags based on statfs(2) info.

Could you apply it and report back?

TIA!

Ludo’.

diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index aca4aad848..304805db62 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -920,14 +920,8 @@ corresponds to the symbols listed in FLAGS."
                           ;; MS_REMOUNT call below fails with EPERM.
                           ;; See <https://bugs.gnu.org/46292>
                           (if (memq 'bind-mount (file-system-flags fs))
-                              (or (and=> (find (let ((devno (stat:dev
-                                                             (lstat source))))
-                                                 (lambda (mount)
-                                                   (= (mount-device-number 
mount)
-                                                      devno)))
-                                               (mounts))
-                                         mount-flags)
-                                  0)
+                              (statfs-flags->mount-flags
+                               (file-system-mount-flags (statfs source)))
                               0)))
          (options (file-system-options fs)))
     (when (file-system-check? fs)
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 552343a481..6ed11a0d69 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -82,6 +82,21 @@
             file-system-fragment-size
             file-system-mount-flags
             statfs
+
+            ST_RDONLY
+            ST_NOSUID
+            ST_NODEV
+            ST_NOEXEC
+            ST_SYNCHRONOUS
+            ST_MANDLOCK
+            ST_WRITE
+            ST_APPEND
+            ST_IMMUTABLE
+            ST_NOATIME
+            ST_NODIRATIME
+            ST_RELATIME
+            statfs-flags->mount-flags
+
             free-disk-space
             device-in-use?
             add-to-entropy-count
@@ -754,6 +769,56 @@ fdatasync(2) on the underlying file descriptor."
 (define-syntax fsword                             ;fsword_t
   (identifier-syntax long))
 
+(define linux? (string-contains %host-type "linux-gnu"))
+
+(define-syntax define-statfs-flags
+  (syntax-rules (linux hurd)
+    "Define the statfs mount flags."
+    ((_ (name (linux linux-value) (hurd hurd-value)) rest ...)
+     (begin
+       (define name
+         (if linux? linux-value hurd-value))
+       (define-statfs-flags rest ...)))
+    ((_ (name value) rest ...)
+     (begin
+       (define name value)
+       (define-statfs-flags rest ...)))
+    ((_) #t)))
+
+(define-statfs-flags                              ;<bits/statfs.h>
+  (ST_RDONLY      1)
+  (ST_NOSUID      2)
+  (ST_NODEV       (linux 4) (hurd 0))
+  (ST_NOEXEC      8)
+  (ST_SYNCHRONOUS 16)
+  (ST_MANDLOCK    (linux 64) (hurd 0))
+  (ST_WRITE       (linux 128) (hurd 0))
+  (ST_APPEND      (linux 256) (hurd 0))
+  (ST_IMMUTABLE   (linux 512) (hurd 0))
+  (ST_NOATIME     (linux 1024) (hurd 32))
+  (ST_NODIRATIME  (linux 2048) (hurd 0))
+  (ST_RELATIME    (linux 4096) (hurd 64)))
+
+(define (statfs-flags->mount-flags flags)
+  "Convert FLAGS, a logical or of ST_* constants as returned by
+'file-system-mount-flags', to the corresponding logical or of MS_* constants."
+  (letrec-syntax ((match-flags (syntax-rules (=>)
+                                 ((_ (statfs => mount) rest ...)
+                                  (logior (if (zero? (logand flags statfs))
+                                              0
+                                              mount)
+                                          (match-flags rest ...)))
+                                 ((_)
+                                  0))))
+    (match-flags
+     (ST_RDONLY     => MS_RDONLY)
+     (ST_NOSUID     => MS_NOSUID)
+     (ST_NODEV      => MS_NODEV)
+     (ST_NOEXEC     => MS_NOEXEC)
+     (ST_NOATIME    => MS_NOATIME)
+     (ST_NODIRATIME => 0)                         ;FIXME
+     (ST_RELATIME   => MS_RELATIME))))
+
 (define-c-struct %statfs                          ;<bits/statfs.h>
   sizeof-statfs                                   ;slightly overestimated
   file-system
@@ -769,7 +834,7 @@ fdatasync(2) on the underlying file descriptor."
   (identifier       (array int 2))
   (name-length      fsword)
   (fragment-size    fsword)
-  (mount-flags      fsword)
+  (mount-flags      fsword)                       ;ST_*
   (spare            (array fsword 4)))
 
 (define statfs