deduplication: pass store directory to replace-with-link.

This causes with-writable-file to take into consideration the actual store
being used, as passed to 'deduplicate', rather than
whatever (%store-directory) may return.

* guix/store/deduplication.scm (replace-with-link): new keyword argument
  'store'.  Pass to with-writable-file.
  (with-writable-file, call-with-writable-file): new store argument.
  (deduplicate): pass store to replace-with-link.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

.dir-locals.el

@@ -37,7 +37,7 @@
    (eval . (put 'with-file-lock 'scheme-indent-function 1))
    (eval . (put 'with-file-lock/no-wait 'scheme-indent-function 1))
    (eval . (put 'with-profile-lock 'scheme-indent-function 1))
-   (eval . (put 'with-writable-file 'scheme-indent-function 1))
+   (eval . (put 'with-writable-file 'scheme-indent-function 2))
 
    (eval . (put 'package 'scheme-indent-function 0))
    (eval . (put 'package/inherit 'scheme-indent-function 1))

guix/store/deduplication.scm

@@ -94,8 +94,8 @@ LINK-PREFIX."
             (try (tempname-in link-prefix))
             (apply throw args))))))
 
-(define (call-with-writable-file file thunk)
+(define (call-with-writable-file file store thunk)
-  (if (string=? file (%store-directory))
+  (if (string=? file store)
       (thunk)                       ;don't meddle with the store's permissions
       (let ((stat (lstat file)))
         (dynamic-wind
@@ -106,17 +106,18 @@ LINK-PREFIX."
             (set-file-time file stat)
             (chmod file (stat:mode stat)))))))
 
-(define-syntax-rule (with-writable-file file exp ...)
+(define-syntax-rule (with-writable-file file store exp ...)
   "Make FILE writable for the dynamic extent of EXP..., except if FILE is the
 store."
-  (call-with-writable-file file (lambda () exp ...)))
+  (call-with-writable-file file store (lambda () exp ...)))
 
 ;; There are 3 main kinds of errors we can get from hardlinking: "Too many
 ;; things link to this" (EMLINK), "this link already exists" (EEXIST), and
 ;; "can't fit more stuff in this directory" (ENOSPC).
 
 (define* (replace-with-link target to-replace
-                            #:key (swap-directory (dirname target)))
+                            #:key (swap-directory (dirname target))
+                            (store (%store-directory)))
   "Atomically replace the file TO-REPLACE with a link to TARGET.  Use
 SWAP-DIRECTORY as the directory to store temporary hard links.  Upon ENOSPC
 and EMLINK, TO-REPLACE is left unchanged.
@@ -137,7 +138,7 @@ Note: TARGET, TO-REPLACE, and SWAP-DIRECTORY must be on the same file system."
   ;; If we couldn't create TEMP-LINK, that's OK: just don't do the
   ;; replacement, which means TO-REPLACE won't be deduplicated.
   (when temp-link
-    (with-writable-file (dirname to-replace)
+    (with-writable-file (dirname to-replace) store
       (catch 'system-error
         (lambda ()
           (rename-file temp-link to-replace))
@@ -176,7 +177,8 @@ under STORE."
                                           (bytevector->nix-base32-string hash))))
             (if (file-exists? link-file)
                 (replace-with-link link-file path
-                                 #:swap-directory links-directory)
+                                   #:swap-directory links-directory
+                                   #:store store)
                 (catch 'system-error
                   (lambda ()
                     (link path link-file))
@@ -186,7 +188,9 @@ under STORE."
                              ;; Someone else put an entry for PATH in
                              ;; LINKS-DIRECTORY before we could.  Let's use it.
                              (replace-with-link path link-file
-                                              #:swap-directory links-directory))
+                                                #:swap-directory
+                                                links-directory
+                                                #:store store))
                             ((= errno ENOSPC)
                              ;; There's not enough room in the directory index for
                              ;; more entries in .links, but that's fine: we can