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authorLudovic Courtès <ludo@gnu.org>2018-12-14 11:10:25 +0100
committerLudovic Courtès <ludo@gnu.org>2018-12-14 12:07:24 +0100
commitadb158b7396cbdcda347fa298978408e531a03fd (patch)
treefd6877e72a20840cd3962f80a89618bd08fcf04b
parentea49fbdea3bbb9b55951b7bff9d9cf768fd23161 (diff)
deduplication: Gracefully handle ENOSPC raised by 'link' calls.
Reported by Andreas Enge <andreas@enge.fr> in <https://bugs.gnu.org/33676>. * guix/store/deduplication.scm (replace-with-link): Catch ENOSPC around 'get-temp-link'. Do nothing when 'get-temp-link' throws ENOSPC. Move code to restore PARENT's permissions outside of 'catch'. * tests/store-deduplication.scm ("deduplicate, ENOSPC"): New test.
-rw-r--r--guix/store/deduplication.scm40
-rw-r--r--tests/store-deduplication.scm44
2 files changed, 70 insertions, 14 deletions
diff --git a/guix/store/deduplication.scm b/guix/store/deduplication.scm
index 21b0c81f3d..a777940f86 100644
--- a/guix/store/deduplication.scm
+++ b/guix/store/deduplication.scm
@@ -99,24 +99,38 @@ LINK-PREFIX."
(define* (replace-with-link target to-replace
#:key (swap-directory (dirname target)))
"Atomically replace the file TO-REPLACE with a link to TARGET. Use
-SWAP-DIRECTORY as the directory to store temporary hard links.
+SWAP-DIRECTORY as the directory to store temporary hard links. Upon ENOSPC
+and EMLINK, TO-REPLACE is left unchanged.
Note: TARGET, TO-REPLACE, and SWAP-DIRECTORY must be on the same file system."
- (let* ((temp-link (get-temp-link target swap-directory))
- (parent (dirname to-replace))
- (stat (stat parent)))
- (make-file-writable parent)
+ (define temp-link
(catch 'system-error
(lambda ()
- (rename-file temp-link to-replace)
-
- ;; Restore PARENT's mtime and permissions.
- (set-file-time parent stat)
- (chmod parent (stat:mode stat)))
+ (get-temp-link target swap-directory))
(lambda args
- (delete-file temp-link)
- (unless (= EMLINK (system-error-errno args))
- (apply throw args))))))
+ ;; We get ENOSPC when we can't fit an additional entry in
+ ;; SWAP-DIRECTORY.
+ (if (= ENOSPC (system-error-errno args))
+ #f
+ (apply throw args)))))
+
+ ;; 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
+ (let* ((parent (dirname to-replace))
+ (stat (stat parent)))
+ (make-file-writable parent)
+ (catch 'system-error
+ (lambda ()
+ (rename-file temp-link to-replace))
+ (lambda args
+ (delete-file temp-link)
+ (unless (= EMLINK (system-error-errno args))
+ (apply throw args))))
+
+ ;; Restore PARENT's mtime and permissions.
+ (set-file-time parent stat)
+ (chmod parent (stat:mode stat)))))
(define* (deduplicate path hash #:key (store %store-directory))
"Check if a store item with sha256 hash HASH already exists. If so,
diff --git a/tests/store-deduplication.scm b/tests/store-deduplication.scm
index e438aa84c6..e2870a363d 100644
--- a/tests/store-deduplication.scm
+++ b/tests/store-deduplication.scm
@@ -48,7 +48,7 @@
(put-bytevector port data))))
identical)
;; Make the parent of IDENTICAL read-only. This should not prevent
- ;; deduplication for inserting its hard link.
+ ;; deduplication from inserting its hard link.
(chmod (dirname (second identical)) #o544)
(call-with-output-file unique
@@ -64,4 +64,46 @@
(stat:nlink (stat unique))
(map (compose stat:nlink stat) identical))))))
+(test-equal "deduplicate, ENOSPC"
+ (cons* #f ;inode comparison
+ (append (make-list 3 4)
+ (make-list 7 1))) ;'nlink' values
+
+ ;; In this scenario the first 3 files are properly deduplicated and then we
+ ;; simulate a full '.links' directory where link(2) gets ENOSPC, thereby
+ ;; preventing deduplication of the subsequent files.
+ (call-with-temporary-directory
+ (lambda (store)
+ (let ((true-link link)
+ (links 0)
+ (data1 (string->utf8 "Hello, world!"))
+ (data2 (string->utf8 "Hi, world!"))
+ (identical (map (lambda (n)
+ (string-append store "/" (number->string n)
+ "/a/b/c"))
+ (iota 10)))
+ (populate (lambda (data)
+ (lambda (file)
+ (mkdir-p (dirname file))
+ (call-with-output-file file
+ (lambda (port)
+ (put-bytevector port data)))))))
+ (for-each (populate data1) (take identical 5))
+ (for-each (populate data2) (drop identical 5))
+ (dynamic-wind
+ (lambda ()
+ (set! link (lambda (old new)
+ (set! links (+ links 1))
+ (if (<= links 3)
+ (true-link old new)
+ (throw 'system-error "link" "~A" '("Whaaat?!")
+ (list ENOSPC))))))
+ (lambda ()
+ (deduplicate store (nar-sha256 store) #:store store))
+ (lambda ()
+ (set! link true-link)))
+
+ (cons (apply = (map (compose stat:ino stat) identical))
+ (map (compose stat:nlink stat) identical))))))
+
(test-end "store-deduplication")