bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

[Michael Albinus]

Using recent master.

I have my ~/.nnmail-cache file on a mounted directory:

--8<---------------cut here---------------start------------->8---
# ls -l ~/.nnmail-cache
lrwxrwxrwx 1 albinus albinus 31 Mar 12  2012 /home/albinus/.nnmail-cache -> /net/ford/albinus/.nnmail-cache
--8<---------------cut here---------------end--------------->8---

This prevents me from reding new mails via gnus:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (file-error "Doing chmod" "Operation not supported" "/home/albinus/.nnmail-cache")
  set-file-modes("~/.nnmail-cache" 384 nofollow)
  nnmail-write-region(1 1891048 "~/.nnmail-cache" nil silent)
  nnmail-cache-close()
  nnmail-get-new-mail-1(nnml nnml-save-incremental-nov "~/Mail" nil nil nil)
  nnmail-get-new-mail(nnml nnml-save-incremental-nov "~/Mail" nil)
  nnml-request-scan(nil "")
  gnus-request-scan(nil (nnml ""))
  gnus-read-active-file-1((nnml "") nil)
  gnus-read-active-for-groups((nnml "") (("nnml:zumbusch" 3 ((1 . 13)) ((unexist) (seen ...) (reply 7 12)) "nnml:" ((timestamp 22158 47874))) ("nnml:yahoo" 3 ((1 . 5)) nil "nnml:") ("nnml:wenzel" 3 ((1 . 96)) ((unexist) (seen ... ... ... 80 82 84 ... 89 ...) (forward 68 78) (reply 1 58 ... 68 71 ... 78 80 82 84 87 89 93 96)) "nnml:" ((timestamp . 1575130099))) ("nnml:vodafone" 3 ((1 . 1)) ((unexist) (seen 1)) "nnml:" ((timestamp 23430 52917))) ("nnml:vio" 3 ((1 . 5)) ((reply 4) (unexist) (seen 1)) "nnml:" ((timestamp 22786 64120))) ("nnml:verein" 3 ((1 . 51)) ((seen ...) (forward 47 51) (reply 47 49)) "nnml:" ((timestamp 19980 58085))) ("nnml:tramp-archive" 3 ((1 . 11506)) ((unexist) (seen ...) (forward 8365 8621 8994 9285 9686 10101 10441 10619) (reply 7750 7763 7766 ... 7809 7812 7844 7846 7848 7852 7855 7891 7893 7901 7904 7913 7915 7921 7923 7925 7937 7939 7942 7944 7954 7965 7977 7980 7982 7984 7986 ...) (tick ... 6904 8007 ... 8084)) "nnml:" ((timestamp . 1561491236))) ("nnml:tramp" 3 ((1 . 12332) (12334 . 12336) 12338 (12341 . 12342) (12344 . 12615) (12617 . 13112) (13114 . 13687) (13689 . 14816) (14818 . 14862) (14864 . 15327) (15329 . 15633) (15635 . 18133) (18135 . 18886) (18888 . 18889) (18891 . 18923) (19110 . 19113)) ((unexist) (seen ... ...) (forward 9654 9985 11619 11980 12431 12667 13152 13698 14092 14545 14954 ... 14975 15050 15575 16060 16140 16674 16677 17568 17795 18235 18456) (reply 9644 9646 9651 9663 9667 9680 ... 9685 9693 9696 9701 ... 9710 ... 9716 9730 9732 9734 9736 9741 9750 9752 9761 9764 9766 ... 9774 ... 9786 9789 9793 ...) (tick 11692 11702)) "nnml:" ((timestamp . 1578399220))) ("nnml:tieto" 3 ((1 . 21)) ((seen ...) (save 9 18) (reply 3 ... ... 16)) "nnml:" ((timestamp 19906 58758))) ("nnml:threads" 3 ((1 . 167) (173 . 175) (177 . 179) (190 . 193) (195 . 273) (281 . 324)) ((unexist) (seen ... 288) (reply 155 199 201 203 ... ... 229 231 233 ... 238 240 248 256 262 269 298)) "nnml:" ((timestamp . 1578398332))) ("nnml:thiel" 3 ((1 . 1)) ((unexist) (seen 1)) "nnml:" ((timestamp 22996 44872))) ("nnml:telekom" 3 ((1 . 88)) nil "nnml:") ("nnml:susann" 3 ((1 . 651)) ((unexist) (seen ... ...) (forward 410 413 432 447 469 499 503 ... 522 531 544 546 594 613 632 644) (save 412 499) (reply 348 368 377 379 381 387 389 394 ... 420 426 428 443 468 471 473 486 488 491 498 501 ... 508 512 518 524 531 536 546 548 ... ...)) "nnml:" ((timestamp . 1567012544))) ("nnml:spezis" 3 ((1 . 53)) ((seen ...) (reply 34 36 40 ... 51 53)) "nnml:" ((timestamp 21049 31758))) ("nnml:sonos" 3 ((1 . 9)) nil "nnml:") ("nnml:sigrid" 3 ((1 . 978) 995) ((unexist) (seen ... ...) (forward ... 410 ... 431 ... 444 ... 475 ... ... 503 508 514 517 528 ... ... ... 593 595 ... 603 ... 617 620 ... 668 679 687 690 705 ...) (save 362 367 397 569 ...) (reply 363 368 412 420 434 458 465 467 484 ... ... 503 508 514 540 542 549 552 ... 564 566 569 579 586 590 597 610 632 643 645 648 ...)) "nnml:" ((timestamp . 1574345954))) ("nnml:shanmug" 3 ((1 . 5)) nil "nnml:") ("nnml:seminartreffen" 3 ((1 . 4)) nil "nnml:") ("nnml:rms" 3 ((1 . 5)) ((seen ...)) "nnml:" ((timestamp 19806 62525))) ("nnml:ristock" 3 ((1 . 20)) nil "nnml:") ("nnml:rimbach" 3 ((1 . 1)) nil "nnml:") ("nnml:ralf" 3 ((1 . 14)) ((unexist) (seen ...)) "nnml:" ((timestamp 22623 44813))) ("nnml:rainer" 3 ((1 . 11)) ((unexist) (seen ...) (forward ...) (save 2) (reply 2 8 11)) "nnml:" ((timestamp 23645 26101))) ("nnml:pospiech" 3 ((1 . 4)) nil "nnml:") ("nnml:pierru" 3 ((1 . 107)) ((unexist) (seen ...) (forward 88 101 103) (reply 88 90 93 95 98 ... 106)) "nnml:" ((timestamp . 1577728372))) ("nnml:pieplow" 3 ((1 . 5)) ((unexist) (seen ...)) "nnml:" ((timestamp 21534 22076))) ("nnml:pgp" 3 ((1 . 4)) nil "nnml:") ("nnml:paypal" 3 ((1 . 222)) ((unexist) (seen ...) (forward 56 60 108 116 180 ... 207 210)) "nnml:" ((timestamp . 1577353063))) ("nnml:paschelke" 3 ((1 . 3)) nil "nnml:") ("nnml:own-messages" 3 ((1 . 201)) ((unexist) (seen ...) (forward ... 80 98 149) (reply 77 ... 93 106 109 111 ... ...)) "nnml:" ((timestamp . 1577435097))) ("nnml:mueller" 3 ((1 . 4)) nil "nnml:") ("nnml:moeller" 3 ((1 . 3)) nil "nnml:") ...) nil)
  gnus-get-unread-articles(nil nil nil)
  gnus-group-get-new-news(nil)
  funcall-interactively(gnus-group-get-new-news nil)
  call-interactively(gnus-group-get-new-news nil nil)
  command-execute(gnus-group-get-new-news)
--8<---------------cut here---------------end--------------->8---

Best regards, Michael.


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.12, cairo version 1.16.0)
 of 2020-02-25 built on detlef
Repository revision: 64af3c94a6197cd0c6a283880c900eeb5bf12961
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12005000
System Description: Ubuntu 19.10

Recent messages:
Reading active file via nnnil...done
Reading active file from news via nntp...
Opening nntp server on news...done
Reading active file via nnml...
Reading incoming mail from pop...
pop3 retrieved 0KB (0%) [6 times]
pop3 retrieved 6KB (100%)
Wrote /home/albinus/Mail/default/28870
nnml: Reading incoming mail (1 new)...done
Entering debugger...

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Load-path shadows:
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~/lisp/telepathy hides /home/albinus/.emacs.d/elpa/telepathy-20131209.1258/telepathy
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/home/albinus/src/tramp/lisp/tramp-cmds hides /usr/local/share/emacs/28.0.50/lisp/net/tramp-cmds
/home/albinus/src/tramp/lisp/tramp-gvfs hides /usr/local/share/emacs/28.0.50/lisp/net/tramp-gvfs
/home/albinus/src/tramp/lisp/tramp-loaddefs hides /usr/local/share/emacs/28.0.50/lisp/net/tramp-loaddefs
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/home/albinus/src/tramp/lisp/tramp-sh hides /usr/local/share/emacs/28.0.50/lisp/net/tramp-sh
/home/albinus/src/tramp/lisp/tramp-cache hides /usr/local/share/emacs/28.0.50/lisp/net/tramp-cache

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rmail-loaddefs text-property-search wid-edit cus-start cus-load vc
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bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

[Paul Eggert]

[-- Attachment #1: Type: text/plain, Size: 94 bytes --]

Thanks for reporting that. I installed the attached patch into master; 
please give it a try.

[-- Attachment #2: 0001-nnmail-cache-close-should-not-use-nofollow.patch --]
[-- Type: text/x-patch, Size: 4836 bytes --]

From 07da629926daf849aab248175c88cf53a5e21558 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 26 Feb 2020 17:10:21 -0800
Subject: [PATCH] nnmail-cache-close should not use nofollow
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

nnmail-cache-close did not work when ~/.nnmail-cache was a symlink
to some other directory.  Reported by Michael Albinus (Bug#39793).
* lisp/gnus/nnbabyl.el (nnbabyl-create-mbox):
* lisp/gnus/nndiary.el (nndiary-generate-nov-file):
* lisp/gnus/nnfolder.el (nnfolder-possibly-change-group):
* lisp/gnus/nnmbox.el (nnmbox-create-mbox):
* lisp/gnus/nnml.el (nnml-generate-nov-file):
Pass ‘excl’ to nnmail-write-region when creating a file, for safety.
* lisp/gnus/nnmail.el (nnmail-write-region):
Add optional MUSTBENEW arg, to stay consistent with write-region.
Past ‘nofollow’ to set-file-modes only when MUSTBENEW is ‘excl’.
---
 lisp/gnus/nnbabyl.el  | 2 +-
 lisp/gnus/nndiary.el  | 2 +-
 lisp/gnus/nnfolder.el | 2 +-
 lisp/gnus/nnmail.el   | 8 +++++---
 lisp/gnus/nnmbox.el   | 2 +-
 lisp/gnus/nnml.el     | 2 +-
 6 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/lisp/gnus/nnbabyl.el b/lisp/gnus/nnbabyl.el
index cb22933b52..480d794b9a 100644
--- a/lisp/gnus/nnbabyl.el
+++ b/lisp/gnus/nnbabyl.el
@@ -544,7 +544,7 @@ nnbabyl-create-mbox
       (setq buffer-file-name nnbabyl-mbox-file)
       (insert "BABYL OPTIONS:\n\n\^_")
       (nnmail-write-region
-       (point-min) (point-max) nnbabyl-mbox-file t 'nomesg))))
+       (point-min) (point-max) nnbabyl-mbox-file t 'nomesg nil 'excl))))
 
 (defun nnbabyl-read-mbox ()
   (nnmail-activate 'nnbabyl)
diff --git a/lisp/gnus/nndiary.el b/lisp/gnus/nndiary.el
index ac394ae53d..945ef0351e 100644
--- a/lisp/gnus/nndiary.el
+++ b/lisp/gnus/nndiary.el
@@ -1115,7 +1115,7 @@ nndiary-generate-nov-file
 	  (widen))
 	(setq files (cdr files)))
       (with-current-buffer nov-buffer
-	(nnmail-write-region 1 (point-max) nov nil 'nomesg)
+	(nnmail-write-region 1 (point-max) nov nil 'nomesg nil 'excl)
 	(kill-buffer (current-buffer))))))
 
 (defun nndiary-nov-delete-article (group article)
diff --git a/lisp/gnus/nnfolder.el b/lisp/gnus/nnfolder.el
index d1eeb04697..c27af1742d 100644
--- a/lisp/gnus/nnfolder.el
+++ b/lisp/gnus/nnfolder.el
@@ -735,7 +735,7 @@ nnfolder-possibly-change-group
 		       (or nnfolder-file-coding-system-for-write
 			   nnfolder-file-coding-system-for-write)))
 		  (nnmail-write-region (point-min) (point-min)
-				       file t 'nomesg)))
+				       file t 'nomesg nil 'excl)))
 	      (when (setq nnfolder-current-buffer (nnfolder-read-folder group))
 		(set-buffer nnfolder-current-buffer)
 		(push (list group nnfolder-current-buffer)
diff --git a/lisp/gnus/nnmail.el b/lisp/gnus/nnmail.el
index 93e4b0e7a8..3be843c91f 100644
--- a/lisp/gnus/nnmail.el
+++ b/lisp/gnus/nnmail.el
@@ -1953,12 +1953,14 @@ nnmail-check-syntax
       (unless (re-search-forward "^Message-ID[ \t]*:" nil t)
 	(insert "Message-ID: " (nnmail-message-id) "\n")))))
 
-(defun nnmail-write-region (start end filename &optional append visit lockname)
+(defun nnmail-write-region (start end filename
+				  &optional append visit lockname mustbenew)
   "Do a `write-region', and then set the file modes."
   (let ((coding-system-for-write nnmail-file-coding-system)
 	(file-name-coding-system nnmail-pathname-coding-system))
-    (write-region start end filename append visit lockname)
-    (set-file-modes filename nnmail-default-file-modes 'nofollow)))
+    (write-region start end filename append visit lockname mustbenew)
+    (set-file-modes filename nnmail-default-file-modes
+		    (when (eq mustbenew 'excl) 'nofollow))))
 
 ;;;
 ;;; Status functions
diff --git a/lisp/gnus/nnmbox.el b/lisp/gnus/nnmbox.el
index a191f887c7..8b3d80266e 100644
--- a/lisp/gnus/nnmbox.el
+++ b/lisp/gnus/nnmbox.el
@@ -613,7 +613,7 @@ nnmbox-create-mbox
 	  (dir (file-name-directory nnmbox-mbox-file)))
       (and dir (gnus-make-directory dir))
       (nnmail-write-region (point-min) (point-min)
-			   nnmbox-mbox-file t 'nomesg))))
+			   nnmbox-mbox-file t 'nomesg nil 'excl))))
 
 (defun nnmbox-read-mbox ()
   (nnmail-activate 'nnmbox)
diff --git a/lisp/gnus/nnml.el b/lisp/gnus/nnml.el
index 2c39ab8e36..baf5d54b74 100644
--- a/lisp/gnus/nnml.el
+++ b/lisp/gnus/nnml.el
@@ -901,7 +901,7 @@ nnml-generate-nov-file
 		(nnheader-insert-nov headers)))
 	    (widen))))
       (with-current-buffer nov-buffer
-	(nnmail-write-region (point-min) (point-max) nov nil 'nomesg)
+	(nnmail-write-region (point-min) (point-max) nov nil 'nomesg nil 'excl)
 	(kill-buffer (current-buffer))))))
 
 (defun nnml-nov-delete-article (group article)
-- 
2.24.1

bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

[Michael Albinus]

Paul Eggert <eggert@cs.ucla.edu> writes:

Hi Paul,

> Thanks for reporting that. I installed the attached patch into master;
> please give it a try.

That works, thanks!

But isn't there the general problem of mounted directories? I fear, that
calling set-file-modes with nofollow over a symlink into a mounted
directory would show the same error. So I guess it might be better to
simply ignore such an error. Like in my case, you cannot predict whether
a symlink points into a mounted directory.

Best regards, Michael.

bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

[Paul Eggert]

On 2/27/20 12:22 AM, Michael Albinus wrote:
> But isn't there the general problem of mounted directories? I fear, that
> calling set-file-modes with nofollow over a symlink into a mounted
> directory would show the same error.

Yes, that would happen. But this issue is independent of whether the 
symlink points into a mounted directory because you'll get the same 
error with set-file-modes with nofollow on a symlink into the same 
directory. That's the point of nofollow: you don't want to follow the 
symlink.

The error that prompted this bug report is that I mistakenly added 
nofollow to a set-file-modes that was actually intended to follow a 
symlink, and my mistake was independent of whether the symlink points to 
a mounted directory.

bug#39793: 28.0.50; set-file-modes nofollow does not work on mounted directories

[Michael Albinus]

Paul Eggert <eggert@cs.ucla.edu> writes:

Hi Paul,

> The error that prompted this bug report is that I mistakenly added
> nofollow to a set-file-modes that was actually intended to follow a
> symlink, and my mistake was independent of whether the symlink points
> to a mounted directory.

I see. So you might close the bug.

Best regards, Michael.