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bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared director
From: |
Bernardo |
Subject: |
bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory |
Date: |
Tue, 29 Oct 2019 19:50:15 +1100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
Robert Pluim <rpluim@gmail.com> writes:
>>>>>> On Mon, 28 Oct 2019 20:23:22 +1100, Bernardo <bernardo.bacic@pobox.com>
>>>>>> said:
> Bernardo> $ git diff src/filelock.c
> Bernardo> diff --git a/src/filelock.c b/src/filelock.c
> Bernardo> index ff25d6475d..79eb8fa91e 100644
> Bernardo> --- a/src/filelock.c
> Bernardo> +++ b/src/filelock.c
> Bernardo> @@ -403,7 +403,7 @@ create_lock_file (char *lfname, char
> *lock_info_str, bool force)
> Bernardo> lock_info_len = strlen (lock_info_str);
> Bernardo> err = 0;
> Bernardo> if (emacs_write (fd, lock_info_str, lock_info_len) !=
> lock_info_len
> Bernardo> - || fchmod (fd, S_IRUSR | S_IRGRP | S_IROTH) != 0)
> Bernardo> + || fchmod (fd, S_IRUSR | S_IWUSR | S_IRGRP |
> S_IROTH) != 0)
> Bernardo> err = errno;
> Bernardo> /* There is no need to call fsync here, as the
> contents of
> Bernardo> the lock file need not survive system crashes. */
>
> Bernardo> and Emacs is happy again, no problems with writing to files in
> Bernardo> VirtualBox shared directory.
>
> Bernardo> Please let me know if you want me to test anything else.
>
> I think Eli's suggestion was more like the below, which only calls
> fchmod if the unlink fails.
>
> diff --git a/src/filelock.c b/src/filelock.c
> index ff25d6475d..7fb14774b0 100644
> --- a/src/filelock.c
> +++ b/src/filelock.c
> @@ -732,6 +732,15 @@ unlock_file (Lisp_Object fn)
> int err = current_lock_owner (0, lfname);
> if (err == -2 && unlink (lfname) != 0 && errno != ENOENT)
> err = errno;
> + /* On certain filesystems the file must be writable for unlink to
> + succeed (Bug#37784). */
> + if (errno == EPERM)
> + {
> + fchmod (fd, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
> + errno = 0;
> + if (unlink (lfname) != 0 && errno != ENOENT)
> + err = errno;
> + }
> if (0 < err)
> report_file_errno ("Unlocking file", filename, err);
>
two changes in that code snippet were needed to get things working:
* replace fchmod() with chmod() (a minor one)
* more importantly, had to set the value of err to 0, otherwise
it would end up with the same problem;
guess you'll have a closer look at the 2nd change and possibly come up
with a better solution
The code that works fine looks like this:
$ git diff
diff --git a/src/filelock.c b/src/filelock.c
index ff25d6475d..046a1b014f 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -732,6 +732,16 @@ unlock_file (Lisp_Object fn)
int err = current_lock_owner (0, lfname);
if (err == -2 && unlink (lfname) != 0 && errno != ENOENT)
err = errno;
+ /* On certain filesystems the file must be writable for unlink to
+ succeed (Bug#37784). */
+ if (errno == EPERM)
+ {
+ chmod (lfname, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+ err = 0;
+ errno = 0;
+ if (unlink (lfname) != 0 && errno != ENOENT)
+ err = errno;
+ }
if (0 < err)
report_file_errno ("Unlocking file", filename, err);
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Bernardo, 2019/10/23
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/24
- Message not available
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/27
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Eli Zaretskii, 2019/10/27
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/27
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Eli Zaretskii, 2019/10/27
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Bernardo, 2019/10/28
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/28
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory,
Bernardo <=
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Andreas Schwab, 2019/10/29
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/29
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Bernardo, 2019/10/30
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/30
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Eli Zaretskii, 2019/10/30
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Paul Eggert, 2019/10/30
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Robert Pluim, 2019/10/31
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Eli Zaretskii, 2019/10/31
- bug#37884: 27.0.50; Cannot write to a file in VirtualBox shared directory, Paul Eggert, 2019/10/31