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tmpfiles: make "f" lines behaviour match what the documentation says

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CHANGE OF BEHAVIOUR — with this commit "f" line's behaviour is altered
to match what the documentation says: if an "argument" string is
specified it is written to the file only when the file didn't exist
before. Previously, it would be appended to the file each time
systemd-tmpfiles was invoked — which is not a particularly useful
behaviour as the tool is not idempotent then and the indicated files
grow without bounds each time the tool is invoked.

I did some spelunking whether this change in behaviour would break
things, but afaics nothing relies on the previous O_APPEND behaviour of
this line type, hence I think it's relatively safe to make "f" lines
work the way the docs say, rather than adding a new modifier for it or
so.

Triggered by:

https://lists.freedesktop.org/archives/systemd-devel/2018-January/040171.html
This commit is contained in:
Lennart Poettering 2018-01-24 10:54:10 +01:00
parent 1302e7aa94
commit 49e87292dc
3 changed files with 29 additions and 20 deletions
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12
NEWS
View File

@ -7,6 +7,18 @@ CHANGES WITH 237 in spe:
keycodes are not recognized by any major desktop. They now produce
Up/Down key events so that they can be used for scrolling.
* INCOMPATIBILITY: systemd-tmpfiles' "f" lines changed behaviour
slightly: previously, if an argument was specified for lines of this
type (i.e. the right-most column was set) this string was appended to
existing files each time systemd-tmpfiles was run. This behaviour was
different from what the documentation said, and not particularly
useful, as repeated systemd-tmpfiles invocations would not be
idempotent and grow such files without bounds. With this release
behaviour has been altered slightly, to match what the documentation
says: lines of this type only have an effect if the indicated files
don't exist yet, and only then the argument string is written to the
file.
— Berlin, 2018-XX-XX
CHANGES WITH 236:

28
man/tmpfiles.d.xml
View File

@ -147,9 +147,8 @@ L /tmp/foobar - - - - /dev/null</programlisting>
<variablelist>
<varlistentry>
<term><varname>f</varname></term>
<listitem><para>Create a file if it does not exist yet. If
the argument parameter is given, it will be written to the
file. Does not follow symlinks.</para></listitem>
<listitem><para>Create a file if it does not exist yet. If the argument parameter is given and the file did
not exist yet, it will be written to the file. Does not follow symlinks.</para></listitem>
</varlistentry>
<varlistentry>
@ -585,21 +584,14 @@ r! /tmp/.X[0-9]*-lock</programlisting>
<refsect2>
<title>Argument</title>
<para>For <varname>L</varname> lines determines the destination
path of the symlink. For <varname>c</varname> and
<varname>b</varname>, determines the major/minor of the device
node, with major and minor formatted as integers, separated by
<literal>:</literal>, e.g. <literal>1:3</literal>. For
<varname>f</varname>, <varname>F</varname>, and
<varname>w</varname>, the argument may be used to specify a short string that
is written to the file, suffixed by a newline. For
<varname>C</varname>, specifies the source file or
directory. For <varname>t</varname> and <varname>T</varname>,
determines extended attributes to be set. For
<varname>a</varname> and <varname>A</varname>, determines ACL
attributes to be set. For <varname>h</varname> and
<varname>H</varname>, determines the file attributes to
set. Ignored for all other lines.</para>
<para>For <varname>L</varname> lines determines the destination path of the symlink. For <varname>c</varname> and
<varname>b</varname>, determines the major/minor of the device node, with major and minor formatted as integers,
separated by <literal>:</literal>, e.g. <literal>1:3</literal>. For <varname>f</varname>, <varname>F</varname>,
and <varname>w</varname>, the argument may be used to specify a short string that is written to the file,
suffixed by a newline. For <varname>C</varname>, specifies the source file or directory. For <varname>t</varname>
and <varname>T</varname>, determines extended attributes to be set. For <varname>a</varname> and
<varname>A</varname>, determines ACL attributes to be set. For <varname>h</varname> and <varname>H</varname>,
determines the file attributes to set. Ignored for all other lines.</para>
<para>This field can contain specifiers, see below.</para>
</refsect2>

9
src/tmpfiles/tmpfiles.c
View File

@ -1189,7 +1189,7 @@ static int write_one_file(Item *i, const char *path) {
assert(i);
assert(path);
flags = i->type == CREATE_FILE ? O_CREAT|O_APPEND|O_NOFOLLOW :
flags = i->type == CREATE_FILE ? O_CREAT|O_EXCL|O_NOFOLLOW :
i->type == TRUNCATE_FILE ? O_CREAT|O_TRUNC|O_NOFOLLOW : 0;
RUN_WITH_UMASK(0000) {
@ -1200,9 +1200,13 @@ static int write_one_file(Item *i, const char *path) {
if (fd < 0) {
if (i->type == WRITE_FILE && errno == ENOENT) {
log_debug_errno(errno, "Not writing \"%s\": %m", path);
log_debug_errno(errno, "Not writing missing file \"%s\": %m", path);
return 0;
}
if (i->type == CREATE_FILE && errno == EEXIST) {
log_debug_errno(errno, "Not writing to pre-existing file \"%s\": %m", path);
goto done;
}
r = -errno;
if (!i->argument && errno == EROFS && stat(path, &st) == 0 &&
@ -1223,6 +1227,7 @@ static int write_one_file(Item *i, const char *path) {
fd = safe_close(fd);
done:
if (stat(path, &st) < 0)
return log_error_errno(errno, "stat(%s) failed: %m", path);