sd-event: add sd_event_add_inotify_fd() call

sd_event_add_inotify_fd() is like sd_event_add_inotify(), but takes an
fd to an inode instead of a path, and is hence a ton nicer.

5 files changed, 94 insertions, 16 deletions

diff --git a/man/rules/meson.build b/man/rules/meson.build
index ad7cc41c98..7bf93fc16b 100644
--- a/man/rules/meson.build
+++ b/man/rules/meson.build
@@ -518,7 +518,9 @@ manpages = [
   ''],
  ['sd_event_add_inotify',
   '3',
-  ['sd_event_inotify_handler_t', 'sd_event_source_get_inotify_mask'],
+  ['sd_event_add_inotify_fd',
+   'sd_event_inotify_handler_t',
+   'sd_event_source_get_inotify_mask'],
   ''],
  ['sd_event_add_io',
   '3',
diff --git a/man/sd_event_add_inotify.xml b/man/sd_event_add_inotify.xml
index 1681143eb1..d632bf7282 100644
--- a/man/sd_event_add_inotify.xml
+++ b/man/sd_event_add_inotify.xml
@@ -17,6 +17,7 @@
 
   <refnamediv>
     <refname>sd_event_add_inotify</refname>
+    <refname>sd_event_add_inotify_fd</refname>
     <refname>sd_event_source_get_inotify_mask</refname>
     <refname>sd_event_inotify_handler_t</refname>
 
@@ -47,6 +48,16 @@
       </funcprototype>
 
       <funcprototype>
+        <funcdef>int <function>sd_event_add_inotify_fd</function></funcdef>
+        <paramdef>sd_event *<parameter>event</parameter></paramdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+        <paramdef>int <parameter>fd</parameter></paramdef>
+        <paramdef>uint32_t <parameter>mask</parameter></paramdef>
+        <paramdef>sd_event_inotify_handler_t <parameter>handler</parameter></paramdef>
+        <paramdef>void *<parameter>userdata</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
         <funcdef>int <function>sd_event_source_get_inotify_mask</function></funcdef>
         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
         <paramdef>uint32_t *<parameter>mask</parameter></paramdef>
@@ -71,6 +82,11 @@
     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
     further information.</para>
 
+    <para><function>sd_event_add_inotify_fd()</function> is identical to
+    <function>sd_event_add_inotify()</function>, except that it takes a file descriptor to an inode (possibly
+    an <constant>O_PATH</constant> one, but any other will do too) instead of a path in the file
+    system.</para>
+
     <para>If multiple event sources are installed for the same inode the backing inotify watch descriptor is
     automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of
     <constant>IN_MASK_ADD</constant>.</para>
@@ -157,6 +173,19 @@
           <listitem><para>The passed event source is not an inotify process event source.</para></listitem>
         </varlistentry>
 
+        <varlistentry>
+          <term><constant>-EBADF</constant></term>
+
+          <listitem><para>The passed file descriptor is not valid.</para></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>-ENOSYS</constant></term>
+
+          <listitem><para><function>sd_event_add_inotify_fd()</function> was called without
+          <filename>/proc/</filename> mounted.</para></listitem>
+        </varlistentry>
+
       </variablelist>
     </refsect2>
   </refsect1>
diff --git a/src/libsystemd/libsystemd.sym b/src/libsystemd/libsystemd.sym
index 04db791f64..5e2fc9e231 100644
--- a/src/libsystemd/libsystemd.sym
+++ b/src/libsystemd/libsystemd.sym
@@ -766,4 +766,5 @@ global:
 LIBSYSTEMD_250 {
 global:
         sd_device_get_diskseq;
+        sd_event_add_inotify_fd;
 } LIBSYSTEMD_249;
diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index 2a15e686d4..0ca0248510 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -1989,24 +1989,25 @@ static int inotify_exit_callback(sd_event_source *s, const struct inotify_event
         return sd_event_exit(sd_event_source_get_event(s), PTR_TO_INT(userdata));
 }
 
-_public_ int sd_event_add_inotify(
+static int event_add_inotify_fd_internal(
                 sd_event *e,
                 sd_event_source **ret,
-                const char *path,
+                int fd,
+                bool donate,
                 uint32_t mask,
                 sd_event_inotify_handler_t callback,
                 void *userdata) {
 
+        _cleanup_close_ int donated_fd = donate ? fd : -1;
+        _cleanup_(source_freep) sd_event_source *s = NULL;
         struct inotify_data *inotify_data = NULL;
         struct inode_data *inode_data = NULL;
-        _cleanup_close_ int fd = -1;
-        _cleanup_(source_freep) sd_event_source *s = NULL;
         struct stat st;
         int r;
 
         assert_return(e, -EINVAL);
         assert_return(e = event_resolve(e), -ENOPKG);
-        assert_return(path, -EINVAL);
+        assert_return(fd >= 0, -EBADF);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -2019,12 +2020,6 @@ _public_ int sd_event_add_inotify(
         if (mask & IN_MASK_ADD)
                 return -EINVAL;
 
-        fd = open(path, O_PATH|O_CLOEXEC|
-                  (mask & IN_ONLYDIR ? O_DIRECTORY : 0)|
-                  (mask & IN_DONT_FOLLOW ? O_NOFOLLOW : 0));
-        if (fd < 0)
-                return -errno;
-
         if (fstat(fd, &st) < 0)
                 return -errno;
 
@@ -2044,14 +2039,24 @@ _public_ int sd_event_add_inotify(
 
         r = event_make_inode_data(e, inotify_data, st.st_dev, st.st_ino, &inode_data);
         if (r < 0) {
-                event_free_inotify_data(e, inotify_data);
+                event_gc_inotify_data(e, inotify_data);
                 return r;
         }
 
         /* Keep the O_PATH fd around until the first iteration of the loop, so that we can still change the priority of
          * the event source, until then, for which we need the original inode. */
         if (inode_data->fd < 0) {
-                inode_data->fd = TAKE_FD(fd);
+                if (donated_fd >= 0)
+                        inode_data->fd = TAKE_FD(donated_fd);
+                else {
+                        inode_data->fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+                        if (inode_data->fd < 0) {
+                                r = -errno;
+                                event_gc_inode_data(e, inode_data);
+                                return r;
+                        }
+                }
+
                 LIST_PREPEND(to_close, e->inode_data_to_close, inode_data);
         }
 
@@ -2064,8 +2069,6 @@ _public_ int sd_event_add_inotify(
         if (r < 0)
                 return r;
 
-        (void) sd_event_source_set_description(s, path);
-
         if (ret)
                 *ret = s;
         TAKE_PTR(s);
@@ -2073,6 +2076,48 @@ _public_ int sd_event_add_inotify(
         return 0;
 }
 
+_public_ int sd_event_add_inotify_fd(
+                sd_event *e,
+                sd_event_source **ret,
+                int fd,
+                uint32_t mask,
+                sd_event_inotify_handler_t callback,
+                void *userdata) {
+
+        return event_add_inotify_fd_internal(e, ret, fd, /* donate= */ false, mask, callback, userdata);
+}
+
+_public_ int sd_event_add_inotify(
+                sd_event *e,
+                sd_event_source **ret,
+                const char *path,
+                uint32_t mask,
+                sd_event_inotify_handler_t callback,
+                void *userdata) {
+
+        sd_event_source *s;
+        int fd, r;
+
+        assert_return(path, -EINVAL);
+
+        fd = open(path, O_PATH|O_CLOEXEC|
+                  (mask & IN_ONLYDIR ? O_DIRECTORY : 0)|
+                  (mask & IN_DONT_FOLLOW ? O_NOFOLLOW : 0));
+        if (fd < 0)
+                return -errno;
+
+        r = event_add_inotify_fd_internal(e, &s, fd, /* donate= */ true, mask, callback, userdata);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_source_set_description(s, path);
+
+        if (ret)
+                *ret = s;
+
+        return r;
+}
+
 static sd_event_source* event_source_free(sd_event_source *s) {
         if (!s)
                 return NULL;
diff --git a/src/systemd/sd-event.h b/src/systemd/sd-event.h
index 2ae2a0da48..f4357aa593 100644
--- a/src/systemd/sd-event.h
+++ b/src/systemd/sd-event.h
@@ -93,6 +93,7 @@ int sd_event_add_signal(sd_event *e, sd_event_source **s, int sig, sd_event_sign
 int sd_event_add_child(sd_event *e, sd_event_source **s, pid_t pid, int options, sd_event_child_handler_t callback, void *userdata);
 int sd_event_add_child_pidfd(sd_event *e, sd_event_source **s, int pidfd, int options, sd_event_child_handler_t callback, void *userdata);
 int sd_event_add_inotify(sd_event *e, sd_event_source **s, const char *path, uint32_t mask, sd_event_inotify_handler_t callback, void *userdata);
+int sd_event_add_inotify_fd(sd_event *e, sd_event_source **s, int fd, uint32_t mask, sd_event_inotify_handler_t callback, void *userdata);
 int sd_event_add_defer(sd_event *e, sd_event_source **s, sd_event_handler_t callback, void *userdata);
 int sd_event_add_post(sd_event *e, sd_event_source **s, sd_event_handler_t callback, void *userdata);
 int sd_event_add_exit(sd_event *e, sd_event_source **s, sd_event_handler_t callback, void *userdata);