util: Introduce virProcess{Get,Set}Limit()

These functions abstract part of the existing logic, which is
the same in all virProcessSetMax*() functions, and changes it
so that which underlying syscall is used depends on their
availability rather than on the context in which they are
called: since prlimit() and {g,s}etrlimit() have slightly
different requirements, using the same one every single time
should make for a more consistent experience.

As part of the change, we also remove the special case for
passing zero to virProcessSetMax*() functions: we have removed
all callers that depended on that functionality in the previous
commit, so this is now safe to do and makes the semantics
simpler.

This commit is better viewed with 'git show -w'.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

diff --git a/src/util/virprocess.c b/src/util/virprocess.c
index 77eeab6a06738a45bba4e085844e46a51f339161..d985bf637beaf1101c815ee25e5f9ac1e3cb8ffe 100644 (file)
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -738,10 +738,66 @@ virProcessPrLimit(pid_t pid G_GNUC_UNUSED,
 }
 #endif
 
+#if WITH_GETRLIMIT
+static int
+virProcessGetRLimit(int resource,
+                    struct rlimit *old_limit)
+{
+    return getrlimit(resource, old_limit);
+}
+#endif /* WITH_GETRLIMIT */
+
+#if WITH_SETRLIMIT
+static int
+virProcessSetRLimit(int resource,
+                    const struct rlimit *new_limit)
+{
+    return setrlimit(resource, new_limit);
+}
+#endif /* WITH_SETRLIMIT */
+
+#if WITH_GETRLIMIT
+static int
+virProcessGetLimit(pid_t pid,
+                   int resource,
+                   struct rlimit *old_limit)
+{
+    pid_t current_pid = getpid();
+    bool same_process = (pid == current_pid);
+
+    if (virProcessPrLimit(pid, resource, NULL, old_limit) == 0)
+        return 0;
+
+    if (same_process && virProcessGetRLimit(resource, old_limit) == 0)
+        return 0;
+
+    return -1;
+}
+#endif /* WITH_GETRLIMIT */
+
+#if WITH_SETRLIMIT
+static int
+virProcessSetLimit(pid_t pid,
+                   int resource,
+                   const struct rlimit *new_limit)
+{
+    pid_t current_pid = getpid();
+    bool same_process = (pid == current_pid);
+
+    if (virProcessPrLimit(pid, resource, new_limit, NULL) == 0)
+        return 0;
+
+    if (same_process && virProcessSetRLimit(resource, new_limit) == 0)
+        return 0;
+
+    return -1;
+}
+#endif /* WITH_SETRLIMIT */
+
 #if WITH_SETRLIMIT && defined(RLIMIT_MEMLOCK)
 /**
  * virProcessSetMaxMemLock:
- * @pid: process to be changed (0 for the current process)
+ * @pid: process to be changed
  * @bytes: new limit (0 for no change)
  *
  * Sets a new limit on the amount of locked memory for a process.
@@ -765,21 +821,11 @@ virProcessSetMaxMemLock(pid_t pid, unsigned long long bytes)
     else
         rlim.rlim_cur = rlim.rlim_max = RLIM_INFINITY;
 
-    if (pid == 0) {
-        if (setrlimit(RLIMIT_MEMLOCK, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit locked memory to %llu"),
-                                 bytes);
-            return -1;
-        }
-    } else {
-        if (virProcessPrLimit(pid, RLIMIT_MEMLOCK, &rlim, NULL) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit locked memory "
-                                   "of process %lld to %llu"),
-                                 (long long int)pid, bytes);
-            return -1;
-        }
+    if (virProcessSetLimit(pid, RLIMIT_MEMLOCK, &rlim) < 0) {
+        virReportSystemError(errno,
+                             _("cannot limit locked memory "
+                               "of process %lld to %llu"),
+                             (long long int)pid, bytes);
     }
 
     VIR_DEBUG("Locked memory for process %lld limited to %llu bytes",
@@ -800,7 +846,7 @@ virProcessSetMaxMemLock(pid_t pid G_GNUC_UNUSED,
 #if WITH_GETRLIMIT && defined(RLIMIT_MEMLOCK)
 /**
  * virProcessGetMaxMemLock:
- * @pid: process to be queried (0 for the current process)
+ * @pid: process to be queried
  * @bytes: return location for the limit
  *
  * Obtain the current limit on the amount of locked memory for a process.
@@ -816,21 +862,12 @@ virProcessGetMaxMemLock(pid_t pid,
     if (!bytes)
         return 0;
 
-    if (pid == 0) {
-        if (getrlimit(RLIMIT_MEMLOCK, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 "%s",
-                                 _("cannot get locked memory limit"));
-            return -1;
-        }
-    } else {
-        if (virProcessPrLimit(pid, RLIMIT_MEMLOCK, NULL, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot get locked memory limit "
-                                   "of process %lld"),
-                                 (long long int) pid);
-            return -1;
-        }
+    if (virProcessGetLimit(pid, RLIMIT_MEMLOCK, &rlim) < 0) {
+        virReportSystemError(errno,
+                             _("cannot get locked memory limit "
+                               "of process %lld"),
+                             (long long int) pid);
+        return -1;
     }
 
     /* virProcessSetMaxMemLock() sets both rlim_cur and rlim_max to the
@@ -858,7 +895,7 @@ virProcessGetMaxMemLock(pid_t pid G_GNUC_UNUSED,
 #if WITH_SETRLIMIT && defined(RLIMIT_NPROC)
 /**
  * virProcessSetMaxProcesses:
- * @pid: process to be changed (0 for the current process)
+ * @pid: process to be changed
  * @procs: new limit (0 for no change)
  *
  * Sets a new limit on the amount of processes for the user the
@@ -875,21 +912,13 @@ virProcessSetMaxProcesses(pid_t pid, unsigned int procs)
         return 0;
 
     rlim.rlim_cur = rlim.rlim_max = procs;
-    if (pid == 0) {
-        if (setrlimit(RLIMIT_NPROC, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit number of subprocesses to %u"),
-                                 procs);
-            return -1;
-        }
-    } else {
-        if (virProcessPrLimit(pid, RLIMIT_NPROC, &rlim, NULL) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit number of subprocesses "
-                                   "of process %lld to %u"),
-                                 (long long int)pid, procs);
-            return -1;
-        }
+
+    if (virProcessSetLimit(pid, RLIMIT_NPROC, &rlim) < 0) {
+        virReportSystemError(errno,
+                _("cannot limit number of subprocesses "
+                  "of process %lld to %u"),
+                (long long int)pid, procs);
+        return -1;
     }
     return 0;
 }
@@ -906,7 +935,7 @@ virProcessSetMaxProcesses(pid_t pid G_GNUC_UNUSED,
 #if WITH_SETRLIMIT && defined(RLIMIT_NOFILE)
 /**
  * virProcessSetMaxFiles:
- * @pid: process to be changed (0 for the current process)
+ * @pid: process to be changed
  * @files: new limit (0 for no change)
  *
  * Sets a new limit on the number of opened files for a process.
@@ -930,22 +959,15 @@ virProcessSetMaxFiles(pid_t pid, unsigned int files)
     * behavior.
     */
     rlim.rlim_cur = rlim.rlim_max = files + 1;
-    if (pid == 0) {
-        if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit number of open files to %u"),
-                                 files);
-            return -1;
-        }
-    } else {
-        if (virProcessPrLimit(pid, RLIMIT_NOFILE, &rlim, NULL) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit number of open files "
-                                   "of process %lld to %u"),
-                                 (long long int)pid, files);
-            return -1;
-        }
+
+    if (virProcessSetLimit(pid, RLIMIT_NOFILE, &rlim) < 0) {
+        virReportSystemError(errno,
+                             _("cannot limit number of open files "
+                               "of process %lld to %u"),
+                             (long long int)pid, files);
+        return -1;
     }
+
     return 0;
 }
 #else /* ! (WITH_SETRLIMIT && defined(RLIMIT_NOFILE)) */
@@ -961,7 +983,7 @@ virProcessSetMaxFiles(pid_t pid G_GNUC_UNUSED,
 #if WITH_SETRLIMIT && defined(RLIMIT_CORE)
 /**
  * virProcessSetMaxCoreSize:
- * @pid: process to be changed (0 for the current process)
+ * @pid: process to be changed
  * @bytes: new limit (0 to disable core dumps)
  *
  * Sets a new limit on the size of core dumps for a process.
@@ -974,22 +996,15 @@ virProcessSetMaxCoreSize(pid_t pid, unsigned long long bytes)
     struct rlimit rlim;
 
     rlim.rlim_cur = rlim.rlim_max = bytes;
-    if (pid == 0) {
-        if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit core file size to %llu"),
-                                 bytes);
-            return -1;
-        }
-    } else {
-        if (virProcessPrLimit(pid, RLIMIT_CORE, &rlim, NULL) < 0) {
-            virReportSystemError(errno,
-                                 _("cannot limit core file size "
-                                   "of process %lld to %llu"),
-                                 (long long int)pid, bytes);
-            return -1;
-        }
+
+    if (virProcessSetLimit(pid, RLIMIT_CORE, &rlim) < 0) {
+        virReportSystemError(errno,
+                _("cannot limit core file size "
+                  "of process %lld to %llu"),
+                (long long int)pid, bytes);
+        return -1;
     }
+
     return 0;
 }
 #else /* ! (WITH_SETRLIMIT && defined(RLIMIT_CORE)) */