commit 75273001a212d1e437434fe30efc72ba582f89c6
author Zim <zezeozue@google.com> Thu Mar 04 12:21:24 2021 +0000
committer Zimuzo Ezeozue <zezeozue@google.com> Fri Mar 05 11:05:16 2021 +0000
tree 94a429c3295945388a67516086c8b59547bd9c8d
parent 2d0ea905388c7bbb8382d768c58cacbf4ef6dd01

Avoid killing the FUSE daemon during unmount

The FUSE daemon is often holding fds on behalf of other apps and if a
volume is ejected the daemon would often get killed first while vold
is walking /proc/<pid>/fd to kill pids with open fds on the
volume. This is required for the volume unmount successfully.

To mitigate this, we avoid killing the FUSE daemon during the usual
/proc walk. This ensures that we first send SIGINT, SIGTERM and
SIGKILL to other apps first. There is an additional SIGKILL attempt
and on that last attempt, we kill the FUSE daemon as a last resort

Test: Manual
Bug: 171673908
Change-Id: I100d2ce4cb4c145cbb49e0696842e97dfba2c1c9

Process.cpp

diff --git a/Process.cpp b/Process.cpp
index 277d6a3..62d51a2 100644
--- a/Process.cpp
+++ b/Process.cpp
@@ -39,6 +39,7 @@
 #include <android-base/strings.h>
 
 #include "Process.h"
+#include "Utils.h"
 
 using android::base::StringPrintf;
 
@@ -127,7 +128,7 @@
     return pids.size();
 }
 
-int KillProcessesWithOpenFiles(const std::string& prefix, int signal) {
+int KillProcessesWithOpenFiles(const std::string& prefix, int signal, bool killFuseDaemon) {
     std::unordered_set<pid_t> pids;
 
     auto proc_d = std::unique_ptr<DIR, int (*)(DIR*)>(opendir("/proc"), closedir);
@@ -164,7 +165,11 @@
         }
 
         if (found) {
-            pids.insert(pid);
+            if (!IsFuseDaemon(pid) || killFuseDaemon) {
+                pids.insert(pid);
+            } else {
+                LOG(WARNING) << "Found FUSE daemon with open file. Skipping...";
+            }
         }
     }
     if (signal != 0) {

Process.h

diff --git a/Process.h b/Process.h
index 1c59812..a56b9ce 100644
--- a/Process.h
+++ b/Process.h
@@ -20,7 +20,7 @@
 namespace android {
 namespace vold {
 
-int KillProcessesWithOpenFiles(const std::string& path, int signal);
+int KillProcessesWithOpenFiles(const std::string& path, int signal, bool killFuseDaemon = true);
 int KillProcessesWithMounts(const std::string& path, int signal);
 
 }  // namespace vold

Utils.cpp

diff --git a/Utils.cpp b/Utils.cpp
index cef0f39..9ff7920 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -525,24 +525,25 @@
 }
 
 status_t KillProcessesUsingPath(const std::string& path) {
-    if (KillProcessesWithOpenFiles(path, SIGINT) == 0) {
+    if (KillProcessesWithOpenFiles(path, SIGINT, false /* killFuseDaemon */) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);
 
-    if (KillProcessesWithOpenFiles(path, SIGTERM) == 0) {
+    if (KillProcessesWithOpenFiles(path, SIGTERM, false /* killFuseDaemon */) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);
 
-    if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
+    if (KillProcessesWithOpenFiles(path, SIGKILL, false /* killFuseDaemon */) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);
 
     // Send SIGKILL a second time to determine if we've
     // actually killed everyone with open files
-    if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
+    // This time, we also kill the FUSE daemon if found
+    if (KillProcessesWithOpenFiles(path, SIGKILL, true /* killFuseDaemon */) == 0) {
         return OK;
     }
     PLOG(ERROR) << "Failed to kill processes using " << path;