1 files changed, 108 insertions, 0 deletions
diff --git a/tests/tail-2/inotify-rotate-resources.sh b/tests/tail-2/inotify-rotate-resources.sh
new file mode 100755
index 0000000..3dc69c7
--- /dev/null
+++ b/tests/tail-2/inotify-rotate-resources.sh
@@ -0,0 +1,108 @@
+#!/bin/sh
+# ensure that tail -F doesn't leak inotify resources
+
+# Copyright (C) 2015-2022 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ tail
+
+# Inotify not used on remote file systems
+require_local_dir_
+
+grep '^#define HAVE_INOTIFY 1' "$CONFIG_HEADER" >/dev/null \
+  || skip_ 'inotify required'
+
+require_strace_ 'inotify_add_watch,inotify_rm_watch'
+
+check_tail_output()
+{
+  local delay="$1"
+  grep "$tail_re" out > /dev/null ||
+    { sleep $delay; return 1; }
+}
+
+# Wait up to 25.5 seconds for grep REGEXP 'out' to succeed.
+grep_timeout() { tail_re="$1" retry_delay_ check_tail_output .1 8; }
+
+check_strace()
+{
+  local delay="$1"
+  grep "$strace_re" strace.out > /dev/null ||
+    { sleep $delay; return 1; }
+}
+
+cleanup_fail()
+{
+  cat out
+  warn_ $1
+  fail=1
+}
+
+# Terminate any background tail process
+cleanup_() { kill $pid 2>/dev/null && wait $pid; }
+
+fastpoll='-s.1 --max-unchanged-stats=1'
+
+touch k || framework_failure_
+
+# Note the timeout guard isn't strictly necessary here,
+# however without it strace will ignore SIGTERM.
+# strace does always honor SIGTERM with the -I2 option,
+# though that's not available on RHEL6 for example.
+timeout 180 strace -e inotify_add_watch,inotify_rm_watch -o strace.out \
+  tail -F $fastpoll k >> out 2>&1 & pid=$!
+
+reverted_to_polling_=0
+for i in $(seq 2); do
+    echo $i
+
+    echo 'tailed' > k;
+
+    # Wait for watch on (new) file
+    strace_re='inotify_add_watch.*MODIFY' retry_delay_ check_strace .1 8 ||
+      no_watch_=1
+
+    # Assume this is not because we're leaking
+    # (resources may already be depleted)
+    # The explicit check for inotify_rm_watch should confirm that.
+    grep -F 'reverting to polling' out >/dev/null && skip_ 'inotify unused'
+
+    # Otherwise failure is unknown
+    test "$no_watch_" && { cat out; framework_failure_ 'no inotify_add_watch'; }
+
+    mv k k.tmp
+    # wait for tail to detect the rename
+    grep_timeout 'inaccessible' ||
+      { cleanup_fail 'failed to detect rename'; break; }
+
+    # Note we strace here rather than consuming all available watches
+    # to be more efficient, but more importantly avoid depleting resources.
+    # Note also available resources can currently be tuned with:
+    #  sudo sysctl -w fs.inotify.max_user_watches=$smallish_number
+    # However that impacts all processes for the current user, and also
+    # may not be supported in future, instead being auto scaled to RAM
+    # like the Linux epoll resources were.
+    if test "$i" -gt 1; then
+      strace_re='inotify_rm_watch' retry_delay_ check_strace .1 8 ||
+        { cleanup_fail 'failed to find inotify_rm_watch syscall'; break; }
+    fi
+
+    >out && >strace.out || framework_failure_ 'failed to reset output files'
+done
+
+cleanup_
+
+Exit $fail