From dd5972b69916fa08b114193d644faf3ae58c550b Mon Sep 17 00:00:00 2001
From: Martin Schwenke <martin@meltin.net>
Date: Mon, 4 Jan 2021 13:35:11 +1100
Subject: ctdb-scripts: Simplify logic in debug_via_proc_locks()

The path of the TDB is known, so calculate the file ID (device number
+ inode number) from it and use this to directly filter /proc/locks to
find processes holding locks.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
---
 ctdb/config/debug_locks.sh                         | 90 ++++++++++++++--------
 .../tests/UNIT/eventscripts/scripts/debug_locks.sh | 21 ++---
 ctdb/tests/UNIT/eventscripts/stubs/stat            | 18 +++++
 3 files changed, 89 insertions(+), 40 deletions(-)

(limited to 'ctdb')

diff --git a/ctdb/config/debug_locks.sh b/ctdb/config/debug_locks.sh
index 892889e86be..1fcb2f70d17 100755
--- a/ctdb/config/debug_locks.sh
+++ b/ctdb/config/debug_locks.sh
@@ -75,40 +75,70 @@ dump_stacks ()
 	done
 }
 
+get_tdb_file_id ()
+{
+	if ! _device_inode=$(stat -c "%d:%i" "$tdb_path" 2>/dev/null) ; then
+		die "Unable to stat \"${tdb_path}\""
+	fi
+	_device="${_device_inode%%:*}"
+	_device_major=$((_device >> 8))
+	_device_minor=$((_device & 0xff))
+	_inode="${_device_inode#*:}"
+	printf '%02x:%02x:%u\n' "$_device_major" "$_device_minor" "$_inode"
+}
+
 debug_via_proc_locks ()
 {
-    # Create sed expression to convert inodes to names.
-    # Filenames don't contain dashes and we want basenames
-    # shellcheck disable=SC2035
-    sed_cmd=$(cd "$CTDB_DBDIR" &&
-		  stat -c "s#[0-9a-f]*:[0-9a-f]*:%i #%n #" *.tdb.* 2>/dev/null ;
-	      cd "$CTDB_DBDIR_PERSISTENT" &&
-		  stat -c "s#[0-9a-f]*:[0-9a-f]*:%i #%n #" *.tdb.* 2>/dev/null)
-
-    # Parse /proc/locks and extract following information
-    #    pid process_name tdb_name offsets [W]
-    out=$( get_proc "locks" |
-    grep -F "POSIX  ADVISORY  WRITE" |
-    awk '{ if($2 == "->") { print $6, $7, $8, $9, "W" } else { print $5, $6, $7, $8 } }' |
-    while read pid rest ; do
-	pname=$(ps -p "$pid" -o comm=)
-	echo "$pid $pname $rest"
-    done | sed -e "$sed_cmd" | grep '\.tdb' )
-
-    if [ -n "$out" ]; then
+	# Get file ID to match relevant column in /proc/locks
+	_file_id=$(get_tdb_file_id)
+
+	# Log information from /proc/locks about the waiting process
+	_tdb=$(basename "$tdb_path")
+	_comm=$(ps -p "$lock_helper_pid" -o comm=)
+	_out=$(get_proc "locks" |
+	       awk -v pid="$lock_helper_pid" \
+		   -v file_id="$_file_id" \
+		   -v file="$_tdb" \
+		   -v comm="$_comm" \
+		   '$2 == "->" &&
+		    $3 == "POSIX" &&
+		    $4 == "ADVISORY" &&
+		    $5 == "WRITE" &&
+		    $6 == pid &&
+		    $7 == file_id { print $6, comm, file, $8, $9 }')
+	if [ -n "$_out" ] ; then
+		echo "Waiter:"
+		echo "$_out"
+	fi
+
+	# Parse /proc/locks and find process holding locks on $tdb_path
+	# extract following information
+	#    pid process_name tdb_name offsets
+	_out=$(get_proc "locks" |
+	       awk -v pid="$lock_helper_pid" \
+		   -v file_id="$_file_id" \
+		   -v file="$_tdb" \
+		   '$2 == "POSIX" &&
+		    $3 == "ADVISORY" &&
+		    $4 == "WRITE" &&
+		    $5 != pid &&
+		    $6 == file_id { print $5, file, $7, $8 }' |
+	       while read -r _pid _rest ; do
+		       _pname=$(ps -p "$_pid" -o comm=)
+		       echo "$_pid $_pname $_rest"
+	       done)
+
+	if [ -z "$_out" ]; then
+		return
+	fi
+
 	# Log information about locks
-	echo "$out"
-
-	# Find processes that are waiting for locks
-	dbs=$(echo "$out" | grep "W$" | awk '{print $3}')
-	all_pids=""
-	for db in $dbs ; do
-	    pids=$(echo "$out" | grep -v "W$" | grep "$db" | grep -v ctdbd | awk '{print $1}')
-	    all_pids="$all_pids $pids"
-	done
+	echo "Lock holders:"
+	echo "$_out"
+
+	_pids=$(echo "$_out" | awk '{ print $1 }')
 
-	lock_holder_pids="${lock_holder_pids:+${lock_holder_pids} }${all_pids}"
-    fi
+	lock_holder_pids="${lock_holder_pids:+${lock_holder_pids} }${_pids}"
 }
 
 (
diff --git a/ctdb/tests/UNIT/eventscripts/scripts/debug_locks.sh b/ctdb/tests/UNIT/eventscripts/scripts/debug_locks.sh
index d9c3df76d57..162dc21b2ac 100644
--- a/ctdb/tests/UNIT/eventscripts/scripts/debug_locks.sh
+++ b/ctdb/tests/UNIT/eventscripts/scripts/debug_locks.sh
@@ -168,25 +168,26 @@ EOF
 '
 	_db="locking.tdb.${FAKE_CTDB_PNN}"
 
-	_pids=''
+	if [ -n "$_helper_lock" ] ; then
+		read -r _ _ _ _ _pid _ _start _end <<EOF
+$_helper_lock
+EOF
+		_out="Waiter:${_nl}"
+		_out="${_out}${_pid} ctdb_lock_helpe ${_db} ${_start} ${_end}"
+	fi
+
 	# fake lock info
+	_pids=''
+	_out="${_out:+${_out}${_nl}}Lock holders:"
 	while read -r _ _ _  _pid _ _start _end ; do
 		_comm="smbd"
-		_out="${_out:+${_out}${_nl}}"
+		_out="${_out}${_nl}"
 		_out="${_out}${_pid} smbd ${_db} ${_start} ${_end}"
 		_pids="${_pids:+${_pids} }${_pid}"
 	done <<EOF
 $_holder_lock
 EOF
 
-	if [ -n "$_helper_lock" ] ; then
-		read -r _ _ _ _ _pid _ _start _end <<EOF
-$_helper_lock
-EOF
-		_out="${_out}${_nl}"
-		_out="${_out}${_pid} ctdb_lock_helpe ${_db} ${_start} ${_end} W"
-	fi
-
 	# fake stack traces
 	for _pid in $_pids ; do
 		_comm="smbd"
diff --git a/ctdb/tests/UNIT/eventscripts/stubs/stat b/ctdb/tests/UNIT/eventscripts/stubs/stat
index 04c654883d2..71508f6795d 100755
--- a/ctdb/tests/UNIT/eventscripts/stubs/stat
+++ b/ctdb/tests/UNIT/eventscripts/stubs/stat
@@ -16,6 +16,19 @@ while getopts "c:h:?" opt ; do
 done
 shift $((OPTIND - 1))
 
+fake_device_id ()
+{
+	_path="$1"
+
+	_t=$(echo "$FAKE_FILE_ID_MAP" |
+	     awk -v path="${_path}" '$1 == path { print $2 }')
+	_major_minor="${_t%:*}"
+	_major="0x${_major_minor%:*}"
+	_minor="0x${_major_minor#*:}"
+	_device_id=$((_major * 256 + _minor))
+	echo "$_device_id"
+}
+
 fake_inode ()
 {
 	_path="$1"
@@ -40,6 +53,11 @@ if [ -n "$format" ] ; then
 			inode=$(fake_inode "$path")
 			echo "s#[0-9a-f]*:[0-9a-f]*:${inode} #${f} #"
 			;;
+		"%d:%i")
+			device_id=$(fake_device_id "$path")
+			inode=$(fake_inode "$path")
+			echo "${device_id}:${inode}"
+			;;
 		*)
 			echo "Unsupported format \"${format}\""
 			usage
-- 
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