[warm-reboot]: added pre-check for ISSU file (sonic-net#915)

* [warm-reboot]: added pre-check for ISSU file

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

* [warm-reboot]: fixed problems according to PR review comments

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

* [warm-reboot]: added distinguish token and error code to clarify when issu_bank.txt was corrupted

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

* [warm-reboot]: fixed indentation problems

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

* [warm-reboot]: removed script interrupt when issu_bank.txt is broken

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

* [warm-reboot]: added script interrupt if issu_bank.txt is broken before call request_pre_shutdown

Signed-off-by: Vadym Hlushko <vadymh@mellanox.com>

scripts/fast-reboot

@@ -156,6 +156,42 @@ function request_pre_shutdown()
     }
 }
 
+function recover_issu_bank_file_instruction()
+{
+    debug "To recover (${ISSU_BANK_FILE}) file, do the following:"
+    debug "$ docker exec -it syncd sx_api_dbg_generate_dump.py"
+    debug "$ docker exec -it syncd cat /tmp/sdkdump | grep 'ISSU Bank'"
+    debug "Command above will print the VALUE of ISSU BANK - 0 or 1, use this VALUE in the next command"
+    debug "$ printf VALUE > /host/warmboot/issu_bank.txt"
+}
+
+function check_issu_bank_file()
+{
+    ISSU_BANK_FILE=/host/warmboot/issu_bank.txt
+    MLNX_ISSU_BANK_BROKEN=102
+
+    if [[ ! -s "$ISSU_BANK_FILE" ]]; then
+        error "(${ISSU_BANK_FILE}) does NOT exist or empty ..."
+        recover_issu_bank_file_instruction
+        if [[ "$1" = true ]]; then
+            exit "${MLNX_ISSU_BANK_BROKEN}"
+        fi
+        return
+    fi
+
+    issu_file_chars_count=`stat -c %s ${ISSU_BANK_FILE}`;
+    issu_file_content=`awk '{print $0}' ${ISSU_BANK_FILE}`
+
+    if [[ $issu_file_chars_count != 1 ]] ||
+        [[ "$issu_file_content" != "0" && "$issu_file_content" != "1" ]]; then
+        error "(${ISSU_BANK_FILE}) is broken ..."
+        recover_issu_bank_file_instruction
+        if [[ "$1" = true ]]; then
+            exit "${MLNX_ISSU_BANK_BROKEN}"
+        fi
+    fi
+}
+
 function wait_for_pre_shutdown_complete_or_fail()
 {
     debug "Waiting for pre-shutdown ..."
@@ -484,10 +520,20 @@ systemctl stop swss
 if [[ "$REBOOT_TYPE" = "warm-reboot" || "$REBOOT_TYPE" = "fastfast-reboot" ]]; then
     initialize_pre_shutdown
 
+    BEFORE_PRE_SHUTDOWN=true
+
+    if [[ "x$sonic_asic_type" == x"mellanox" ]]; then
+        check_issu_bank_file "$BEFORE_PRE_SHUTDOWN"
+    fi
+
     request_pre_shutdown
 
     wait_for_pre_shutdown_complete_or_fail
 
+    if [[ "x$sonic_asic_type" == x"mellanox" ]]; then
+        check_issu_bank_file
+    fi
+
     # Warm reboot: dump state to host disk
     if [[ "$REBOOT_TYPE" = "fastfast-reboot" ]]; then
         sonic-db-cli ASIC_DB FLUSHDB > /dev/null