add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/tools/hv/hv_fcopy_daemon.c
..
..
@@ -1,19 +1,10 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * An implementation of host to guest copy functionality for Linux.
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  *
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  * Copyright (C) 2014, Microsoft, Inc.
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  *
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  * Author : K. Y. Srinivasan <kys@microsoft.com>
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- *
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- * This program is free software; you can redistribute it and/or modify it
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- * under the terms of the GNU General Public License version 2 as published
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- * by the Free Software Foundation.
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- *
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- * This program is distributed in the hope that it will be useful, but
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- * WITHOUT ANY WARRANTY; without even the implied warranty of
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- * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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- * NON INFRINGEMENT.  See the GNU General Public License for more
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- * details.
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  */
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9
 
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10
 
..
..
@@ -89,6 +80,8 @@
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 	error = 0;
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 done:
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+	if (error)
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+		target_fname[0] = '\0';
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 	return error;
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 }
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..
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@@ -117,15 +110,29 @@
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 	return ret;
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 }
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+/*
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+ * Reset target_fname to "" in the two below functions for hibernation: if
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+ * the fcopy operation is aborted by hibernation, the daemon should remove the
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+ * partially-copied file; to achieve this, the hv_utils driver always fakes a
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+ * CANCEL_FCOPY message upon suspend, and later when the VM resumes back,
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+ * the daemon calls hv_copy_cancel() to remove the file; if a file is copied
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+ * successfully before suspend, hv_copy_finished() must reset target_fname to
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+ * avoid that the file can be incorrectly removed upon resume, since the faked
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+ * CANCEL_FCOPY message is spurious in this case.
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+ */
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 static int hv_copy_finished(void)
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 {
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 	close(target_fd);
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+	target_fname[0] = '\0';
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 	return 0;
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 }
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 static int hv_copy_cancel(void)
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 {
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 	close(target_fd);
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-	unlink(target_fname);
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+	if (strlen(target_fname) > 0) {
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+		unlink(target_fname);
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+		target_fname[0] = '\0';
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+	}
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 	return 0;
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 }
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@@ -140,7 +147,7 @@
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 int main(int argc, char *argv[])
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 {
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-	int fcopy_fd;
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+	int fcopy_fd = -1;
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 	int error;
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 	int daemonize = 1, long_index = 0, opt;
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 	int version = FCOPY_CURRENT_VERSION;
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@@ -150,7 +157,7 @@
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 		struct hv_do_fcopy copy;
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 		__u32 kernel_modver;
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 	} buffer = { };
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-	int in_handshake = 1;
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+	int in_handshake;
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 	static struct option long_options[] = {
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 		{"help",	no_argument,	   0,  'h' },
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@@ -179,6 +186,12 @@
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 	openlog("HV_FCOPY", 0, LOG_USER);
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 	syslog(LOG_INFO, "starting; pid is:%d", getpid());
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188
 
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+reopen_fcopy_fd:
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+	if (fcopy_fd != -1)
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+		close(fcopy_fd);
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+	/* Remove any possible partially-copied file on error */
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+	hv_copy_cancel();
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+	in_handshake = 1;
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 	fcopy_fd = open("/dev/vmbus/hv_fcopy", O_RDWR);
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 	if (fcopy_fd < 0) {
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@@ -205,7 +218,7 @@
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 		len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);
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 		if (len < 0) {
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 			syslog(LOG_ERR, "pread failed: %s", strerror(errno));
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-			exit(EXIT_FAILURE);
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+			goto reopen_fcopy_fd;
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 		}
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 		if (in_handshake) {
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@@ -240,9 +253,14 @@
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 		}
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+		/*
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+		 * pwrite() may return an error due to the faked CANCEL_FCOPY
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+		 * message upon hibernation. Ignore the error by resetting the
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+		 * dev file, i.e. closing and re-opening it.
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+		 */
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 		if (pwrite(fcopy_fd, &error, sizeof(int), 0) != sizeof(int)) {
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 			syslog(LOG_ERR, "pwrite failed: %s", strerror(errno));
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-			exit(EXIT_FAILURE);
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+			goto reopen_fcopy_fd;
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 		}
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 	}
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 }