101 lines
2.9 KiB
Diff
101 lines
2.9 KiB
Diff
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From a67c0c5632fe6f68c02b0b5623217782b094c00e Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Tue, 14 Jun 2016 16:07:29 +0100
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Subject: [PATCH 4/7] init: Delete initramfs files before chrooting into the
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appliance.
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After supermin has finished running, the initramfs files sit around
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occupying non-swappable memory but serving no further purpose.
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This saves a little memory, at the cost of about 1ms of extra boot
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time.
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---
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init/init.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++--
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1 file changed, 48 insertions(+), 2 deletions(-)
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diff --git a/init/init.c b/init/init.c
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index 733d66e..5ac53e9 100644
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--- a/init/init.c
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+++ b/init/init.c
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@@ -1,5 +1,5 @@
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/* supermin-helper reimplementation in C.
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- * Copyright (C) 2009-2014 Red Hat Inc.
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+ * Copyright (C) 2009-2016 Red Hat Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@@ -80,6 +80,7 @@ static void mount_proc (void);
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static void print_uptime (void);
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static void read_cmdline (void);
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static void insmod (const char *filename);
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+static void delete_initramfs_files (void);
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static void show_directory (const char *dir);
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static char cmdline[1024];
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@@ -264,9 +265,12 @@ main ()
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exit (EXIT_FAILURE);
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}
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+ if (!quiet)
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+ fprintf (stderr, "supermin: deleting initramfs files\n");
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+ delete_initramfs_files ();
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+
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/* Note that pivot_root won't work. See the note in
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* Documentation/filesystems/ramfs-rootfs-initramfs.txt
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- * We could remove the old initramfs files, but let's not bother.
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*/
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if (!quiet)
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fprintf (stderr, "supermin: chroot\n");
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@@ -396,6 +400,48 @@ read_cmdline (void)
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cmdline[len-1] = '\0';
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}
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+/* By deleting the files in the initramfs before we chroot, we save a
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+ * little bit of memory (or quite a lot of memory if the user is using
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+ * unstripped kmods).
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+ *
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+ * We only delete files in the root directory. We don't delete
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+ * directories because they only take a tiny amount of space and
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+ * because we must not delete any mountpoints, especially not /root
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+ * where we are about to chroot.
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+ *
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+ * We don't recursively look for files because that would be too
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+ * complex and risky, and the normal supermin initramfs doesn't have
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+ * any files except in the root directory.
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+ */
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+static void
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+delete_initramfs_files (void)
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+{
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+ DIR *dir;
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+ struct dirent *d;
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+ struct stat statbuf;
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+
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+ if (chdir ("/") == -1) {
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+ perror ("chdir: /");
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+ return;
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+ }
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+
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+ dir = opendir (".");
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+ if (!dir) {
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+ perror ("opendir: /");
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+ return;
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+ }
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+
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+ while ((d = readdir (dir)) != NULL) {
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+ /* "." and ".." are directories, so the S_ISREG test ignores them. */
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+ if (lstat (d->d_name, &statbuf) >= 0 && S_ISREG (statbuf.st_mode)) {
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+ if (unlink (d->d_name) == -1)
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+ perror (d->d_name);
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+ }
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+ }
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+
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+ closedir (dir);
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+}
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+
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/* Display a directory on stderr. This is used for debugging only. */
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static char
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dirtype (int dt)
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--
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2.7.4
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