1 files changed, 488 insertions, 0 deletions
diff --git a/lib/ext2fs/mmp.c b/lib/ext2fs/mmp.c
new file mode 100644
index 0000000..eb94170
--- /dev/null
+++ b/lib/ext2fs/mmp.c
@@ -0,0 +1,488 @@
+/*
+ * Helper functions for multiple mount protection (MMP).
+ *
+ * Copyright (C) 2011 Whamcloud, Inc.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#ifndef _DEFAULT_SOURCE
+#define _DEFAULT_SOURCE	/* since glibc 2.20 _SVID_SOURCE is deprecated */
+#endif
+
+#include "config.h"
+
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <sys/time.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "ext2fs/ext2_fs.h"
+#include "ext2fs/ext2fs.h"
+
+#ifndef O_DIRECT
+#define O_DIRECT 0
+#endif
+
+#if __GNUC_PREREQ (4, 6)
+#pragma GCC diagnostic push
+#ifndef CONFIG_MMP
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+#endif
+
+errcode_t ext2fs_mmp_read(ext2_filsys fs, blk64_t mmp_blk, void *buf)
+{
+#ifdef CONFIG_MMP
+	struct mmp_struct *mmp_cmp;
+	errcode_t retval = 0;
+
+	if ((mmp_blk <= fs->super->s_first_data_block) ||
+	    (mmp_blk >= ext2fs_blocks_count(fs->super)))
+		return EXT2_ET_MMP_BAD_BLOCK;
+
+	/* ext2fs_open() reserves fd0,1,2 to avoid stdio collision, so checking
+	 * mmp_fd <= 0 is OK to validate that the fd is valid.  This opens its
+	 * own fd to read the MMP block to ensure that it is using O_DIRECT,
+	 * regardless of how the io_manager is doing reads, to avoid caching of
+	 * the MMP block by the io_manager or the VM.  It needs to be fresh. */
+	if (fs->mmp_fd <= 0) {
+		struct stat st;
+		int flags = O_RDONLY | O_DIRECT;
+
+		/*
+		 * There is no reason for using O_DIRECT if we're working with
+		 * regular file. Disabling it also avoids problems with
+		 * alignment when the device of the host file system has sector
+		 * size larger than blocksize of the fs we're working with.
+		 */
+		if (stat(fs->device_name, &st) == 0 &&
+		    S_ISREG(st.st_mode))
+			flags &= ~O_DIRECT;
+
+		fs->mmp_fd = open(fs->device_name, flags);
+		if (fs->mmp_fd < 0) {
+			retval = EXT2_ET_MMP_OPEN_DIRECT;
+			goto out;
+		}
+	}
+
+	if (fs->mmp_cmp == NULL) {
+		int align = ext2fs_get_dio_alignment(fs->mmp_fd);
+
+		retval = ext2fs_get_memalign(fs->blocksize, align,
+					     &fs->mmp_cmp);
+		if (retval)
+			return retval;
+	}
+
+	if ((blk64_t) ext2fs_llseek(fs->mmp_fd, mmp_blk * fs->blocksize,
+				    SEEK_SET) !=
+	    mmp_blk * fs->blocksize) {
+		retval = EXT2_ET_LLSEEK_FAILED;
+		goto out;
+	}
+
+	if (read(fs->mmp_fd, fs->mmp_cmp, fs->blocksize) != fs->blocksize) {
+		retval = EXT2_ET_SHORT_READ;
+		goto out;
+	}
+
+	mmp_cmp = fs->mmp_cmp;
+
+	if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+	    !ext2fs_mmp_csum_verify(fs, mmp_cmp))
+		retval = EXT2_ET_MMP_CSUM_INVALID;
+
+#ifdef WORDS_BIGENDIAN
+	ext2fs_swap_mmp(mmp_cmp);
+#endif
+
+	if (buf != NULL && buf != fs->mmp_cmp)
+		memcpy(buf, fs->mmp_cmp, fs->blocksize);
+
+	if (mmp_cmp->mmp_magic != EXT4_MMP_MAGIC) {
+		retval = EXT2_ET_MMP_MAGIC_INVALID;
+		goto out;
+	}
+
+out:
+	return retval;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+errcode_t ext2fs_mmp_write(ext2_filsys fs, blk64_t mmp_blk, void *buf)
+{
+#ifdef CONFIG_MMP
+	struct mmp_struct *mmp_s = buf;
+	struct timeval tv;
+	errcode_t retval = 0;
+
+	gettimeofday(&tv, 0);
+	mmp_s->mmp_time = tv.tv_sec;
+	fs->mmp_last_written = tv.tv_sec;
+
+	if (fs->super->s_mmp_block < fs->super->s_first_data_block ||
+	    fs->super->s_mmp_block > ext2fs_blocks_count(fs->super))
+		return EXT2_ET_MMP_BAD_BLOCK;
+
+#ifdef WORDS_BIGENDIAN
+	ext2fs_swap_mmp(mmp_s);
+#endif
+
+	retval = ext2fs_mmp_csum_set(fs, mmp_s);
+	if (retval)
+		return retval;
+
+	/* I was tempted to make this use O_DIRECT and the mmp_fd, but
+	 * this caused no end of grief, while leaving it as-is works. */
+	retval = io_channel_write_blk64(fs->io, mmp_blk, -(int)sizeof(struct mmp_struct), buf);
+
+#ifdef WORDS_BIGENDIAN
+	ext2fs_swap_mmp(mmp_s);
+#endif
+
+	/* Make sure the block gets to disk quickly */
+	io_channel_flush(fs->io);
+	return retval;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+#ifdef HAVE_SRANDOM
+#define srand(x)	srandom(x)
+#define rand()		random()
+#endif
+
+unsigned ext2fs_mmp_new_seq(void)
+{
+#ifdef CONFIG_MMP
+	unsigned new_seq;
+	struct timeval tv;
+	unsigned long pid = getpid();
+
+	gettimeofday(&tv, 0);
+	pid = (pid >> 16) | ((pid & 0xFFFF) << 16);
+	srand(pid ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
+
+	gettimeofday(&tv, 0);
+	/* Crank the random number generator a few times */
+	for (new_seq = (tv.tv_sec ^ tv.tv_usec) & 0x1F; new_seq > 0; new_seq--)
+		rand();
+
+	do {
+		new_seq = rand();
+	} while (new_seq > EXT4_MMP_SEQ_MAX);
+
+	return new_seq;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+#ifdef CONFIG_MMP
+static errcode_t ext2fs_mmp_reset(ext2_filsys fs)
+{
+	struct mmp_struct *mmp_s = NULL;
+	errcode_t retval = 0;
+
+	if (fs->mmp_buf == NULL) {
+		retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
+		if (retval)
+			goto out;
+	}
+
+	memset(fs->mmp_buf, 0, fs->blocksize);
+	mmp_s = fs->mmp_buf;
+
+	mmp_s->mmp_magic = EXT4_MMP_MAGIC;
+	mmp_s->mmp_seq = EXT4_MMP_SEQ_CLEAN;
+	mmp_s->mmp_time = 0;
+#ifdef HAVE_GETHOSTNAME
+	gethostname((char *) mmp_s->mmp_nodename, sizeof(mmp_s->mmp_nodename));
+#else
+	mmp_s->mmp_nodename[0] = '\0';
+#endif
+	strncpy((char *) mmp_s->mmp_bdevname, fs->device_name,
+		sizeof(mmp_s->mmp_bdevname));
+
+	mmp_s->mmp_check_interval = fs->super->s_mmp_update_interval;
+	if (mmp_s->mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
+		mmp_s->mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
+
+	retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
+out:
+	return retval;
+}
+#endif
+
+errcode_t ext2fs_mmp_update(ext2_filsys fs)
+{
+	return ext2fs_mmp_update2(fs, 0);
+}
+
+errcode_t ext2fs_mmp_clear(ext2_filsys fs)
+{
+#ifdef CONFIG_MMP
+	errcode_t retval = 0;
+
+	if (!(fs->flags & EXT2_FLAG_RW))
+		return EXT2_ET_RO_FILSYS;
+
+	retval = ext2fs_mmp_reset(fs);
+
+	return retval;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+errcode_t ext2fs_mmp_init(ext2_filsys fs)
+{
+#ifdef CONFIG_MMP
+	struct ext2_super_block *sb = fs->super;
+	blk64_t mmp_block;
+	errcode_t retval;
+
+	if (sb->s_mmp_update_interval == 0)
+		sb->s_mmp_update_interval = EXT4_MMP_UPDATE_INTERVAL;
+	/* This is probably excessively large, but who knows? */
+	else if (sb->s_mmp_update_interval > EXT4_MMP_MAX_UPDATE_INTERVAL)
+		return EXT2_ET_INVALID_ARGUMENT;
+
+	if (fs->mmp_buf == NULL) {
+		retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
+		if (retval)
+			goto out;
+	}
+
+	retval = ext2fs_alloc_block2(fs, 0, fs->mmp_buf, &mmp_block);
+	if (retval)
+		goto out;
+
+	sb->s_mmp_block = mmp_block;
+
+	retval = ext2fs_mmp_reset(fs);
+	if (retval)
+		goto out;
+
+out:
+	return retval;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+#ifndef min
+#define min(x, y) ((x) < (y) ? (x) : (y))
+#endif
+
+/*
+ * Make sure that the fs is not mounted or being fsck'ed while opening the fs.
+ */
+errcode_t ext2fs_mmp_start(ext2_filsys fs)
+{
+#ifdef CONFIG_MMP
+	struct mmp_struct *mmp_s;
+	unsigned seq;
+	unsigned int mmp_check_interval;
+	errcode_t retval = 0;
+
+	if (fs->mmp_buf == NULL) {
+		retval = ext2fs_get_mem(fs->blocksize, &fs->mmp_buf);
+		if (retval)
+			goto mmp_error;
+	}
+
+	retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
+	if (retval)
+		goto mmp_error;
+
+	mmp_s = fs->mmp_buf;
+
+	mmp_check_interval = fs->super->s_mmp_update_interval;
+	if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
+		mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
+
+	seq = mmp_s->mmp_seq;
+	if (seq == EXT4_MMP_SEQ_CLEAN)
+		goto clean_seq;
+	if (seq == EXT4_MMP_SEQ_FSCK) {
+		retval = EXT2_ET_MMP_FSCK_ON;
+		goto mmp_error;
+	}
+
+	if (seq > EXT4_MMP_SEQ_FSCK) {
+		retval = EXT2_ET_MMP_UNKNOWN_SEQ;
+		goto mmp_error;
+	}
+
+	/*
+	 * If check_interval in MMP block is larger, use that instead of
+	 * check_interval from the superblock.
+	 */
+	if (mmp_s->mmp_check_interval > mmp_check_interval)
+		mmp_check_interval = mmp_s->mmp_check_interval;
+
+	sleep(min(mmp_check_interval * 2 + 1, mmp_check_interval + 60));
+
+	retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
+	if (retval)
+		goto mmp_error;
+
+	if (seq != mmp_s->mmp_seq) {
+		retval = EXT2_ET_MMP_FAILED;
+		goto mmp_error;
+	}
+
+clean_seq:
+	if (!(fs->flags & EXT2_FLAG_RW))
+		goto mmp_error;
+
+	mmp_s->mmp_seq = seq = ext2fs_mmp_new_seq();
+#ifdef HAVE_GETHOSTNAME
+	gethostname((char *) mmp_s->mmp_nodename, sizeof(mmp_s->mmp_nodename));
+#else
+	strcpy((char *) mmp_s->mmp_nodename, "unknown host");
+#endif
+	strncpy((char *) mmp_s->mmp_bdevname, fs->device_name,
+		sizeof(mmp_s->mmp_bdevname));
+
+	retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
+	if (retval)
+		goto mmp_error;
+
+	sleep(min(2 * mmp_check_interval + 1, mmp_check_interval + 60));
+
+	retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, fs->mmp_buf);
+	if (retval)
+		goto mmp_error;
+
+	if (seq != mmp_s->mmp_seq) {
+		retval = EXT2_ET_MMP_FAILED;
+		goto mmp_error;
+	}
+
+	mmp_s->mmp_seq = EXT4_MMP_SEQ_FSCK;
+	retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
+	if (retval)
+		goto mmp_error;
+
+	return 0;
+
+mmp_error:
+	return retval;
+#else
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+/*
+ * Clear the MMP usage in the filesystem.  If this function returns an
+ * error EXT2_ET_MMP_CHANGE_ABORT it means the filesystem was modified
+ * by some other process while in use, and changes should be dropped, or
+ * risk filesystem corruption.
+ */
+errcode_t ext2fs_mmp_stop(ext2_filsys fs)
+{
+#ifdef CONFIG_MMP
+	struct mmp_struct *mmp, *mmp_cmp;
+	errcode_t retval = 0;
+
+	if (!ext2fs_has_feature_mmp(fs->super) ||
+	    !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP) ||
+	    (fs->mmp_buf == NULL) || (fs->mmp_cmp == NULL))
+		goto mmp_error;
+
+	retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, NULL);
+	if (retval)
+		goto mmp_error;
+
+	/* Check if the MMP block is not changed. */
+	mmp = fs->mmp_buf;
+	mmp_cmp = fs->mmp_cmp;
+	if (memcmp(mmp, mmp_cmp, sizeof(*mmp_cmp))) {
+		retval = EXT2_ET_MMP_CHANGE_ABORT;
+		goto mmp_error;
+	}
+
+	mmp_cmp->mmp_seq = EXT4_MMP_SEQ_CLEAN;
+	retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_cmp);
+
+mmp_error:
+	if (fs->mmp_fd > 0) {
+		close(fs->mmp_fd);
+		fs->mmp_fd = -1;
+	}
+
+	return retval;
+#else
+	if (!ext2fs_has_feature_mmp(fs->super) ||
+	    !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
+		return 0;
+
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+
+#define EXT2_MIN_MMP_UPDATE_INTERVAL 60
+
+/*
+ * Update the on-disk mmp buffer, after checking that it hasn't been changed.
+ */
+errcode_t ext2fs_mmp_update2(ext2_filsys fs, int immediately)
+{
+#ifdef CONFIG_MMP
+	struct mmp_struct *mmp, *mmp_cmp;
+	struct timeval tv;
+	errcode_t retval = 0;
+
+	if (!ext2fs_has_feature_mmp(fs->super) ||
+	    !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
+		return 0;
+
+	gettimeofday(&tv, 0);
+	if (!immediately &&
+	    tv.tv_sec - fs->mmp_last_written < EXT2_MIN_MMP_UPDATE_INTERVAL)
+		return 0;
+
+	retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, NULL);
+	if (retval)
+		goto mmp_error;
+
+	mmp = fs->mmp_buf;
+	mmp_cmp = fs->mmp_cmp;
+
+	if (memcmp(mmp, mmp_cmp, sizeof(*mmp_cmp)))
+		return EXT2_ET_MMP_CHANGE_ABORT;
+
+	mmp->mmp_time = tv.tv_sec;
+	mmp->mmp_seq = EXT4_MMP_SEQ_FSCK;
+	retval = ext2fs_mmp_write(fs, fs->super->s_mmp_block, fs->mmp_buf);
+
+mmp_error:
+	return retval;
+#else
+	if (!ext2fs_has_feature_mmp(fs->super) ||
+	    !(fs->flags & EXT2_FLAG_RW) || (fs->flags & EXT2_FLAG_SKIP_MMP))
+		return 0;
+
+	return EXT2_ET_OP_NOT_SUPPORTED;
+#endif
+}
+#if __GNUC_PREREQ (4, 6)
+#pragma GCC diagnostic pop
+#endif