This I/O manager saves the contents of the location being overwritten
to a tdb database. This helps in undoing the changes done to the
file system.
The call sequence involve
set_undo_io_backing_manager(unix_io_manager);
set_undo_io_backup_file("/tmp/test.tdb");
retval = ext2fs_open2(dev_name, 0, flags,
superblock, block_size, undo_io_manager,
¤t_fs);
The patch is on top of e2fsprogs-upstream mercurial repo
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
----
diff -r 11b6e3e021f0 lib/ext2fs/Makefile.in
--- a/lib/ext2fs/Makefile.in Thu May 31 12:39:02 2007 -0400
+++ b/lib/ext2fs/Makefile.in Fri Jun 08 12:31:02 2007 +0530
@@ -66,7 +66,8 @@ OBJS= $(DEBUGFS_LIB_OBJS) $(RESIZE_LIB_O
unix_io.o \
unlink.o \
valid_blk.o \
- version.o
+ version.o \
+ undo_io.o
SRCS= ext2_err.c \
$(srcdir)/alloc.c \
@@ -134,7 +135,8 @@ SRCS= ext2_err.c \
$(srcdir)/tst_bitops.c \
$(srcdir)/tst_byteswap.c \
$(srcdir)/tst_getsize.c \
- $(srcdir)/tst_iscan.c
+ $(srcdir)/tst_iscan.c \
+ $(srcdir)/undo_io.c
HFILES= bitops.h ext2fs.h ext2_io.h ext2_fs.h ext2_ext_attr.h ext3_extents.h \
tdb.h
@@ -583,3 +585,4 @@ tst_iscan.o: $(srcdir)/tst_iscan.c $(src
$(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
$(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
$(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h $(srcdir)/bitops.h
+undo_io.o: $(srcdir)/undo_io.c $(srcdir)/ext2_fs.h $(srcdir)/ext2fs.h
diff -r 11b6e3e021f0 lib/ext2fs/ext2_io.h
--- a/lib/ext2fs/ext2_io.h Thu May 31 12:39:02 2007 -0400
+++ b/lib/ext2fs/ext2_io.h Fri Jun 08 12:31:02 2007 +0530
@@ -96,6 +96,11 @@ extern errcode_t io_channel_write_byte(i
/* unix_io.c */
extern io_manager unix_io_manager;
+/* undo_io.c */
+extern io_manager undo_io_manager;
+extern errcode_t set_undo_io_backing_manager(io_manager manager);
+extern errcode_t set_undo_io_backup_file(char *file_name);
+
/* test_io.c */
extern io_manager test_io_manager, test_io_backing_manager;
extern void (*test_io_cb_read_blk)
diff -r 11b6e3e021f0 lib/ext2fs/undo_io.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/ext2fs/undo_io.c Fri Jun 08 13:53:16 2007 +0530
@@ -0,0 +1,469 @@
+/*
+ * undo_io.c --- This is the undo io manager that copies the old data that
+ * copies the old data being overwritten into a tdb database
+ *
+ * Copyright (C) 2007 Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>, IBM Corporation
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Public
+ * License.
+ * %End-Header%
+ */
+
+#define _LARGEFILE_SOURCE
+#define _LARGEFILE64_SOURCE
+
+#include <stdio.h>
+#include <string.h>
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#if HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <fcntl.h>
+#include <time.h>
+#ifdef __linux__
+#include <sys/utsname.h>
+#endif
+#if HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+#if HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#if HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>
+#endif
+
+#include "tdb.h"
+
+#include "ext2_fs.h"
+#include "ext2fs.h"
+
+/*
+ * For checking structure magic numbers...
+ */
+
+#define EXT2_CHECK_MAGIC(struct, code) \
+ if ((struct)->magic != (code)) return (code)
+
+
+
+struct undo_private_data {
+ int magic;
+ TDB_CONTEXT *tdb;
+ char *tdb_file;
+
+ /* The backing io channel */
+ io_channel real;
+
+ /* to support offset in unix I/O manager */
+ ext2_loff_t offset;
+};
+
+static errcode_t undo_open(const char *name, int flags, io_channel *channel);
+static errcode_t undo_close(io_channel channel);
+static errcode_t undo_set_blksize(io_channel channel, int blksize);
+static errcode_t undo_read_blk(io_channel channel, unsigned long block,
+ int count, void *data);
+static errcode_t undo_write_blk(io_channel channel, unsigned long block,
+ int count, const void *data);
+static errcode_t undo_flush(io_channel channel);
+static errcode_t undo_write_byte(io_channel channel, unsigned long offset,
+ int size, const void *data);
+static errcode_t undo_set_option(io_channel channel, const char *option,
+ const char *arg);
+
+static struct struct_io_manager struct_undo_manager = {
+ EXT2_ET_MAGIC_IO_MANAGER,
+ "Undo I/O Manager",
+ undo_open,
+ undo_close,
+ undo_set_blksize,
+ undo_read_blk,
+ undo_write_blk,
+ undo_flush,
+ undo_write_byte,
+ undo_set_option
+};
+
+io_manager undo_io_manager = &struct_undo_manager;
+static io_manager undo_io_backing_manager ;
+static char *tdb_file ;
+static int tdb_data_size = 0;
+
+errcode_t set_undo_io_backing_manager(io_manager manager)
+{
+ /*
+ * We may want to do some validation later
+ */
+ undo_io_backing_manager = manager;
+ return 0;
+}
+
+errcode_t set_undo_io_backup_file(char *file_name)
+{
+ tdb_file = strdup(file_name);
+
+ if (tdb_file == NULL) {
+ return EXT2_ET_NO_MEMORY;
+ }
+
+ return 0;
+}
+
+
+static errcode_t undo_write_tdb(io_channel channel,
+ unsigned long block, int count)
+
+{
+ int size, loop_count = 0, i;
+ unsigned long block_num, backing_blk_num;
+ errcode_t retval = 0;
+ ext2_loff_t offset;
+ struct undo_private_data *data;
+ TDB_DATA tdb_key, tdb_data;
+ char *read_ptr;
+
+ data = (struct undo_private_data *) channel->private_data;
+
+
+ if (data->tdb == NULL) {
+ /*
+ * Transaction database not initialized
+ */
+ return 0;
+ }
+
+ /*
+ * Set the block size used to read for tdb
+ */
+ if (!tdb_data_size)
+ tdb_data_size = channel->block_size;
+
+ if (count == 1)
+ size = channel->block_size;
+ else {
+ if (count < 0)
+ size = -count;
+ else
+ size = count * channel->block_size;
+ }
+
+ /*
+ * Data is stored in tdb database as blocks of tdb_data_size size
+ * This helps in efficient lookup further.
+ *
+ * We divide the disk to blocks of tdb_data_size.
+ */
+
+ block_num = ((block * channel->block_size) + data->offset) / tdb_data_size;
+
+
+ loop_count = (size + tdb_data_size -1)/tdb_data_size;
+
+ tdb_transaction_start(data->tdb);
+ for (i = 0; i < loop_count; i++) {
+
+ block_num += i;
+ tdb_key.dptr = (unsigned char *)&block_num;
+ tdb_key.dsize = sizeof(block_num);
+
+ /*
+ * Check if we have the record already
+ */
+ if (tdb_exists(data->tdb, tdb_key)) {
+
+ /* Try the next block */
+ continue;
+ }
+
+ /*
+ * Read one block using the backing I/O manager
+ * The backing I/O manager block size may be
+ * different from the tdb_data_size.
+ * Also we need to recalcuate the block number with respect
+ * to the backing I/O manager.
+ */
+
+ offset = block_num * tdb_data_size;
+ backing_blk_num = (offset - data->offset) / channel->block_size;
+ count = tdb_data_size + ((offset - data->offset) % channel->block_size);
+
+ retval = ext2fs_get_mem(count, &read_ptr);
+ if (retval)
+ return retval;
+
+ memset(read_ptr, 0, count);
+
+ retval = io_channel_read_blk(data->real,
+ backing_blk_num, -count, read_ptr);
+ if (retval) {
+ free(read_ptr);
+ return retval;
+ }
+
+
+ tdb_data.dptr = read_ptr + ((offset - data->offset) % channel->block_size);
+ tdb_data.dsize = tdb_data_size;
+
+#ifdef DEBUG
+ printf("Printing with key %ld data %x and size %d\n",
+ block_num, tdb_data.dptr, tdb_data_size);
+#endif
+
+ retval = tdb_store(data->tdb, tdb_key, tdb_data, TDB_INSERT);
+ if (retval == -1) {
+ /*
+ * TDB_ERR_EXISTS cannot happen because we
+ * have already verified it doesn't exist
+ */
+ tdb_transaction_cancel(data->tdb);
+ retval = EXT2_ET_TDB_ERR_IO;
+ free(read_ptr);
+ return retval;
+
+ }
+ free(read_ptr);
+ }
+
+ tdb_transaction_commit(data->tdb);
+
+ return retval;
+
+}
+
+static TDB_CONTEXT *undo_setup_tdb(char *tdb_file,
+ struct undo_private_data *data)
+{
+ errcode_t retval;
+
+ data->tdb = tdb_open(tdb_file, 0, TDB_CLEAR_IF_FIRST,
+ O_RDWR | O_CREAT | O_TRUNC, 0600);
+ return data->tdb;
+
+}
+static errcode_t undo_open(const char *name, int flags, io_channel *channel)
+{
+ io_channel io = NULL;
+ struct undo_private_data *data = NULL;
+ errcode_t retval;
+ int open_flags;
+ struct stat st;
+
+ if (name == 0)
+ return EXT2_ET_BAD_DEVICE_NAME;
+ retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
+ if (retval)
+ return retval;
+ memset(io, 0, sizeof(struct struct_io_channel));
+ io->magic = EXT2_ET_MAGIC_IO_CHANNEL;
+ retval = ext2fs_get_mem(sizeof(struct undo_private_data), &data);
+ if (retval)
+ goto cleanup;
+
+ io->manager = undo_io_manager;
+ retval = ext2fs_get_mem(strlen(name)+1, &io->name);
+ if (retval)
+ goto cleanup;
+
+ strcpy(io->name, name);
+ io->private_data = data;
+ io->block_size = 1024;
+ io->read_error = 0;
+ io->write_error = 0;
+ io->refcount = 1;
+
+ memset(data, 0, sizeof(struct undo_private_data));
+ data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;
+
+ if (undo_io_backing_manager) {
+ retval = undo_io_backing_manager->open(name, flags,
+ &data->real);
+ if (retval)
+ goto cleanup;
+ } else {
+ data->real = 0;
+ }
+
+ /* setup the tdb file */
+ if (undo_setup_tdb(tdb_file, data) == NULL )
+ goto cleanup;
+
+ *channel = io;
+ return 0;
+
+cleanup:
+ if (data->real)
+ io_channel_close(data->real);
+
+ if (data)
+ ext2fs_free_mem(&data);
+
+ if (io)
+ ext2fs_free_mem(&io);
+
+ return retval;
+}
+
+static errcode_t undo_close(io_channel channel)
+{
+ struct undo_private_data *data;
+ errcode_t retval = 0;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ if (--channel->refcount > 0)
+ return 0;
+
+ if (data->real)
+ retval = io_channel_close(data->real);
+
+ if (data->tdb)
+ tdb_close(data->tdb);
+
+ ext2fs_free_mem(&channel->private_data);
+ if (channel->name)
+ ext2fs_free_mem(&channel->name);
+ ext2fs_free_mem(&channel);
+
+ return retval;
+}
+
+static errcode_t undo_set_blksize(io_channel channel, int blksize)
+{
+ struct undo_private_data *data;
+ errcode_t retval;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ if (data->real)
+ retval = io_channel_set_blksize(data->real, blksize);
+
+ channel->block_size = blksize;
+ return 0;
+}
+
+
+static errcode_t undo_read_blk(io_channel channel, unsigned long block,
+ int count, void *buf)
+{
+ errcode_t retval;
+ struct undo_private_data *data;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ if (data->real)
+ retval = io_channel_read_blk(data->real, block, count, buf);
+
+ return retval;
+}
+
+static errcode_t undo_write_blk(io_channel channel, unsigned long block,
+ int count, const void *buf)
+{
+ struct undo_private_data *data;
+ errcode_t retval = 0;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ /*
+ * First write the existing content into database
+ */
+ retval = undo_write_tdb(channel, block, count);
+ if (retval)
+ return retval;
+
+
+ if (data->real)
+ retval = io_channel_write_blk(data->real, block, count, buf);
+
+ return retval;
+
+}
+
+static errcode_t undo_write_byte(io_channel channel, unsigned long offset,
+ int size, const void *buf)
+{
+ struct undo_private_data *data;
+ errcode_t retval = 0;
+ ssize_t actual;
+ ext2_loff_t location;
+ unsigned long blk_num, count;;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ location = offset + data->offset;
+ blk_num = location/channel->block_size;
+ /*
+ * the size specified may spread across multiple blocks
+ * also make sure we account for the fact that block start
+ * offset for tdb is different from the backing I/O manager
+ * due to possible different block size
+ */
+ count = (size + (location % channel->block_size) + channel->block_size -1)/channel->block_size;
+ retval = undo_write_tdb(channel, blk_num, count);
+ if (retval)
+ return retval;
+
+ if (data->real && data->real->manager->write_byte)
+ retval = io_channel_write_byte(data->real, offset, size, buf);
+
+ return retval;
+}
+
+/*
+ * Flush data buffers to disk.
+ */
+static errcode_t undo_flush(io_channel channel)
+{
+ errcode_t retval = 0;
+ struct undo_private_data *data;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ if (data->real)
+ retval = io_channel_flush(data->real);
+
+ return retval;
+}
+
+static errcode_t undo_set_option(io_channel channel, const char *option,
+ const char *arg)
+{
+ struct undo_private_data *data;
+ unsigned long tmp;
+ char *end;
+
+ EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+ data = (struct undo_private_data *) channel->private_data;
+ EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+ /*
+ * Need to support offset option to work with
+ * Unix I/O manager
+ */
+ if (!strcmp(option, "offset")) {
+ if (!arg)
+ return EXT2_ET_INVALID_ARGUMENT;
+
+ tmp = strtoul(arg, &end, 0);
+ if (*end)
+ return EXT2_ET_INVALID_ARGUMENT;
+ data->offset = tmp;
+ return 0;
+ }
+}
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