It's really inefficient to (ab)use the TDB key store as a bitmap to
find out if we've already written a block to the undo file, because
the tdb code is reads the database key btree disk blocks for *every*
query. Changing that logic to a bitmap reduces overhead by a large
margin -- the overhead of using undo_io while converting a 2TB FS to
metadata_csum is reduced from 55 minutes to 45.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
lib/ext2fs/undo_io.c | 69 +++++++++++++++++++++++++++++++++++++-------------
1 file changed, 51 insertions(+), 18 deletions(-)
diff --git a/lib/ext2fs/undo_io.c b/lib/ext2fs/undo_io.c
index 70b90d5..9a01e30 100644
--- a/lib/ext2fs/undo_io.c
+++ b/lib/ext2fs/undo_io.c
@@ -70,6 +70,9 @@ struct undo_private_data {
/* to support offset in unix I/O manager */
ext2_loff_t offset;
+
+ ext2fs_block_bitmap written_block_map;
+ struct struct_ext2_filsys fake_fs;
};
static io_manager undo_io_backing_manager;
@@ -164,6 +167,38 @@ static errcode_t write_block_size(TDB_CONTEXT *tdb, int block_size)
return retval;
}
+static errcode_t undo_setup_tdb(struct undo_private_data *data)
+{
+ errcode_t retval;
+
+ if (data->tdb_written == 1)
+ return 0;
+
+ data->tdb_written = 1;
+
+ /* Make a bitmap to track what we've written */
+ memset(&data->fake_fs, 0, sizeof(data->fake_fs));
+ data->fake_fs.blocksize = data->tdb_data_size;
+ retval = ext2fs_alloc_generic_bmap(&data->fake_fs,
+ EXT2_ET_MAGIC_BLOCK_BITMAP64,
+ EXT2FS_BMAP64_RBTREE,
+ 0, ~1ULL, ~1ULL,
+ "undo block map", &data->written_block_map);
+ if (retval)
+ return retval;
+
+ /* Write the blocksize to tdb file */
+ tdb_transaction_start(data->tdb);
+ retval = write_block_size(data->tdb,
+ data->tdb_data_size);
+ if (retval) {
+ tdb_transaction_cancel(data->tdb);
+ return EXT2_ET_TDB_ERR_IO;
+ }
+ tdb_transaction_commit(data->tdb);
+ return 0;
+}
+
static errcode_t undo_write_tdb(io_channel channel,
unsigned long long block, int count)
@@ -194,6 +229,10 @@ static errcode_t undo_write_tdb(io_channel channel,
else
size = count * channel->block_size;
}
+
+ retval = undo_setup_tdb(data);
+ if (retval)
+ return retval;
/*
* Data is stored in tdb database as blocks of tdb_data_size size
* This helps in efficient lookup further.
@@ -212,11 +251,14 @@ static errcode_t undo_write_tdb(io_channel channel,
/*
* Check if we have the record already
*/
- if (tdb_exists(data->tdb, tdb_key)) {
+ if (ext2fs_test_block_bitmap2(data->written_block_map,
+ block_num)) {
/* Try the next block */
block_num++;
continue;
}
+ ext2fs_mark_block_bitmap2(data->written_block_map, block_num);
+
/*
* Read one block using the backing I/O manager
* The backing I/O manager block size may be
@@ -265,19 +307,7 @@ static errcode_t undo_write_tdb(io_channel channel,
tdb_data.dptr,
tdb_data.dsize);
#endif
- if (data->tdb_written != 1) {
- data->tdb_written = 1;
- /* Write the blocksize to tdb file */
- retval = write_block_size(data->tdb,
- data->tdb_data_size);
- if (retval) {
- tdb_transaction_cancel(data->tdb);
- retval = EXT2_ET_TDB_ERR_IO;
- free(read_ptr);
- return retval;
- }
- }
- retval = tdb_store(data->tdb, tdb_key, tdb_data, TDB_INSERT);
+ retval = tdb_store(data->tdb, tdb_key, tdb_data, TDB_REPLACE);
if (retval == -1) {
/*
* TDB_ERR_EXISTS cannot happen because we
@@ -345,6 +375,7 @@ static errcode_t undo_open(const char *name, int flags, io_channel *channel)
memset(data, 0, sizeof(struct undo_private_data));
data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;
+ data->written_block_map = NULL;
if (undo_io_backing_manager) {
retval = undo_io_backing_manager->open(name, flags,
@@ -390,7 +421,7 @@ cleanup:
static errcode_t undo_close(io_channel channel)
{
struct undo_private_data *data;
- errcode_t retval = 0;
+ errcode_t err, retval = 0;
EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
data = (struct undo_private_data *) channel->private_data;
@@ -399,20 +430,22 @@ static errcode_t undo_close(io_channel channel)
if (--channel->refcount > 0)
return 0;
/* Before closing write the file system identity */
- retval = write_file_system_identity(channel, data->tdb);
- if (retval)
- return retval;
+ err = write_file_system_identity(channel, data->tdb);
if (data->real)
retval = io_channel_close(data->real);
if (data->tdb) {
tdb_flush(data->tdb);
tdb_close(data->tdb);
}
+ if (data->written_block_map)
+ ext2fs_free_generic_bitmap(data->written_block_map);
ext2fs_free_mem(&channel->private_data);
if (channel->name)
ext2fs_free_mem(&channel->name);
ext2fs_free_mem(&channel);
+ if (err)
+ return err;
return retval;
}
--
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