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Message-ID: <20150506231700.GB30577@birch.djwong.org>
Date: Wed, 6 May 2015 16:17:00 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org
Subject: [PATCH] undo-io: write out index block after every write
Write out the undo file's index block after writing a block to the
undo file. This ensures that we always have a consistent undo file
in the page cache, even if the program crashes. When we fill up a
key block in the undo file, we'll call fsync to force the whole
thing to storage; this should happen about every 255 blocks given
the usual 4K block size.
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
lib/ext2fs/undo_io.c | 47 ++++++++++++++++++++++-------------------------
1 file changed, 22 insertions(+), 25 deletions(-)
diff --git a/lib/ext2fs/undo_io.c b/lib/ext2fs/undo_io.c
index 4a48193..b9294c3 100644
--- a/lib/ext2fs/undo_io.c
+++ b/lib/ext2fs/undo_io.c
@@ -165,7 +165,7 @@ errcode_t set_undo_io_backup_file(char *file_name)
return 0;
}
-static errcode_t write_undo_indexes(struct undo_private_data *data)
+static errcode_t write_undo_indexes(struct undo_private_data *data, int flush)
{
errcode_t retval;
struct ext2_super_block super;
@@ -187,9 +187,14 @@ static errcode_t write_undo_indexes(struct undo_private_data *data)
1, data->keyb);
if (retval)
return retval;
- memset(data->keyb, 0, data->tdb_data_size);
- data->keys_in_block = 0;
- data->key_blk_num = data->undo_blk_num;
+ /* Move on to the next key block if it's full. */
+ if (data->keys_in_block == KEYS_PER_BLOCK(data)) {
+ memset(data->keyb, 0, data->tdb_data_size);
+ data->keys_in_block = 0;
+ data->key_blk_num = data->undo_blk_num;
+ data->undo_blk_num++;
+ flush = 1;
+ }
}
/* Prepare superblock for write */
@@ -230,7 +235,8 @@ static errcode_t write_undo_indexes(struct undo_private_data *data)
if (retval)
goto err_out;
- retval = io_channel_flush(data->undo_file);
+ if (flush)
+ retval = io_channel_flush(data->undo_file);
err_out:
io_channel_set_blksize(channel, block_size);
return retval;
@@ -261,7 +267,7 @@ static errcode_t undo_setup_tdb(struct undo_private_data *data)
retval = ext2fs_get_mem(data->tdb_data_size, &data->keyb);
if (retval)
return retval;
- data->key_blk_num = data->undo_blk_num;
+ data->key_blk_num = data->first_key_blk;
/* Record block size */
dbg_printf("Undo block size %llu\n", data->tdb_data_size);
@@ -348,22 +354,6 @@ static errcode_t undo_write_tdb(io_channel channel,
}
ext2fs_mark_block_bitmap2(data->written_block_map, block_num);
- /* Spit out a key block */
- if (data->keys_in_block == KEYS_PER_BLOCK(data)) {
- retval = write_undo_indexes(data);
- if (retval)
- return retval;
- retval = io_channel_write_blk64(data->undo_file,
- data->key_blk_num, 1,
- data->keyb);
- if (retval)
- return retval;
- }
-
- /* Allocate new key block */
- if (data->keys_in_block == 0)
- data->undo_blk_num++;
-
/*
* Read one block using the backing I/O manager
* The backing I/O manager block size may be
@@ -458,6 +448,12 @@ static errcode_t undo_write_tdb(io_channel channel,
}
data->undo_blk_num++;
free(read_ptr);
+
+ /* Write out the key block */
+ retval = write_undo_indexes(data, 0);
+ if (retval)
+ return retval;
+
/* Next block */
block_num++;
}
@@ -668,7 +664,7 @@ static void undo_atexit(void *p)
struct undo_private_data *data = p;
errcode_t err;
- err = write_undo_indexes(data);
+ err = write_undo_indexes(data, 1);
io_channel_close(data->undo_file);
com_err(data->tdb_file, err, "while force-closing undo file");
@@ -707,7 +703,8 @@ 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->super_blk_num = 1;
- data->undo_blk_num = data->first_key_blk = 2;
+ data->first_key_blk = 2;
+ data->undo_blk_num = 3;
if (undo_io_backing_manager) {
retval = undo_io_backing_manager->open(name, flags,
@@ -789,7 +786,7 @@ static errcode_t undo_close(io_channel channel)
/* Before closing write the file system identity */
if (!getenv("UNDO_IO_SIMULATE_UNFINISHED"))
data->hdr.state = ext2fs_cpu_to_le32(E2UNDO_STATE_FINISHED);
- err = write_undo_indexes(data);
+ err = write_undo_indexes(data, 1);
ext2fs_remove_exit_fn(undo_atexit, data);
if (data->real)
retval = io_channel_close(data->real);
--
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