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Btrfs: avoid tree log commit when there are no changes

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rpm has a habit of running fdatasync when the file hasn't
changed.  We already detect if a file hasn't been changed
in the current transaction but it might have been sent to
the tree-log in this transaction and not changed since
the last call to fsync.

In this case, we want to avoid a tree log sync, which includes
a number of synchronous writes and barriers.  This commit
extends the existing tracking of the last transaction to change
a file to also track the last sub-transaction.

The end result is that rpm -ivh and -Uvh are roughly twice as fast,
and on par with ext3.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2009-10-13 13:21:08 -04:00
parent 4722607db6
commit 257c62e1bc
8 changed files with 71 additions and 16 deletions
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41
fs/btrfs/file.c
View File

@@ -1087,8 +1087,10 @@ out_nolock:
btrfs_end_transaction(trans, root);
else
btrfs_commit_transaction(trans, root);
} else {
} else if (ret != BTRFS_NO_LOG_SYNC) {
btrfs_commit_transaction(trans, root);
} else {
btrfs_end_transaction(trans, root);
}
}
if (file->f_flags & O_DIRECT) {
@@ -1138,6 +1140,13 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
int ret = 0;
struct btrfs_trans_handle *trans;
/* we wait first, since the writeback may change the inode */
root->log_batch++;
/* the VFS called filemap_fdatawrite for us */
btrfs_wait_ordered_range(inode, 0, (u64)-1);
root->log_batch++;
/*
* check the transaction that last modified this inode
* and see if its already been committed
@@ -1145,6 +1154,11 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
if (!BTRFS_I(inode)->last_trans)
goto out;
/*
* if the last transaction that changed this file was before
* the current transaction, we can bail out now without any
* syncing
*/
mutex_lock(&root->fs_info->trans_mutex);
if (BTRFS_I(inode)->last_trans <=
root->fs_info->last_trans_committed) {
@@ -1154,13 +1168,6 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
}
mutex_unlock(&root->fs_info->trans_mutex);
root->log_batch++;
filemap_fdatawrite(inode->i_mapping);
btrfs_wait_ordered_range(inode, 0, (u64)-1);
root->log_batch++;
if (datasync && !(inode->i_state & I_DIRTY_PAGES))
goto out;
/*
* ok we haven't committed the transaction yet, lets do a commit
*/
@@ -1189,14 +1196,18 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
*/
mutex_unlock(&dentry->d_inode->i_mutex);
if (ret > 0) {
ret = btrfs_commit_transaction(trans, root);
} else {
ret = btrfs_sync_log(trans, root);
if (ret == 0)
ret = btrfs_end_transaction(trans, root);
else
if (ret != BTRFS_NO_LOG_SYNC) {
if (ret > 0) {
ret = btrfs_commit_transaction(trans, root);
} else {
ret = btrfs_sync_log(trans, root);
if (ret == 0)
ret = btrfs_end_transaction(trans, root);
else
ret = btrfs_commit_transaction(trans, root);
}
} else {
ret = btrfs_end_transaction(trans, root);
}
mutex_lock(&dentry->d_inode->i_mutex);
out: