Commit 257c62e1 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: avoid tree log commit when there are no changes 



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: default avatarChris Mason <chris.mason@oracle.com>
parent 4722607d

fs/btrfs/btrfs_inode.h

+6 −0
Original line number Diff line number Diff line
@@ -86,6 +86,12 @@ struct btrfs_inode { 
	 * transid of the trans_handle that last modified this inode

	 */

	u64 last_trans;



	/*

	 * log transid when this inode was last modified

	 */

	u64 last_sub_trans;



	/*

	 * transid that last logged this inode

	 */

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -1009,6 +1009,7 @@ struct btrfs_root { 
	atomic_t log_writers;

	atomic_t log_commit[2];

	unsigned long log_transid;

	unsigned long last_log_commit;

	unsigned long log_batch;

	pid_t log_start_pid;

	bool log_multiple_pids;

fs/btrfs/disk-io.c

+2 −0
Original line number Diff line number Diff line
@@ -919,6 +919,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize, 
	atomic_set(&root->log_writers, 0);

	root->log_batch = 0;

	root->log_transid = 0;

	root->last_log_commit = 0;

	extent_io_tree_init(&root->dirty_log_pages,

			     fs_info->btree_inode->i_mapping, GFP_NOFS);
@@ -1089,6 +1090,7 @@ int btrfs_add_log_tree(struct btrfs_trans_handle *trans, 
	WARN_ON(root->log_root);

	root->log_root = log_root;

	root->log_transid = 0;

	root->last_log_commit = 0;

	return 0;

}

fs/btrfs/file.c

+26 −15
Original line number Diff line number Diff line
@@ -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

	 */
@@ -1189,6 +1196,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync) 
	 */

	mutex_unlock(&dentry->d_inode->i_mutex);



	if (ret != BTRFS_NO_LOG_SYNC) {

		if (ret > 0) {

			ret = btrfs_commit_transaction(trans, root);

		} else {
@@ -1198,6 +1206,9 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync) 
			else

				ret = btrfs_commit_transaction(trans, root);

		}

	} else {

		ret = btrfs_end_transaction(trans, root);

	}

	mutex_lock(&dentry->d_inode->i_mutex);

out:

	return ret > 0 ? EIO : ret;

fs/btrfs/inode.c

+5 −1
Original line number Diff line number Diff line
@@ -3480,6 +3480,7 @@ static noinline void init_btrfs_i(struct inode *inode) 
	bi->generation = 0;

	bi->sequence = 0;

	bi->last_trans = 0;

	bi->last_sub_trans = 0;

	bi->logged_trans = 0;

	bi->delalloc_bytes = 0;

	bi->reserved_bytes = 0;
@@ -4980,7 +4981,9 @@ again: 
	set_page_dirty(page);

	SetPageUptodate(page);



	BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;

	BTRFS_I(inode)->last_trans = root->fs_info->generation;

	BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;



	unlock_extent(io_tree, page_start, page_end, GFP_NOFS);



out_unlock:
@@ -5100,6 +5103,7 @@ struct inode *btrfs_alloc_inode(struct super_block *sb) 
	if (!ei)

		return NULL;

	ei->last_trans = 0;

	ei->last_sub_trans = 0;

	ei->logged_trans = 0;

	ei->outstanding_extents = 0;

	ei->reserved_extents = 0;

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