linux-ext4 - [PATCH] ext4: Automatically allocate delay allocated blocks before rename

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Message-ID: <87wrntsq7h.fsf@dmon-lap.sw.ru>
Date:	Wed, 01 Dec 2010 14:11:14 +0300
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	linux-ext4@...r.kernel.org, Ted Ts'o <tytso@....edu>
Subject: [PATCH] ext4: Automatically allocate delay allocated blocks before rename



Ext4 already performs block allocation on rename, but it does it after
rename was complete, so race window is much tighter but still exist.
In order to guarantee atomic behavior let's force block allocation before
actual rename. This rearrangement should not affect IO performance.

- Code cleanup: It is possible to move some checks out of transaction
  which theoretically may result in better performance.

Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
---
 fs/ext4/namei.c |   32 +++++++++++++++++---------------
 1 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 92203b8..7fe187f 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2333,7 +2333,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 	struct inode *old_inode, *new_inode;
 	struct buffer_head *old_bh, *new_bh, *dir_bh;
 	struct ext4_dir_entry_2 *old_de, *new_de;
-	int retval, force_da_alloc = 0;
+	int retval;
 
 	dquot_initialize(old_dir);
 	dquot_initialize(new_dir);
@@ -2344,14 +2344,6 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 	 * in separate transaction */
 	if (new_dentry->d_inode)
 		dquot_initialize(new_dentry->d_inode);
-	handle = ext4_journal_start(old_dir, 2 *
-					EXT4_DATA_TRANS_BLOCKS(old_dir->i_sb) +
-					EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2);
-	if (IS_ERR(handle))
-		return PTR_ERR(handle);
-
-	if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))
-		ext4_handle_sync(handle);
 
 	old_bh = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de);
 	/*
@@ -2363,7 +2355,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 	old_inode = old_dentry->d_inode;
 	retval = -ENOENT;
 	if (!old_bh || le32_to_cpu(old_de->inode) != old_inode->i_ino)
-		goto end_rename;
+		goto out_release;
 
 	new_inode = new_dentry->d_inode;
 	new_bh = ext4_find_entry(new_dir, &new_dentry->d_name, &new_de);
@@ -2373,6 +2365,19 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 			new_bh = NULL;
 		}
 	}
+
+	if (!test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC) && new_inode)
+ 		ext4_alloc_da_blocks(old_inode);
+
+	handle = ext4_journal_start(old_dir, 2 *
+					EXT4_DATA_TRANS_BLOCKS(old_dir->i_sb) +
+					EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))
+		ext4_handle_sync(handle);
+
 	if (S_ISDIR(old_inode->i_mode)) {
 		if (new_inode) {
 			retval = -ENOTEMPTY;
@@ -2476,18 +2481,15 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 		ext4_mark_inode_dirty(handle, new_inode);
 		if (!new_inode->i_nlink)
 			ext4_orphan_add(handle, new_inode);
-		if (!test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC))
-			force_da_alloc = 1;
 	}
 	retval = 0;
 
 end_rename:
+	ext4_journal_stop(handle);
+out_release:
 	brelse(dir_bh);
 	brelse(old_bh);
 	brelse(new_bh);
-	ext4_journal_stop(handle);
-	if (retval == 0 && force_da_alloc)
-		ext4_alloc_da_blocks(old_inode);
 	return retval;
 }
 
-- 
1.7.2.3

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