Btrfs: pin log earlier when renaming (c4aba954) · Commits · 戴 / test

We were pinning the log right after the first step in the rename operation (inserting inode ref for the new name in the destination directory) instead of doing it before. This behaviour was introduced in 2009 for some reason that was not mentioned neither on the changelog nor any comment, with the drawback of a small time window where concurrent log writers can end up logging the new inode reference for the inode we are renaming while the rename operation is in progress (so that we can end up with a log containing both the new and old references). As of today there's no reason to not pin the log before that first step anymore, so just fix this. Signed-off-by:

Filipe Manana <fdmanana@suse.com>

fs/btrfs/inode.c

+2 −9

Original line number	Diff line number	Diff line
		@@ -9479,6 +9479,8 @@ static int btrfs_rename(struct inode old_dir, struct dentry old_dentry,
		/* force full log commit if subvolume involved. */
		btrfs_set_log_full_commit(root->fs_info, trans);
		} else {
		btrfs_pin_log_trans(root);
		log_pinned = true;
		ret = btrfs_insert_inode_ref(trans, dest,
		new_dentry->d_name.name,
		new_dentry->d_name.len,
		@@ -9486,15 +9488,6 @@ static int btrfs_rename(struct inode old_dir, struct dentry old_dentry,
		btrfs_ino(new_dir), index);
		if (ret)
		goto out_fail;
		/*
		* this is an ugly little race, but the rename is required
		* to make sure that if we crash, the inode is either at the
		* old name or the new one. pinning the log transaction lets
		* us make sure we don't allow a log commit to come in after
		* we unlink the name but before we add the new name back in.
		*/
		btrfs_pin_log_trans(root);
		log_pinned = true;
		}

		inode_inc_iversion(old_dir);

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