Re: [Ocfs2-devel] [PATCH] ocfs2: avoid getting dlm lock of the target directory multiple times during reflink process

[Gang He <ghe@suse.com>]

Hello Joseph and Wengang,

When you have time, please help review this patch.
About the deadlock problem which was caused by ocfs2_downconvert_lock 
failure, we have the fix patch, it is very key.
But I feel this patch is still useful as a optimization patch, the user
case is to reflink the files to the same directory concurrently, our 
users usually backup the files(via reflink) from the cluster nodes 
concurrently(via crontab) every day/hour.
The current design, during the reflink process, the node will 
acquire/release dlm lock of the target directory multiple times,
this is very inefficient in concurrently reflink.


Thanks
Gang

On 2021/8/26 15:59, Gang He wrote:
> During the reflink process, we should acquire the target directory
> inode dlm lock at the beginning, and hold this dlm lock until end
> of the function.
> With this patch, we avoid dlm lock ping-pong effect when clone
> files to the same directory simultaneously from multiple nodes.
> There is a typical user scenario, users regularly back up files
> to a specified directory through the reflink feature from the
> multiple nodes.
> 
> Signed-off-by: Gang He <ghe@suse.com>
> ---
>   fs/ocfs2/namei.c        | 32 +++++++++++++-------------------
>   fs/ocfs2/namei.h        |  2 ++
>   fs/ocfs2/refcounttree.c | 15 +++++++++++----
>   fs/ocfs2/xattr.c        | 12 +-----------
>   fs/ocfs2/xattr.h        |  1 +
>   5 files changed, 28 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
> index 2c46ff6ba4ea..f8bbb22cc60b 100644
> --- a/fs/ocfs2/namei.c
> +++ b/fs/ocfs2/namei.c
> @@ -2489,6 +2489,7 @@ static int ocfs2_prep_new_orphaned_file(struct inode *dir,
>   }
>   
>   int ocfs2_create_inode_in_orphan(struct inode *dir,
> +				 struct buffer_head **dir_bh,
>   				 int mode,
>   				 struct inode **new_inode)
>   {
> @@ -2597,13 +2598,16 @@ int ocfs2_create_inode_in_orphan(struct inode *dir,
>   
>   	brelse(new_di_bh);
>   
> -	if (!status)
> -		*new_inode = inode;
> -
>   	ocfs2_free_dir_lookup_result(&orphan_insert);
>   
> -	ocfs2_inode_unlock(dir, 1);
> -	brelse(parent_di_bh);
> +	if (!status) {
> +		*new_inode = inode;
> +		*dir_bh = parent_di_bh;
> +	} else {
> +		ocfs2_inode_unlock(dir, 1);
> +		brelse(parent_di_bh);
> +	}
> +
>   	return status;
>   }
>   
> @@ -2760,11 +2764,11 @@ int ocfs2_del_inode_from_orphan(struct ocfs2_super *osb,
>   }
>   
>   int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
> +				   struct buffer_head *dir_bh,
>   				   struct inode *inode,
>   				   struct dentry *dentry)
>   {
>   	int status = 0;
> -	struct buffer_head *parent_di_bh = NULL;
>   	handle_t *handle = NULL;
>   	struct ocfs2_super *osb = OCFS2_SB(dir->i_sb);
>   	struct ocfs2_dinode *dir_di, *di;
> @@ -2778,14 +2782,7 @@ int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
>   				(unsigned long long)OCFS2_I(dir)->ip_blkno,
>   				(unsigned long long)OCFS2_I(inode)->ip_blkno);
>   
> -	status = ocfs2_inode_lock(dir, &parent_di_bh, 1);
> -	if (status < 0) {
> -		if (status != -ENOENT)
> -			mlog_errno(status);
> -		return status;
> -	}
> -
> -	dir_di = (struct ocfs2_dinode *) parent_di_bh->b_data;
> +	dir_di = (struct ocfs2_dinode *) dir_bh->b_data;
>   	if (!dir_di->i_links_count) {
>   		/* can't make a file in a deleted directory. */
>   		status = -ENOENT;
> @@ -2798,7 +2795,7 @@ int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
>   		goto leave;
>   
>   	/* get a spot inside the dir. */
> -	status = ocfs2_prepare_dir_for_insert(osb, dir, parent_di_bh,
> +	status = ocfs2_prepare_dir_for_insert(osb, dir, dir_bh,
>   					      dentry->d_name.name,
>   					      dentry->d_name.len, &lookup);
>   	if (status < 0) {
> @@ -2862,7 +2859,7 @@ int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
>   	ocfs2_journal_dirty(handle, di_bh);
>   
>   	status = ocfs2_add_entry(handle, dentry, inode,
> -				 OCFS2_I(inode)->ip_blkno, parent_di_bh,
> +				 OCFS2_I(inode)->ip_blkno, dir_bh,
>   				 &lookup);
>   	if (status < 0) {
>   		mlog_errno(status);
> @@ -2886,10 +2883,7 @@ int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
>   	iput(orphan_dir_inode);
>   leave:
>   
> -	ocfs2_inode_unlock(dir, 1);
> -
>   	brelse(di_bh);
> -	brelse(parent_di_bh);
>   	brelse(orphan_dir_bh);
>   
>   	ocfs2_free_dir_lookup_result(&lookup);
> diff --git a/fs/ocfs2/namei.h b/fs/ocfs2/namei.h
> index 9cc891eb874e..03a2c526e2c1 100644
> --- a/fs/ocfs2/namei.h
> +++ b/fs/ocfs2/namei.h
> @@ -24,6 +24,7 @@ int ocfs2_orphan_del(struct ocfs2_super *osb,
>   		     struct buffer_head *orphan_dir_bh,
>   		     bool dio);
>   int ocfs2_create_inode_in_orphan(struct inode *dir,
> +				 struct buffer_head **dir_bh,
>   				 int mode,
>   				 struct inode **new_inode);
>   int ocfs2_add_inode_to_orphan(struct ocfs2_super *osb,
> @@ -32,6 +33,7 @@ int ocfs2_del_inode_from_orphan(struct ocfs2_super *osb,
>   		struct inode *inode, struct buffer_head *di_bh,
>   		int update_isize, loff_t end);
>   int ocfs2_mv_orphaned_inode_to_new(struct inode *dir,
> +				   struct buffer_head *dir_bh,
>   				   struct inode *new_inode,
>   				   struct dentry *new_dentry);
>   
> diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
> index 7f6355cbb587..a9a0c7c37e8e 100644
> --- a/fs/ocfs2/refcounttree.c
> +++ b/fs/ocfs2/refcounttree.c
> @@ -4250,7 +4250,7 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
>   {
>   	int error, had_lock;
>   	struct inode *inode = d_inode(old_dentry);
> -	struct buffer_head *old_bh = NULL;
> +	struct buffer_head *old_bh = NULL, *dir_bh = NULL;
>   	struct inode *new_orphan_inode = NULL;
>   	struct ocfs2_lock_holder oh;
>   
> @@ -4258,7 +4258,7 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
>   		return -EOPNOTSUPP;
>   
>   
> -	error = ocfs2_create_inode_in_orphan(dir, inode->i_mode,
> +	error = ocfs2_create_inode_in_orphan(dir, &dir_bh, inode->i_mode,
>   					     &new_orphan_inode);
>   	if (error) {
>   		mlog_errno(error);
> @@ -4304,13 +4304,15 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
>   
>   	/* If the security isn't preserved, we need to re-initialize them. */
>   	if (!preserve) {
> -		error = ocfs2_init_security_and_acl(dir, new_orphan_inode,
> +		error = ocfs2_init_security_and_acl(dir, dir_bh,
> +						    new_orphan_inode,
>   						    &new_dentry->d_name);
>   		if (error)
>   			mlog_errno(error);
>   	}
>   	if (!error) {
> -		error = ocfs2_mv_orphaned_inode_to_new(dir, new_orphan_inode,
> +		error = ocfs2_mv_orphaned_inode_to_new(dir, dir_bh,
> +						       new_orphan_inode,
>   						       new_dentry);
>   		if (error)
>   			mlog_errno(error);
> @@ -4328,6 +4330,11 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
>   			iput(new_orphan_inode);
>   	}
>   
> +	if (dir_bh) {
> +		ocfs2_inode_unlock(dir, 1);
> +		brelse(dir_bh);
> +	}
> +
>   	return error;
>   }
>   
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index dd784eb0cd7c..3f23e3a5018c 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -7203,16 +7203,13 @@ int ocfs2_reflink_xattrs(struct inode *old_inode,
>   /*
>    * Initialize security and acl for a already created inode.
>    * Used for reflink a non-preserve-security file.
> - *
> - * It uses common api like ocfs2_xattr_set, so the caller
> - * must not hold any lock expect i_mutex.
>    */
>   int ocfs2_init_security_and_acl(struct inode *dir,
> +				struct buffer_head *dir_bh,
>   				struct inode *inode,
>   				const struct qstr *qstr)
>   {
>   	int ret = 0;
> -	struct buffer_head *dir_bh = NULL;
>   
>   	ret = ocfs2_init_security_get(inode, dir, qstr, NULL);
>   	if (ret) {
> @@ -7220,17 +7217,10 @@ int ocfs2_init_security_and_acl(struct inode *dir,
>   		goto leave;
>   	}
>   
> -	ret = ocfs2_inode_lock(dir, &dir_bh, 0);
> -	if (ret) {
> -		mlog_errno(ret);
> -		goto leave;
> -	}
>   	ret = ocfs2_init_acl(NULL, inode, dir, NULL, dir_bh, NULL, NULL);
>   	if (ret)
>   		mlog_errno(ret);
>   
> -	ocfs2_inode_unlock(dir, 0);
> -	brelse(dir_bh);
>   leave:
>   	return ret;
>   }
> diff --git a/fs/ocfs2/xattr.h b/fs/ocfs2/xattr.h
> index 00308b57f64f..b27fd8ba0019 100644
> --- a/fs/ocfs2/xattr.h
> +++ b/fs/ocfs2/xattr.h
> @@ -83,6 +83,7 @@ int ocfs2_reflink_xattrs(struct inode *old_inode,
>   			 struct buffer_head *new_bh,
>   			 bool preserve_security);
>   int ocfs2_init_security_and_acl(struct inode *dir,
> +				struct buffer_head *dir_bh,
>   				struct inode *inode,
>   				const struct qstr *qstr);
>   #endif /* OCFS2_XATTR_H */
> 


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