diff mbox series

[RFC,3/7] libfs: Add simple_offset_empty()

Message ID	170786025969.11135.16880338029664682984.stgit@91.116.238.104.host.secureserver.net
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel+bounces-64344-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249; Subject: [PATCH RFC 3/7] libfs: Add simple_offset_empty() From: Chuck Lever <cel@kernel.org> To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, hughd@google.com, akpm@linux-foundation.org, Liam.Howlett@oracle.com, oliver.sang@intel.com, feng.tang@intel.com Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, maple-tree@lists.infradead.org, linux-mm@kvack.org, lkp@intel.com Date: Tue, 13 Feb 2024 16:37:39 -0500 Message-ID: <170786025969.11135.16880338029664682984.stgit@91.116.238.104.host.secureserver.net> In-Reply-To: <170785993027.11135.8830043889278631735.stgit@91.116.238.104.host.secureserver.net> References: <170785993027.11135.8830043889278631735.stgit@91.116.238.104.host.secureserver.net> User-Agent: StGit/1.5 Precedence: bulk MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX
Series	Use Maple Trees for simple_offset utilities \| [RFC,0/7] Use Maple Trees for simple_offset utilities [RFC,1/7] libfs: Rename "so_ctx" [RFC,2/7] libfs: Define a minimum directory offset [RFC,3/7] libfs: Add simple_offset_empty() [RFC,4/7] maple_tree: Add mtree_alloc_cyclic() [RFC,5/7] test_maple_tree: testing the cyclic allocation [RFC,6/7] libfs: Convert simple directory offsets to use a Maple Tree [RFC,7/7] libfs: Re-arrange locking in offset_iterate_dir()

Commit Message

Chuck Lever Feb. 13, 2024, 9:37 p.m. UTC

  From: Chuck Lever <chuck.lever@oracle.com>

For simple filesystems that use directory offset mapping, rely
strictly on the directory offset map to tell when a directory has
no children.

After this patch is applied, the emptiness test holds only the RCU
read lock when the directory being tested has no children.

In addition, this adds another layer of confirmation that
simple_offset_add/remove() are working as expected.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/libfs.c         |   32 ++++++++++++++++++++++++++++++++
 include/linux/fs.h |    1 +
 mm/shmem.c         |    4 ++--
 3 files changed, 35 insertions(+), 2 deletions(-)

Comments

Jan Kara Feb. 15, 2024, 12:53 p.m. UTC | #1

On Tue 13-02-24 16:37:39, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> For simple filesystems that use directory offset mapping, rely
> strictly on the directory offset map to tell when a directory has
> no children.
> 
> After this patch is applied, the emptiness test holds only the RCU
> read lock when the directory being tested has no children.
> 
> In addition, this adds another layer of confirmation that
> simple_offset_add/remove() are working as expected.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Makes sense. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/libfs.c         |   32 ++++++++++++++++++++++++++++++++
>  include/linux/fs.h |    1 +
>  mm/shmem.c         |    4 ++--
>  3 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/libfs.c b/fs/libfs.c
> index a38af72f4719..3cf773950f93 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -313,6 +313,38 @@ void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
>  	offset_set(dentry, 0);
>  }
>  
> +/**
> + * simple_offset_empty - Check if a dentry can be unlinked
> + * @dentry: dentry to be tested
> + *
> + * Returns 0 if @dentry is a non-empty directory; otherwise returns 1.
> + */
> +int simple_offset_empty(struct dentry *dentry)
> +{
> +	struct inode *inode = d_inode(dentry);
> +	struct offset_ctx *octx;
> +	struct dentry *child;
> +	unsigned long index;
> +	int ret = 1;
> +
> +	if (!inode || !S_ISDIR(inode->i_mode))
> +		return ret;
> +
> +	index = 2;
> +	octx = inode->i_op->get_offset_ctx(inode);
> +	xa_for_each(&octx->xa, index, child) {
> +		spin_lock(&child->d_lock);
> +		if (simple_positive(child)) {
> +			spin_unlock(&child->d_lock);
> +			ret = 0;
> +			break;
> +		}
> +		spin_unlock(&child->d_lock);
> +	}
> +
> +	return ret;
> +}
> +
>  /**
>   * simple_offset_rename_exchange - exchange rename with directory offsets
>   * @old_dir: parent of dentry being moved
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ed5966a70495..03d141809a2c 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3267,6 +3267,7 @@ struct offset_ctx {
>  void simple_offset_init(struct offset_ctx *octx);
>  int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry);
>  void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry);
> +int simple_offset_empty(struct dentry *dentry);
>  int simple_offset_rename_exchange(struct inode *old_dir,
>  				  struct dentry *old_dentry,
>  				  struct inode *new_dir,
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d7c84ff62186..6fed524343cb 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -3374,7 +3374,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry)
>  
>  static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
>  {
> -	if (!simple_empty(dentry))
> +	if (!simple_offset_empty(dentry))
>  		return -ENOTEMPTY;
>  
>  	drop_nlink(d_inode(dentry));
> @@ -3431,7 +3431,7 @@ static int shmem_rename2(struct mnt_idmap *idmap,
>  		return simple_offset_rename_exchange(old_dir, old_dentry,
>  						     new_dir, new_dentry);
>  
> -	if (!simple_empty(new_dentry))
> +	if (!simple_offset_empty(new_dentry))
>  		return -ENOTEMPTY;
>  
>  	if (flags & RENAME_WHITEOUT) {
> 
>

diff mbox series

Patch

diff --git a/fs/libfs.c b/fs/libfs.c
index a38af72f4719..3cf773950f93 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -313,6 +313,38 @@  void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
 	offset_set(dentry, 0);
 }
 
+/**
+ * simple_offset_empty - Check if a dentry can be unlinked
+ * @dentry: dentry to be tested
+ *
+ * Returns 0 if @dentry is a non-empty directory; otherwise returns 1.
+ */
+int simple_offset_empty(struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct offset_ctx *octx;
+	struct dentry *child;
+	unsigned long index;
+	int ret = 1;
+
+	if (!inode || !S_ISDIR(inode->i_mode))
+		return ret;
+
+	index = 2;
+	octx = inode->i_op->get_offset_ctx(inode);
+	xa_for_each(&octx->xa, index, child) {
+		spin_lock(&child->d_lock);
+		if (simple_positive(child)) {
+			spin_unlock(&child->d_lock);
+			ret = 0;
+			break;
+		}
+		spin_unlock(&child->d_lock);
+	}
+
+	return ret;
+}
+
 /**
  * simple_offset_rename_exchange - exchange rename with directory offsets
  * @old_dir: parent of dentry being moved
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed5966a70495..03d141809a2c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3267,6 +3267,7 @@  struct offset_ctx {
 void simple_offset_init(struct offset_ctx *octx);
 int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry);
 void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry);
+int simple_offset_empty(struct dentry *dentry);
 int simple_offset_rename_exchange(struct inode *old_dir,
 				  struct dentry *old_dentry,
 				  struct inode *new_dir,
diff --git a/mm/shmem.c b/mm/shmem.c
index d7c84ff62186..6fed524343cb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3374,7 +3374,7 @@  static int shmem_unlink(struct inode *dir, struct dentry *dentry)
 
 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
 {
-	if (!simple_empty(dentry))
+	if (!simple_offset_empty(dentry))
 		return -ENOTEMPTY;
 
 	drop_nlink(d_inode(dentry));
@@ -3431,7 +3431,7 @@  static int shmem_rename2(struct mnt_idmap *idmap,
 		return simple_offset_rename_exchange(old_dir, old_dentry,
 						     new_dir, new_dentry);
 
-	if (!simple_empty(new_dentry))
+	if (!simple_offset_empty(new_dentry))
 		return -ENOTEMPTY;
 
 	if (flags & RENAME_WHITEOUT) {