Patch "hostfs: convert hostfs to use the new mount API" has been added to the 6.6-stable tree

This is a note to let you know that I've just added the patch titled

hostfs: convert hostfs to use the new mount API

to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hostfs-convert-hostfs-to-use-the-new-mount-api.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

commit 6f2433956e6ade80d59bd673d4062ec2c1bacc3e

Author: Hongbo Li <[email protected]>
Date:   Thu May 30 20:01:11 2024 +0800

hostfs: convert hostfs to use the new mount API

[ Upstream commit cd140ce9f611a5e9d2a5989a282b75e55c71dab3 ]

Convert the hostfs filesystem to the new internal mount API as the old one will be obsoleted and removed. This allows greater flexibility in communication of mount parameters between userspace, the VFS and the filesystem.

See Documentation/filesystems/mount_api.txt for more information.

Signed-off-by Hongbo Li <[email protected]>

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Christian Brauner <[email protected]>

Stable-dep-of: 60a600243244 ("hostfs: fix string handling in __dentry_name()")

Signed-off-by Sasha Levin <[email protected]>

fs/hostfs/hostfs_kern.c +62 -21

index ff201753fd181..1fb8eacb9817f 100644
@@ -16,11 +16,16 @@
  #include <linux/seq_file.h>
  #include <linux/writeback.h>
  #include <linux/mount.h>
+#include <linux/fs_context.h>
  #include <linux/namei.h>
  #include "hostfs.h"
  #include <init.h>
  #include <kern.h>
 
+struct hostfs_fs_info {
+	char *host_root_path;
+};
+
  struct hostfs_inode_info {
  	int fd;
  	fmode_t mode;

@@ -90,8 +95,10 @@ static char *__dentry_name(struct dentry *dentry, char *name)
  	char *p = dentry_path_raw(dentry, name, PATH_MAX);
  	char *root;
  	size_t len;
+	struct hostfs_fs_info *fsi;
 
-	root = dentry->d_sb->s_fs_info;
+	fsi = dentry->d_sb->s_fs_info;
+	root = fsi->host_root_path;
  	len = strlen(root);
  	if (IS_ERR(p)) {
  		__putname(name);

@@ -196,8 +203,10 @@ static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
  	long long f_bavail;
  	long long f_files;
  	long long f_ffree;
+	struct hostfs_fs_info *fsi;
 
-	err = do_statfs(dentry->d_sb->s_fs_info,
+	fsi = dentry->d_sb->s_fs_info;
+	err = do_statfs(fsi->host_root_path,
  			&sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
  			&f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
  			&sf->f_namelen);

@@ -245,7 +254,11 @@ static void hostfs_free_inode(struct inode *inode)
 
  static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
  {
-	const char *root_path = root->d_sb->s_fs_info;
+	struct hostfs_fs_info *fsi;
+	const char *root_path;
+
+	fsi = root->d_sb->s_fs_info;
+	root_path = fsi->host_root_path;
  	size_t offset = strlen(root_ino) + 1;
 
  	if (strlen(root_path) > offset)

@@ -924,10 +937,11 @@ static const struct inode_operations hostfs_link_iops = {
  	.get_link	= hostfs_get_link,
  };
 
-static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
+static int hostfs_fill_super(struct super_block *sb, struct fs_context *fc)
  {
+	struct hostfs_fs_info *fsi = sb->s_fs_info;
  	struct inode *root_inode;
-	char *host_root_path, *req_root = d;
+	char *host_root = fc->source;
  	int err;
 
  	sb->s_blocksize = 1024;

@@ -941,15 +955,15 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
  		return err;
 
  	/* NULL is printed as '(null)' by printf(): avoid that. */
-	if (req_root == NULL)
-		req_root = "";
+	if (fc->source == NULL)
+		host_root = "";
 
-	sb->s_fs_info = host_root_path =
-		kasprintf(GFP_KERNEL, "%s/%s", root_ino, req_root);
-	if (host_root_path == NULL)
+	fsi->host_root_path =
+		kasprintf(GFP_KERNEL, "%s/%s", root_ino, host_root);
+	if (fsi->host_root_path == NULL)
  		return -ENOMEM;
 
-	root_inode = hostfs_iget(sb, host_root_path);
+	root_inode = hostfs_iget(sb, fsi->host_root_path);
  	if (IS_ERR(root_inode))
  		return PTR_ERR(root_inode);
 

@@ -957,7 +971,7 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
  		char *name;
 
  		iput(root_inode);
-		name = follow_link(host_root_path);
+		name = follow_link(fsi->host_root_path);
  		if (IS_ERR(name))
  			return PTR_ERR(name);
 

@@ -974,11 +988,38 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
  	return 0;
  }
 
-static struct dentry *hostfs_read_sb(struct file_system_type *type,
-			  int flags, const char *dev_name,
-			  void *data)
+static int hostfs_fc_get_tree(struct fs_context *fc)
  {
-	return mount_nodev(type, flags, data, hostfs_fill_sb_common);
+	return get_tree_nodev(fc, hostfs_fill_super);
+}
+
+static void hostfs_fc_free(struct fs_context *fc)
+{
+	struct hostfs_fs_info *fsi = fc->s_fs_info;
+
+	if (!fsi)
+		return;
+
+	kfree(fsi->host_root_path);
+	kfree(fsi);
+}
+
+static const struct fs_context_operations hostfs_context_ops = {
+	.get_tree	= hostfs_fc_get_tree,
+	.free		= hostfs_fc_free,
+};
+
+static int hostfs_init_fs_context(struct fs_context *fc)
+{
+	struct hostfs_fs_info *fsi;
+
+	fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
+	if (!fsi)
+		return -ENOMEM;
+
+	fc->s_fs_info = fsi;
+	fc->ops = &hostfs_context_ops;
+	return 0;
  }
 
  static void hostfs_kill_sb(struct super_block *s)

@@ -988,11 +1029,11 @@ static void hostfs_kill_sb(struct super_block *s)
  }
 
  static struct file_system_type hostfs_type = {
-	.owner 		= THIS_MODULE,
-	.name 		= "hostfs",
-	.mount	 	= hostfs_read_sb,
-	.kill_sb	= hostfs_kill_sb,
-	.fs_flags 	= 0,
+	.owner			= THIS_MODULE,
+	.name			= "hostfs",
+	.init_fs_context	= hostfs_init_fs_context,
+	.kill_sb		= hostfs_kill_sb,
+	.fs_flags		= 0,
  };
  MODULE_ALIAS_FS("hostfs");
 

Quoted 7 lines · Sasha Levin

This is a note to let you know that I've just added the patch titled

hostfs: convert hostfs to use the new mount API

to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

Hi Sasha,

If this, the fix : ef9ca17ca458 ("hostfs: fix the host directory parse when mounting.") also should be added. It fixes the mounting bug when pass the host directory.

Quoted 11 lines · Hongbo Li

Quoted 7 lines · Sasha Levin

This is a note to let you know that I've just added the patch titled

hostfs: convert hostfs to use the new mount API

to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

Quoted 5 lines

Hi Sasha,

If this, the fix : ef9ca17ca458 ("hostfs: fix the host directory parse when mounting.") also should be added. It fixes the mounting bug when pass the host directory.

I've swept the queues and have added the "fixes for the fixes" commits like this one now, thanks!

greg k-h

Well, by the way, is the patch added because there are use cases for the new mount API in hostfs?

Quoted 2 lines · Hongbo Li

Well, by the way, is the patch added because there are use cases for the new mount API in hostfs?

I am sorry, I don't understand the question.

greg k-h

Quoted 1 line · Greg KH

On Thu, Feb 06, 2025 at 09:09:17AM +0800, Hongbo Li wrote:

Quoted 5 lines

Quoted 2 lines

Well, by the way, is the patch added because there are use cases for the new mount API in hostfs?

I am sorry, I don't understand the question.

Sorry for my poor expression, I just wonder why this patch should be backported to the 6.6-stable tree. :)