[RFC][PATCH] btrfs_get_tree_subvol(): switch from fc_mount() to vfs_create_mount()

Al Viro
2025-05-05T03:03:46Z

it's simpler to do btrfs_reconfigure_for_mount() right after vfs_get_tree() -
no need to mess with ->s_umount.

Objections?

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 7121d8c7a318..a3634e7f2304 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1984,17 +1984,13 @@ static int btrfs_get_tree_super(struct fs_context *fc)
* btrfs or not, setting the whole super block RO. To make per-subvolume mounting
* work with different options work we need to keep backward compatibility.
*/
-static int btrfs_reconfigure_for_mount(struct fs_context *fc, struct vfsmount *mnt)
+static int btrfs_reconfigure_for_mount(struct fs_context *fc)
{
int ret = 0;

- if (fc->sb_flags & SB_RDONLY)
- return ret;
-
- down_write(&mnt->mnt_sb->s_umount);
- if (!(fc->sb_flags & SB_RDONLY) && (mnt->mnt_sb->s_flags & SB_RDONLY))
+ if (!(fc->sb_flags & SB_RDONLY) && (fc->root->d_sb->s_flags & SB_RDONLY))
ret = btrfs_reconfigure(fc);
- up_write(&mnt->mnt_sb->s_umount);
+
return ret;
}

@@ -2047,17 +2043,18 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
security_free_mnt_opts(&fc->security);
fc->security = NULL;

- mnt = fc_mount(dup_fc);
- if (IS_ERR(mnt)) {
- put_fs_context(dup_fc);
- return PTR_ERR(mnt);
+ ret = vfs_get_tree(dup_fc);
+ if (!ret) {
+ ret = btrfs_reconfigure_for_mount(dup_fc);
+ up_write(&fc->root->d_sb->s_umount);
}
- ret = btrfs_reconfigure_for_mount(dup_fc, mnt);
+ if (!ret)
+ mnt = vfs_create_mount(fc);
+ else
+ mnt = ERR_PTR(ret);
put_fs_context(dup_fc);
- if (ret) {
- mntput(mnt);
- return ret;
- }
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);

/*
* This free's ->subvol_name, because if it isn't set we have to