On Wed, Jun 29, 2022 at 04:53:57PM -0600, Khalid Aziz wrote: > mmap is used to establish address range for mshare region and map the > region into process's address space. Add basic mmap operation that > supports setting address range. Also fix code to not allocate new > mm_struct for files in msharefs that exist for information and not > for defining a new mshare region. > > Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx> > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > --- > mm/mshare.c | 48 +++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 41 insertions(+), 7 deletions(-) > > diff --git a/mm/mshare.c b/mm/mshare.c > index d238b68b0576..088a6cab1e93 100644 > --- a/mm/mshare.c > +++ b/mm/mshare.c > @@ -9,7 +9,8 @@ > * > * > * Copyright (C) 2022 Oracle Corp. All rights reserved. > - * Author: Khalid Aziz <khalid.aziz@xxxxxxxxxx> > + * Authors: Khalid Aziz <khalid.aziz@xxxxxxxxxx> > + * Matthew Wilcox <willy@xxxxxxxxxxxxx> > * > */ > > @@ -60,9 +61,36 @@ msharefs_read(struct kiocb *iocb, struct iov_iter *iov) > return ret; > } > > +static int > +msharefs_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + struct mshare_data *info = file->private_data; > + struct mm_struct *mm = info->mm; > + > + /* > + * If this mshare region has been set up once already, bail out > + */ > + if (mm->mmap_base != 0) > + return -EINVAL; > + > + if ((vma->vm_start | vma->vm_end) & (PGDIR_SIZE - 1)) > + return -EINVAL; > + > + mm->mmap_base = vma->vm_start; > + mm->task_size = vma->vm_end - vma->vm_start; > + if (!mm->task_size) > + mm->task_size--; > + info->minfo->start = mm->mmap_base; > + info->minfo->size = mm->task_size; So, uh, if the second mmap() caller decides to ignore the mshare_info, should they get an -EINVAL here since the memory mappings won't be at the same process virtual address? > + vma->vm_flags |= VM_SHARED_PT; > + vma->vm_private_data = info; > + return 0; > +} > + > static const struct file_operations msharefs_file_operations = { > .open = msharefs_open, > .read_iter = msharefs_read, > + .mmap = msharefs_mmap, > .llseek = no_llseek, > }; > > @@ -119,7 +147,12 @@ msharefs_fill_mm(struct inode *inode) > goto err_free; > } > info->mm = mm; > - info->minfo = NULL; > + info->minfo = kzalloc(sizeof(struct mshare_info), GFP_KERNEL); > + if (info->minfo == NULL) { > + retval = -ENOMEM; > + goto err_free; > + } > + > refcount_set(&info->refcnt, 1); > inode->i_private = info; > > @@ -128,13 +161,14 @@ msharefs_fill_mm(struct inode *inode) > err_free: > if (mm) > mmput(mm); > + kfree(info->minfo); > kfree(info); > return retval; > } > > static struct inode > *msharefs_get_inode(struct super_block *sb, const struct inode *dir, > - umode_t mode) > + umode_t mode, bool newmm) > { > struct inode *inode = new_inode(sb); > if (inode) { > @@ -147,7 +181,7 @@ static struct inode > case S_IFREG: > inode->i_op = &msharefs_file_inode_ops; > inode->i_fop = &msharefs_file_operations; > - if (msharefs_fill_mm(inode) != 0) { > + if (newmm && msharefs_fill_mm(inode) != 0) { > discard_new_inode(inode); > inode = ERR_PTR(-ENOMEM); > } > @@ -177,7 +211,7 @@ msharefs_mknod(struct user_namespace *mnt_userns, struct inode *dir, > struct inode *inode; > int err = 0; > > - inode = msharefs_get_inode(dir->i_sb, dir, mode); > + inode = msharefs_get_inode(dir->i_sb, dir, mode, true); > if (IS_ERR(inode)) > return PTR_ERR(inode); > > @@ -267,7 +301,7 @@ prepopulate_files(struct super_block *s, struct inode *dir, > if (!dentry) > return -ENOMEM; > > - inode = msharefs_get_inode(s, dir, S_IFREG | files->mode); > + inode = msharefs_get_inode(s, dir, S_IFREG | files->mode, false); I was wondering why the information files were getting their own mshare_data. TBH I'm not really sure what the difference is between mshare_data and mshare_info, since those names are not especially distinct. > if (!inode) { > dput(dentry); > return -ENOMEM; > @@ -301,7 +335,7 @@ msharefs_fill_super(struct super_block *sb, struct fs_context *fc) > sb->s_d_op = &msharefs_d_ops; > sb->s_time_gran = 1; > > - inode = msharefs_get_inode(sb, NULL, S_IFDIR | 0777); > + inode = msharefs_get_inode(sb, NULL, S_IFDIR | 0777, false); Is it wise to default to world-writable? Surely whatever userspace software wraps an msharefs can relax permissions as needed. --D > if (!inode) { > err = -ENOMEM; > goto out; > -- > 2.32.0 >