Re: [PATCH v2 3/9] mm/mshare: make msharefs writable and support directories
From: Khalid Aziz
Date: Thu Jun 30 2022 - 18:50:10 EST
On 6/30/22 15:34, Darrick J. Wong wrote:
On Wed, Jun 29, 2022 at 04:53:54PM -0600, Khalid Aziz wrote:
Make msharefs filesystem writable and allow creating directories
to support better access control to mshare'd regions defined in
msharefs.
Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
---
mm/mshare.c | 195 +++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 186 insertions(+), 9 deletions(-)
diff --git a/mm/mshare.c b/mm/mshare.c
index 3e448e11c742..2d5924d39221 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -21,11 +21,21 @@
#include <linux/fileattr.h>
#include <uapi/linux/magic.h>
#include <uapi/linux/limits.h>
+#include <uapi/linux/mman.h>
static struct super_block *msharefs_sb;
+static const struct inode_operations msharefs_dir_inode_ops;
+static const struct inode_operations msharefs_file_inode_ops;
+
+static int
+msharefs_open(struct inode *inode, struct file *file)
+{
+ return simple_open(inode, file);
+}
+
static const struct file_operations msharefs_file_operations = {
- .open = simple_open,
+ .open = msharefs_open,
.llseek = no_llseek,
};
@@ -42,6 +52,113 @@ msharefs_d_hash(const struct dentry *dentry, struct qstr *qstr)
return 0;
}
+static struct dentry
+*msharefs_alloc_dentry(struct dentry *parent, const char *name)
+{
+ struct dentry *d;
+ struct qstr q;
+ int err;
+
+ q.name = name;
+ q.len = strlen(name);
+
+ err = msharefs_d_hash(parent, &q);
+ if (err)
+ return ERR_PTR(err);
+
+ d = d_alloc(parent, &q);
+ if (d)
+ return d;
+
+ return ERR_PTR(-ENOMEM);
+}
+
+static struct inode
+*msharefs_get_inode(struct super_block *sb, const struct inode *dir,
+ umode_t mode)
+{
+ struct inode *inode = new_inode(sb);
+
+ if (inode) {
Not sure why you wouldn't go with the less-indently version:
if (!inode)
return ERR_PTR(-ENOMEM);
inode->i_ino = get_next_ino();
<etc>
Yeah, good idea. I will change it.
+ inode->i_ino = get_next_ino();
+ inode_init_owner(&init_user_ns, inode, dir, mode);
+
+ inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
+
+ switch (mode & S_IFMT) {
Shouldn't we set the mode somewhere?
mode is passed in as parameter to msharefs_get_inode() which uses this value to determine its actions.
+ case S_IFREG:
+ inode->i_op = &msharefs_file_inode_ops;
+ inode->i_fop = &msharefs_file_operations;
+ break;
+ case S_IFDIR:
+ inode->i_op = &msharefs_dir_inode_ops;
+ inode->i_fop = &simple_dir_operations;
+ inc_nlink(inode);
+ break;
+ case S_IFLNK:
+ inode->i_op = &page_symlink_inode_operations;
+ break;
+ default:
+ discard_new_inode(inode);
+ inode = NULL;
+ break;
+ }
+ }
+
+ return inode;
+}
+
+static int
+msharefs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+ struct dentry *dentry, umode_t mode, dev_t dev)
+{
+ struct inode *inode;
+ int err = 0;
+
+ inode = msharefs_get_inode(dir->i_sb, dir, mode);
+ if (IS_ERR(inode))
+ return PTR_ERR(inode);
...and if @inode is NULL?
Oh right, IS_ERR() does not check for NULL value. I will add a check for that and return ENOMEM.
+
+ d_instantiate(dentry, inode);
+ dget(dentry);
+ dir->i_mtime = dir->i_ctime = current_time(dir);
+
+ return err;
+}
+
+static int
+msharefs_create(struct user_namespace *mnt_userns, struct inode *dir,
+ struct dentry *dentry, umode_t mode, bool excl)
+{
+ return msharefs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
+}
+
+static int
+msharefs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+ struct dentry *dentry, umode_t mode)
+{
+ int ret = msharefs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0);
+
+ if (!ret)
+ inc_nlink(dir);
+ return ret;
+}
+
+static const struct inode_operations msharefs_file_inode_ops = {
+ .setattr = simple_setattr,
+ .getattr = simple_getattr,
+};
+static const struct inode_operations msharefs_dir_inode_ops = {
+ .create = msharefs_create,
+ .lookup = simple_lookup,
+ .link = simple_link,
+ .unlink = simple_unlink,
+ .mkdir = msharefs_mkdir,
+ .rmdir = simple_rmdir,
+ .mknod = msharefs_mknod,
+ .rename = simple_rename,
+};
+
static void
mshare_evict_inode(struct inode *inode)
{
@@ -58,7 +175,7 @@ mshare_info_read(struct file *file, char __user *buf, size_t nbytes,
{
char s[80];
- sprintf(s, "%ld", PGDIR_SIZE);
+ sprintf(s, "%ld\n", PGDIR_SIZE);
Changing this already?
Possibly. There is one suggestion to change it to PMD and it might be a better choice.
return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
}
@@ -72,6 +189,38 @@ static const struct super_operations mshare_s_ops = {
.evict_inode = mshare_evict_inode,
};
+static int
+prepopulate_files(struct super_block *s, struct inode *dir,
+ struct dentry *root, const struct tree_descr *files)
+{
+ int i;
+ struct inode *inode;
+ struct dentry *dentry;
+
+ for (i = 0; !files->name || files->name[0]; i++, files++) {
+ if (!files->name)
+ continue;
What ends the array? NULL name or empty name?
Do we have to erase all of these when the fs gets unmounted?
This code is very similar to simple_fill_super() and I reused the code from there. inodes and dentries will need to be
erased on unmount through evict_inode.
Thanks,
Khalid