[PATCH 3/5] vfs: Allow fsinfo() to query what's in an fs_context [ver #12]

From: David Howells
Date: Fri Sep 21 2018 - 12:38:17 EST


Allow fsinfo() to be used to query the filesystem attached to an fs_context
once a superblock has been created or if it comes from fspick().

This is done with something like:

fd = fsopen("ext4", 0);
...
fsconfig(fd, fsconfig_cmd_create, ...);
fsinfo(fd, NULL, ...);

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

fs/statfs.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/fs/statfs.c b/fs/statfs.c
index f3cf8aa42a3d..790e21367d70 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -636,7 +636,8 @@ int vfs_fsinfo(struct path *path, struct fsinfo_kparams *params)
return ret;

if (params->request == FSINFO_ATTR_IDS &&
- params->buffer) {
+ params->buffer &&
+ path->mnt) {
struct fsinfo_ids *p = params->buffer;

p->f_flags |= flags_by_mnt(path->mnt->mnt_flags);
@@ -677,13 +678,40 @@ static int vfs_fsinfo_path(int dfd, const char __user *filename,
return ret;
}

+static int vfs_fsinfo_fscontext(struct fs_context *fc,
+ struct fsinfo_kparams *params)
+{
+ int ret;
+
+ if (fc->ops == &legacy_fs_context_ops)
+ return -EOPNOTSUPP;
+
+ ret = mutex_lock_interruptible(&fc->uapi_mutex);
+ if (ret < 0)
+ return ret;
+
+ ret = -EIO;
+ if (fc->root) {
+ struct path path = { .dentry = fc->root };
+
+ ret = vfs_fsinfo(&path, params);
+ }
+
+ mutex_unlock(&fc->uapi_mutex);
+ return ret;
+}
+
static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_kparams *params)
{
struct fd f = fdget_raw(fd);
int ret = -EBADF;

if (f.file) {
- ret = vfs_fsinfo(&f.file->f_path, params);
+ if (f.file->f_op == &fscontext_fops)
+ ret = vfs_fsinfo_fscontext(f.file->private_data,
+ params);
+ else
+ ret = vfs_fsinfo(&f.file->f_path, params);
fdput(f);
}
return ret;