[PATCH 03/11] vfs: Allow fsinfo() to query what's in an fs_context [ver #15]
From: David Howells <dhowells@redhat.com>
Date: 2019-06-28 15:44:41
Also in:
linux-fsdevel, lkml
Subsystem:
file locking (flock() and fcntl()/lockf()), filesystems (vfs and infrastructure), the rest · Maintainers:
Jeff Layton, Chuck Lever, Alexander Viro, Christian Brauner, Linus Torvalds
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().
The caller must specify AT_FSINFO_FROM_FSOPEN in the parameters and must
supply the fd from fsopen() as dfd and must set filename to NULL.
This is done with something like:
fd = fsopen("ext4", 0);
...
struct fsinfo_params params = {
.at_flags = AT_FSINFO_FROM_FSOPEN;
...
};
fsinfo(fd, NULL, ¶ms, ...);
Signed-off-by: David Howells <dhowells@redhat.com>
---
fs/fsinfo.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
fs/statfs.c | 2 +-
include/uapi/linux/fcntl.h | 2 ++
3 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index 09e743b16235..d419cccbf3db 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c@@ -13,6 +13,7 @@ #include <linux/security.h> #include <linux/uaccess.h> #include <linux/fsinfo.h> +#include <linux/fs_context.h> #include <uapi/linux/mount.h> #include "internal.h"
@@ -347,6 +348,42 @@ static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_kparams *params) return ret; } +/* + * Allow access to an fs_context object as created by fsopen() or fspick(). + */ +static int vfs_fsinfo_fscontext(int fd, struct fsinfo_kparams *params) +{ + struct fs_context *fc; + struct fd f = fdget(fd); + int ret; + + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op != &fscontext_fops) + goto out_f; + ret = -EOPNOTSUPP; + if (fc->ops == &legacy_fs_context_ops) + goto out_f; + + ret = mutex_lock_interruptible(&fc->uapi_mutex); + if (ret == 0) { + ret = -EBADFD; + if (fc->root) { + struct path path = { .dentry = fc->root }; + + ret = vfs_fsinfo(&path, params); + } + + mutex_unlock(&fc->uapi_mutex); + } + +out_f: + fdput(f); + return ret; +} + /* * Return buffer information by requestable attribute. *
@@ -452,6 +489,9 @@ SYSCALL_DEFINE5(fsinfo, kparams.request = user_params.request; kparams.Nth = user_params.Nth; kparams.Mth = user_params.Mth; + + if ((kparams.at_flags & AT_FSINFO_FROM_FSOPEN) && pathname) + return -EINVAL; } else { kparams.request = FSINFO_ATTR_STATFS; }
@@ -508,7 +548,9 @@ SYSCALL_DEFINE5(fsinfo, if (!kparams.buffer) goto error_scratch; - if (pathname) + if (kparams.at_flags & AT_FSINFO_FROM_FSOPEN) + ret = vfs_fsinfo_fscontext(dfd, &kparams); + else if (pathname) ret = vfs_fsinfo_path(dfd, pathname, &kparams); else ret = vfs_fsinfo_fd(dfd, &kparams);
diff --git a/fs/statfs.c b/fs/statfs.c
index eea7af6f2f22..b9b63d9f4f24 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c@@ -86,7 +86,7 @@ int vfs_statfs(const struct path *path, struct kstatfs *buf) int error; error = statfs_by_dentry(path->dentry, buf); - if (!error) + if (!error && path->mnt) buf->f_flags = calculate_f_flags(path->mnt); return error; }
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 1d338357df8a..6a2402a8fa30 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h@@ -91,6 +91,8 @@ #define AT_STATX_FORCE_SYNC 0x2000 /* - Force the attributes to be sync'd with the server */ #define AT_STATX_DONT_SYNC 0x4000 /* - Don't sync attributes with the server */ +#define AT_FSINFO_FROM_FSOPEN 0x2000 /* Examine the fs_context attached to dfd by fsopen() */ + #define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */