add f_flags to struct statfs(64)

Add a flags field to help glibc implementing statvfs(3) efficiently.

We copy the flag values from glibc, and add a new ST_VALID flag to
denote that f_flags is implemented.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 46 insertions, 1 deletions

diff --git a/fs/statfs.c b/fs/statfs.c
index 6a305709a4da..30ea8c8a996b 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -2,11 +2,49 @@
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/file.h>
+#include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/statfs.h>
 #include <linux/security.h>
 #include <linux/uaccess.h>
 
+static int flags_by_mnt(int mnt_flags)
+{
+	int flags = 0;
+
+	if (mnt_flags & MNT_READONLY)
+		flags |= ST_RDONLY;
+	if (mnt_flags & MNT_NOSUID)
+		flags |= ST_NOSUID;
+	if (mnt_flags & MNT_NODEV)
+		flags |= ST_NODEV;
+	if (mnt_flags & MNT_NOEXEC)
+		flags |= ST_NOEXEC;
+	if (mnt_flags & MNT_NOATIME)
+		flags |= ST_NOATIME;
+	if (mnt_flags & MNT_NODIRATIME)
+		flags |= ST_NODIRATIME;
+	if (mnt_flags & MNT_RELATIME)
+		flags |= ST_RELATIME;
+	return flags;
+}
+
+static int flags_by_sb(int s_flags)
+{
+	int flags = 0;
+	if (s_flags & MS_SYNCHRONOUS)
+		flags |= ST_SYNCHRONOUS;
+	if (s_flags & MS_MANDLOCK)
+		flags |= ST_MANDLOCK;
+	return flags;
+}
+
+static int calculate_f_flags(struct vfsmount *mnt)
+{
+	return ST_VALID | flags_by_mnt(mnt->mnt_flags) |
+		flags_by_sb(mnt->mnt_sb->s_flags);
+}
+
 int statfs_by_dentry(struct dentry *dentry, struct kstatfs *buf)
 {
 	int retval;
@@ -26,7 +64,12 @@ int statfs_by_dentry(struct dentry *dentry, struct kstatfs *buf)
 
 int vfs_statfs(struct path *path, struct kstatfs *buf)
 {
-	return statfs_by_dentry(path->dentry, buf);
+	int error;
+
+	error = statfs_by_dentry(path->dentry, buf);
+	if (!error)
+		buf->f_flags = calculate_f_flags(path->mnt);
+	return error;
 }
 EXPORT_SYMBOL(vfs_statfs);
 
@@ -69,6 +112,7 @@ static int do_statfs_native(struct path *path, struct statfs *buf)
 		buf->f_fsid = st.f_fsid;
 		buf->f_namelen = st.f_namelen;
 		buf->f_frsize = st.f_frsize;
+		buf->f_flags = st.f_flags;
 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
 	}
 	return 0;
@@ -96,6 +140,7 @@ static int do_statfs64(struct path *path, struct statfs64 *buf)
 		buf->f_fsid = st.f_fsid;
 		buf->f_namelen = st.f_namelen;
 		buf->f_frsize = st.f_frsize;
+		buf->f_flags = st.f_flags;
 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
 	}
 	return 0;