Re: [d_path 0/7] Fixes to d_path: Respin

[Andreas Gruenbacher <agruen@suse.de>]

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On Sunday 22 April 2007 11:10, Christoph Hellwig wrote:
> So what about stopping the flaming here and implementing real statvfs/
> fstatvfs syscalls instead of these horrible hacks glibc has to do
> currently?

I could imagine two approaches to that: either add statvfs and fstatvfs 
syscalls, or use one of the reserved fields in struct statfs, and return the 
missing flags in there.

Here is a very rough shot at the latter (i386 and x86_64 only so far). One of 
the uglinesses with that is that all those flags could be cleared at the same 
time, and so we can't tell whether the field is used from the flags alone and 
need some other mechanism like an extra bit, or a successive field that is 
guaranteed to be nonzero. Not sure whether that's acceptable considering the 
alternative of adding two syscalls and duplicating all the ugly compatibility 
scaffolding.

struct statvfs also defines a f_favail field, the ``number of file serial 
numbers available to non-privileged process''. Glibc currently sets this to 
the same value as f_ffree, the ``total number of free file serial numbers''. 
We don't seem to have this information, so adding this field wouldn't help 
immediately.

Andreas

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---
 fs/compat.c                  |   13 +++++-----
 fs/ecryptfs/super.c          |    5 +++-
 fs/nfsd/nfs4xdr.c            |    2 -
 fs/nfsd/vfs.c                |    2 -
 fs/open.c                    |   53 ++++++++++++++++++++++++++++++++++---------
 fs/super.c                   |    2 -
 include/asm-generic/statfs.h |    9 ++++---
 include/asm-x86_64/compat.h  |    3 +-
 include/asm-x86_64/statfs.h  |    9 ++++---
 include/linux/fs.h           |    2 -
 include/linux/statfs.h       |   13 +++++++++-
 kernel/acct.c                |    2 -
 12 files changed, 84 insertions(+), 31 deletions(-)

--- a/fs/compat.c
+++ b/fs/compat.c
@@ -194,7 +194,7 @@ static int put_compat_statfs(struct comp
 	    __put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) ||
 	    __put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) ||
 	    __put_user(kbuf->f_frsize, &ubuf->f_frsize) ||
-	    __put_user(0, &ubuf->f_spare[0]) || 
+	    __put_user(kbuf->f_flag, &ubuf->f_flag) ||
 	    __put_user(0, &ubuf->f_spare[1]) || 
 	    __put_user(0, &ubuf->f_spare[2]) || 
 	    __put_user(0, &ubuf->f_spare[3]) || 
@@ -215,7 +215,7 @@ asmlinkage long compat_sys_statfs(const 
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(nd.dentry, &tmp);
+		error = vfs_statfs(nd.dentry, nd.mnt, &tmp);
 		if (!error)
 			error = put_compat_statfs(buf, &tmp);
 		path_release(&nd);
@@ -233,7 +233,7 @@ asmlinkage long compat_sys_fstatfs(unsig
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_path.dentry, &tmp);
+	error = vfs_statfs(file->f_path.dentry, file->f_path.mnt, &tmp);
 	if (!error)
 		error = put_compat_statfs(buf, &tmp);
 	fput(file);
@@ -267,7 +267,8 @@ static int put_compat_statfs64(struct co
 	    __put_user(kbuf->f_namelen, &ubuf->f_namelen) ||
 	    __put_user(kbuf->f_fsid.val[0], &ubuf->f_fsid.val[0]) ||
 	    __put_user(kbuf->f_fsid.val[1], &ubuf->f_fsid.val[1]) ||
-	    __put_user(kbuf->f_frsize, &ubuf->f_frsize))
+	    __put_user(kbuf->f_frsize, &ubuf->f_frsize) ||
+	    __put_user(kbuf->f_flag, &ubuf->f_flag))
 		return -EFAULT;
 	return 0;
 }
@@ -283,7 +284,7 @@ asmlinkage long compat_sys_statfs64(cons
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(nd.dentry, &tmp);
+		error = vfs_statfs(nd.dentry, nd.mnt, &tmp);
 		if (!error)
 			error = put_compat_statfs64(buf, &tmp);
 		path_release(&nd);
@@ -304,7 +305,7 @@ asmlinkage long compat_sys_fstatfs64(uns
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_path.dentry, &tmp);
+	error = vfs_statfs(file->f_path.dentry, file->f_path.mnt, &tmp);
 	if (!error)
 		error = put_compat_statfs64(buf, &tmp);
 	fput(file);
--- a/fs/ecryptfs/super.c
+++ b/fs/ecryptfs/super.c
@@ -119,7 +119,10 @@ static void ecryptfs_put_super(struct su
  */
 static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	return vfs_statfs(ecryptfs_dentry_to_lower(dentry), buf);
+	struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
+	struct vfsmount *lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
+
+	return vfs_statfs(lower_dentry, lower_mnt, buf);
 }
 
 /**
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1457,7 +1457,7 @@ nfsd4_encode_fattr(struct svc_fh *fhp, s
 	if ((bmval0 & (FATTR4_WORD0_FILES_FREE | FATTR4_WORD0_FILES_TOTAL)) ||
 	    (bmval1 & (FATTR4_WORD1_SPACE_AVAIL | FATTR4_WORD1_SPACE_FREE |
 		       FATTR4_WORD1_SPACE_TOTAL))) {
-		err = vfs_statfs(dentry, &statfs);
+		err = vfs_statfs(dentry, exp->ex_mnt, &statfs);
 		if (err)
 			goto out_nfserr;
 	}
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1767,7 +1767,7 @@ __be32
 nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat)
 {
 	__be32 err = fh_verify(rqstp, fhp, 0, MAY_NOP);
-	if (!err && vfs_statfs(fhp->fh_dentry,stat))
+	if (!err && vfs_statfs(fhp->fh_dentry, fhp->fh_export->ex_mnt, stat))
 		err = nfserr_io;
 	return err;
 }
--- a/fs/open.c
+++ b/fs/open.c
@@ -28,7 +28,7 @@
 #include <linux/rcupdate.h>
 #include <linux/audit.h>
 
-int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+int vfs_statfs(struct dentry *dentry, struct vfsmount *mnt, struct kstatfs *buf)
 {
 	int retval = -ENODEV;
 
@@ -40,8 +40,35 @@ int vfs_statfs(struct dentry *dentry, st
 			if (retval)
 				return retval;
 			retval = dentry->d_sb->s_op->statfs(dentry, buf);
-			if (retval == 0 && buf->f_frsize == 0)
-				buf->f_frsize = buf->f_bsize;
+			if (retval == 0) {
+				unsigned long f_flag = ST_IN_USE;
+				unsigned long x;
+
+				if (buf->f_frsize == 0)
+					buf->f_frsize = buf->f_bsize;
+
+				x = dentry->d_inode->i_sb->s_flags;
+				if (x & MS_RDONLY)
+					f_flag |= ST_RDONLY;
+				if (x & MS_SYNCHRONOUS)
+					f_flag |= ST_SYNCHRONOUS;
+				if (x & MS_MANDLOCK)
+					f_flag |= ST_MANDLOCK;
+
+				if (mnt) {
+					int x = mnt->mnt_flags;
+
+					if (x & MNT_NOSUID)
+						f_flag |= ST_NOSUID;
+					if (x & MNT_NODEV)
+						f_flag |= ST_NODEV;
+					if (x & MNT_NOATIME)
+						f_flag |= ST_NOATIME;
+					if (x & MNT_NODIRATIME)
+						f_flag |= ST_NODIRATIME;
+				}
+				buf->f_flag = f_flag;
+			}
 		}
 	}
 	return retval;
@@ -49,12 +76,13 @@ int vfs_statfs(struct dentry *dentry, st
 
 EXPORT_SYMBOL(vfs_statfs);
 
-static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf)
+static int vfs_statfs_native(struct dentry *dentry, struct vfsmount *mnt,
+			     struct statfs *buf)
 {
 	struct kstatfs st;
 	int retval;
 
-	retval = vfs_statfs(dentry, &st);
+	retval = vfs_statfs(dentry, mnt, &st);
 	if (retval)
 		return retval;
 
@@ -87,17 +115,19 @@ static int vfs_statfs_native(struct dent
 		buf->f_fsid = st.f_fsid;
 		buf->f_namelen = st.f_namelen;
 		buf->f_frsize = st.f_frsize;
+		buf->f_flag = st.f_flag;
 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
 	}
 	return 0;
 }
 
-static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf)
+static int vfs_statfs64(struct dentry *dentry, struct vfsmount *mnt,
+			struct statfs64 *buf)
 {
 	struct kstatfs st;
 	int retval;
 
-	retval = vfs_statfs(dentry, &st);
+	retval = vfs_statfs(dentry, mnt, &st);
 	if (retval)
 		return retval;
 
@@ -114,6 +144,7 @@ static int vfs_statfs64(struct dentry *d
 		buf->f_fsid = st.f_fsid;
 		buf->f_namelen = st.f_namelen;
 		buf->f_frsize = st.f_frsize;
+		buf->f_flag = st.f_flag;
 		memset(buf->f_spare, 0, sizeof(buf->f_spare));
 	}
 	return 0;
@@ -127,7 +158,7 @@ asmlinkage long sys_statfs(const char __
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct statfs tmp;
-		error = vfs_statfs_native(nd.dentry, &tmp);
+		error = vfs_statfs_native(nd.dentry, nd.mnt, &tmp);
 		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 			error = -EFAULT;
 		path_release(&nd);
@@ -146,7 +177,7 @@ asmlinkage long sys_statfs64(const char 
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct statfs64 tmp;
-		error = vfs_statfs64(nd.dentry, &tmp);
+		error = vfs_statfs64(nd.dentry, nd.mnt, &tmp);
 		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 			error = -EFAULT;
 		path_release(&nd);
@@ -165,7 +196,7 @@ asmlinkage long sys_fstatfs(unsigned int
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs_native(file->f_path.dentry, &tmp);
+	error = vfs_statfs_native(file->f_path.dentry, file->f_path.mnt, &tmp);
 	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 		error = -EFAULT;
 	fput(file);
@@ -186,7 +217,7 @@ asmlinkage long sys_fstatfs64(unsigned i
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs64(file->f_path.dentry, &tmp);
+	error = vfs_statfs64(file->f_path.dentry, file->f_path.mnt, &tmp);
 	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 		error = -EFAULT;
 	fput(file);
--- a/fs/super.c
+++ b/fs/super.c
@@ -542,7 +542,7 @@ asmlinkage long sys_ustat(unsigned dev, 
         s = user_get_super(new_decode_dev(dev));
         if (s == NULL)
                 goto out;
-	err = vfs_statfs(s->s_root, &sbuf);
+	err = vfs_statfs(s->s_root, NULL, &sbuf);
 	drop_super(s);
 	if (err)
 		goto out;
--- a/include/asm-generic/statfs.h
+++ b/include/asm-generic/statfs.h
@@ -17,7 +17,8 @@ struct statfs {
 	__kernel_fsid_t f_fsid;
 	__u32 f_namelen;
 	__u32 f_frsize;
-	__u32 f_spare[5];
+	__u32 f_flag;
+	__u32 f_spare[4];
 };
 
 struct statfs64 {
@@ -31,7 +32,8 @@ struct statfs64 {
 	__kernel_fsid_t f_fsid;
 	__u32 f_namelen;
 	__u32 f_frsize;
-	__u32 f_spare[5];
+	__u32 f_flag;
+	__u32 f_spare[4];
 };
 
 struct compat_statfs64 {
@@ -45,7 +47,8 @@ struct compat_statfs64 {
 	__kernel_fsid_t f_fsid;
 	__u32 f_namelen;
 	__u32 f_frsize;
-	__u32 f_spare[5];
+	__u32 f_flag;
+	__u32 f_spare[4];
 };
 
 #endif
--- a/include/asm-x86_64/compat.h
+++ b/include/asm-x86_64/compat.h
@@ -104,7 +104,8 @@ struct compat_statfs {
 	compat_fsid_t	f_fsid;
 	int		f_namelen;	/* SunOS ignores this field. */
 	int		f_frsize;
-	int		f_spare[5];
+	int		f_flag;
+	int		f_spare[4];
 };
 
 #define COMPAT_RLIM_OLD_INFINITY	0x7fffffff
--- a/include/asm-x86_64/statfs.h
+++ b/include/asm-x86_64/statfs.h
@@ -24,7 +24,8 @@ struct statfs {
 	__kernel_fsid_t f_fsid;
 	long f_namelen;
 	long f_frsize;
-	long f_spare[5];
+	long f_flag;
+	long f_spare[4];
 };
 
 struct statfs64 {
@@ -38,7 +39,8 @@ struct statfs64 {
 	__kernel_fsid_t f_fsid;
 	long f_namelen;
 	long f_frsize;
-	long f_spare[5];
+	long f_flag;
+	long f_spare[4];
 };
 
 struct compat_statfs64 {
@@ -52,7 +54,8 @@ struct compat_statfs64 {
 	__kernel_fsid_t f_fsid;
 	__u32 f_namelen;
 	__u32 f_frsize;
-	__u32 f_spare[5];
+	__u32 f_flag;
+	__u32 f_spare[4];
 } __attribute__((packed));
 
 #endif
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1408,7 +1408,7 @@ extern struct vfsmount *copy_tree(struct
 extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *,
 				  struct vfsmount *);
 
-extern int vfs_statfs(struct dentry *, struct kstatfs *);
+extern int vfs_statfs(struct dentry *, struct vfsmount *, struct kstatfs *);
 
 /* /sys/fs */
 extern struct subsystem fs_subsys;
--- a/include/linux/statfs.h
+++ b/include/linux/statfs.h
@@ -16,7 +16,18 @@ struct kstatfs {
 	__kernel_fsid_t f_fsid;
 	long f_namelen;
 	long f_frsize;
-	long f_spare[5];
+	unsigned long f_flag;
+	long f_spare[4];
 };
 
+#define ST_RDONLY	1
+#define ST_NOSUID	2
+#define ST_NODEV	4
+#define ST_NOEXEC	8
+#define ST_SYNCHRONOUS	16
+#define ST_MANDLOCK	64
+#define ST_NOATIME	1024
+#define ST_NODIRATIME	2048
+#define ST_IN_USE	(1 << 31)
+
 #endif
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -118,7 +118,7 @@ static int check_free_space(struct file 
 	spin_unlock(&acct_globals.lock);
 
 	/* May block */
-	if (vfs_statfs(file->f_path.dentry, &sbuf))
+	if (vfs_statfs(file->f_path.dentry, file->f_path.mnt, &sbuf))
 		return res;
 	suspend = sbuf.f_blocks * SUSPEND;
 	resume = sbuf.f_blocks * RESUME;