Part I: Update extended attribute API and ABI:

o Modify the system call syntax for extattr_{get,set}_{fd,file}() so
  as not to use the scatter gather API (which appeared not to be used
  by any consumers, and be less portable), rather, accepts 'data'
  and 'nbytes' in the style of other simple read/write interfaces.
  This changes the API and ABI.

o Modify system call semantics so that extattr_get_{fd,file}() return
  a size_t.  When performing a read, the number of bytes read will
  be returned, unless the data pointer is NULL, in which case the
  number of bytes of data are returned.  This changes the API only.

o Modify the VOP_GETEXTATTR() vnode operation to accept a *size_t
  argument so as to return the size, if desirable.  If set to NULL,
  the size will not be returned.

o Update various filesystems (pseodofs, ufs) to DTRT.

These changes should make extended attributes more useful and more
portable.  More commits to rebuild the system call files, as well
as update userland utilities to follow.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

1 files changed, 31 insertions, 20 deletions

diff --git a/sys/ufs/ufs/ufs_extattr.c b/sys/ufs/ufs/ufs_extattr.c
index 71ed166..34e0bed 100644
--- a/sys/ufs/ufs/ufs_extattr.c
+++ b/sys/ufs/ufs/ufs_extattr.c
@@ -80,7 +80,8 @@ static int	ufs_extattr_enable(struct ufsmount *ump, int attrnamespace,
 static int	ufs_extattr_disable(struct ufsmount *ump, int attrnamespace,
     const char *attrname, struct thread *td);
 static int	ufs_extattr_get(struct vnode *vp, int attrnamespace,
-    const char *name, struct uio *uio, struct ucred *cred, struct thread *td);
+    const char *name, struct uio *uio, size_t *size, struct ucred *cred,
+    struct thread *td);
 static int	ufs_extattr_set(struct vnode *vp, int attrnamespace,
     const char *name, struct uio *uio, struct ucred *cred, struct thread *td);
 static int	ufs_extattr_rm(struct vnode *vp, int attrnamespace,
@@ -825,6 +826,7 @@ vop_getextattr {
 	IN int a_attrnamespace;
 	IN const char *a_name;
 	INOUT struct uio *a_uio;
+	OUT struct size_t *a_size;
 	IN struct ucred *a_cred;
 	IN struct thread *a_td;
 };
@@ -837,7 +839,7 @@ vop_getextattr {
 	ufs_extattr_uepm_lock(ump, ap->a_td);
 
 	error = ufs_extattr_get(ap->a_vp, ap->a_attrnamespace, ap->a_name,
-	    ap->a_uio, ap->a_cred, ap->a_td);
+	    ap->a_uio, ap->a_size, ap->a_cred, ap->a_td);
 
 	ufs_extattr_uepm_unlock(ump, ap->a_td);
 
@@ -850,7 +852,7 @@ vop_getextattr {
  */
 static int
 ufs_extattr_get(struct vnode *vp, int attrnamespace, const char *name,
-    struct uio *uio, struct ucred *cred, struct thread *td)
+    struct uio *uio, size_t *size, struct ucred *cred, struct thread *td)
 {
 	struct ufs_extattr_list_entry	*attribute;
 	struct ufs_extattr_header	ueh;
@@ -860,7 +862,7 @@ ufs_extattr_get(struct vnode *vp, int attrnamespace, const char *name,
 	struct ufsmount	*ump = VFSTOUFS(mp);
 	struct inode	*ip = VTOI(vp);
 	off_t	base_offset;
-	size_t	size, old_size;
+	size_t	len, old_len;
 	int	error = 0;
 
 	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
@@ -885,7 +887,7 @@ ufs_extattr_get(struct vnode *vp, int attrnamespace, const char *name,
 	 * extended attribute semantic.  Otherwise we can't guarantee
 	 * atomicity, as we don't provide locks for extended attributes.
 	 */
-	if (uio->uio_offset != 0)
+	if (uio != NULL && uio->uio_offset != 0)
 		return (ENXIO);
 
 	/*
@@ -956,27 +958,36 @@ ufs_extattr_get(struct vnode *vp, int attrnamespace, const char *name,
 		goto vopunlock_exit;
 	}
 
-	/* Allow for offset into the attribute data. */
-	uio->uio_offset = base_offset + sizeof(struct ufs_extattr_header);
+	/* Return full data size if caller requested it. */
+	if (size != NULL)
+		*size = ueh.ueh_len;
 
-	/*
-	 * Figure out maximum to transfer -- use buffer size and local data
-	 * limit.
-	 */
-	size = MIN(uio->uio_resid, ueh.ueh_len);
-	old_size = uio->uio_resid;
-	uio->uio_resid = size;
+	/* Return data if the caller requested it. */
+	if (uio != NULL) {
+		/* Allow for offset into the attribute data. */
+		uio->uio_offset = base_offset + sizeof(struct
+		    ufs_extattr_header);
 
-	error = VOP_READ(attribute->uele_backing_vnode, uio,
-	    IO_NODELOCKED, ump->um_extattr.uepm_ucred);
-	if (error)
-		goto vopunlock_exit;
+		/*
+		 * Figure out maximum to transfer -- use buffer size and
+		 * local data limit.
+		 */
+		len = MIN(uio->uio_resid, ueh.ueh_len);
+		old_len = uio->uio_resid;
+		uio->uio_resid = len;
 
-	uio->uio_resid = old_size - (size - uio->uio_resid);
+		error = VOP_READ(attribute->uele_backing_vnode, uio,
+		    IO_NODELOCKED, ump->um_extattr.uepm_ucred);
+		if (error)
+			goto vopunlock_exit;
+
+		uio->uio_resid = old_len - (len - uio->uio_resid);
+	}
 
 vopunlock_exit:
 
-	uio->uio_offset = 0;
+	if (uio != NULL)
+		uio->uio_offset = 0;
 
 	if (attribute->uele_backing_vnode != vp)
 		VOP_UNLOCK(attribute->uele_backing_vnode, 0, td);