From aa6d8c10864dd532b1577a84a22da2eaee10fcfd Mon Sep 17 00:00:00 2001
From: "Ned A. Bass" <bass6@llnl.gov>
Date: Mon, 9 May 2011 12:31:56 -0700
Subject: [PATCH] Don't store rdev in SA for FIFOs and sockets

Update the handling of named pipes and sockets to be consistent with
other platforms with regard to the rdev attribute.  While all ZFS
ipmlementations store the rdev for device files in a system attribute
(SA), this is not the case for FIFOs and sockets.  Indeed, Linux always
passes rdev=0 to mknod() for FIFOs and sockets, so the value is not
needed.  Add an ASSERT that rdev==0 for FIFOs and sockets to detect if
the expected behavior ever changes.

Closes #216
---
 module/zfs/zfs_znode.c | 16 +++++++++-------
 module/zfs/zpl_inode.c |  7 +++++++
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index 936b950f3..faf1161c9 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -278,7 +278,7 @@ zfs_inode_destroy(struct inode *ip)
 static void
 zfs_inode_set_ops(zfs_sb_t *zsb, struct inode *ip)
 {
-	uint64_t rdev;
+	uint64_t rdev = 0;
 
 	switch (ip->i_mode & S_IFMT) {
 	case S_IFREG:
@@ -297,12 +297,16 @@ zfs_inode_set_ops(zfs_sb_t *zsb, struct inode *ip)
 		ip->i_op = &zpl_symlink_inode_operations;
 		break;
 
+	/*
+	 * rdev is only stored in a SA only for device files.
+	 */
 	case S_IFCHR:
 	case S_IFBLK:
-	case S_IFIFO:
-	case S_IFSOCK:
 		VERIFY(sa_lookup(ITOZ(ip)->z_sa_hdl, SA_ZPL_RDEV(zsb),
 		    &rdev, sizeof (rdev)) == 0);
+		/*FALLTHROUGH*/
+	case S_IFIFO:
+	case S_IFSOCK:
 		init_special_inode(ip, ip->i_mode, rdev);
 		ip->i_op = &zpl_special_inode_operations;
 		break;
@@ -556,8 +560,7 @@ zfs_mknode(znode_t *dzp, vattr_t *vap, dmu_tx_t *tx, cred_t *cr,
 		size = links = 0;
 	}
 
-	if (S_ISBLK(vap->va_mode)  || S_ISCHR(vap->va_mode) ||
-	    S_ISFIFO(vap->va_mode) || S_ISSOCK(vap->va_mode))
+	if (S_ISBLK(vap->va_mode) || S_ISCHR(vap->va_mode))
 		rdev = vap->va_rdev;
 
 	parent = dzp->z_id;
@@ -648,8 +651,7 @@ zfs_mknode(znode_t *dzp, vattr_t *vap, dmu_tx_t *tx, cred_t *cr,
 		    &empty_xattr, 8);
 	}
 	if (obj_type == DMU_OT_ZNODE ||
-	    (S_ISBLK(vap->va_mode)  || S_ISCHR(vap->va_mode) ||
-	     S_ISFIFO(vap->va_mode) || S_ISSOCK(vap->va_mode))) {
+	    (S_ISBLK(vap->va_mode) || S_ISCHR(vap->va_mode))) {
 		SA_ADD_BULK_ATTR(sa_attrs, cnt, SA_ZPL_RDEV(zsb),
 		    NULL, &rdev, 8);
 	}
diff --git a/module/zfs/zpl_inode.c b/module/zfs/zpl_inode.c
index 029a4038b..8376673f1 100644
--- a/module/zfs/zpl_inode.c
+++ b/module/zfs/zpl_inode.c
@@ -85,6 +85,13 @@ zpl_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
 	vattr_t *vap;
 	int error;
 
+	/*
+	 * We currently expect Linux to supply rdev=0 for all sockets
+	 * and fifos, but we want to know if this behavior ever changes.
+	 */
+	if (S_ISSOCK(mode) || S_ISFIFO(mode))
+		ASSERT(rdev == 0);
+
 	crhold(cr);
 	vap = kmem_zalloc(sizeof(vattr_t), KM_SLEEP);
 	vap->va_mode = mode;