Fix unlinked file cannot do xattr operations

Currently, doing things like fsetxattr(2) on an unlinked file will result in
ENODATA. There's two places that cause this: zfs_dirent_lock and zfs_zget.

The fix in zfs_dirent_lock is pretty straightforward. In zfs_zget though, we
need it to not return error when the zp is unlinked. This is a pretty big
change in behavior, but skimming through all the callers, I don't think this
change would cause any problem. Also there's nothing preventing z_unlinked
from being set after the z_lock mutex is dropped before but before zfs_zget
returns anyway.

The rest of the stuff is to make sure we don't log xattr stuff when owner is
unlinked.

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>

include/sys/zfs_znode.h

@@ -194,6 +194,7 @@ typedef struct znode {
 	zfs_acl_t	*z_acl_cached;	/* cached acl */
 	krwlock_t	z_xattr_lock;	/* xattr data lock */
 	nvlist_t	*z_xattr_cached; /* cached xattrs */
+	uint64_t	z_xattr_parent;	/* parent obj for this xattr */
 	list_node_t	z_link_node;	/* all znodes in fs link */
 	sa_handle_t	*z_sa_hdl;	/* handle to sa data */
 	boolean_t	z_is_sa;	/* are we native sa? */

module/zfs/zfs_acl.c

@@ -2492,15 +2492,8 @@ zfs_zaccess(znode_t *zp, int mode, int flags, boolean_t skipaclchk, cred_t *cr)
 	 * If attribute then validate against base file
 	 */
 	if (is_attr) {
-		uint64_t	parent;
-
-		if ((error = sa_lookup(zp->z_sa_hdl,
-		    SA_ZPL_PARENT(ZTOZSB(zp)), &parent,
-		    sizeof (parent))) != 0)
-			return (error);
-
 		if ((error = zfs_zget(ZTOZSB(zp),
-		    parent, &xzp)) != 0)	{
+		    zp->z_xattr_parent, &xzp)) != 0) {
 			return (error);
 		}
 

module/zfs/zfs_dir.c

@@ -240,7 +240,7 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 
 	mutex_enter(&dzp->z_lock);
 	for (;;) {
-		if (dzp->z_unlinked) {
+		if (dzp->z_unlinked && !(flag & ZXATTR)) {
 			mutex_exit(&dzp->z_lock);
 			if (!(flag & ZHAVELOCK))
 				rw_exit(&dzp->z_name_lock);
@@ -998,8 +998,9 @@ zfs_make_xattrdir(znode_t *zp, vattr_t *vap, struct inode **xipp, cred_t *cr)
 	VERIFY(0 == sa_update(zp->z_sa_hdl, SA_ZPL_XATTR(zsb), &xzp->z_id,
 	    sizeof (xzp->z_id), tx));
 
-	(void) zfs_log_create(zsb->z_log, tx, TX_MKXATTR, zp,
-	    xzp, "", NULL, acl_ids.z_fuidp, vap);
+	if (!zp->z_unlinked)
+		(void) zfs_log_create(zsb->z_log, tx, TX_MKXATTR, zp,
+		    xzp, "", NULL, acl_ids.z_fuidp, vap);
 
 	zfs_acl_ids_free(&acl_ids);
 	dmu_tx_commit(tx);

module/zfs/zfs_log.c

@@ -211,6 +211,34 @@ zfs_log_fuid_domains(zfs_fuid_info_t *fuidp, void *start)
 	return (start);
 }
 
+/*
+ * If zp is an xattr node, check whether the xattr owner is unlinked.
+ * We don't want to log anything if the owner is unlinked.
+ */
+static int
+zfs_xattr_owner_unlinked(znode_t *zp)
+{
+	int unlinked = 0;
+	znode_t *dzp;
+	igrab(ZTOI(zp));
+	/*
+	 * if zp is XATTR node, keep walking up via z_xattr_parent until we
+	 * get the owner
+	 */
+	while (zp->z_pflags & ZFS_XATTR) {
+		ASSERT3U(zp->z_xattr_parent, !=, 0);
+		if (zfs_zget(ZTOZSB(zp), zp->z_xattr_parent, &dzp) != 0) {
+			unlinked = 1;
+			break;
+		}
+		iput(ZTOI(zp));
+		zp = dzp;
+		unlinked = zp->z_unlinked;
+	}
+	iput(ZTOI(zp));
+	return (unlinked);
+}
+
 /*
  * Handles TX_CREATE, TX_CREATE_ATTR, TX_MKDIR, TX_MKDIR_ATTR and
  * TK_MKXATTR transactions.
@@ -247,7 +275,7 @@ zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	size_t namesize = strlen(name) + 1;
 	size_t fuidsz = 0;
 
-	if (zil_replaying(zilog, tx))
+	if (zil_replaying(zilog, tx) || zfs_xattr_owner_unlinked(dzp))
 		return;
 
 	/*
@@ -352,7 +380,7 @@ zfs_log_remove(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	lr_remove_t *lr;
 	size_t namesize = strlen(name) + 1;
 
-	if (zil_replaying(zilog, tx))
+	if (zil_replaying(zilog, tx) || zfs_xattr_owner_unlinked(dzp))
 		return;
 
 	itx = zil_itx_create(txtype, sizeof (*lr) + namesize);
@@ -463,7 +491,8 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	uintptr_t fsync_cnt;
 	ssize_t immediate_write_sz;
 
-	if (zil_replaying(zilog, tx) || zp->z_unlinked) {
+	if (zil_replaying(zilog, tx) || zp->z_unlinked ||
+	    zfs_xattr_owner_unlinked(zp)) {
 		if (callback != NULL)
 			callback(callback_data);
 		return;
@@ -543,7 +572,8 @@ zfs_log_truncate(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	itx_t *itx;
 	lr_truncate_t *lr;
 
-	if (zil_replaying(zilog, tx) || zp->z_unlinked)
+	if (zil_replaying(zilog, tx) || zp->z_unlinked ||
+	    zfs_xattr_owner_unlinked(zp))
 		return;
 
 	itx = zil_itx_create(txtype, sizeof (*lr));

module/zfs/zfs_znode.c

@@ -119,6 +119,7 @@ zfs_znode_cache_constructor(void *buf, void *arg, int kmflags)
 	zp->z_dirlocks = NULL;
 	zp->z_acl_cached = NULL;
 	zp->z_xattr_cached = NULL;
+	zp->z_xattr_parent = 0;
 	zp->z_moved = 0;
 	return (0);
 }
@@ -590,6 +591,10 @@ zfs_znode_alloc(zfs_sb_t *zsb, dmu_buf_t *db, int blksz,
 	zfs_uid_write(ip, z_uid);
 	zfs_gid_write(ip, z_gid);
 
+	/* Cache the xattr parent id */
+	if (zp->z_pflags & ZFS_XATTR)
+		zp->z_xattr_parent = parent;
+
 	ZFS_TIME_DECODE(&ip->i_atime, atime);
 	ZFS_TIME_DECODE(&ip->i_mtime, mtime);
 	ZFS_TIME_DECODE(&ip->i_ctime, ctime);
@@ -1060,34 +1065,30 @@ zfs_zget(zfs_sb_t *zsb, uint64_t obj_num, znode_t **zpp)
 
 		mutex_enter(&zp->z_lock);
 		ASSERT3U(zp->z_id, ==, obj_num);
-		if (zp->z_unlinked) {
-			err = SET_ERROR(ENOENT);
-		} else {
-			/*
-			 * If igrab() returns NULL the VFS has independently
-			 * determined the inode should be evicted and has
-			 * called iput_final() to start the eviction process.
-			 * The SA handle is still valid but because the VFS
-			 * requires that the eviction succeed we must drop
-			 * our locks and references to allow the eviction to
-			 * complete.  The zfs_zget() may then be retried.
-			 *
-			 * This unlikely case could be optimized by registering
-			 * a sops->drop_inode() callback.  The callback would
-			 * need to detect the active SA hold thereby informing
-			 * the VFS that this inode should not be evicted.
-			 */
-			if (igrab(ZTOI(zp)) == NULL) {
-				mutex_exit(&zp->z_lock);
-				sa_buf_rele(db, NULL);
-				zfs_znode_hold_exit(zsb, zh);
-				/* inode might need this to finish evict */
-				cond_resched();
-				goto again;
-			}
-			*zpp = zp;
-			err = 0;
+		/*
+		 * If igrab() returns NULL the VFS has independently
+		 * determined the inode should be evicted and has
+		 * called iput_final() to start the eviction process.
+		 * The SA handle is still valid but because the VFS
+		 * requires that the eviction succeed we must drop
+		 * our locks and references to allow the eviction to
+		 * complete.  The zfs_zget() may then be retried.
+		 *
+		 * This unlikely case could be optimized by registering
+		 * a sops->drop_inode() callback.  The callback would
+		 * need to detect the active SA hold thereby informing
+		 * the VFS that this inode should not be evicted.
+		 */
+		if (igrab(ZTOI(zp)) == NULL) {
+			mutex_exit(&zp->z_lock);
+			sa_buf_rele(db, NULL);
+			zfs_znode_hold_exit(zsb, zh);
+			/* inode might need this to finish evict */
+			cond_resched();
+			goto again;
 		}
+		*zpp = zp;
+		err = 0;
 		mutex_exit(&zp->z_lock);
 		sa_buf_rele(db, NULL);
 		zfs_znode_hold_exit(zsb, zh);