Simplify time handling logic in zfs_settattr

Simplify time handling in zfs_setattr by mimicking the logic in
setattr_copy from the linux kernel. In order to achieve this
in the case when ZFS' log is being replayed it is necessary
to unconditionally set the ctime in zfs_replay_setattr.

Also use the timespec_trunc function when assigning values to the
generic inode struct. This is currently a noop since zfs sets
s_time_gran to 1, however in the future rules about precision might
change.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Closes openzfs#4916

module/zfs/zfs_replay.c

@@ -805,6 +805,8 @@ zfs_replay_setattr(zfs_sb_t *zsb, lr_setattr_t *lr, boolean_t byteswap)
 	vap->va_size = lr->lr_size;
 	ZFS_TIME_DECODE(&vap->va_atime, lr->lr_atime);
 	ZFS_TIME_DECODE(&vap->va_mtime, lr->lr_mtime);
+	gethrestime(&vap->va_ctime);
+	vap->va_mask |= ATTR_CTIME;
 
 	/*
 	 * Fill in xvattr_t portions if necessary.

module/zfs/zfs_vnops.c

@@ -3001,7 +3001,6 @@ zfs_setattr(struct inode *ip, vattr_t *vap, int flags, cred_t *cr)
 		aclp = NULL;
 	}
 
-
 	if ((mask & ATTR_ATIME) || zp->z_atime_dirty) {
 		zp->z_atime_dirty = 0;
 		ZFS_TIME_ENCODE(&ip->i_atime, atime);
@@ -3011,29 +3010,27 @@ zfs_setattr(struct inode *ip, vattr_t *vap, int flags, cred_t *cr)
 
 	if (mask & ATTR_MTIME) {
 		ZFS_TIME_ENCODE(&vap->va_mtime, mtime);
+		ZTOI(zp)->i_mtime = timespec_trunc(vap->va_mtime,
+		    ZTOI(zp)->i_sb->s_time_gran);
+
 		SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb), NULL,
 		    mtime, sizeof (mtime));
 	}
 
-	/* XXX - shouldn't this be done *before* the ATIME/MTIME checks? */
-	if (mask & ATTR_SIZE && !(mask & ATTR_MTIME)) {
-		SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zsb),
-		    NULL, mtime, sizeof (mtime));
+	if (mask & ATTR_CTIME) {
+		ZFS_TIME_ENCODE(&vap->va_ctime, ctime);
+		ZTOI(zp)->i_ctime = timespec_trunc(vap->va_ctime,
+		    ZTOI(zp)->i_sb->s_time_gran);
 		SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL,
-		    &ctime, sizeof (ctime));
-		zfs_tstamp_update_setup(zp, CONTENT_MODIFIED, mtime, ctime);
-	} else if (mask != 0) {
-		SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zsb), NULL,
-		    &ctime, sizeof (ctime));
-		zfs_tstamp_update_setup(zp, STATE_CHANGED, mtime, ctime);
-		if (attrzp) {
-			SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
-			    SA_ZPL_CTIME(zsb), NULL,
-			    &ctime, sizeof (ctime));
-			zfs_tstamp_update_setup(attrzp, STATE_CHANGED,
-			    mtime, ctime);
-		}
+		    ctime, sizeof (ctime));
 	}
+
+	if (attrzp && mask) {
+		SA_ADD_BULK_ATTR(xattr_bulk, xattr_count,
+		    SA_ZPL_CTIME(zsb), NULL, &ctime,
+		    sizeof (ctime));
+	}
+
 	/*
 	 * Do this after setting timestamps to prevent timestamp
 	 * update from toggling bit

module/zfs/zpl_inode.c

@@ -335,7 +335,8 @@ zpl_setattr(struct dentry *dentry, struct iattr *ia)
 	vap->va_ctime = ia->ia_ctime;
 
 	if (vap->va_mask & ATTR_ATIME)
-		ip->i_atime = ia->ia_atime;
+		ip->i_atime = timespec_trunc(ia->ia_atime,
+				ip->i_sb->s_time_gran);
 
 	cookie = spl_fstrans_mark();
 	error = -zfs_setattr(ip, vap, 0, cr);