OS-1429 `tail -f ...` doesn't notice file truncation

10 files changed, 398 insertions, 83 deletions

diff --git a/usr/src/cmd/tail/forward.c b/usr/src/cmd/tail/forward.c
index e4f22582f3..63e3c46e5b 100644
--- a/usr/src/cmd/tail/forward.c
+++ b/usr/src/cmd/tail/forward.c
@@ -31,9 +31,7 @@
  */
 
 /*
- * Solaris porting notes:  the original FreeBSD version made use of the
- *                         BSD kqueue event notification framework; this
- *                         was changed to use usleep()
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/param.h>
@@ -53,6 +51,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 #include "extern.h"
@@ -63,9 +62,11 @@ static void set_events(file_info_t *files);
 
 /* defines for inner loop actions */
 #define	USE_SLEEP	0
+#define	USE_PORT	1
 #define	ADD_EVENTS	2
 
-int action = USE_SLEEP;
+int port;
+int action = USE_PORT;
 
 static const file_info_t *last;
 
@@ -261,6 +262,58 @@ show(file_info_t *file)
 }
 
 static void
+associate(file_info_t *file, boolean_t assoc)
+{
+	char buf[64];
+	file_obj_t fobj;
+
+	if (action != USE_PORT || file->fp == NULL)
+		return;
+
+	if (!S_ISREG(file->st.st_mode)) {
+		/*
+		 * For FIFOs, we use PORT_SOURCE_FD as our port event source.
+		 */
+		if (assoc) {
+			(void) port_associate(port, PORT_SOURCE_FD,
+			    fileno(file->fp), POLLIN, file);
+		} else {
+			(void) port_dissociate(port, PORT_SOURCE_FD,
+			    fileno(file->fp));
+		}
+
+		return;
+	}
+
+	bzero(&fobj, sizeof (fobj));
+
+	/*
+	 * We pull a bit of a stunt here.  PORT_SOURCE_FILE only allows us to
+	 * specify a file name -- not a file descriptor.  If we were to specify
+	 * the name of the file to port_associate() and that file were moved
+	 * aside, we would not be able to reassociate an event because we would
+	 * not know a name that would resolve to the new file (indeed, there
+	 * might not be such a name -- the file may have been unlinked).  But
+	 * there _is_ a name that we know maps to the file and doesn't change:
+	 * the name of the representation of the open file descriptor in /proc.
+	 * We therefore associate with this name (and the underlying file),
+	 * not the name of the file as specified at the command line.
+	 */
+	(void) snprintf(buf,
+	    sizeof (buf), "/proc/self/fd/%d", fileno(file->fp));
+
+	fobj.fo_name = buf;
+
+	if (assoc) {
+		(void) port_associate(port, PORT_SOURCE_FILE,
+		    (uintptr_t)&fobj, FILE_MODIFIED | FILE_TRUNC, file);
+	} else {
+		(void) port_dissociate(port, PORT_SOURCE_FILE,
+		    (uintptr_t)&fobj);
+	}
+}
+
+static void
 set_events(file_info_t *files)
 {
 	int i;
@@ -271,6 +324,8 @@ set_events(file_info_t *files)
 			continue;
 
 		(void) fstat(fileno(file->fp), &file->st);
+
+		associate(file, B_TRUE);
 	}
 }
 
@@ -284,6 +339,8 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 	int active, ev_change, i, n = -1;
 	struct stat sb2;
 	file_info_t *file;
+	struct timespec ts;
+	port_event_t ev;
 
 	/* Position each of the files */
 
@@ -307,6 +364,10 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 		return;
 
 	last = --file;
+
+	if (action == USE_PORT && (port = port_create()) == -1)
+		action = USE_SLEEP;
+
 	set_events(files);
 
 	for (;;) {
@@ -341,12 +402,13 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 				    sb2.st_dev != file->st.st_dev ||
 				    sb2.st_nlink == 0) {
 					(void) show(file);
+					associate(file, B_FALSE);
 					file->fp = freopen(file->file_name, "r",
 					    file->fp);
-					if (file->fp != NULL)
+					if (file->fp != NULL) {
 						(void) memcpy(&file->st, &sb2,
 						    sizeof (struct stat));
-					else if (errno != ENOENT)
+					} else if (errno != ENOENT)
 						ierr(file->file_name);
 					ev_change++;
 				}
@@ -361,6 +423,26 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 			set_events(files);
 
 		switch (action) {
+		case USE_PORT:
+			ts.tv_sec = 1;
+			ts.tv_nsec = 0;
+
+			/*
+			 * In the -F case we set a timeout to ensure that
+			 * we re-stat the file at least once every second.
+			 */
+			n = port_get(port, &ev, Fflag ? &ts : NULL);
+
+			if (n == 0) {
+				file = (file_info_t *)ev.portev_user;
+				associate(file, B_TRUE);
+
+				if (ev.portev_events & FILE_TRUNC)
+					(void) fseek(file->fp, 0, SEEK_SET);
+			}
+
+			break;
+
 		case USE_SLEEP:
 			(void) usleep(250000);
 			break;
diff --git a/usr/src/cmd/tail/tests/tailtests.sh b/usr/src/cmd/tail/tests/tailtests.sh
index 57ec1c46cc..f9591c8ad1 100644
--- a/usr/src/cmd/tail/tests/tailtests.sh
+++ b/usr/src/cmd/tail/tests/tailtests.sh
@@ -13,14 +13,34 @@
 
 #
 # Copyright 2010 Chris Love.  All rights reserved.
+# Copyright (c) 2012, Joyent, Inc. All rights reserved.
 #
 
+checktest()
+{
+	local actual=$1
+	local output=$2
+	local test=$3
+
+	if [[ "$a" != "$o" ]]; then
+		echo "$CMD: test $test: FAIL"
+		echo -e "$CMD: test $test: expected output:\n$o"
+		echo -e "$CMD: test $test: actual output:\n$a"
+	else
+		echo "$CMD: test $test: pass"
+	fi
+}
 
 # 
 # Test cases for 'tail', some based on CoreUtils test cases (validated
-# with legacy Solaris 'tail' and/or xpg4 'tail')
+# with legacy Solaris 'tail' and/or xpg4 'tail').  Note that this is designed
+# to be able to run on BSD systems as well to check our behavior against
+# theirs (some behavior that is known to be idiosyncratic to illumos is
+# skipped on non-illumos systems).
 #
 PROG=/usr/bin/tail
+CMD=`basename $0`
+DIR=""
 
 case $1 in 
     -x)
@@ -29,113 +49,273 @@ case $1 in
     -o)
     	PROG=$2
 	;;
+    -d)
+	DIR=$2
+	;;
     -?)
     	echo "Usage: tailtests.sh [-x][-o <override tail executable>]"
 	exit 1
 	;;
 esac
 
-echo "Using $PROG"
+#
+# Shut bash up upon receiving a term so we can drop it on our children
+# without disrupting the output.
+#
+trap "exit 0" TERM
+
+echo "$CMD: program is $PROG"
+
+if [[ $DIR != "" ]]; then
+	echo "$CMD: directory is $DIR"
+fi
 
 o=`echo -e "bcd"`
 a=`echo -e "abcd" | $PROG +2c`
-[[ "$a" != "$o" ]] && echo "Fail test 1 - $a"
+checktest "$a" "$o" 1
 
 o=`echo -e ""`
 a=`echo "abcd" | $PROG +8c`
-[[ "$a" != "$o" ]] && echo "Fail test 2 - $a"
+checktest "$a" "$o" 2
 
 o=`echo -e "abcd"`
 a=`echo "abcd" | $PROG -9c`
-[[ "$a" != "$o" ]] && echo "Fail test 3 - $a"
+checktest "$a" "$o" 3
 
 o=`echo -e "x"`
 a=`echo -e "x" | $PROG -1l`
-[[ "$a" != "x" ]] && echo "Fail test 4 - $a"
+checktest "$a" "$o" 4
 
 o=`echo -e "\n"`
 a=`echo -e "x\ny\n" | $PROG -1l`
-[[ "$a" != "$o" ]] && echo "Fail test 5 - $a"
+checktest "$a" "$o" 5
 
 o=`echo -e "y\n"`
 a=`echo -e "x\ny\n" | $PROG -2l`
-[[ "$a" != "$o" ]] && echo "Fail test 6 - $a"
+checktest "$a" "$o" 6
 
 o=`echo -e "y"`
 a=`echo -e "x\ny" | $PROG -1l`
-[[ "$a" != "$o" ]] && echo "Fail test 7 - $a"
+checktest "$a" "$o" 7
 
 o=`echo -e "x\ny\n"`
 a=`echo -e "x\ny\n" | $PROG +1l`
-[[ "$a" != "$o" ]] && echo "Fail test 8 - $a"
+checktest "$a" "$o" 8
 
 o=`echo -e "y\n"`
 a=`echo -e "x\ny\n" | $PROG +2l`
-[[ "$a" != "$o" ]] && echo "Fail test 9 - $a"
+checktest "$a" "$o" 9
 
 o=`echo -e "x"`
 a=`echo -e "x" | $PROG -1`
-[[ "$a" != "$o" ]] && echo "Fail test 10 - $a"
+checktest "$a" "$o" 10
 
 o=`echo -e "\n"`
 a=`echo -e "x\ny\n" | $PROG -1`
-[[ "$a" != "$o" ]] && echo "Fail test 11 - $a"
+checktest "$a" "$o" 11
 
 o=`echo -e "y\n"`
 a=`echo -e "x\ny\n" | $PROG -2`
-[[ "$a" != "$o" ]] && echo "Fail test 12 - $a"
+checktest "$a" "$o" 12
 
 o=`echo -e "y"`
 a=`echo -e "x\ny" | $PROG -1`
-[[ "$a" != "$o" ]] && echo "Fail test 13 - $a"
+checktest "$a" "$o" 13
 
 o=`echo -e "x\ny\n"`
 a=`echo -e "x\ny\n" | $PROG +1`
-[[ "$a" != "$o" ]] && echo "Fail test 14 - $a"
+checktest "$a" "$o" 14
 
 o=`echo -e "y\n"`
 a=`echo -e "x\ny\n" | $PROG +2`
-[[ "$a" != "$o" ]] && echo "Fail test 15 - $a"
+checktest "$a" "$o" 15
 
-# For compatibility with Legacy Solaris tail this should also work as '+c'
 o=`echo -e "yyz"`
 a=`echo -e "xyyyyyyyyyyz" | $PROG +10c`
-[[ "$a" != "$o" ]] && echo "Fail test 16 - $a"
+checktest "$a" "$o" 16
 
-o=`echo -e "yyz"`
-a=`echo -e "xyyyyyyyyyyz" | $PROG +c`
-[[ "$a" != "$o" ]] && echo "Fail test 16a - $a"
-
-
-# For compatibility with Legacy Solaris tail this should also work as '+l'
 o=`echo -e "y\ny\nz"`
 a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG +10l`
-[[ "$a" != "$o" ]] && echo "Fail test 17 - $a"
-
-o=`echo -e "y\ny\nz"`
-a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG +l`
-[[ "$a" != "$o" ]] && echo "Fail test 17a - $a"
-
+checktest "$a" "$o" 17
 
-# For compatibility with Legacy Solaris tail this should also work as '-l'
 o=`echo -e "y\ny\ny\ny\ny\ny\ny\ny\ny\nz"`
 a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG -10l`
-[[ "$a" != "$o" ]] && echo "Fail test 18 - $a"
+checktest "$a" "$o" 18
 
-o=`echo -e "y\ny\ny\ny\ny\ny\ny\ny\ny\nz"`
-a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG -l`
-[[ "$a" != "$o" ]] && echo "Fail test 18a - $a"
+#
+# For reasons that are presumably as accidental as they are ancient, legacy
+# (and closed) Solaris tail(1) allows +c, +l and -l to be aliases for +10c,
+# +10l and -10l, respectively.  If we are on SunOS, verify that this silly
+# behavior is functional.
+#
+if [[ `uname -s` == "SunOS" ]]; then
+	o=`echo -e "yyz"`
+	a=`echo -e "xyyyyyyyyyyz" | $PROG +c`
+	checktest "$a" "$o" 16a
+
+	o=`echo -e "y\ny\nz"`
+	a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG +l`
+	checktest "$a" "$o" 17a
+
+	o=`echo -e "y\ny\ny\ny\ny\ny\ny\ny\ny\nz"`
+	a=`echo -e "x\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\nz" | $PROG -l`
+	checktest "$a" "$o" 18a
+fi
 
 o=`echo -e "c\nb\na"`
 a=`echo -e "a\nb\nc" | $PROG -r`
-[[ "$a" != "$o" ]] && echo "Fail test 19 - $a"
+checktest "$a" "$o" 19
+
+#
+# Now we want to do a series of follow tests.
+#
+if [[ $DIR == "" ]]; then
+	tdir=$(mktemp -d -t tailtest.XXXXXXXX || exit 1)
+else
+	tdir=$(mktemp -d $DIR/tailtest.XXXXXXXX || exit 1)
+fi
+
+follow=$tdir/follow
+moved=$tdir/follow.moved
+out=$tdir/out
+
+#
+# First, verify that following works in its most basic sense.
+#
+echo -e "a\nb\nc" > $follow
+$PROG -f $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+echo -e "d\ne\nf" >> $follow
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\n"`
+a=`cat $out`
+checktest "$a" "$o" 20
+rm $follow
+
+#
+# Now verify that following correctly follows the file being moved.
+#
+echo -e "a\nb\nc" > $follow
+$PROG -f $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+mv $follow $moved
+
+echo -e "d\ne\nf" >> $moved
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\n"`
+a=`cat $out`
+checktest "$a" "$o" 21
+rm $moved
+
+#
+# And now truncation with the new offset being less than the old offset.
+#
+echo -e "a\nb\nc" > $follow
+$PROG -f $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+echo -e "d\ne\nf" >> $follow
+sleep 1
+echo -e "g\nh\ni" > $follow
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\ng\nh\ni\n"`
+a=`cat $out`
+checktest "$a" "$o" 22
+rm $follow
+
+#
+# And truncation with the new offset being greater than the old offset.
+#
+echo -e "a\nb\nc" > $follow
+sleep 1
+$PROG -f $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+echo -e "d\ne\nf" >> $follow
+sleep 1
+echo -e "g\nh\ni\nj\nk\nl\nm\no\np\nq" > $follow
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\no\np\nq"`
+a=`cat $out`
+checktest "$a" "$o" 23
+rm $follow
+
+#
+# Verify that we can follow the moved file and correctly see a truncation.
+#
+echo -e "a\nb\nc" > $follow
+$PROG -f $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+mv $follow $moved
+
+echo -e "d\ne\nf" >> $moved
+sleep 1
+echo -e "g\nh\ni\nj\nk\nl\nm\no\np\nq" > $moved
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\no\np\nq"`
+a=`cat $out`
+checktest "$a" "$o" 24
+rm $moved
+
+#
+# Verify that capital-F follow properly deals with truncation
+#
+echo -e "a\nb\nc" > $follow
+$PROG -F $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+echo -e "d\ne\nf" >> $follow
+sleep 1
+echo -e "g\nh\ni" > $follow
+sleep 1
+kill $child
+sleep 1
+
+o=`echo -e "a\nb\nc\nd\ne\nf\ng\nh\ni\n"`
+a=`cat $out`
+checktest "$a" "$o" 25
+rm $follow
+
+#
+# Verify that capital-F follow _won't_ follow the moved file and will
+# correctly deal with recreation of the original file.
+#
+echo -e "a\nb\nc" > $follow
+$PROG -F $follow > $out 2> /dev/null &
+child=$!
+sleep 2
+mv $follow $moved
+
+echo -e "x\ny\nz" >> $moved
+echo -e "d\ne\nf" > $follow
+sleep 1
+kill $child
+sleep 1
 
+o=`echo -e "a\nb\nc\nd\ne\nf\n"`
+a=`cat $out`
+checktest "$a" "$o" 26
+rm $moved
 
-echo "Completed"
+echo "$CMD: completed"
 
-exit 0
+exit $errs
 
-# Template for additional test cases
-#o=`echo -e ""`
-#a=`echo -e "" | $PROG `
-#[[ "$a" != "$o" ]] && echo "Fail test  - $a"
diff --git a/usr/src/man/man3c/port_associate.3c b/usr/src/man/man3c/port_associate.3c
index d876b5c9d7..f6e66b0d65 100644
--- a/usr/src/man/man3c/port_associate.3c
+++ b/usr/src/man/man3c/port_associate.3c
@@ -73,21 +73,21 @@ the port.
 .LP
 Objects of type \fBPORT_SOURCE_FILE\fR are pointer to the structure
 \fBfile_obj\fR defined in \fB<sys/port.h>\fR. This event source provides event
-notification when the specified file/directory is accessed or modified or when
-its status changes. The path name of the file/directory to be watched is passed
-in the \fBstruct file_obj\fR along with the \fBaccess\fR, \fBmodification\fR,
-and \fBchange\fR time stamps acquired from a \fBstat\fR(2) call. If the file
-name is a symbolic links, it is followed by default. The \fBFILE_NOFOLLOW\fR
-needs to be passed in along with the specified events if the symbolic link
-itself needs to be watched and \fBlstat()\fR needs to be used to get the file
-status of the symbolic link file.
+notification when the specified file/directory is accessed, modified,
+truncated or when its status changes. The path name of the file/directory to
+be watched is passed in the \fBstruct file_obj\fR along with the \fBaccess\fR,
+\fBmodification\fR, and \fBchange\fR time stamps acquired from a \fBstat\fR(2)
+call. If the file name is a symbolic link, it is followed by default. The
+\fBFILE_NOFOLLOW\fR needs to be passed in along with the specified events if
+the symbolic link itself needs to be watched and \fBlstat()\fR needs to be
+used to get the file status of the symbolic link file.
 .sp
 .LP
 The \fBstruct file_obj\fR contains the following elements:
 .sp
 .in +2
 .nf
-timestruc_t     fo_atime;  /* Access time got from stat() */
+timestruc_t     fo_atime;  /* Access time from stat() */
 timestruc_t     fo_mtime;  /* Modification time from stat() */
 timestruc_t     fo_ctime;  /* Change time from stat() */
 char            *fo_name;  /* Pointer to a null terminated path name */
@@ -104,11 +104,13 @@ occurs.
 .sp
 .LP
 The event types that can be specified at \fBport_associate()\fR time for
-\fBPORT_SOURCE_FILE\fR are \fBFILE_ACCESS\fR, \fBFILE_MODIFIED\fR, and
-\fBFILE_ATTRIB\fR, corresponding to the three time stamps. An \fBfo_atime\fR
-change results in the \fBFILE_ACCESS\fR event, an \fBfo_mtime\fR change results
-in the \fBFILE_MODIFIED\fR event, and an \fBfo_time\fR change results in the
-\fBFILE_ATTRIB\fR event.
+\fBPORT_SOURCE_FILE\fR are \fBFILE_ACCESS\fR, \fBFILE_MODIFIED\fR,
+\fBFILE_ATTRIB\fR, and \fbFILE_TRUNC\fR. The first three of these correspond
+to the three time stamps: an \fBfo_atime\fR change results in the
+\fBFILE_ACCESS\fR event, an \fBfo_mtime\fR change results in the
+\fBFILE_MODIFIED\fR event, and an \fBfo_ctime\fR change results in the
+\fBFILE_ATTRIB\fR event. If the operation that induced the time stamp update
+also truncated the file, \fBFILE_TRUNC\fR will be set in the resulting event.
 .sp
 .LP
 The following exception events are delivered when they occur. These event types
diff --git a/usr/src/uts/common/fs/nfs/nfs3_vnops.c b/usr/src/uts/common/fs/nfs/nfs3_vnops.c
index d31b53d2e9..4e5882ad7c 100644
--- a/usr/src/uts/common/fs/nfs/nfs3_vnops.c
+++ b/usr/src/uts/common/fs/nfs/nfs3_vnops.c
@@ -28,6 +28,10 @@
  *	All rights reserved.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/param.h>
 #include <sys/types.h>
 #include <sys/systm.h>
@@ -2298,6 +2302,12 @@ top:
 						vattr.va_mask = AT_SIZE;
 						error = nfs3setattr(vp,
 						    &vattr, 0, cr);
+
+						/*
+						 * Existing file was truncated;
+						 * emit a create event.
+						 */
+						vnevent_create(vp, ct);
 					}
 				}
 			}
@@ -2306,12 +2316,9 @@ top:
 		if (error) {
 			VN_RELE(vp);
 		} else {
-			/*
-			 * existing file got truncated, notify.
-			 */
-			vnevent_create(vp, ct);
 			*vpp = vp;
 		}
+
 		return (error);
 	}
 
diff --git a/usr/src/uts/common/fs/nfs/nfs4_vnops.c b/usr/src/uts/common/fs/nfs/nfs4_vnops.c
index 97521f8e3a..a5b6bbfdc1 100644
--- a/usr/src/uts/common/fs/nfs/nfs4_vnops.c
+++ b/usr/src/uts/common/fs/nfs/nfs4_vnops.c
@@ -28,6 +28,10 @@
  *	All Rights Reserved
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/param.h>
 #include <sys/types.h>
 #include <sys/systm.h>
@@ -6651,16 +6655,20 @@ top:
 	} else {
 		vnode_t *tvp;
 		rnode4_t *trp;
-		/*
-		 * existing file got truncated, notify.
-		 */
 		tvp = vp;
 		if (vp->v_type == VREG) {
 			trp = VTOR4(vp);
 			if (IS_SHADOW(vp, trp))
 				tvp = RTOV4(trp);
 		}
-		vnevent_create(tvp, ct);
+
+		if (must_trunc) {
+			/*
+			 * existing file got truncated, notify.
+			 */
+			vnevent_create(tvp, ct);
+		}
+
 		*vpp = vp;
 	}
 	return (error);
diff --git a/usr/src/uts/common/fs/nfs/nfs_vnops.c b/usr/src/uts/common/fs/nfs/nfs_vnops.c
index a3f43a4e95..fa31e3693f 100644
--- a/usr/src/uts/common/fs/nfs/nfs_vnops.c
+++ b/usr/src/uts/common/fs/nfs/nfs_vnops.c
@@ -25,6 +25,10 @@
  *	All rights reserved.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/param.h>
 #include <sys/types.h>
 #include <sys/systm.h>
@@ -2030,6 +2034,14 @@ nfs_create(vnode_t *dvp, char *nm, struct vattr *va, enum vcexcl exclusive,
 				    vp->v_type == VREG) {
 					vattr.va_mask = AT_SIZE;
 					error = nfssetattr(vp, &vattr, 0, cr);
+
+					if (!error) {
+						/*
+						 * Existing file was truncated;
+						 * emit a create event.
+						 */
+						vnevent_create(vp, ct);
+					}
 				}
 			}
 		}
@@ -2037,10 +2049,6 @@ nfs_create(vnode_t *dvp, char *nm, struct vattr *va, enum vcexcl exclusive,
 		if (error) {
 			VN_RELE(vp);
 		} else {
-			/*
-			 * existing file got truncated, notify.
-			 */
-			vnevent_create(vp, ct);
 			*vpp = vp;
 		}
 		return (error);
diff --git a/usr/src/uts/common/fs/portfs/port_fop.c b/usr/src/uts/common/fs/portfs/port_fop.c
index 2852a98f52..48792394a5 100644
--- a/usr/src/uts/common/fs/portfs/port_fop.c
+++ b/usr/src/uts/common/fs/portfs/port_fop.c
@@ -23,6 +23,9 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
 
 /*
  * File Events Notification
@@ -1965,7 +1968,9 @@ port_fop(vnode_t *vp, int op, int retval)
 	if (op & FOP_ATTRIB_MASK) {
 		event  |= FILE_ATTRIB;
 	}
-
+	if (op & FOP_TRUNC_MASK) {
+		event  |= FILE_TRUNC;
+	}
 	if (event) {
 		port_fop_sendevent(vp, 	event, NULL, NULL);
 	}
@@ -2147,6 +2152,9 @@ port_fop_setattr(femarg_t *vf, vattr_t *vap, int flags, cred_t *cr,
 	int		events = 0;
 
 	retval = vnext_setattr(vf, vap, flags, cr, ct);
+	if (vap->va_mask & AT_SIZE) {
+		events |= FOP_FILE_TRUNC;
+	}
 	if (vap->va_mask & (AT_SIZE|AT_MTIME)) {
 		events |= FOP_FILE_SETATTR_MTIME;
 	}
@@ -2322,8 +2330,8 @@ port_fop_vnevent(femarg_t *vf, vnevent_t vnevent, vnode_t *dvp, char *name,
 			port_fop_sendevent(vp, FILE_DELETE, dvp, name);
 		break;
 	case	VE_CREATE:
-			port_fop_sendevent(vp, FILE_MODIFIED|FILE_ATTRIB,
-			    NULL, NULL);
+			port_fop_sendevent(vp,
+			    FILE_MODIFIED|FILE_ATTRIB|FILE_TRUNC, NULL, NULL);
 		break;
 	case	VE_LINK:
 			port_fop_sendevent(vp, FILE_ATTRIB, NULL, NULL);
diff --git a/usr/src/uts/common/fs/tmpfs/tmp_vnops.c b/usr/src/uts/common/fs/tmpfs/tmp_vnops.c
index 61d72a4015..461016aa52 100644
--- a/usr/src/uts/common/fs/tmpfs/tmp_vnops.c
+++ b/usr/src/uts/common/fs/tmpfs/tmp_vnops.c
@@ -24,6 +24,10 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/t_lock.h>
@@ -978,6 +982,8 @@ again:
 	}
 
 	if (error == 0) {	/* name found */
+		boolean_t trunc = B_FALSE;
+
 		ASSERT(oldtp);
 
 		rw_enter(&oldtp->tn_rwlock, RW_WRITER);
@@ -1005,6 +1011,7 @@ again:
 			rw_enter(&oldtp->tn_contents, RW_WRITER);
 			(void) tmpnode_trunc(tm, oldtp, 0);
 			rw_exit(&oldtp->tn_contents);
+			trunc = B_TRUE;
 		}
 		rw_exit(&oldtp->tn_rwlock);
 		if (IS_DEVVP(*vpp)) {
@@ -1019,9 +1026,9 @@ again:
 			*vpp = newvp;
 		}
 
-		if (error == 0) {
+		if (trunc)
 			vnevent_create(*vpp, ct);
-		}
+
 		return (0);
 	}
 
diff --git a/usr/src/uts/common/sys/port.h b/usr/src/uts/common/sys/port.h
index ccb0308255..d4d74d55ea 100644
--- a/usr/src/uts/common/sys/port.h
+++ b/usr/src/uts/common/sys/port.h
@@ -24,11 +24,13 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #ifndef	_SYS_PORT_H
 #define	_SYS_PORT_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #ifdef	__cplusplus
 extern "C" {
 #endif
@@ -106,6 +108,7 @@ typedef	struct	port_notify32 {
 #define	FILE_ACCESS		0x00000001
 #define	FILE_MODIFIED		0x00000002
 #define	FILE_ATTRIB		0x00000004
+#define	FILE_TRUNC		0x00100000
 #define	FILE_NOFOLLOW		0x10000000
 
 /*
diff --git a/usr/src/uts/common/sys/port_impl.h b/usr/src/uts/common/sys/port_impl.h
index 9f3f291874..504fb9ece1 100644
--- a/usr/src/uts/common/sys/port_impl.h
+++ b/usr/src/uts/common/sys/port_impl.h
@@ -24,6 +24,10 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
 #ifndef	_SYS_PORT_IMPL_H
 #define	_SYS_PORT_IMPL_H
 
@@ -311,6 +315,7 @@ typedef struct portfop_vp {
 #define	FOP_FILE_SETATTR_MTIME	0x00080000
 #define	FOP_FILE_SETATTR_CTIME	0x00100000
 #define	FOP_FILE_LINK_SRC	0x00200000
+#define	FOP_FILE_TRUNC		0x00400000
 
 /*
  * File modification event.
@@ -339,10 +344,15 @@ typedef struct portfop_vp {
 
 
 /*
+ * File trunc event
+ */
+#define	FOP_TRUNC_MASK		(FOP_FILE_TRUNC|FOP_FILE_CREATE)
+
+/*
  * valid watchable events
  */
 #define	FILE_EVENTS_MASK	(FILE_ACCESS|FILE_MODIFIED|FILE_ATTRIB \
-				|FILE_NOFOLLOW)
+				|FILE_NOFOLLOW|FILE_TRUNC)
 /* --- End file events --- */
 
 /*