fspacectl(2): Changes on rmsr.r_offset's minimum value returned

rmsr.r_offset now is set to rqsr.r_offset plus the number of bytes
zeroed before hitting the end-of-file. After this change rmsr.r_offset
no longer contains the EOF when the requested operation range is
completely beyond the end-of-file. Instead in such case rmsr.r_offset is
equal to rqsr.r_offset.  Callers can obtain the number of bytes zeroed
by subtracting rqsr.r_offset from rmsr.r_offset.

Sponsored by:	The FreeBSD Foundation
Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D31677

5 files changed, 11 insertions, 20 deletions

diff --git a/lib/libc/sys/fspacectl.2 b/lib/libc/sys/fspacectl.2
index 0e369785b883..430f3de950df 100644
--- a/lib/libc/sys/fspacectl.2
+++ b/lib/libc/sys/fspacectl.2
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 18, 2021
+.Dd August 25, 2021
 .Dt FSPACECTL 2
 .Os
 .Sh NAME
@@ -73,10 +73,9 @@ operation range,
 .Fa "rmsr->r_len"
 is updated to be the value 0, and
 .Fa "rmsr->r_offset"
-is updated to be the smallest of
-.Fa "rqsr->r_offset" +
-.Fa "rqsr->r_len" ;
-and the end-of-file offset.
+is updated to be
+.Fa "rqsr->r_offset"
+plus the number of bytes zeroed before the end-of-file.
 The file descriptor's file offset is not used or modified by the system call.
 Both
 .Fa rqsr
diff --git a/share/man/man9/VOP_DEALLOCATE.9 b/share/man/man9/VOP_DEALLOCATE.9
index 2ec915c6fef3..d20fe1590314 100644
--- a/share/man/man9/VOP_DEALLOCATE.9
+++ b/share/man/man9/VOP_DEALLOCATE.9
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 11, 2021
+.Dd August 25, 2021
 .Dt VOP_DEALLOCATE 9
 .Os
 .Sh NAME
@@ -74,14 +74,11 @@ and
 are updated to reflect the portion of the range that
 still needs to be zeroed/deallocated on return.
 Partial result is considered a successful operation.
-For a successful completion without an unprocessed portion of the range,
+For a non-partial successful completion,
 .Fa *len
 is updated to be the value 0, and
 .Fa *offset
-is updated to be the smallest of
-.Fa *offset +
-.Fa *len
-passed to the call and the end-of-file offset.
+is incremented by the number of bytes zeroed before the end-of-file.
 .Sh LOCKS
 The vnode should be locked on entry and will still be locked on exit.
 .Sh RETURN VALUES
diff --git a/share/man/man9/vn_deallocate.9 b/share/man/man9/vn_deallocate.9
index 08f4e92ec597..ce1515ddaaa1 100644
--- a/share/man/man9/vn_deallocate.9
+++ b/share/man/man9/vn_deallocate.9
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 11, 2021
+.Dd August 25, 2021
 .Dt VN_DEALLOCATE 9
 .Os
 .Sh NAME
@@ -99,10 +99,7 @@ For a successful completion,
 .Fa *length
 is updated to be the value 0, and
 .Fa *offset
-is updated to be the smallest of
-.Fa *offset +
-.Fa *length
-passed to the call and the end-of-file offset.
+is incremented by the number of bytes zeroed before the end-of-file.
 .Sh RETURN VALUES
 Upon successful completion, the value 0 is returned; otherwise the
 appropriate error is returned.
diff --git a/sys/kern/uipc_shm.c b/sys/kern/uipc_shm.c
index c632c7f150df..c672c0477b95 100644
--- a/sys/kern/uipc_shm.c
+++ b/sys/kern/uipc_shm.c
@@ -1917,7 +1917,6 @@ shm_deallocate(struct shmfd *shmfd, off_t *offset, off_t *length, int flags)
 
 	/* Handle the case when offset is on or beyond shm size. */
 	if ((off_t)len <= 0) {
-		*offset = shmfd->shm_size;
 		*length = 0;
 		return (0);
 	}
diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index d5df9cd8bf7b..9fd43004b8fd 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -1156,6 +1156,7 @@ vop_stddeallocate(struct vop_deallocate_args *ap)
 			/*
 			 * No more data region to be filled
 			 */
+			offset += len;
 			len = 0;
 			error = 0;
 			break;
@@ -1185,10 +1186,8 @@ vop_stddeallocate(struct vop_deallocate_args *ap)
 			break;
 	}
 	/* Handle the case when offset is beyond EOF */
-	if (len < 0) {
-		offset += len;
+	if (len < 0)
 		len = 0;
-	}
 out:
 	*ap->a_offset = offset;
 	*ap->a_len = len;