VOP_COPY_FILE_RANGE: Add a COPY_FILE_RANGE_TIMEO1SEC flag

Although it is not specified in the RFCs, the concept that
the NFSv4 server should reply to an RPC request within a
reasonable time is accepted practice within the NFSv4 community.

Without this patch, the NFSv4.2 server attempts to reply to
a Copy operation within 1second by limiting the copy to
vfs.nfs.maxcopyrange bytes (default 10Mbytes). This is crude at
best, given the large variation in I/O subsystem performance.

This patch adds a kernel only flag COPY_FILE_RANGE_TIMEO1SEC
that the NFSv4.2 can specify, which tells VOP_COPY_FILE_RANGE()
to return after approximately 1 second with a partial result and
implements this in vn_generic_copy_file_range(), used by
vop_stdcopyfilerange().

Modifying the NFSv4.2 server to set this flag will be done in
a separate patch.  Also under consideration is exposing the
COPY_FILE_RANGE_TIMEO1SEC to userland for use on the FreeBSD
copy_file_range(2) syscall.

MFC after:	2 weeks
Reviewed by:	khng
Differential Revision:	https://reviews.freebsd.org/D31829

1 files changed, 29 insertions, 2 deletions

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index bf1270dc8ad8..93d5a9e6b127 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -3162,6 +3162,7 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
 	size_t copylen, len, rem, savlen;
 	char *dat;
 	long holein, holeout;
+	struct timespec curts, endts;
 
 	holein = holeout = 0;
 	savlen = len = *lenp;
@@ -3258,7 +3259,15 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
 	 * in the inner loop where the data copying is done.
 	 * Note that some file systems such as NFSv3, NFSv4.0 and NFSv4.1 may
 	 * support holes on the server, but do not support FIOSEEKHOLE.
+	 * The kernel flag COPY_FILE_RANGE_TIMEO1SEC is used to indicate
+	 * that this function should return after 1second with a partial
+	 * completion.
 	 */
+	if ((flags & COPY_FILE_RANGE_TIMEO1SEC) != 0) {
+		getnanouptime(&endts);
+		endts.tv_sec++;
+	} else
+		timespecclear(&endts);
 	holetoeof = eof = false;
 	while (len > 0 && error == 0 && !eof && interrupted == 0) {
 		endoff = 0;			/* To shut up compilers. */
@@ -3327,8 +3336,17 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
 					*inoffp += xfer;
 					*outoffp += xfer;
 					len -= xfer;
-					if (len < savlen)
+					if (len < savlen) {
 						interrupted = sig_intr();
+						if (timespecisset(&endts) &&
+						    interrupted == 0) {
+							getnanouptime(&curts);
+							if (timespeccmp(&curts,
+							    &endts, >=))
+								interrupted =
+								    EINTR;
+						}
+					}
 				}
 			}
 			copylen = MIN(len, endoff - startoff);
@@ -3391,8 +3409,17 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
 					*outoffp += xfer;
 					copylen -= xfer;
 					len -= xfer;
-					if (len < savlen)
+					if (len < savlen) {
 						interrupted = sig_intr();
+						if (timespecisset(&endts) &&
+						    interrupted == 0) {
+							getnanouptime(&curts);
+							if (timespeccmp(&curts,
+							    &endts, >=))
+								interrupted =
+								    EINTR;
+						}
+					}
 				}
 			}
 			xfer = blksize;