install: Remove the mmap(2) option.

We already removed it from cp(1) over a year ago but never followed up
here.  Do so now, for the same reasons: significant complexity for
little to no benefit.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D44809

usr.bin/xinstall/install.1

@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 10, 2024
+.Dd April 16, 2024
 .Dt INSTALL 1
 .Os
 .Sh NAME
@@ -325,7 +325,6 @@ The default was changed to copy in
 .Xr cp 1 ,
 .Xr mv 1 ,
 .Xr strip 1 ,
-.Xr mmap 2 ,
 .Xr getgrnam 3 ,
 .Xr getpwnam 3 ,
 .Xr chown 8

usr.bin/xinstall/xinstall.c

@@ -30,9 +30,6 @@
  * SUCH DAMAGE.
  */
 
-#include <sys/param.h>
-#include <sys/mman.h>
-#include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/wait.h>
@@ -159,7 +156,6 @@ static void	metadata_log(const char *, const char *, struct timespec *,
 		    const char *, const char *, off_t);
 static int	parseid(const char *, id_t *);
 static int	strip(const char *, int, const char *, char **);
-static int	trymmap(size_t);
 static void	usage(void);
 
 int
@@ -1093,54 +1089,30 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 	int to_fd, const char *to_name __unused, size_t to_len,
 	char **dresp)
 {
-	char *p, *q;
 	int rv;
-	int do_digest, done_compare;
+	int do_digest;
 	DIGEST_CTX ctx;
 
-	rv = 0;
 	if (from_len != to_len)
 		return 1;
 
 	do_digest = (digesttype != DIGEST_NONE && dresp != NULL &&
 	    *dresp == NULL);
 	if (from_len <= MAX_CMP_SIZE) {
-		if (do_digest)
-			digest_init(&ctx);
-		done_compare = 0;
-		if (trymmap(from_len) && trymmap(to_len)) {
-			p = mmap(NULL, from_len, PROT_READ, MAP_SHARED,
-			    from_fd, (off_t)0);
-			if (p == MAP_FAILED)
-				goto out;
-			q = mmap(NULL, from_len, PROT_READ, MAP_SHARED,
-			    to_fd, (off_t)0);
-			if (q == MAP_FAILED) {
-				munmap(p, from_len);
-				goto out;
-			}
-
-			rv = memcmp(p, q, from_len);
-			if (do_digest)
-				digest_update(&ctx, p, from_len);
-			munmap(p, from_len);
-			munmap(q, from_len);
-			done_compare = 1;
-		}
-	out:
-		if (!done_compare) {
 		static char *buf, *buf1, *buf2;
 		static size_t bufsize;
 		int n1, n2;
 
+		if (do_digest)
+			digest_init(&ctx);
+
 		if (buf == NULL) {
 			/*
 			 * Note that buf and bufsize are static. If
 			 * malloc() fails, it will fail at the start
 			 * and not copy only some files.
 			 */
-				if (sysconf(_SC_PHYS_PAGES) >
-				    PHYSPAGES_THRESHOLD)
+			if (sysconf(_SC_PHYS_PAGES) > PHYSPAGES_THRESHOLD)
 				bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
 			else
 				bufsize = BUFSIZE_SMALL;
@@ -1170,9 +1142,9 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 		}
 		lseek(from_fd, 0, SEEK_SET);
 		lseek(to_fd, 0, SEEK_SET);
-		}
-	} else
+	} else {
 		rv = 1;	/* don't bother in this case */
+	}
 
 	if (do_digest) {
 		if (rv == 0)
@@ -1219,8 +1191,6 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 #ifndef BOOTSTRAP_XINSTALL
 	ssize_t ret;
 #endif
-	char *p;
-	int done_copy;
 	DIGEST_CTX ctx;
 
 	/* Rewind file descriptors. */
@@ -1246,40 +1216,16 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 		}
 		/* Fall back */
 	}
-
 #endif
 	digest_init(&ctx);
 
-	done_copy = 0;
-	if (trymmap((size_t)size) &&
-	    (p = mmap(NULL, (size_t)size, PROT_READ, MAP_SHARED,
-		    from_fd, (off_t)0)) != MAP_FAILED) {
-		nw = write(to_fd, p, size);
-		if (nw != size) {
-			serrno = errno;
-			(void)unlink(to_name);
-			if (nw >= 0) {
-				errx(EX_OSERR,
-     "short write to %s: %jd bytes written, %jd bytes asked to write",
-				    to_name, (uintmax_t)nw, (uintmax_t)size);
-			} else {
-				errno = serrno;
-				err(EX_OSERR, "%s", to_name);
-			}
-		}
-		digest_update(&ctx, p, size);
-		(void)munmap(p, size);
-		done_copy = 1;
-	}
-	if (!done_copy) {
 	if (buf == NULL) {
 		/*
 		 * Note that buf and bufsize are static. If
 		 * malloc() fails, it will fail at the start
 		 * and not copy only some files.
 		 */
-			if (sysconf(_SC_PHYS_PAGES) >
-			    PHYSPAGES_THRESHOLD)
+		if (sysconf(_SC_PHYS_PAGES) > PHYSPAGES_THRESHOLD)
 			bufsize = MIN(BUFSIZE_MAX, MAXPHYS * 8);
 		else
 			bufsize = BUFSIZE_SMALL;
@@ -1293,7 +1239,8 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 			(void)unlink(to_name);
 			if (nw >= 0) {
 				errx(EX_OSERR,
-     "short write to %s: %jd bytes written, %jd bytes asked to write",
+				    "short write to %s: %jd bytes written, "
+				    "%jd bytes asked to write",
 				    to_name, (uintmax_t)nw,
 				    (uintmax_t)size);
 			} else {
@@ -1309,7 +1256,6 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 		errno = serrno;
 		err(EX_OSERR, "%s", from_name);
 	}
-	}
 done:
 	if (safecopy && fsync(to_fd) == -1) {
 		serrno = errno;
@@ -1543,29 +1489,3 @@ usage(void)
 	exit(EX_USAGE);
 	/* NOTREACHED */
 }
-
-/*
- * trymmap --
- *	return true (1) if mmap should be tried, false (0) if not.
- */
-static int
-trymmap(size_t filesize)
-{
-	/*
-	 * This function existed to skip mmap() for NFS file systems whereas
-	 * nowadays mmap() should be perfectly safe. Nevertheless, using mmap()
-	 * only reduces the number of system calls if we need multiple read()
-	 * syscalls, i.e. if the file size is > MAXBSIZE. However, mmap() is
-	 * more expensive than read() so set the threshold at 4 fewer syscalls.
-	 * Additionally, for larger file size mmap() can significantly increase
-	 * the number of page faults, so avoid it in that case.
-	 *
-	 * Note: the 8MB limit is not based on any meaningful benchmarking
-	 * results, it is simply reusing the same value that was used before
-	 * and also matches bin/cp.
-	 *
-	 * XXX: Maybe we shouldn't bother with mmap() at all, since we use
-	 * MAXBSIZE the syscall overhead of read() shouldn't be too high?
-	 */
-	return (filesize > 4 * MAXBSIZE && filesize < 8 * 1024 * 1024);
-}