Increase Linux pipe buffer on zfs recv size to the maximum system size

Closes openzfs#1161

Signed-off-by: Richard Yao <[email protected]>

lib/libzfs/libzfs_sendrecv.c

@@ -43,6 +43,7 @@
 #include <sys/mnttab.h>
 #include <sys/avl.h>
 #include <sys/debug.h>
+#include <sys/stat.h>
 #include <stddef.h>
 #include <pthread.h>
 #include <umem.h>
@@ -3293,11 +3294,33 @@ int
 zfs_receive(libzfs_handle_t *hdl, const char *tosnap, recvflags_t *flags,
     int infd, avl_tree_t *stream_avl)
 {
+	struct stat sb;
 	char *top_zfs = NULL;
 	int err;
 	int cleanup_fd;
 	uint64_t action_handle = 0;
 
+	if (fstat(infd, &sb) == -1) {
+		perror("fstat");
+		return (-2);
+	}
+
+	/*
+	 * It is not uncommon for gigabytes to be processed in zfs receive.
+	 * Speculatively increase the buffer size via Linux-specific fcntl()
+	 * call.
+	 */
+	if (S_ISFIFO(sb.st_mode)) {
+		FILE *procf = fopen("/proc/sys/fs/pipe-max-size", "r");
+
+		if (procf != NULL) {
+			unsigned long pipe_max_size;
+			fscanf(procf, "%lu", &pipe_max_size);
+			(void) fcntl(infd, F_SETPIPE_SZ, pipe_max_size);
+			fclose(procf);
+		}
+	}
+
 	cleanup_fd = open(ZFS_DEV, O_RDWR);
 	VERIFY(cleanup_fd >= 0);