# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1679180266 -3600
# Node ID 0a8544715240165b367325f6f1504b7ec30d4c9c
# Parent  79622a75409c887a03413de9d74c9dd79d785f0f
Fixed unwanted mapped region growth due to adjustment of region boundaries.
As the region size would be effectively rounded up from the current size every
time a region was remapped, repeated remapping would cause steadily larger
regions to be mapped. This appeared to cause a failure to map regions in
testing, although it might not be the actual cause of such failures.

diff -r 79622a75409c -r 0a8544715240 libfsclient/Control
--- a/libfsclient/Control	Sat Mar 18 00:52:53 2023 +0100
+++ b/libfsclient/Control	Sat Mar 18 23:57:46 2023 +0100
@@ -1,3 +1,3 @@
-requires: libstdc++ libc libipc
+requires: libstdc++ libc libipc libmem
 provides: libfsclient
 maintainer: paul@boddie.org.uk
diff -r 79622a75409c -r 0a8544715240 libfsclient/lib/src/Makefile
--- a/libfsclient/lib/src/Makefile	Sat Mar 18 00:52:53 2023 +0100
+++ b/libfsclient/lib/src/Makefile	Sat Mar 18 23:57:46 2023 +0100
@@ -31,7 +31,7 @@
 				$(CLIENT_INTERFACES_SRC_CC) \
 				$(PLAIN_SRC_CC)
 
-REQUIRES_LIBS	= l4re_c-util libipc libstdc++ libsystypes
+REQUIRES_LIBS	= l4re_c-util libipc libstdc++ libsystypes libmem
 
 PRIVATE_INCDIR	= $(PKGDIR)/include/fsclient $(IDL_BUILD_DIR) $(IDL_EXPORT_DIR)
 CONTRIB_INCDIR	= libfsclient
diff -r 79622a75409c -r 0a8544715240 libfsclient/lib/src/client.cc
--- a/libfsclient/lib/src/client.cc	Sat Mar 18 00:52:53 2023 +0100
+++ b/libfsclient/lib/src/client.cc	Sat Mar 18 23:57:46 2023 +0100
@@ -26,6 +26,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <mem/memory_utils.h>
 #include <systypes/env.h>
 #include <systypes/fcntl.h>
 
@@ -79,11 +80,24 @@
 
   if (file->object_flags & OBJECT_SUPPORTS_MMAP)
   {
+    offset_t adjusted_position = position;
+
     /* Where the position is outside the current region, re-map. */
 
     if ((position < file->start_pos) || (position >= file->end_pos))
     {
-      if (file_mmap(file, position, file_span(file), 0, 0,
+      offset_t length = file_span(file);
+
+      if (!length)
+        length = PAGE_SIZE;
+
+      /* Avoid growth of the mapped region when the end of the region is
+         calculated to be position + span, which is then rounded up, whereas the
+         start of the region is rounded down. */
+
+      adjusted_position = trunc(position, PAGE_SIZE);
+
+      if (file_mmap(file, adjusted_position, length, 0, 0,
                     file_region_flags(file->flags)))
         return -L4_EIO;
     }