* libio/fileops.c (_IO_file_sync_mmap): New function.

	(_IO_file_jumps_mmap): Use it.
	(_IO_file_underflow_mmap): Rewritten.  If after EOF or fflush,
	repeat the stat check and resize the mapped buffer as necessary.

2002-07-31  Roland McGrath  <roland@frob.com>

	* libio/fileops.c (decide_maybe_mmap): New static function.
	Code taken from libio/iofopen.c:__fopen_maybe_mmap to try to
	mmap the file contents.  Then switch the jump tables to the mmap
	tables if it worked, or the vanilla file tables if not.
	(_IO_file_underflow_maybe_mmap): New function.
	(_IO_file_seekoff_maybe_mmap): New function.
	(_IO_file_xsgetn_maybe_mmap): New function.
	(_IO_file_jumps_maybe_mmap): New variable, jump table using those.
	* libio/libioP.h: Declare those.
	* libio/wfileops.c (_IO_wfile_underflow_maybe_mmap): New function.
	(_IO_wfile_jumps_maybe_mmap): New variable, jump table using that.
	* libio/iofopen.c (__fopen_maybe_mmap): Don't try to mmap here.
	If the stream is read-only, set its jump tables to those new ones.
	* libio/iofdopen.c (_IO_new_fdopen) [_G_HAVE_MMAP]: Set the initial
	jump tables to the maybe_mmap ones, and don't call __fopen_maybe_mmap.
	We need the tables set before _IO_file_attach.

	* libio/tst-mmap-eofsync.c: New file.
	* libio/tst-mmap-fflushsync.c: New file.
	* libio/bug-mmap-fflush.c: New file.
	* libio/tst-mmap2-eofsync.c: New file.
	* libio/Makefile (tests): Add them.

	* libio/wfileops.c (_IO_wfile_underflow_mmap): Don't set EOF bit when
	_IO_file_underflow_mmap fails, it already set the appropriate bit.

7 files changed, 689 insertions, 32 deletions

diff --git a/libio/Makefile b/libio/Makefile
index f5e69e3..28d8519 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -51,7 +51,9 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc   \
 	tst_wprintf2 tst-widetext test-fmemopen tst-ext tst-fopenloc	      \
 	tst-fgetws tst-ungetwc1 tst-ungetwc2 tst-swscanf tst-sscanf	      \
 	tst-mmap-setvbuf bug-ungetwc1 bug-ungetwc2 tst-atime tst-eof          \
-	tst-freopen bug-rewind bug-ungetc bug-fseek
+	tst-freopen bug-rewind bug-ungetc bug-fseek \
+	tst-mmap-eofsync tst-mmap-fflushsync bug-mmap-fflush \
+	tst-mmap2-eofsync
 test-srcs = test-freopen
 
 all: # Make this the default target; it will be defined in Rules.
diff --git a/libio/bug-mmap-fflush.c b/libio/bug-mmap-fflush.c
new file mode 100644
index 0000000..984acb4
--- /dev/null
+++ b/libio/bug-mmap-fflush.c
@@ -0,0 +1,27 @@
+/* Test for bug in fflush synchronization behavior.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main (void)
+{
+  FILE *f;
+  off_t o;
+  char buffer [1024];
+
+  system ("echo 'From foo@bar.com' > test");
+  f = fopen ("test", "r");
+  fseek (f, 0, SEEK_END);
+  o = ftello (f);
+  fseek (f, 0, SEEK_SET);
+  fflush (f);
+  system ("echo 'From bar@baz.edu' >> test");
+  fseek (f, o, SEEK_SET);
+  if (fgets (buffer, 1024, f) == NULL)
+    abort ();
+  if (strncmp (buffer, "From ", 5) != 0)
+    abort ();
+  fclose (f);
+  exit (0);
+}
diff --git a/libio/fileops.c b/libio/fileops.c
index 2941296..979825e 100644
--- a/libio/fileops.c
+++ b/libio/fileops.c
@@ -601,42 +601,207 @@ _IO_new_file_underflow (fp)
 }
 INTDEF2(_IO_new_file_underflow, _IO_file_underflow)
 
-/* Special callback replacing the underflow callbacks if we mmap the
-   file.  */
-int
-_IO_file_underflow_mmap (_IO_FILE *fp)
+/* Guts of underflow callback if we mmap the file.  This stats the file and
+   updates the stream state to match.  In the normal case we return zero.
+   If the file is no longer eligible for mmap, its jump tables are reset to
+   the vanilla ones and we return nonzero.  */
+static int
+mmap_remap_check (_IO_FILE *fp)
 {
-  if (fp->_IO_read_end < fp->_IO_buf_end)
+  struct _G_stat64 st;
+
+  if (_IO_SYSSTAT (fp, &st) == 0
+      && S_ISREG (st.st_mode) && st.st_size != 0
+      /* Limit the file size to 1MB for 32-bit machines.  */
+      && (sizeof (ptrdiff_t) > 4 || st.st_size < 1*1024*1024))
     {
-      /* A stupid requirement in POSIX says that the first read on a
-	 stream must update the atime.  Just read a single byte.  We
-	 don't have to worry about repositioning the file descriptor
-	 since the following seek defines its position anyway.  */
-      char ignore[1];
-      read (fp->_fileno, ignore, 1);
+      const size_t pagesize = __getpagesize ();
+# define ROUNDED(x)	(((x) + pagesize - 1) & ~(pagesize - 1))
+      if (ROUNDED (st.st_size) < ROUNDED (fp->_IO_buf_end
+					  - fp->_IO_buf_base))
+	{
+	  /* We can trim off some pages past the end of the file.  */
+	  (void) __munmap (fp->_IO_buf_base + ROUNDED (st.st_size),
+			   ROUNDED (fp->_IO_buf_end - fp->_IO_buf_base)
+			   - ROUNDED (st.st_size));
+	  fp->_IO_buf_end = fp->_IO_buf_base + st.st_size;
+	}
+      else if (ROUNDED (st.st_size) > ROUNDED (fp->_IO_buf_end
+					       - fp->_IO_buf_base))
+	{
+	  /* The file added some pages.  We need to remap it.  */
+	  void *p;
+#if defined __linux__		/* XXX */
+	  p = __mremap (fp->_IO_buf_base, ROUNDED (fp->_IO_buf_end
+						   - fp->_IO_buf_base),
+			ROUNDED (st.st_size), MREMAP_MAYMOVE);
+	  if (p == MAP_FAILED)
+	    {
+	      (void) __munmap (fp->_IO_buf_base,
+			       fp->_IO_buf_end - fp->_IO_buf_base);
+	      goto punt;
+	    }
+#else
+	  (void) __munmap (fp->_IO_buf_base,
+			   fp->_IO_buf_end - fp->_IO_buf_base);
+# ifdef _G_MMAP64
+	  p = _G_MMAP64 (NULL, st.st_size, PROT_READ, MAP_SHARED,
+			 fp->_fileno, 0);
+# else
+	  p = __mmap (NULL, st.st_size, PROT_READ, MAP_SHARED,
+		      fp->_fileno, 0);
+# endif
+	  if (p == MAP_FAILED)
+	    goto punt;
+#endif
+	  fp->_IO_buf_base = p;
+	  fp->_IO_buf_end = fp->_IO_buf_base + st.st_size;
+	}
+      else
+	{
+	  /* The number of pages didn't change.  */
+	  fp->_IO_buf_end = fp->_IO_buf_base + st.st_size;
+	}
+# undef ROUNDED
+
+      fp->_offset -= fp->_IO_read_end - fp->_IO_read_ptr;
+      _IO_setg (fp, fp->_IO_buf_base, fp->_IO_buf_base + fp->_offset,
+		fp->_IO_buf_end);
 
       if (
 # ifdef _G_LSEEK64
-	  _G_LSEEK64 (fp->_fileno, fp->_IO_buf_end - fp->_IO_buf_base,
-		      SEEK_SET)
+	  _G_LSEEK64
 # else
-	  __lseek (fp->_fileno, fp->_IO_buf_end - fp->_IO_buf_base, SEEK_SET)
+	  __lseek
 # endif
+	  (fp->_fileno, fp->_IO_buf_end - fp->_IO_buf_base, SEEK_SET)
 	  != fp->_IO_buf_end - fp->_IO_buf_base)
 	{
 	  fp->_flags |= _IO_ERR_SEEN;
 	  return EOF;
 	}
-
       fp->_offset = fp->_IO_buf_end - fp->_IO_buf_base;
-      fp->_IO_read_end = fp->_IO_buf_end;
-      return *(unsigned char *) fp->_IO_read_ptr;
+
+      return 0;
+    }
+  else
+    {
+      /* Life is no longer good for mmap.  Punt it.  */
+      (void) __munmap (fp->_IO_buf_base,
+		       fp->_IO_buf_end - fp->_IO_buf_base);
+    punt:
+      fp->_IO_buf_base = fp->_IO_buf_end = NULL;
+      _IO_setg (fp, NULL, NULL, NULL);
+      if (fp->_mode <= 0)
+	_IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_file_jumps;
+      else
+	_IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_wfile_jumps;
+      fp->_wide_data->_wide_vtable = &_IO_wfile_jumps;
+
+      return 1;
     }
+}
+
+/* Special callback replacing the underflow callbacks if we mmap the file.  */
+int
+_IO_file_underflow_mmap (_IO_FILE *fp)
+{
+  if (fp->_IO_read_ptr < fp->_IO_read_end)
+    return *(unsigned char *) fp->_IO_read_ptr;
+
+  if (__builtin_expect (mmap_remap_check (fp), 0))
+    /* We punted to the regular file functions.  */
+    return _IO_UNDERFLOW (fp);
+
+  if (fp->_IO_read_ptr < fp->_IO_read_end)
+    return *(unsigned char *) fp->_IO_read_ptr;
 
   fp->_flags |= _IO_EOF_SEEN;
   return EOF;
 }
 
+static void
+decide_maybe_mmap (_IO_FILE *fp)
+{
+  /* We use the file in read-only mode.  This could mean we can
+     mmap the file and use it without any copying.  But not all
+     file descriptors are for mmap-able objects and on 32-bit
+     machines we don't want to map files which are too large since
+     this would require too much virtual memory.  */
+  struct _G_stat64 st;
+
+  if (_IO_SYSSTAT (fp, &st) == 0
+      && S_ISREG (st.st_mode) && st.st_size != 0
+      /* Limit the file size to 1MB for 32-bit machines.  */
+      && (sizeof (ptrdiff_t) > 4 || st.st_size < 1*1024*1024)
+      /* Sanity check.  */
+      && (fp->_offset == _IO_pos_BAD || fp->_offset <= st.st_size))
+    {
+      /* Try to map the file.  */
+      void *p;
+
+# ifdef _G_MMAP64
+      p = _G_MMAP64 (NULL, st.st_size, PROT_READ, MAP_SHARED, fp->_fileno, 0);
+# else
+      p = __mmap (NULL, st.st_size, PROT_READ, MAP_SHARED, fp->_fileno, 0);
+# endif
+      if (p != MAP_FAILED)
+	{
+	  /* OK, we managed to map the file.  Set the buffer up and use a
+	     special jump table with simplified underflow functions which
+	     never tries to read anything from the file.  */
+
+	  if (
+# ifdef _G_LSEEK64
+	      _G_LSEEK64
+# else
+	      __lseek
+# endif
+	      (fp->_fileno, st.st_size, SEEK_SET) != st.st_size)
+	    {
+	      (void) __munmap (p, st.st_size);
+	      fp->_offset = _IO_pos_BAD;
+	    }
+	  else
+	    {
+	      INTUSE(_IO_setb) (fp, p, (char *) p + st.st_size, 0);
+
+	      if (fp->_offset == _IO_pos_BAD)
+		fp->_offset = 0;
+
+	      _IO_setg (fp, p, p + fp->_offset, p + st.st_size);
+	      fp->_offset = st.st_size;
+
+	      if (fp->_mode <= 0)
+		_IO_JUMPS ((struct _IO_FILE_plus *)fp) = &_IO_file_jumps_mmap;
+	      else
+		_IO_JUMPS ((struct _IO_FILE_plus *)fp) = &_IO_wfile_jumps_mmap;
+	      fp->_wide_data->_wide_vtable = &_IO_wfile_jumps_mmap;
+
+	      return;
+	    }
+	}
+    }
+
+  /* We couldn't use mmap, so revert to the vanilla file operations.  */
+
+  if (fp->_mode <= 0)
+    _IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_file_jumps;
+  else
+    _IO_JUMPS ((struct _IO_FILE_plus *) fp) = &_IO_wfile_jumps;
+  fp->_wide_data->_wide_vtable = &_IO_wfile_jumps;
+}
+
+int
+_IO_file_underflow_maybe_mmap (_IO_FILE *fp)
+{
+  /* This is the first read attempt.  Choose mmap or vanilla operations
+     and then punt to the chosen underflow routine.  */
+  decide_maybe_mmap (fp);
+  return _IO_UNDERFLOW (fp);
+}
+
+
 int
 _IO_new_file_overflow (f, ch)
       _IO_FILE *f;
@@ -726,6 +891,34 @@ _IO_new_file_sync (fp)
 }
 INTDEF2(_IO_new_file_sync, _IO_file_sync)
 
+static int
+_IO_file_sync_mmap (_IO_FILE *fp)
+{
+  if (fp->_IO_read_ptr != fp->_IO_read_end)
+    {
+#ifdef TODO
+      if (_IO_in_backup (fp))
+	delta -= eGptr () - Gbase ();
+#endif
+      if (
+# ifdef _G_LSEEK64
+	  _G_LSEEK64
+# else
+	  __lseek
+# endif
+	  (fp->_fileno, fp->_IO_read_ptr - fp->_IO_buf_base, SEEK_SET)
+	  != fp->_IO_read_ptr - fp->_IO_buf_base)
+	{
+	  fp->_flags |= _IO_ERR_SEEN;
+	  return EOF;
+	}
+    }
+  fp->_offset = fp->_IO_read_ptr - fp->_IO_buf_base;
+  fp->_IO_read_end = fp->_IO_read_ptr = fp->_IO_read_base;
+  return 0;
+}
+
+
 _IO_off64_t
 _IO_new_file_seekoff (fp, offset, dir, mode)
      _IO_FILE *fp;
@@ -968,6 +1161,25 @@ _IO_file_seekoff_mmap (fp, offset, dir, mode)
   return offset;
 }
 
+_IO_off64_t
+_IO_file_seekoff_maybe_mmap (fp, offset, dir, mode)
+     _IO_FILE *fp;
+     _IO_off64_t offset;
+     int dir;
+     int mode;
+{
+  /* We only get here when we haven't tried to read anything yet.
+     So there is nothing more useful for us to do here than just
+     the underlying lseek call.  */
+
+  _IO_off64_t result = _IO_SYSSEEK (fp, offset, dir);
+  if (result < 0)
+    return EOF;
+
+  fp->_offset = result;
+  return result;
+}
+
 _IO_ssize_t
 _IO_file_read (fp, buf, size)
      _IO_FILE *fp;
@@ -1009,9 +1221,8 @@ int
 _IO_file_close_mmap (fp)
      _IO_FILE *fp;
 {
-  /* In addition to closing the file descriptor we have to unmap the
-     file.  */
-  (void) munmap (fp->_IO_buf_base, fp->_IO_buf_end - fp->_IO_buf_base);
+  /* In addition to closing the file descriptor we have to unmap the file.  */
+  (void) __munmap (fp->_IO_buf_base, fp->_IO_buf_end - fp->_IO_buf_base);
   fp->_IO_buf_base = fp->_IO_buf_end = NULL;
   return close (fp->_fileno);
 }
@@ -1270,11 +1481,13 @@ _IO_file_xsgetn_mmap (fp, data, n)
 
       if (have < n)
 	{
-	  /* Maybe the read buffer is not yet fully set up.  */
-	  fp->_IO_read_ptr = fp->_IO_read_end;
-	  if (fp->_IO_read_end < fp->_IO_buf_end
-	      && _IO_file_underflow_mmap (fp) != EOF)
-	    have = fp->_IO_read_end - read_ptr;
+	  /* Check that we are mapping all of the file, in case it grew.  */
+	  if (__builtin_expect (mmap_remap_check (fp), 0))
+	    /* We punted mmap, so complete with the vanilla code.  */
+	    return s - (char *) data + _IO_XSGETN (fp, data, n);
+
+	  read_ptr = fp->_IO_read_ptr;
+	  have = fp->_IO_read_end - read_ptr;
 	}
     }
 
@@ -1296,6 +1509,21 @@ _IO_file_xsgetn_mmap (fp, data, n)
   return s - (char *) data;
 }
 
+static _IO_size_t _IO_file_xsgetn_maybe_mmap __P ((_IO_FILE *, void *,
+						   _IO_size_t));
+static _IO_size_t
+_IO_file_xsgetn_maybe_mmap (fp, data, n)
+     _IO_FILE *fp;
+     void *data;
+     _IO_size_t n;
+{
+  /* We only get here if this is the first attempt to read something.
+     Decide which operations to use and then punt to the chosen one.  */
+
+  decide_maybe_mmap (fp);
+  return _IO_XSGETN (fp, data, n);
+}
+
 struct _IO_jump_t _IO_file_jumps =
 {
   JUMP_INIT_DUMMY,
@@ -1334,7 +1562,7 @@ struct _IO_jump_t _IO_file_jumps_mmap =
   JUMP_INIT(seekoff, _IO_file_seekoff_mmap),
   JUMP_INIT(seekpos, _IO_default_seekpos),
   JUMP_INIT(setbuf, (_IO_setbuf_t) _IO_file_setbuf_mmap),
-  JUMP_INIT(sync, _IO_new_file_sync),
+  JUMP_INIT(sync, _IO_file_sync_mmap),
   JUMP_INIT(doallocate, INTUSE(_IO_file_doallocate)),
   JUMP_INIT(read, INTUSE(_IO_file_read)),
   JUMP_INIT(write, _IO_new_file_write),
@@ -1345,6 +1573,30 @@ struct _IO_jump_t _IO_file_jumps_mmap =
   JUMP_INIT(imbue, _IO_default_imbue)
 };
 
+struct _IO_jump_t _IO_file_jumps_maybe_mmap =
+{
+  JUMP_INIT_DUMMY,
+  JUMP_INIT(finish, INTUSE(_IO_file_finish)),
+  JUMP_INIT(overflow, INTUSE(_IO_file_overflow)),
+  JUMP_INIT(underflow, _IO_file_underflow_maybe_mmap),
+  JUMP_INIT(uflow, INTUSE(_IO_default_uflow)),
+  JUMP_INIT(pbackfail, INTUSE(_IO_default_pbackfail)),
+  JUMP_INIT(xsputn, _IO_new_file_xsputn),
+  JUMP_INIT(xsgetn, _IO_file_xsgetn_maybe_mmap),
+  JUMP_INIT(seekoff, _IO_file_seekoff_maybe_mmap),
+  JUMP_INIT(seekpos, _IO_default_seekpos),
+  JUMP_INIT(setbuf, (_IO_setbuf_t) _IO_file_setbuf_mmap),
+  JUMP_INIT(sync, _IO_new_file_sync),
+  JUMP_INIT(doallocate, INTUSE(_IO_file_doallocate)),
+  JUMP_INIT(read, INTUSE(_IO_file_read)),
+  JUMP_INIT(write, _IO_new_file_write),
+  JUMP_INIT(seek, INTUSE(_IO_file_seek)),
+  JUMP_INIT(close, _IO_file_close),
+  JUMP_INIT(stat, INTUSE(_IO_file_stat)),
+  JUMP_INIT(showmanyc, _IO_default_showmanyc),
+  JUMP_INIT(imbue, _IO_default_imbue)
+};
+
 #ifdef _LIBC
 versioned_symbol (libc, _IO_new_do_write, _IO_do_write, GLIBC_2_1);
 versioned_symbol (libc, _IO_new_file_attach, _IO_file_attach, GLIBC_2_1);
diff --git a/libio/tst-mmap-eofsync.c b/libio/tst-mmap-eofsync.c
new file mode 100644
index 0000000..909e868
--- /dev/null
+++ b/libio/tst-mmap-eofsync.c
@@ -0,0 +1,106 @@
+/* Test program for synchronization of stdio state with file after EOF.  */
+
+#include <stdio.h>
+#include <error.h>
+#include <errno.h>
+
+static void do_prepare (void);
+#define PREPARE(argc, argv) do_prepare ()
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static char *temp_file;
+static int temp_fd;
+
+static char text1[] = "Line the first\n";
+static char text2[] = "Line the second\n";
+
+static void
+do_prepare (void)
+{
+  temp_fd = create_temp_file ("tst-mmap-eofsync.", &temp_file);
+  if (temp_fd == -1)
+    error (1, errno, "cannot create temporary file");
+  else
+    {
+      ssize_t cc = write (temp_fd, text1, sizeof text1 - 1);
+      if (cc != sizeof text1 - 1)
+	error (1, errno, "cannot write to temporary file");
+    }
+}
+
+static int
+do_test (void)
+{
+  FILE *f;
+  char buf[128];
+  int result = 0;
+  int c;
+
+  f = fopen (temp_file, "r");
+  if (f == NULL)
+    {
+      perror (temp_file);
+      return 1;
+    }
+
+  if (fgets (buf, sizeof buf, f) == NULL)
+    {
+      perror ("fgets");
+      return 1;
+    }
+
+  if (strcmp (buf, text1))
+    {
+      printf ("read \"%s\", expected \"%s\"\n", buf, text1);
+      result = 1;
+    }
+
+  printf ("feof = %d, ferror = %d immediately after fgets\n",
+	  feof (f), ferror (f));
+
+#if 1
+  c = fgetc (f);
+  if (c == EOF)
+    printf ("fgetc -> EOF (feof = %d, ferror = %d)\n",
+	    feof (f), ferror (f));
+  else
+    {
+      printf ("fgetc returned %o (feof = %d, ferror = %d)\n",
+	      c, feof (f), ferror (f));
+      result = 1;
+    }
+#endif
+
+  c = write (temp_fd, text2, sizeof text2 - 1);
+  if (c == sizeof text2 - 1)
+    printf ("wrote more to file\n");
+  else
+    {
+      printf ("wrote %d != %d (%m)\n", c, sizeof text2 - 1);
+      result = 1;
+    }
+
+  if (fgets (buf, sizeof buf, f) == NULL)
+    {
+      printf ("second fgets fails: feof = %d, ferror = %d (%m)\n",
+	      feof (f), ferror (f));
+      clearerr (f);
+      if (fgets (buf, sizeof buf, f) == NULL)
+	{
+	  printf ("retry fgets fails: feof = %d, ferror = %d (%m)\n",
+		  feof (f), ferror (f));
+	  result = 1;
+	}
+    }
+  if (result == 0 && strcmp (buf, text2))
+    {
+      printf ("second time read \"%s\", expected \"%s\"\n", buf, text2);
+      result = 1;
+    }
+
+  fclose (f);
+
+  return result;
+}
diff --git a/libio/tst-mmap-fflushsync.c b/libio/tst-mmap-fflushsync.c
new file mode 100644
index 0000000..f4d688f
--- /dev/null
+++ b/libio/tst-mmap-fflushsync.c
@@ -0,0 +1,99 @@
+/* Test program for synchronization of stdio state with file after fflush.  */
+
+#include <stdio.h>
+#include <error.h>
+#include <errno.h>
+
+static void do_prepare (void);
+#define PREPARE(argc, argv) do_prepare ()
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static char *temp_file;
+static int temp_fd;
+
+static char text1[] = "Line the first\n";
+static char text2[] = "Line the second\n";
+
+static void
+do_prepare (void)
+{
+  temp_fd = create_temp_file ("tst-mmap-eofsync.", &temp_file);
+  if (temp_fd == -1)
+    error (1, errno, "cannot create temporary file");
+  else
+    {
+      ssize_t cc = write (temp_fd, text1, sizeof text1 - 1);
+      if (cc != sizeof text1 - 1)
+	error (1, errno, "cannot write to temporary file");
+    }
+}
+
+static int
+do_test (void)
+{
+  FILE *f;
+  char buf[128];
+  int result = 0;
+  int c;
+
+  f = fopen (temp_file, "r");
+  if (f == NULL)
+    {
+      perror (temp_file);
+      return 1;
+    }
+
+  if (fgets (buf, sizeof buf, f) == NULL)
+    {
+      perror ("fgets");
+      return 1;
+    }
+
+  if (strcmp (buf, text1))
+    {
+      printf ("read \"%s\", expected \"%s\"\n", buf, text1);
+      result = 1;
+    }
+
+  printf ("feof = %d, ferror = %d immediately after fgets\n",
+	  feof (f), ferror (f));
+
+  if (fflush (f) != 0)
+    {
+      printf ("fflush failed! %m\n");
+      result = 1;
+    }
+
+  c = write (temp_fd, text2, sizeof text2 - 1);
+  if (c == sizeof text2 - 1)
+    printf ("wrote more to file\n");
+  else
+    {
+      printf ("wrote %d != %d (%m)\n", c, sizeof text2 - 1);
+      result = 1;
+    }
+
+  if (fgets (buf, sizeof buf, f) == NULL)
+    {
+      printf ("second fgets fails: feof = %d, ferror = %d (%m)\n",
+	      feof (f), ferror (f));
+      clearerr (f);
+      if (fgets (buf, sizeof buf, f) == NULL)
+	{
+	  printf ("retry fgets fails: feof = %d, ferror = %d (%m)\n",
+		  feof (f), ferror (f));
+	  result = 1;
+	}
+    }
+  if (result == 0 && strcmp (buf, text2))
+    {
+      printf ("second time read \"%s\", expected \"%s\"\n", buf, text2);
+      result = 1;
+    }
+
+  fclose (f);
+
+  return result;
+}
diff --git a/libio/tst-mmap2-eofsync.c b/libio/tst-mmap2-eofsync.c
new file mode 100644
index 0000000..4275d4a
--- /dev/null
+++ b/libio/tst-mmap2-eofsync.c
@@ -0,0 +1,137 @@
+/* Test program for synchronization of stdio state with file after EOF.  */
+
+#include <stdio.h>
+#include <error.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+static void do_prepare (void);
+#define PREPARE(argc, argv) do_prepare ()
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static char *temp_file;
+static int temp_fd;
+
+static char *pages;
+
+static void
+do_prepare (void)
+{
+  pages = malloc (getpagesize () * 2);
+  memset (pages, 'a', getpagesize ());
+  memset (pages + getpagesize (), 'b', getpagesize ());
+
+  temp_fd = create_temp_file ("tst-mmap2-eofsync.", &temp_file);
+  if (temp_fd == -1)
+    error (1, errno, "cannot create temporary file");
+  else
+    {
+      ssize_t cc = write (temp_fd, pages, getpagesize ());
+      if (cc != getpagesize ())
+	error (1, errno, "cannot write to temporary file");
+    }
+}
+
+static int
+do_test (void)
+{
+  const size_t pagesize = getpagesize ();
+  FILE *f;
+  char buf[pagesize];
+  int result = 0;
+  int c;
+
+  f = fopen (temp_file, "r");
+  if (f == NULL)
+    {
+      perror (temp_file);
+      return 1;
+    }
+
+  if (fread (buf, pagesize, 1, f) != 1)
+    {
+      perror ("fread");
+      return 1;
+    }
+
+  if (memcmp (buf, pages, pagesize))
+    {
+      puts ("data mismatch in page 1");
+      result = 1;
+    }
+
+  printf ("feof = %d, ferror = %d immediately after fread\n",
+	  feof (f), ferror (f));
+
+  c = fgetc (f);
+  if (c == EOF)
+    printf ("fgetc -> EOF (feof = %d, ferror = %d)\n",
+	    feof (f), ferror (f));
+  else
+    {
+      printf ("fgetc returned %o (feof = %d, ferror = %d)\n",
+	      c, feof (f), ferror (f));
+      result = 1;
+    }
+
+  c = write (temp_fd, pages + pagesize, pagesize);
+  if (c == pagesize)
+    printf ("wrote more to file\n");
+  else
+    {
+      printf ("wrote %d != %d (%m)\n", c, pagesize);
+      result = 1;
+    }
+
+  if (fread (buf, pagesize, 1, f) != 1)
+    {
+      printf ("second fread fails: feof = %d, ferror = %d (%m)\n",
+	      feof (f), ferror (f));
+      clearerr (f);
+      if (fread (buf, pagesize, 1, f) != 1)
+	{
+	  printf ("retry fread fails: feof = %d, ferror = %d (%m)\n",
+		  feof (f), ferror (f));
+	  result = 1;
+	}
+    }
+  if (result == 0 && memcmp (buf, pages + pagesize, pagesize))
+    {
+      puts ("data mismatch in page 2");
+      result = 1;
+    }
+
+  fseek (f, pagesize - 1, SEEK_SET);
+  c = fgetc (f);
+  if (c != 'a')
+    {
+      printf ("fgetc at end of page 1 read '%c' (%m)\n", c);
+      result = 1;
+    }
+
+  if (ftruncate (temp_fd, pagesize) < 0)
+    {
+      printf ("ftruncate failed: %m\n");
+      result = 1;
+    }
+
+  fflush (f);
+
+  c = fgetc (f);
+  if (c == EOF)
+    printf ("after truncate fgetc -> EOF (feof = %d, ferror = %d)\n",
+	    feof (f), ferror (f));
+  else
+    {
+      printf ("after truncate fgetc returned '%c' (feof = %d, ferror = %d)\n",
+	      c, feof (f), ferror (f));
+      result = 1;
+    }
+
+  fclose (f);
+
+  return result;
+}
diff --git a/libio/wfileops.c b/libio/wfileops.c
index 04a8f27..be4a963 100644
--- a/libio/wfileops.c
+++ b/libio/wfileops.c
@@ -314,11 +314,9 @@ _IO_wfile_underflow_mmap (_IO_FILE *fp)
   if (fp->_IO_read_ptr >= fp->_IO_read_end
       /* No.  But maybe the read buffer is not fully set up.  */
       && _IO_file_underflow_mmap (fp) == EOF)
-    {
-      /* Nothing available.  */
-      fp->_flags |= _IO_EOF_SEEN;
-      return WEOF;
-    }
+    /* Nothing available.  _IO_file_underflow_mmap has set the EOF or error
+       flags as appropriate.  */
+    return WEOF;
 
   /* There is more in the external.  Convert it.  */
   read_stop = (const char *) fp->_IO_read_ptr;
@@ -356,6 +354,18 @@ _IO_wfile_underflow_mmap (_IO_FILE *fp)
   return WEOF;
 }
 
+static wint_t
+_IO_wfile_underflow_maybe_mmap (_IO_FILE *fp)
+{
+  /* This is the first read attempt.  Doing the underflow will choose mmap
+     or vanilla operations and then punt to the chosen underflow routine.
+     Then we can punt to ours.  */
+  if (_IO_file_underflow_maybe_mmap (fp) == EOF)
+    return WEOF;
+
+  return _IO_WUNDERFLOW (fp);
+}
+
 
 wint_t
 _IO_wfile_overflow (f, wch)
@@ -896,3 +906,27 @@ struct _IO_jump_t _IO_wfile_jumps_mmap =
   JUMP_INIT(showmanyc, _IO_default_showmanyc),
   JUMP_INIT(imbue, _IO_default_imbue)
 };
+
+struct _IO_jump_t _IO_wfile_jumps_maybe_mmap =
+{
+  JUMP_INIT_DUMMY,
+  JUMP_INIT(finish, _IO_new_file_finish),
+  JUMP_INIT(overflow, (_IO_overflow_t) INTUSE(_IO_wfile_overflow)),
+  JUMP_INIT(underflow, (_IO_underflow_t) _IO_wfile_underflow_maybe_mmap),
+  JUMP_INIT(uflow, (_IO_underflow_t) INTUSE(_IO_wdefault_uflow)),
+  JUMP_INIT(pbackfail, (_IO_pbackfail_t) INTUSE(_IO_wdefault_pbackfail)),
+  JUMP_INIT(xsputn, INTUSE(_IO_wfile_xsputn)),
+  JUMP_INIT(xsgetn, INTUSE(_IO_file_xsgetn)),
+  JUMP_INIT(seekoff, INTUSE(_IO_wfile_seekoff)),
+  JUMP_INIT(seekpos, _IO_default_seekpos),
+  JUMP_INIT(setbuf, _IO_file_setbuf_mmap),
+  JUMP_INIT(sync, (_IO_sync_t) INTUSE(_IO_wfile_sync)),
+  JUMP_INIT(doallocate, _IO_wfile_doallocate),
+  JUMP_INIT(read, INTUSE(_IO_file_read)),
+  JUMP_INIT(write, _IO_new_file_write),
+  JUMP_INIT(seek, INTUSE(_IO_file_seek)),
+  JUMP_INIT(close, _IO_file_close),
+  JUMP_INIT(stat, INTUSE(_IO_file_stat)),
+  JUMP_INIT(showmanyc, _IO_default_showmanyc),
+  JUMP_INIT(imbue, _IO_default_imbue)
+};