libc: add fallocate() and fallocate64()

We add the Linux-specific function fallocate() which allows the user to
directly manipulate allocate space for a file.  fallocate() can operate
in different modes, but the default mode is equivalent to posix_fallocate()
which is specified in POSIX.1.

Recent releases of e2fsprogs 1.42.11 and above expect fallocate64() to be
available.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 166 insertions, 0 deletions

diff --git a/test/unistd/tst-fallocate.c b/test/unistd/tst-fallocate.c
new file mode 100644
index 000000000..fc81781bb
--- /dev/null
+++ b/test/unistd/tst-fallocate.c
@@ -0,0 +1,166 @@
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#ifndef TST_FALLOCATE64
+# define stat64 stat
+# define fstat64 fstat
+# else
+# ifndef O_LARGEFILE
+#  error no O_LARGEFILE but you want to test with LFS enabled
+# endif
+#endif
+
+static void do_prepare(void);
+static int do_test(void);
+#define PREPARE(argc, argv) do_prepare ()
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static int fd;
+static void
+do_prepare (void)
+{
+  fd = create_temp_file ("tst-fallocate.", NULL);
+  if (fd == -1)
+    {
+      printf ("cannot create temporary file: %m\n");
+      exit (1);
+    }
+}
+
+
+static int
+do_test (void)
+{
+  struct stat64 st;
+  int c;
+  char garbage[4096];
+  blkcnt_t blksb4;
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("1st fstat failed");
+      return 1;
+    }
+
+  if (st.st_size != 0)
+    {
+      puts ("file not created with size 0");
+      return 1;
+    }
+
+  /* This is the default mode which is identical to posix_fallocate().
+     Note: we need a few extra blocks for FALLOC_FL_PUNCH_HOLE below.
+     While block sizes vary, we'll assume eight 4K blocks for good measure. */
+  if (fallocate (fd, 0, 8 * 4096, 128) != 0)
+    {
+      puts ("1st fallocate call failed");
+      return 1;
+    }
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("2nd fstat failed");
+      return 1;
+    }
+
+  if (st.st_size != 8 * 4096 + 128)
+    {
+      printf ("file size after 1st fallocate call is %llu, expected %u\n",
+	      (unsigned long long int) st.st_size, 8u * 4096u + 128u);
+      return 1;
+    }
+
+  /* Without FALLOC_FL_KEEP_SIZE, this would increaste the size of the file. */
+  if (fallocate (fd, FALLOC_FL_KEEP_SIZE, 0, 16 * 4096) != 0)
+    {
+      puts ("2nd fallocate call failed");
+      return 1;
+    }
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("3rd fstat failed");
+      return 1;
+    }
+
+  if (st.st_size != 8 * 4096 + 128)
+    {
+      printf ("file size changed in 2nd fallocate call to %llu, expected %u\n",
+	      (unsigned long long int) st.st_size, 8u * 4096u + 128u);
+      return 1;
+    }
+
+  /* Let's fill up the first eight 4k blocks with 'x' to force some allocations. */
+
+  memset(garbage, 'x', 4096);
+  for(c=0; c < 8; c++)
+    if(write(fd, garbage, 4096) == -1)
+      {
+        puts ("write failed");
+        return 1;
+      }
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("4th fstat failed");
+      return 1;
+    }
+
+  blksb4 = st.st_blocks;
+
+  /* Let's punch a hole in the entire file, turning it effectively into a sparse file. */
+  if (fallocate (fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0, 8 * 4096 + 128) != 0)
+    {
+      puts ("3rd fallocate call failed");
+      return 1;
+    }
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("5th fstat failed");
+      return 1;
+    }
+
+  if (st.st_size != 8 * 4096 + 128)
+    {
+      printf ("file size after 3rd fallocate call is %llu, expected %u\n",
+	      (unsigned long long int) st.st_size, 8u * 4096u + 128u);
+      return 1;
+    }
+
+  /* The number of allocated blocks should decrease.  I hope this works on
+     all filesystems! */
+  if (st.st_blocks >= blksb4)
+    {
+      printf ("number of blocks after 3rd fallocate call is %lu, expected less than %lu\n",
+	      (unsigned long int) st.st_blocks, blksb4);
+      return 1;
+    }
+
+#ifdef TST_FALLOCATE64
+  /* We'll just do a mode = 0 test for fallocate64() */
+  if (fallocate64 (fd, 0, 4097ULL, 4294967295ULL + 2ULL) != 0)
+    {
+      puts ("1st fallocate64 call failed");
+      return 1;
+    }
+
+  if (fstat64 (fd, &st) != 0)
+    {
+      puts ("6th fstat failed");
+      return 1;
+    }
+
+  if (st.st_size != 4097ULL + 4294967295ULL + 2ULL)
+    {
+      printf ("file size after 1st fallocate64 call is %llu, expected %llu\n",
+	      (unsigned long long int) st.st_size, 4097ULL + 4294967295ULL + 2ULL);
+      return 1;
+    }
+#endif
+  close (fd);
+
+  return 0;
+}
+