Add debug APIs: bmap-file, bmap-device, bmap.

Add *interim* support for a block mapping API, used by the 'virt-bmap'
tool.  These are debug APIs so they will eventually be replaced by
real APIs along the lines described here:

https://www.redhat.com/archives/libguestfs/2014-November/msg00197.html

daemon/Makefile.am

@@ -98,6 +98,7 @@ guestfsd_SOURCES = \
 	daemon.h \
 	dd.c \
 	debug.c \
+	debug-bmap.c \
 	devsparts.c \
 	df.c \
 	dir.c \

daemon/daemon.h

@@ -257,6 +257,11 @@ extern int copy_xattrs (const char *src, const char *dest);
 /* Documented in xfs_admin(8). */
 #define XFS_LABEL_MAX 12
 
+/*-- debug-bmap.c --*/
+extern char *debug_bmap (const char *subcmd, size_t argc, char *const *const argv);
+extern char *debug_bmap_file (const char *subcmd, size_t argc, char *const *const argv);
+extern char *debug_bmap_device (const char *subcmd, size_t argc, char *const *const argv);
+
 /* ordinary daemon functions use these to indicate errors
  * NB: you don't need to prefix the string with the current command,
  * it is added automatically by the client-side RPC stubs.

daemon/debug-bmap.c

@@ -0,0 +1,216 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2014 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/* This file provides some interim APIs for virt-bmap.  They will
+ * eventually be replaced by real APIs, see:
+ * https://www.redhat.com/archives/libguestfs/2014-November/msg00197.html
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+
+#include "daemon.h"
+#include "actions.h"
+
+static int fd = -1;
+static DIR *dir = NULL;
+static struct stat statbuf;
+
+static void bmap_finalize (void) __attribute__((destructor));
+static void
+bmap_finalize (void)
+{
+  if (fd >= 0) {
+    close (fd);
+    fd = -1;
+  }
+  if (dir != NULL) {
+    closedir (dir);
+    dir = NULL;
+  }
+}
+
+static char *
+bmap_prepare (const char *path, const char *orig_path)
+{
+  char *ret;
+
+  bmap_finalize ();
+
+  if (stat (path, &statbuf) == -1) {
+    reply_with_perror ("%s", orig_path);
+    return NULL;
+  }
+
+  if (S_ISDIR (statbuf.st_mode)) {
+    /* Open a directory. */
+    dir = opendir (path);
+    if (dir == NULL) {
+      reply_with_perror ("opendir: %s", orig_path);
+      return NULL;
+    }
+  }
+  else {
+    /* Open a regular file. */
+    fd = open (path, O_RDONLY | O_CLOEXEC);
+    if (fd == -1) {
+      reply_with_perror ("%s", orig_path);
+      return NULL;
+    }
+
+    posix_fadvise (fd, 0, 0,
+                   POSIX_FADV_SEQUENTIAL |
+                   POSIX_FADV_NOREUSE |
+                   POSIX_FADV_DONTNEED);
+  }
+
+  ret = strdup ("ok");
+  if (ret == NULL) {
+    reply_with_perror ("strdup");
+    return NULL;
+  }
+  return ret;
+}
+
+char *
+debug_bmap_file (const char *subcmd, size_t argc, char *const *const argv)
+{
+  CLEANUP_FREE char *buf = NULL;
+  const char *path;
+
+  if (argc != 1) {
+    reply_with_error ("bmap-file: missing path");
+    return NULL;
+  }
+  path = argv[0];
+
+  buf = sysroot_path (path);
+  if (!buf) {
+    reply_with_perror ("malloc");
+    return NULL;
+  }
+
+  return bmap_prepare (buf, path);
+}
+
+char *
+debug_bmap_device (const char *subcmd, size_t argc, char *const *const argv)
+{
+  const char *device;
+
+  if (argc != 1) {
+    reply_with_error ("bmap-device: missing device");
+    return NULL;
+  }
+  device = argv[0];
+
+  return bmap_prepare (device, device);
+}
+
+static char buffer[BUFSIZ];
+
+char *
+debug_bmap (const char *subcmd, size_t argc, char *const *const argv)
+{
+  uint64_t n;
+  ssize_t r;
+  struct dirent *d;
+  char *ret;
+
+  if (argc != 0) {
+    reply_with_error ("bmap: extra parameters on command line");
+    return NULL;
+  }
+
+  /* Drop caches before starting the read. */
+  if (do_drop_caches (3) == -1)
+    return NULL;
+
+  if (fd >= 0) {
+    if (S_ISBLK (statbuf.st_mode)) {
+      /* Get size of block device. */
+      if (ioctl (fd, BLKGETSIZE64, &n) == -1) {
+        reply_with_perror ("ioctl: BLKGETSIZE64");
+        return NULL;
+      }
+    }
+    else
+      n = statbuf.st_size;
+
+    while (n > 0) {
+      r = read (fd, buffer, n > BUFSIZ ? BUFSIZ : n);
+      if (r == -1) {
+        reply_with_perror ("read");
+        close (fd);
+        fd = -1;
+        return NULL;
+      }
+      n -= r;
+    }
+
+    if (close (fd) == -1) {
+      reply_with_perror ("close");
+      fd = -1;
+      return NULL;
+    }
+    fd = -1;
+  }
+
+  if (dir != NULL) {
+    for (;;) {
+      errno = 0;
+      d = readdir (dir);
+      if (!d) break;
+    }
+
+    /* Check readdir didn't fail */
+    if (errno != 0) {
+      reply_with_perror ("readdir");
+      closedir (dir);
+      dir = NULL;
+      return NULL;
+    }
+
+    /* Close the directory handle */
+    if (closedir (dir) == -1) {
+      reply_with_perror ("closedir");
+      dir = NULL;
+      return NULL;
+    }
+    dir = NULL;
+  }
+
+  ret = strdup ("ok");
+  if (ret == NULL) {
+    reply_with_perror ("strdup");
+    return NULL;
+  }
+  return ret;
+}

daemon/debug.c

@@ -83,6 +83,9 @@ static void deliberately_cause_a_segfault (void);
 static struct cmd cmds[] = {
   { "help", debug_help },
   { "binaries", debug_binaries },
+  { "bmap", debug_bmap },
+  { "bmap_device", debug_bmap_device },
+  { "bmap_file", debug_bmap_file },
   { "core_pattern", debug_core_pattern },
   { "device_speed", debug_device_speed },
   { "env", debug_env },

po/POTFILES

@@ -32,6 +32,7 @@ daemon/copy.c
 daemon/cpio.c
 daemon/cpmv.c
 daemon/dd.c
+daemon/debug-bmap.c
 daemon/debug.c
 daemon/devsparts.c
 daemon/df.c