Re: [Libguestfs] [PATCH 3/3] New APIs: bmap-file, bmap-device, bmap.

Add support for a block mapping API, used by the 'virt-bmap' tool. --- daemon/Makefile.am | 1 + daemon/bmap.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++ generator/actions.ml | 44 ++++++++++++++ po/POTFILES | 1 + src/MAX_PROC_NR | 2 +- 5 files changed, 215 insertions(+), 1 deletion(-) create mode 100644 daemon/bmap.c diff --git a/daemon/Makefile.am b/daemon/Makefile.am index 8ccf322..b6444fa 100644 --- a/daemon/Makefile.am +++ b/daemon/Makefile.am @@ -86,6 +86,7 @@ guestfsd_SOURCES = \ blkdiscard.c \ blkid.c \ blockdev.c \ + bmap.c \ btrfs.c \ cap.c \ checksum.c \ diff --git a/daemon/bmap.c b/daemon/bmap.c new file mode 100644 index 0000000..555f776 --- /dev/null +++ b/daemon/bmap.c @@ -0,0 +1,168 @@ +/* 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. + */ + +#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 "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 int +bmap_prepare (const char *path, const char *orig_path) +{ + bmap_finalize (); + + if (stat (path, &statbuf) == -1) { + reply_with_perror ("%s", orig_path); + return -1; + } + + if (S_ISDIR (statbuf.st_mode)) { + /* Open a directory. */ + dir = opendir (path); + if (dir == NULL) { + reply_with_perror ("opendir: %s", orig_path); + return -1; + } + } + else { + /* Open a regular file. */ + fd = open (path, O_RDONLY | O_CLOEXEC); + if (fd == -1) { + reply_with_perror ("%s", orig_path); + return -1; + }

+ + posix_fadvise (fd, 0, 0, + POSIX_FADV_SEQUENTIAL | + POSIX_FADV_NOREUSE | + POSIX_FADV_DONTNEED); + } + + return 0; +} + +int +do_bmap_file (const char *path) +{ + CLEANUP_FREE char *buf = NULL; + + buf = sysroot_path (path); + if (!buf) { + reply_with_perror ("malloc"); + return -1; + } + + return bmap_prepare (buf, path); +} + +int +do_bmap_device (const char *device) +{ + return bmap_prepare (device, device); +} + +static char buffer[BUFSIZ]; + +int +do_bmap (void) +{ + size_t n; + ssize_t r; + struct dirent *d; + + /* Drop caches before starting the read. */ + if (do_drop_caches (3) == -1) + return -1; + + if (fd >= 0) { + 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 -1; + } + n -= r; + } + + if (close (fd) == -1) { + reply_with_perror ("close"); + fd = -1; + return -1; + } + 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 -1; + } + + /* Close the directory handle */ + if (closedir (dir) == -1) { + reply_with_perror ("closedir"); + dir = NULL; + return -1; + } + dir = NULL; + } + + return 0; +} diff --git a/generator/actions.ml b/generator/actions.ml index baa7679..0f2e040 100644 --- a/generator/actions.ml +++ b/generator/actions.ml @@ -12017,6 +12017,50 @@ Set readahead (in 512-byte sectors) for the device. This uses the L<blockdev(8)> command." }; + { defaults with + name = "bmap_file"; + style = RErr, [Pathname "path"], []; + proc_nr = Some 425; + shortdesc = "prepare a file for block mapping"; + longdesc = "\ +This is a specialized function used by L<virt-bmap(1)> to map which +blocks are used by a file. It is unlikely to be useful outside +virt-bmap. + +This call prepares C<path> (which may be a regular file or directory) +to be mapped. You have to call C<guestfs_bmap> immediately afterwards." }; + + { defaults with + name = "bmap_device"; + style = RErr, [Device "device"], []; + proc_nr = Some 426; + shortdesc = "prepare a device for block mapping"; + longdesc = "\ +This is a specialized function used by L<virt-bmap(1)> to map which +blocks are used by a device. It is unlikely to be useful outside +virt-bmap. + +This call prepares C<device> to be mapped. You have to call C<guestfs_bmap> +immediately afterwards." }; + + { defaults with + name = "bmap"; + style = RErr, [], []; + proc_nr = Some 427; + shortdesc = "block map file or device"; + longdesc = "\ +This is a specialized function used by L<virt-bmap(1)> to map which +blocks are used by a file or device. It is unlikely to be useful outside +virt-bmap. + +This performs the specialized read of the file or device which was +previously prepared (see C<guestfs_bmap_file> and C<guestfs_bmap_device>). +The file/directory/device is read from start to end without any caching +or readahead. + +L<virt-bmap(1)> uses this call in conjunction with an nbdkit plugin +which monitors which disk blocks are read during the operation." }; + ]