[Libguestfs] [PATCH nbdkit] New ondemand plugin.

This creates filesystems on demand. A client simply connects with a desired export name and a new export is created. The export is persistent (until deleted by the server admin), and clients may disconnect and reconnect. In some respects this is similar to the nbdkit-tmpdisk-plugin, or nbdkit-file-plugin with the dir= option. --- plugins/ondemand/nbdkit-ondemand-plugin.pod | 190 ++++++ plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod | 3 +- configure.ac | 2 + plugins/ondemand/Makefile.am | 81 +++ tests/Makefile.am | 10 + plugins/ondemand/ondemand.c | 634 ++++++++++++++++++++ plugins/ondemand/default-command.sh.in | 57 ++ tests/test-ondemand-list.sh | 66 ++ tests/test-ondemand.sh | 74 +++ .gitignore | 1 + TODO | 7 + 11 files changed, 1124 insertions(+), 1 deletion(-) diff --git a/plugins/ondemand/nbdkit-ondemand-plugin.pod b/plugins/ondemand/nbdkit-ondemand-plugin.pod new file mode 100644 index 00000000..be46b1c2 --- /dev/null +++ b/plugins/ondemand/nbdkit-ondemand-plugin.pod @@ -0,0 +1,190 @@ +=head1 NAME + +nbdkit-ondemand-plugin - create filesystems on demand + +=head1 SYNOPSIS + + nbdkit ondemand dir=EXPORTSDIR [size=]SIZE + { [type=ext4|xfs|vfat|...] [label=LABEL] + | command=COMMAND [VAR=VALUE ...] } + +=head1 DESCRIPTION + +This is a plugin for L<nbdkit(1)> which creates persistent filesystems +on demand. Clients may simply connect to the server, requesting a +particular export name, and a new filesystem is created if it does not +exist already. Clients can also disconnect and reconnect with the +same export name and the same filesystem will still be available. +Filesystems are stored in a directory on the server, so they also +persist over nbdkit and server restarts. + +Each filesystem is locked while it is in use by a client, preventing +two clients from accessing the same filesystem (which would cause +corruption). + +Similar plugins include L<nbdkit-file-plugin(1)> which can serve a +predefined set of exports (clients cannot create more), +L<nbdkit-tmpdisk-plugin(1)> which creates a fresh temporary filesystem +for each client, and L<nbdkit-linuxdisk-plugin(1)> which exports a +single filesystem from a local directory on the server. + +When a new export name is requested by a client, a sparse file of the +same name is created in C<dir=EXPORTSDIR> on the server. The file +will be formatted with L<mkfs(8)>. The size of the file is currently +fixed by the C<size=SIZE> parameter, but we intend to make this +client-configurable in future. The filesystem type and label may also +be specified, otherwise C<ext4> and no label is used. + +Export names must be E<le> C<NAME_MAX> (usually 255) bytes in length +and must not contain certain characters including C<.>, C</> and C<:>. +There may be other limitations added in future. Client requests which +do not obey these restrictions are rejected. As a special case, +export name C<""> is mapped to the file name F<default>. + +=head2 Security considerations + +You should B<only> use this in an environment where you trust all your +clients, since clients can use this plugin to consume arbitrary +amounts of disk space by creating unlimited exports. It is therefore +best to take steps to limit where clients can connect from using +L<nbdkit-ip-filter(1)>, firewalls, or TLS client certificates. + +=head2 The command parameter + +Instead of running mkfs you can run an arbitrary command (a shell +script fragment) to create the disk. + +The other parameters to the plugin are turned into shell variables +passed to the command. For example C<type> becomes the shell variable +C<$type>, etc. Any parameters you want can be passed to the plugin +and will be turned into shell variables (not only C<type> and +C<label>) making this a very flexible method to create filesystems and +disks of all kinds. + +Two special variables are also passed to the shell script fragment: + +=over 4 + +=item C<$disk> + +The absolute path of the disk file. This is partially controlled by +the client so you should quote it carefully. This file is not +pre-created, the command must create it for example using: + + truncate -s $size "$disk" + +=item C<$size> + +The virtual size in bytes. This is the C<size> parameter, converted +to bytes. Note the final size served to the client is whatever disk +size C<command> creates. + +=back + +=head1 EXAMPLE + +Run the server like this: + + mkdir /var/tmp/exports + nbdkit ondemand dir=/var/tmp/exports 1G + +Clients can connect and create 1G ext4 filesystems on demand using +commands such as these (note the different export names): + + nbd-client -b 512 server /dev/nbd0 -N export1 + mount /dev/nbd0 /mnt + + guestfish --format=raw -a nbd://localhost/export2 -m /dev/sda + + qemu-img info nbd:localhost:10809:exportname=export2 + +On the server you would see two filesystems created: + + $ ls -l /var/tmp/exports + -rw-rw-r--. 1 rjones rjones 1073741824 Aug 13 21:40 export1 + -rw-rw-r--. 1 rjones rjones 1073741824 Aug 13 21:40 export2 + +The plugin does not clean these up. If they are no longer needed then +the server admin should delete them (or use a tmp cleaner). + +=head1 PARAMETERS + +=over 4 + +=item B<command='>COMMANDB<'> + +Instead of running L<mkfs(8)> to create the initial filesystem, run +C<COMMAND> (a shell script fragment which usually must be quoted to +protect it from the shell). See L</The command parameter> and +L</EXAMPLES> sections above. + +=item B<dir=>EXPORTSDIR + +The directory where filesystems are saved. When first using this +plugin you should point this to an empty directory. When clients +connect, filesystems are created here. + +This parameter is required. + +=item B<label=>LABEL + +Select the filesystem label. The default is not set. + +=item [B<size=>]SIZE + +Specify the virtual size of all of the filesystems. + +If using C<command>, this is only a suggested size. The actual size +of the resulting disk will be the size of the disk created by +C<command>. + +This parameter is required. + +C<size=> is a magic config key and may be omitted in most cases. +See L<nbdkit(1)/Magic parameters>. + +=item B<type=>FS + +Select the filesystem type. The default is C<ext4>. Most +non-networked, non-cluster filesystem types supported by the +L<mkfs(8)> command can be used here. + +=back + +=head1 FILES + +=over 4 + +=item F<$plugindir/nbdkit-ondemand-plugin.so> + +The plugin. + +Use C<nbdkit --dump-config> to find the location of C<$plugindir>. + +=back + +=head1 VERSION + +C<nbdkit-ondemand-plugin> first appeared in nbdkit 1.22. + +=head1 SEE ALSO + +L<nbdkit(1)>, +L<nbdkit-plugin(3)>, +L<nbdkit-file-plugin(1)>, +L<nbdkit-ip-filter(1)>, +L<nbdkit-limit-filter(1)>, +L<nbdkit-linuxdisk-plugin(1)>, +L<nbdkit-memory-plugin(1)>, +L<nbdkit-tmpdisk-plugin(1)>, +L<nbdkit-tls(1)>, +L<mkfs(8)>, +L<mke2fs(8)>. + +=head1 AUTHORS + +Richard W.M. Jones + +=head1 COPYRIGHT + +Copyright (C) 2018-2020 Red Hat Inc. diff --git a/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod b/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod index be56d68a..9cecad34 100644 --- a/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod +++ b/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod @@ -13,7 +13,8 @@ nbdkit-tmpdisk-plugin - create a fresh temporary filesystem for each client This L<nbdkit(1)> plugin is used for creating temporary filesystems for thin clients. Each time a client connects it will see a fresh, empty filesystem for its exclusive use. B<The filesystem is deleted> -when the client disconnects. +when the client disconnects. If you want a persistent filesystem, use +L<nbdkit-ondemand-plugin(1)> instead. When a new client connects, a blank, sparse file of the required size is created in C<$TMPDIR> (or F</var/tmp>). L<mkfs(8)> is then run on diff --git a/configure.ac b/configure.ac index fee6fe9a..5d74251a 100644 --- a/configure.ac +++ b/configure.ac @@ -81,6 +81,7 @@ non_lang_plugins="\ memory \ nbd \ null \ + ondemand \ partitioning \ pattern \ random \ @@ -1119,6 +1120,7 @@ AC_CONFIG_FILES([Makefile plugins/nbd/Makefile plugins/null/Makefile plugins/ocaml/Makefile + plugins/ondemand/Makefile plugins/partitioning/Makefile plugins/pattern/Makefile plugins/perl/Makefile diff --git a/plugins/ondemand/Makefile.am b/plugins/ondemand/Makefile.am new file mode 100644 index 00000000..a1bc00d6 --- /dev/null +++ b/plugins/ondemand/Makefile.am @@ -0,0 +1,81 @@ +# nbdkit +# Copyright (C) 2017-2020 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +include $(top_srcdir)/common-rules.mk + +EXTRA_DIST = \ + default-command.sh.in \ + nbdkit-ondemand-plugin.pod \ + $(NULL) + +# The default command we use (if we don't use command=) comes from a +# shell script which is turned into a C source file. +BUILT_SOURCES = default-command.c + +default-command.c: default-command.sh.in Makefile + rm -f $@ $@-t + echo 'const char *command =' > $@-t + $(SED) -e '/^#/d' -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/' < $< >> $@-t + echo ';' >> $@-t + mv $@-t $@ + +plugin_LTLIBRARIES = nbdkit-ondemand-plugin.la + +nbdkit_ondemand_plugin_la_SOURCES = \ + default-command.c \ + ondemand.c \ + $(top_srcdir)/include/nbdkit-plugin.h \ + $(NULL) + +nbdkit_ondemand_plugin_la_CPPFLAGS = \ + -I$(top_srcdir)/include \ + -I$(top_srcdir)/common/utils \ + $(NULL) +nbdkit_ondemand_plugin_la_CFLAGS = $(WARNINGS_CFLAGS) +nbdkit_ondemand_plugin_la_LDFLAGS = \ + -module -avoid-version -shared $(SHARED_LDFLAGS) \ + -Wl,--version-script=$(top_srcdir)/plugins/plugins.syms \ + $(NULL) +nbdkit_ondemand_plugin_la_LIBADD = \ + $(top_builddir)/common/utils/libutils.la \ + $(NULL) + +if HAVE_POD + +man_MANS = nbdkit-ondemand-plugin.1 +CLEANFILES += $(man_MANS) + +nbdkit-ondemand-plugin.1: nbdkit-ondemand-plugin.pod + $(PODWRAPPER) --section=1 --man $@ \ + --html $(top_builddir)/html/$@.html \ + $< + +endif HAVE_POD diff --git a/tests/Makefile.am b/tests/Makefile.am index ca1e76d1..96c8b900 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -757,6 +757,16 @@ test_null_SOURCES = test-null.c test_null_CFLAGS = $(WARNINGS_CFLAGS) $(LIBNBD_CFLAGS) test_null_LDADD = $(LIBNBD_LIBS) +# ondemand plugin test. +TESTS += \ + test-ondemand.sh \ + test-ondemand-list.sh \ + $(NULL) +EXTRA_DIST += \ + test-ondemand.sh \ + test-ondemand-list.sh \ + $(NULL) + # partitioning plugin test. TESTS += \ test-partitioning1.sh \ diff --git a/plugins/ondemand/ondemand.c b/plugins/ondemand/ondemand.c new file mode 100644 index 00000000..f85d630d --- /dev/null +++ b/plugins/ondemand/ondemand.c @@ -0,0 +1,634 @@ +/* nbdkit + * Copyright (C) 2017-2020 Red Hat Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdbool.h> +#include <stdint.h> +#include <inttypes.h> +#include <string.h> +#include <unistd.h> +#include <fcntl.h> +#include <dirent.h> +#include <errno.h> +#include <assert.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/wait.h> + +#include <pthread.h> + +#define NBDKIT_API_VERSION 2 +#include <nbdkit-plugin.h> + +#include "cleanup.h" +#include "utils.h" + +static char *dir; /* dir parameter */ +static DIR *exportsdir; /* opened exports dir */ +static int64_t requested_size = -1; /* size parameter on the command line */ + +/* Shell variables. */ +static struct var { + struct var *next; + const char *key, *value; +} *vars, *last_var; + +/* This comes from default-command.c which is generated from + * default-command.sh.in. + */ +extern const char *command; + +static void +ondemand_unload (void) +{ + struct var *v, *v_next; + + for (v = vars; v != NULL; v = v_next) { + v_next = v->next; + free (v); + } + + closedir (exportsdir); + free (dir); +} + +static int +ondemand_config (const char *key, const char *value) +{ + if (strcmp (key, "command") == 0) { + command = value; + } + else if (strcmp (key, "size") == 0) { + requested_size = nbdkit_parse_size (value); + if (requested_size == -1) + return -1; + } + else if (strcmp (key, "dir") == 0) { + dir = nbdkit_realpath (value); + if (dir == NULL) + return -1; + } + + /* This parameter cannot be set on the command line since it is used + * to pass the disk name to the command. + */ + else if (strcmp (key, "disk") == 0) { + nbdkit_error ("'disk' parameter cannot be set on the command line"); + return -1; + } + + /* Any other parameter will be forwarded to a shell variable. */ + else { + struct var *new_var; + + new_var = malloc (sizeof *new_var); + if (new_var == NULL) { + perror ("malloc"); + exit (EXIT_FAILURE); + } + + new_var->next = NULL; + new_var->key = key; + new_var->value = value; + + /* Append it to the linked list. */ + if (vars == NULL) { + assert (last_var == NULL); + vars = last_var = new_var; + } + else { + assert (last_var != NULL); + last_var->next = new_var; + last_var = new_var; + } + } + + return 0; +} + +static int +ondemand_config_complete (void) +{ + if (dir == NULL || requested_size == -1) { + nbdkit_error ("dir and size parameters are required"); + return -1; + } + + return 0; +} + +static int +ondemand_get_ready (void) +{ + exportsdir = opendir (dir); + if (exportsdir == NULL) { + nbdkit_error ("opendir: %s: %m", dir); + return -1; + } + + return 0; +} + +#define ondemand_config_help \ + "dir=<EXPORTSDIR> (required) Directory containing filesystems.\n" \ + "size=<SIZE> (required) Virtual filesystem size.\n" \ + "label=<LABEL> The filesystem label.\n" \ + "type=ext4|... The filesystem type.\n" \ + "command=<COMMAND> Alternate command instead of mkfs." + +/* Because we rewind the exportsdir handle, we need a lock to protect + * list_exports from being called in parallel. + */ +static pthread_mutex_t exports_lock = PTHREAD_MUTEX_INITIALIZER; + +static int +ondemand_list_exports (int readonly, int default_only, + struct nbdkit_exports *exports) +{ + ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&exports_lock); + struct dirent *d; + + /* First entry should be the default export. XXX Should we check if + * the "default" file was created? I don't think we need to. + */ + if (nbdkit_add_export (exports, "", NULL) == -1) + return -1; + if (default_only) return 0; + + /* Read the rest of the exports. */ + rewinddir (exportsdir); + + /* XXX Output is not sorted. Does it matter? */ + while (errno = 0, (d = readdir (exportsdir)) != NULL) { + /* Skip all dot files. "." anywhere in the export name is + * rejected by the plugin, so commands can use dot files to "hide" + * files in the export dir (eg. if needing to keep state). + */ + if (d->d_name[0] == '.') + continue; + + /* Skip the "default" filename which refers to the "" export. */ + if (strcmp (d->d_name, "default") == 0) + continue; + + if (nbdkit_add_export (exports, d->d_name, NULL) == -1) + return -1; + } + + /* Did readdir fail? */ + if (errno != 0) { + nbdkit_error ("readdir: %s: %m", dir); + return -1; + } + + return 0; +} + +struct handle { + int fd; + int64_t size; + const char *exportname; + bool can_punch_hole; +}; + +/* Since clients that want multi-conn should all pass the same export + * name, this is safe. + */ +static int +ondemand_can_multi_conn (void *handle) +{ + return 1; +} + +static int +ondemand_can_trim (void *handle) +{ +#ifdef FALLOC_FL_PUNCH_HOLE + return 1; +#else + return 0; +#endif +} + +static int +ondemand_can_fua (void *handle) +{ + return NBDKIT_FUA_NATIVE; +} + +/* This creates and runs the full "mkfs" (or whatever) command. */ +static int +run_command (const char *disk) +{ + FILE *fp; + CLEANUP_FREE char *cmd = NULL; + size_t len = 0; + int r; + struct var *v; + + fp = open_memstream (&cmd, &len); + if (fp == NULL) { + nbdkit_error ("open_memstream: %m"); + return -1; + } + + /* Avoid stdin/stdout leaking (because of nbdkit -s). */ + fprintf (fp, "exec </dev/null >/dev/null\n"); + + /* Set the standard shell variables. */ + fprintf (fp, "disk="); + shell_quote (disk, fp); + putc ('\n', fp); + fprintf (fp, "size=%" PRIi64 "\n", requested_size); + putc ('\n', fp); + + /* The other parameters/shell variables. */ + for (v = vars; v != NULL; v = v->next) { + /* Keys probably can never contain shell-unsafe chars (because of + * nbdkit's own restrictions), but quoting it makes it safe. + */ + shell_quote (v->key, fp); + putc ('=', fp); + shell_quote (v->value, fp); + putc ('\n', fp); + } + putc ('\n', fp); + + /* The command. */ + fprintf (fp, "%s", command); + + if (fclose (fp) == EOF) { + nbdkit_error ("memstream failed"); + return -1; + } + + r = system (cmd); + if (r == -1) { + nbdkit_error ("failed to execute command: %m"); + return -1; + } + if (WIFEXITED (r) && WEXITSTATUS (r) != 0) { + nbdkit_error ("command exited with code %d", WEXITSTATUS (r)); + return -1; + } + else if (WIFSIGNALED (r)) { + nbdkit_error ("command killed by signal %d", WTERMSIG (r)); + return -1; + } + else if (WIFSTOPPED (r)) { + nbdkit_error ("command stopped by signal %d", WSTOPSIG (r)); + return -1; + } + + return 0; +} + +/* For block devices, stat->st_size is not the true size. */ +static int64_t +block_device_size (int fd) +{ + off_t size; + + size = lseek (fd, 0, SEEK_END); + if (size == -1) { + nbdkit_error ("lseek: %m"); + return -1; + } + + return size; +} + +static void * +ondemand_open (int readonly) +{ + struct handle *h; + CLEANUP_FREE char *disk = NULL; + int flags, err; + struct stat statbuf; + struct flock lock; + + h = malloc (sizeof *h); + if (h == NULL) { + nbdkit_error ("malloc: %m"); + goto error; + } + h->fd = -1; + h->size = -1; + h->can_punch_hole = true; + + /* This is safe since we're only storing it in the handle, so only + * for the lifetime of this connection. + */ + h->exportname = nbdkit_export_name (); + if (!h->exportname) { + nbdkit_error ("internal error: expected nbdkit_export_name () != NULL"); + goto error; + } + if (strcmp (h->exportname, "") == 0) + h->exportname = "default"; + + /* Verify that the export name is valid. */ + if (strlen (h->exportname) > NAME_MAX || + strchr (h->exportname, '.') || + strchr (h->exportname, '/') || + strchr (h->exportname, ':')) { + nbdkit_error ("invalid exportname ‘%s’ rejected", h->exportname); + goto error; + } + + /* Try to open the filesystem. */ + if (readonly) + flags = O_RDONLY | O_CLOEXEC; + else + flags = O_RDWR | O_CLOEXEC; + h->fd = openat (dirfd (exportsdir), h->exportname, flags); + if (h->fd == -1) { + if (errno != ENOENT) { + nbdkit_error ("open: %s/%s: %m", dir, h->exportname); + goto error; + } + + /* Create the filesystem. */ + if (asprintf (&disk, "%s/%s", dir, h->exportname) == -1) { + nbdkit_error ("asprintf: %m"); + goto error; + } + + /* Now run the mkfs command. */ + if (run_command (disk) == -1) + goto error; + + h->fd = openat (dirfd (exportsdir), h->exportname, flags); + if (h->fd == -1) { + nbdkit_error ("open: %s/%s: %m", dir, h->exportname); + goto error; + } + } + + /* Lock the file to prevent filesystem corruption. It's safe for + * all clients to be reading. If a client wants to write it must + * have exclusive access. + * + * This uses a currently Linux-specific extension. It requires + * Linux >= 3.15 (released in 2014, later backported to RHEL 7). + * There is no sensible way to do this in pure POSIX. + */ +#ifdef F_OFD_SETLK + memset (&lock, 0, sizeof lock); + if (readonly) + lock.l_type = F_RDLCK; + else + lock.l_type = F_WRLCK; + lock.l_whence = SEEK_SET; + lock.l_start = 0; + lock.l_len = 0; + if (fcntl (h->fd, F_OFD_SETLK, &lock) == -1) { + if (errno == EACCES || errno == EAGAIN) { + nbdkit_error ("%s: filesystem is locked by another client", + h->exportname); + /* XXX Would be nice if NBD protocol supported some kind of "is + * locked" indication. If it did we could use it here. + */ + errno = EINVAL; + goto error; + } + else { + nbdkit_error ("fcntl: %s/%s: %m", dir, h->exportname); + goto error; + } + } +#endif + + /* Find the size of the disk. */ + if (fstat (h->fd, &statbuf) == -1) { + nbdkit_error ("fstat: %s: %m", disk); + goto error; + } + + /* The command could set $disk to a regular file or a block device + * (or a symlink to either), so we must check that here. + */ + if (S_ISBLK (statbuf.st_mode)) { + h->size = block_device_size (h->fd); + if (h->size == -1) + goto error; + } + else /* Regular file. */ + h->size = statbuf.st_size; + nbdkit_debug ("ondemand: requested_size = %" PRIi64 ", size = %" PRIi64, + requested_size, h->size); + + /* Return the handle. */ + return h; + + error: + err = errno; + if (h) { + if (h->fd >= 0) + close (h->fd); + free (h); + } + errno = err; + return NULL; +} + +static void +ondemand_close (void *handle) +{ + struct handle *h = handle; + + close (h->fd); + free (h); +} + +static int64_t +ondemand_get_size (void *handle) +{ + struct handle *h = handle; + + return h->size; +} + +/* Read data from the file. */ +static int +ondemand_pread (void *handle, void *buf, + uint32_t count, uint64_t offset, + uint32_t flags) +{ + struct handle *h = handle; + + while (count > 0) { + ssize_t r = pread (h->fd, buf, count, offset); + if (r == -1) { + nbdkit_error ("pread: %m"); + return -1; + } + if (r == 0) { + nbdkit_error ("pread: unexpected end of file"); + return -1; + } + buf += r; + count -= r; + offset += r; + } + + return 0; +} + +/* Flush the file to disk. */ +static int +ondemand_flush (void *handle, uint32_t flags) +{ + struct handle *h = handle; + + if (fdatasync (h->fd) == -1) { + nbdkit_error ("fdatasync: %m"); + return -1; + } + + return 0; +} + +/* Write data to the file. */ +static int +ondemand_pwrite (void *handle, const void *buf, + uint32_t count, uint64_t offset, + uint32_t flags) +{ + struct handle *h = handle; + + while (count > 0) { + ssize_t r = pwrite (h->fd, buf, count, offset); + if (r == -1) { + nbdkit_error ("pwrite: %m"); + return -1; + } + buf += r; + count -= r; + offset += r; + } + + if ((flags & NBDKIT_FLAG_FUA) && ondemand_flush (handle, 0) == -1) + return -1; + + return 0; +} + +#if defined (FALLOC_FL_PUNCH_HOLE) +static int +do_fallocate (int fd, int mode, off_t offset, off_t len) +{ + int r = fallocate (fd, mode, offset, len); + if (r == -1 && errno == ENODEV) { + /* kernel 3.10 fails with ENODEV for block device. Kernel >= 4.9 fails + * with EOPNOTSUPP in this case. Normalize errno to simplify callers. + */ + errno = EOPNOTSUPP; + } + return r; +} + +static bool +is_enotsup (int err) +{ + return err == ENOTSUP || err == EOPNOTSUPP; +} +#endif + +/* Punch a hole in the file. */ +static int +ondemand_trim (void *handle, uint32_t count, uint64_t offset, uint32_t flags) +{ +#ifdef FALLOC_FL_PUNCH_HOLE + struct handle *h = handle; + int r; + + if (h->can_punch_hole) { + r = do_fallocate (h->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, + offset, count); + if (r == -1) { + /* Trim is advisory; we don't care if it fails for anything other + * than EIO or EPERM. + */ + if (errno == EPERM || errno == EIO) { + nbdkit_error ("fallocate: %m"); + return -1; + } + + if (is_enotsup (EOPNOTSUPP)) + h->can_punch_hole = false; + + nbdkit_debug ("ignoring failed fallocate during trim: %m"); + } + } +#endif + + if ((flags & NBDKIT_FLAG_FUA) && ondemand_flush (handle, 0) == -1) + return -1; + + return 0; +} + +#define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL + +static struct nbdkit_plugin plugin = { + .name = "ondemand", + .version = PACKAGE_VERSION, + + .unload = ondemand_unload, + .config = ondemand_config, + .config_complete = ondemand_config_complete, + .config_help = ondemand_config_help, + .magic_config_key = "size", + .get_ready = ondemand_get_ready, + + .list_exports = ondemand_list_exports, + + .can_multi_conn = ondemand_can_multi_conn, + .can_trim = ondemand_can_trim, + .can_fua = ondemand_can_fua, + .get_size = ondemand_get_size, + + .open = ondemand_open, + .close = ondemand_close, + .pread = ondemand_pread, + .pwrite = ondemand_pwrite, + .flush = ondemand_flush, + .trim = ondemand_trim, + + .errno_is_preserved = 1, +}; + +NBDKIT_REGISTER_PLUGIN(plugin) diff --git a/plugins/ondemand/default-command.sh.in b/plugins/ondemand/default-command.sh.in new file mode 100644 index 00000000..d60402b5 --- /dev/null +++ b/plugins/ondemand/default-command.sh.in @@ -0,0 +1,57 @@ +# nbdkit +# -*- mode: shell-script -*- +# Copyright (C) 2017-2020 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +# If not set, default to ext4. +type="${type:-ext4}" + +labelopt='-L' + +case "$type" in + ext?) + extra='-F' ;; + *fat|msdos) + extra='-I' ;; + ntfs) + extra='-Q -F' + labelopt='-n' ;; + xfs) + extra='-f' ;; +esac + +# Create the output disk. +truncate -s $size "$disk" + +if [ "x$label" = "x" ]; then + mkfs -t "$type" $extra "$disk" +else + mkfs -t "$type" $extra $labelopt "$label" "$disk" +fi diff --git a/tests/test-ondemand-list.sh b/tests/test-ondemand-list.sh new file mode 100755 index 00000000..5e848e8d --- /dev/null +++ b/tests/test-ondemand-list.sh @@ -0,0 +1,66 @@ +#!/usr/bin/env bash +# nbdkit +# Copyright (C) 2020 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +source ./functions.sh +set -e +set -x + +requires qemu-nbd --version + +dir=`mktemp -d` +cleanup_fn rm -rf $dir + +out=test-ondemand-list.out +rm -f $out +cleanup_fn rm -f $out + +# Put some files into the exports directory to pretend that we're +# restarting nbdkit after a previous run. +touch $dir/default +touch $dir/export1 +touch $dir/export2 +touch $dir/export3 + +export LANG=C +nbdkit -U - ondemand dir=$dir size=1M \ + --run 'qemu-nbd -k $unixsocket -L' > $out +cat $out + +# We should have 4 exports, since "default" file is the same as the +# default export. +grep "exports available: 4" $out + +# Check the 4 exports are present. +grep "export: ''" $out +grep "export: 'export1'" $out +grep "export: 'export2'" $out +grep "export: 'export3'" $out diff --git a/tests/test-ondemand.sh b/tests/test-ondemand.sh new file mode 100755 index 00000000..758c2565 --- /dev/null +++ b/tests/test-ondemand.sh @@ -0,0 +1,74 @@ +#!/usr/bin/env bash +# nbdkit +# Copyright (C) 2020 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +source ./functions.sh +set -e +set -x + +requires guestfish --version +requires qemu-img --version + +dir=`mktemp -d` +cleanup_fn rm -rf $dir + +sock=`mktemp -u` +files="ondemand.pid $sock" +rm -f $files +cleanup_fn rm -f $files + +# Run nbdkit. +start_nbdkit -P ondemand.pid -U $sock --log=stderr ondemand dir=$dir size=100M + +# Simply querying an export will create the filesystem. +qemu-img info nbd:unix:$sock +qemu-img info nbd:unix:$sock:exportname=test + +test -f $dir/default +test -f $dir/test + +# These should fail because the exportname is invalid. +if qemu-img info nbd:unix:$sock:exportname=/bad || + qemu-img info nbd:unix:$sock:exportname=.bad || + qemu-img info nbd:unix:$sock:exportname=bad. || + qemu-img info nbd:unix:$sock:exportname=bad:bad +then + echo "$0: expected failure trying to create bad exportname" + exit 1 +fi + +# Check the filesystem is persistent. +guestfish --format=raw -a "nbd://?socket=$sock" -m /dev/sda <<EOF + write /test.txt "hello" +EOF +guestfish --ro --format=raw -a "nbd://?socket=$sock" -m /dev/sda <<EOF + cat /test.txt +EOF diff --git a/.gitignore b/.gitignore index 255a97a5..2c463909 100644 --- a/.gitignore +++ b/.gitignore @@ -77,6 +77,7 @@ plugins/*/*.3 /plugins/golang/examples/*/nbdkit-*-plugin.h /plugins/golang/examples/*/nbdkit-*-plugin.so /plugins/ocaml/nbdkit-ocamlexample-plugin.so +/plugins/ondemand/default-command.c /plugins/rust/Cargo.lock /plugins/rust/target /plugins/tmpdisk/default-command.c diff --git a/TODO b/TODO index c329382d..d5802974 100644 --- a/TODO +++ b/TODO @@ -154,6 +154,13 @@ nbdkit-torrent-plugin: * The C++ could be a lot more natural. At the moment it's a kind of “C with C++ extensions”. +nbdkit-ondemand-plugin: + +* Implement more callbacks, eg. .zero + +* Allow client to select size up to a limit, eg. by sending export + names like ‘export:4G’. + Suggestions for language plugins -------------------------------- -- 2.27.0