diff options
| -rw-r--r-- | MAINTAINERS | 6 | ||||
| -rw-r--r-- | block.c | 1 | ||||
| -rw-r--r-- | block/export/export.c | 4 | ||||
| -rw-r--r-- | block/export/fuse.c | 295 | ||||
| -rw-r--r-- | block/export/meson.build | 2 | ||||
| -rw-r--r-- | include/block/fuse.h | 30 | ||||
| -rw-r--r-- | qapi/block-export.json | 23 |
7 files changed, 359 insertions, 2 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index aa39490..1950592 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3114,6 +3114,12 @@ F: include/qemu/vhost-user-server.h F: tests/qtest/libqos/vhost-user-blk.c F: util/vhost-user-server.c +FUSE block device exports +M: Max Reitz <mreitz@redhat.com> +L: qemu-block@nongnu.org +S: Supported +F: block/export/fuse.c + Replication M: Wen Congyang <wencongyang2@huawei.com> M: Xie Changlong <xiechanglong.d@gmail.com> @@ -26,6 +26,7 @@ #include "block/trace.h" #include "block/block_int.h" #include "block/blockjob.h" +#include "block/fuse.h" #include "block/nbd.h" #include "block/qdict.h" #include "qemu/error-report.h" diff --git a/block/export/export.c b/block/export/export.c index bad6f21..b716c15 100644 --- a/block/export/export.c +++ b/block/export/export.c @@ -17,6 +17,7 @@ #include "sysemu/block-backend.h" #include "sysemu/iothread.h" #include "block/export.h" +#include "block/fuse.h" #include "block/nbd.h" #include "qapi/error.h" #include "qapi/qapi-commands-block-export.h" @@ -31,6 +32,9 @@ static const BlockExportDriver *blk_exp_drivers[] = { #ifdef CONFIG_VHOST_USER_BLK_SERVER &blk_exp_vhost_user_blk, #endif +#ifdef CONFIG_FUSE + &blk_exp_fuse, +#endif }; /* Only accessed from the main thread */ diff --git a/block/export/fuse.c b/block/export/fuse.c new file mode 100644 index 0000000..0553bcd --- /dev/null +++ b/block/export/fuse.c @@ -0,0 +1,295 @@ +/* + * Present a block device as a raw image through FUSE + * + * Copyright (c) 2020 Max Reitz <mreitz@redhat.com> + * + * 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; under version 2 or later of the License. + * + * 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, see <http://www.gnu.org/licenses/>. + */ + +#define FUSE_USE_VERSION 31 + +#include "qemu/osdep.h" +#include "block/aio.h" +#include "block/block.h" +#include "block/export.h" +#include "block/fuse.h" +#include "block/qapi.h" +#include "qapi/error.h" +#include "qapi/qapi-commands-block.h" +#include "sysemu/block-backend.h" + +#include <fuse.h> +#include <fuse_lowlevel.h> + + +/* Prevent overly long bounce buffer allocations */ +#define FUSE_MAX_BOUNCE_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 64 * 1024 * 1024)) + + +typedef struct FuseExport { + BlockExport common; + + struct fuse_session *fuse_session; + struct fuse_buf fuse_buf; + bool mounted, fd_handler_set_up; + + char *mountpoint; + bool writable; +} FuseExport; + +static GHashTable *exports; +static const struct fuse_lowlevel_ops fuse_ops; + +static void fuse_export_shutdown(BlockExport *exp); +static void fuse_export_delete(BlockExport *exp); + +static void init_exports_table(void); + +static int setup_fuse_export(FuseExport *exp, const char *mountpoint, + Error **errp); +static void read_from_fuse_export(void *opaque); + +static bool is_regular_file(const char *path, Error **errp); + + +static int fuse_export_create(BlockExport *blk_exp, + BlockExportOptions *blk_exp_args, + Error **errp) +{ + FuseExport *exp = container_of(blk_exp, FuseExport, common); + BlockExportOptionsFuse *args = &blk_exp_args->u.fuse; + int ret; + + assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE); + + init_exports_table(); + + /* + * It is important to do this check before calling is_regular_file() -- + * that function will do a stat(), which we would have to handle if we + * already exported something on @mountpoint. But we cannot, because + * we are currently caught up here. + * (Note that ideally we would want to resolve relative paths here, + * but bdrv_make_absolute_filename() might do the wrong thing for + * paths that contain colons, and realpath() would resolve symlinks, + * which we do not want: The mount point is not going to be the + * symlink's destination, but the link itself.) + * So this will not catch all potential clashes, but hopefully at + * least the most common one of specifying exactly the same path + * string twice. + */ + if (g_hash_table_contains(exports, args->mountpoint)) { + error_setg(errp, "There already is a FUSE export on '%s'", + args->mountpoint); + ret = -EEXIST; + goto fail; + } + + if (!is_regular_file(args->mountpoint, errp)) { + ret = -EINVAL; + goto fail; + } + + exp->mountpoint = g_strdup(args->mountpoint); + exp->writable = blk_exp_args->writable; + + ret = setup_fuse_export(exp, args->mountpoint, errp); + if (ret < 0) { + goto fail; + } + + return 0; + +fail: + fuse_export_delete(blk_exp); + return ret; +} + +/** + * Allocates the global @exports hash table. + */ +static void init_exports_table(void) +{ + if (exports) { + return; + } + + exports = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL); +} + +/** + * Create exp->fuse_session and mount it. + */ +static int setup_fuse_export(FuseExport *exp, const char *mountpoint, + Error **errp) +{ + const char *fuse_argv[4]; + char *mount_opts; + struct fuse_args fuse_args; + int ret; + + /* Needs to match what fuse_init() sets. Only max_read must be supplied. */ + mount_opts = g_strdup_printf("max_read=%zu", FUSE_MAX_BOUNCE_BYTES); + + fuse_argv[0] = ""; /* Dummy program name */ + fuse_argv[1] = "-o"; + fuse_argv[2] = mount_opts; + fuse_argv[3] = NULL; + fuse_args = (struct fuse_args)FUSE_ARGS_INIT(3, (char **)fuse_argv); + + exp->fuse_session = fuse_session_new(&fuse_args, &fuse_ops, + sizeof(fuse_ops), exp); + g_free(mount_opts); + if (!exp->fuse_session) { + error_setg(errp, "Failed to set up FUSE session"); + ret = -EIO; + goto fail; + } + + ret = fuse_session_mount(exp->fuse_session, mountpoint); + if (ret < 0) { + error_setg(errp, "Failed to mount FUSE session to export"); + ret = -EIO; + goto fail; + } + exp->mounted = true; + + g_hash_table_insert(exports, g_strdup(mountpoint), NULL); + + aio_set_fd_handler(exp->common.ctx, + fuse_session_fd(exp->fuse_session), true, + read_from_fuse_export, NULL, NULL, exp); + exp->fd_handler_set_up = true; + + return 0; + +fail: + fuse_export_shutdown(&exp->common); + return ret; +} + +/** + * Callback to be invoked when the FUSE session FD can be read from. + * (This is basically the FUSE event loop.) + */ +static void read_from_fuse_export(void *opaque) +{ + FuseExport *exp = opaque; + int ret; + + blk_exp_ref(&exp->common); + + do { + ret = fuse_session_receive_buf(exp->fuse_session, &exp->fuse_buf); + } while (ret == -EINTR); + if (ret < 0) { + goto out; + } + + fuse_session_process_buf(exp->fuse_session, &exp->fuse_buf); + +out: + blk_exp_unref(&exp->common); +} + +static void fuse_export_shutdown(BlockExport *blk_exp) +{ + FuseExport *exp = container_of(blk_exp, FuseExport, common); + + if (exp->fuse_session) { + fuse_session_exit(exp->fuse_session); + + if (exp->fd_handler_set_up) { + aio_set_fd_handler(exp->common.ctx, + fuse_session_fd(exp->fuse_session), true, + NULL, NULL, NULL, NULL); + exp->fd_handler_set_up = false; + } + } + + if (exp->mountpoint) { + /* + * Safe to drop now, because we will not handle any requests + * for this export anymore anyway. + */ + g_hash_table_remove(exports, exp->mountpoint); + } +} + +static void fuse_export_delete(BlockExport *blk_exp) +{ + FuseExport *exp = container_of(blk_exp, FuseExport, common); + + if (exp->fuse_session) { + if (exp->mounted) { + fuse_session_unmount(exp->fuse_session); + } + + fuse_session_destroy(exp->fuse_session); + } + + free(exp->fuse_buf.mem); + g_free(exp->mountpoint); +} + +/** + * Check whether @path points to a regular file. If not, put an + * appropriate message into *errp. + */ +static bool is_regular_file(const char *path, Error **errp) +{ + struct stat statbuf; + int ret; + + ret = stat(path, &statbuf); + if (ret < 0) { + error_setg_errno(errp, errno, "Failed to stat '%s'", path); + return false; + } + + if (!S_ISREG(statbuf.st_mode)) { + error_setg(errp, "'%s' is not a regular file", path); + return false; + } + + return true; +} + +/** + * A chance to set change some parameters supplied to FUSE_INIT. + */ +static void fuse_init(void *userdata, struct fuse_conn_info *conn) +{ + /* + * MIN_NON_ZERO() would not be wrong here, but what we set here + * must equal what has been passed to fuse_session_new(). + * Therefore, as long as max_read must be passed as a mount option + * (which libfuse claims will be changed at some point), we have + * to set max_read to a fixed value here. + */ + conn->max_read = FUSE_MAX_BOUNCE_BYTES; + + conn->max_write = MIN_NON_ZERO(BDRV_REQUEST_MAX_BYTES, conn->max_write); +} + +static const struct fuse_lowlevel_ops fuse_ops = { + .init = fuse_init, +}; + +const BlockExportDriver blk_exp_fuse = { + .type = BLOCK_EXPORT_TYPE_FUSE, + .instance_size = sizeof(FuseExport), + .create = fuse_export_create, + .delete = fuse_export_delete, + .request_shutdown = fuse_export_shutdown, +}; diff --git a/block/export/meson.build b/block/export/meson.build index 135b356..0a08e38 100644 --- a/block/export/meson.build +++ b/block/export/meson.build @@ -3,3 +3,5 @@ blockdev_ss.add(files('export.c')) if have_vhost_user_blk_server blockdev_ss.add(files('vhost-user-blk-server.c')) endif + +blockdev_ss.add(when: fuse, if_true: files('fuse.c')) diff --git a/include/block/fuse.h b/include/block/fuse.h new file mode 100644 index 0000000..ffa91fe --- /dev/null +++ b/include/block/fuse.h @@ -0,0 +1,30 @@ +/* + * Present a block device as a raw image through FUSE + * + * Copyright (c) 2020 Max Reitz <mreitz@redhat.com> + * + * 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; under version 2 or later of the License. + * + * 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, see <http://www.gnu.org/licenses/>. + */ + +#ifndef BLOCK_FUSE_H +#define BLOCK_FUSE_H + +#ifdef CONFIG_FUSE + +#include "block/export.h" + +extern const BlockExportDriver blk_exp_fuse; + +#endif /* CONFIG_FUSE */ + +#endif diff --git a/qapi/block-export.json b/qapi/block-export.json index 4eeac78..430bc69 100644 --- a/qapi/block-export.json +++ b/qapi/block-export.json @@ -121,6 +121,21 @@ '*num-queues': 'uint16'} } ## +# @BlockExportOptionsFuse: +# +# Options for exporting a block graph node on some (file) mountpoint +# as a raw image. +# +# @mountpoint: Path on which to export the block device via FUSE. +# This must point to an existing regular file. +# +# Since: 6.0 +## +{ 'struct': 'BlockExportOptionsFuse', + 'data': { 'mountpoint': 'str' }, + 'if': 'defined(CONFIG_FUSE)' } + +## # @NbdServerAddOptions: # # An NBD block export, per legacy nbd-server-add command. @@ -222,11 +237,13 @@ # # @nbd: NBD export # @vhost-user-blk: vhost-user-blk export (since 5.2) +# @fuse: FUSE export (since: 6.0) # # Since: 4.2 ## { 'enum': 'BlockExportType', - 'data': [ 'nbd', 'vhost-user-blk' ] } + 'data': [ 'nbd', 'vhost-user-blk', + { 'name': 'fuse', 'if': 'defined(CONFIG_FUSE)' } ] } ## # @BlockExportOptions: @@ -267,7 +284,9 @@ 'discriminator': 'type', 'data': { 'nbd': 'BlockExportOptionsNbd', - 'vhost-user-blk': 'BlockExportOptionsVhostUserBlk' + 'vhost-user-blk': 'BlockExportOptionsVhostUserBlk', + 'fuse': { 'type': 'BlockExportOptionsFuse', + 'if': 'defined(CONFIG_FUSE)' } } } ## |