[02/18] fuse: Allow exporting BDSs via FUSE

Message ID	20191219143818.1646168-3-mreitz@redhat.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=kgwk=2J=nongnu.org=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F81F21D7D From: Max Reitz <mreitz@redhat.com> To: qemu-block@nongnu.org Subject: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE Date: Thu, 19 Dec 2019 15:38:02 +0100 Message-Id: <20191219143818.1646168-3-mreitz@redhat.com> In-Reply-To: <20191219143818.1646168-1-mreitz@redhat.com> References: <20191219143818.1646168-1-mreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Precedence: list Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com> Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" <qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org>
Series	block: Allow exporting BDSs via FUSE \| expand [00/18] block: Allow exporting BDSs via FUSE [01/18] configure: Detect libfuse [02/18] fuse: Allow exporting BDSs via FUSE [03/18] fuse: Implement standard FUSE operations [04/18] fuse: Add fuse-export-remove [05/18] fuse: Allow growable exports [06/18] fuse: (Partially) implement fallocate() [07/18] fuse: Implement hole detection through lseek [08/18] iotests: Do not needlessly filter _make_test_img [09/18] iotests: Do not pipe _make_test_img [10/18] iotests: Use convert -n in some cases [11/18] iotests: Avoid renaming images [12/18] iotests: Derive image names from $TEST_IMG [13/18] iotests/091: Use _cleanup_qemu instad of "wait" [14/18] iotests: Restrict some Python tests to file [15/18] iotests: Let _make_test_img guess $TEST_IMG_FILE [16/18] iotests: Allow testing FUSE exports [17/18] iotests: Enable fuse for many tests [18/18] iotests/281: Add test for FUSE exports

diff --git a/block.c b/block.c index c390ec6461..887c0b105e 100644 --- a/block.c +++ b/block.c @@ -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" @@ -4077,6 +4078,9 @@ void bdrv_close_all(void) { assert(job_next(NULL) == NULL); nbd_export_close_all(); +#ifdef CONFIG_FUSE + fuse_export_close_all(); +#endif /* Drop references from requests still in flight, such as canceled block * jobs whose AIO context has not been polled yet */ diff --git a/block/Makefile.objs b/block/Makefile.objs index e394fe0b6c..b02846a6e7 100644 --- a/block/Makefile.objs +++ b/block/Makefile.objs @@ -43,6 +43,7 @@ block-obj-y += crypto.o block-obj-y += aio_task.o block-obj-y += backup-top.o +block-obj-$(CONFIG_FUSE) += fuse.o common-obj-y += stream.o @@ -67,3 +68,5 @@ qcow.o-libs := -lz linux-aio.o-libs := -laio parallels.o-cflags := $(LIBXML2_CFLAGS) parallels.o-libs := $(LIBXML2_LIBS) +fuse.o-cflags := $(FUSE_CFLAGS) +fuse.o-libs := $(FUSE_LIBS) diff --git a/block/fuse.c b/block/fuse.c new file mode 100644 index 0000000000..3a22579dca --- /dev/null +++ b/block/fuse.c @@ -0,0 +1,260 @@ +/* + * Present a block device as a raw image through FUSE + * + * Copyright (c) 2019 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/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> + + +typedef struct BdrvFuseSession { + struct fuse_session *fuse_session; + struct fuse_buf fuse_buf; + BlockBackend *blk; + uint64_t perm, shared_perm; + bool mounted, fd_handler_set_up; + bool writable; +} BdrvFuseSession; + +static GHashTable *sessions; +static const struct fuse_lowlevel_ops fuse_ops; + +static void init_fuse(void); +static int setup_fuse_session(BdrvFuseSession *session, const char *mountpoint, + Error **errp); +static void read_from_fuse_session(void *opaque); +static void close_fuse_session(BdrvFuseSession *session); +static void drop_fuse_session_from_hash_table(gpointer value); + +static bool is_regular_file(const char *path, Error **errp); + + +void qmp_fuse_export_add(const char *node_name, const char *mountpoint, + bool has_writable, bool writable, + Error **errp) +{ + BlockDriverState *bs; + BdrvFuseSession *session = NULL; + + if (!has_writable) { + writable = false; + } + + init_fuse(); + + /* + * 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. + */ + if (g_hash_table_contains(sessions, mountpoint)) { + error_setg(errp, "There already is a FUSE export on '%s'", mountpoint); + goto fail; + } + + if (!is_regular_file(mountpoint, errp)) { + goto fail; + } + + bs = bdrv_find_node(node_name); + if (!bs) { + error_setg(errp, "Node '%s' not found", node_name); + goto fail; + } + + session = g_new(BdrvFuseSession, 1); + *session = (BdrvFuseSession){ + .fuse_buf = { + .mem = NULL, + }, + + .writable = writable, + }; + + session->perm = BLK_PERM_CONSISTENT_READ; + if (writable) { + session->perm |= BLK_PERM_WRITE; + } + session->shared_perm = BLK_PERM_ALL; + + session->blk = blk_new(bdrv_get_aio_context(bs), + session->perm, session->shared_perm); + if (blk_insert_bs(session->blk, bs, errp) < 0) { + goto fail; + } + + if (setup_fuse_session(session, mountpoint, errp) < 0) { + goto fail; + } + + g_hash_table_insert(sessions, g_strdup(mountpoint), session); + return; + +fail: + close_fuse_session(session); +} + +/** + * Drop all FUSE exports. + */ +void fuse_export_close_all(void) +{ + if (sessions) { + g_hash_table_destroy(sessions); + } +} + + +/** + * Ensure that the global FUSE context is set up. + */ +static void init_fuse(void) +{ + if (sessions) { + return; + } + + sessions = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, + drop_fuse_session_from_hash_table); +} + +/** + * Create session->fuse_session and mount it. + */ +static int setup_fuse_session(BdrvFuseSession *session, const char *mountpoint, + Error **errp) +{ + const char *fuse_argv[2]; + struct fuse_args fuse_args; + int ret; + + fuse_argv[0] = ""; /* Dummy program name */ + fuse_argv[1] = NULL; + fuse_args = (struct fuse_args)FUSE_ARGS_INIT(1, (char **)fuse_argv); + + session->fuse_session = fuse_session_new(&fuse_args, &fuse_ops, + sizeof(fuse_ops), session); + if (!session->fuse_session) { + error_setg(errp, "Failed to set up FUSE session"); + return -EIO; + } + + ret = fuse_session_mount(session->fuse_session, mountpoint); + if (ret < 0) { + error_setg(errp, "Failed to mount FUSE session to export"); + return -EIO; + } + session->mounted = true; + + aio_set_fd_handler(blk_get_aio_context(session->blk), + fuse_session_fd(session->fuse_session), true, + read_from_fuse_session, NULL, NULL, session); + session->fd_handler_set_up = true; + + return 0; +} + +/** + * 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_session(void *opaque) +{ + BdrvFuseSession *session = opaque; + int ret; + + ret = fuse_session_receive_buf(session->fuse_session, &session->fuse_buf); + if (ret < 0) { + return; + } + + fuse_session_process_buf(session->fuse_session, &session->fuse_buf); +} + +/** + * Drop a FUSE session (unmount it and free all associated resources). + * It is not removed from the @sessions hash table. + */ +static void close_fuse_session(BdrvFuseSession *session) +{ + if (!session) { + return; + } + + if (session->fuse_session) { + if (session->mounted) { + fuse_session_unmount(session->fuse_session); + } + if (session->fd_handler_set_up) { + aio_set_fd_handler(blk_get_aio_context(session->blk), + fuse_session_fd(session->fuse_session), true, + NULL, NULL, NULL, NULL); + } + fuse_session_destroy(session->fuse_session); + } + blk_unref(session->blk); + + g_free(session); +} + +/** + * Wrapper around close_fuse_session() for use with + * g_hash_table_new_full(). This allows dropping sessions by removing + * them from the @sessions hash table. + */ +static void drop_fuse_session_from_hash_table(gpointer value) +{ + return close_fuse_session(value); +} + + +/** + * 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; +} + +static const struct fuse_lowlevel_ops fuse_ops = { +}; diff --git a/include/block/fuse.h b/include/block/fuse.h new file mode 100644 index 0000000000..1d24dded50 --- /dev/null +++ b/include/block/fuse.h @@ -0,0 +1,24 @@ +/* + * Present a block device as a raw image through FUSE + * + * Copyright (c) 2019 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 + +void fuse_export_close_all(void); + +#endif diff --git a/qapi/block.json b/qapi/block.json index 145c268bb6..03f8d1b537 100644 --- a/qapi/block.json +++ b/qapi/block.json @@ -317,6 +317,29 @@ ## { 'command': 'nbd-server-stop' } +## +# @fuse-export-add: +# +# Exports a block graph node on some (file) mountpoint as a raw image. +# +# @node-name: Node to be exported +# +# @mountpoint: Path on which to export the block device via FUSE. +# This must point to an existing regular file. +# +# @writable: Whether clients should be able to write to the block +# device via the FUSE export. (default: false) +# +# Since: 5.0 +## +{ 'command': 'fuse-export-add', + 'data': { + 'node-name': 'str', + 'mountpoint': 'str', + '*writable': 'bool' + }, + 'if': 'defined(CONFIG_FUSE)' } + ## # @DEVICE_TRAY_MOVED: #

[02/18] fuse: Allow exporting BDSs via FUSE

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