diff --git a/block/export/fuse.c b/block/export/fuse.c index 0553bcd630..d995829ab7 100644 --- a/block/export/fuse.c +++ b/block/export/fuse.c @@ -282,8 +282,250 @@ static void fuse_init(void *userdata, struct fuse_conn_info *conn) conn->max_write = MIN_NON_ZERO(BDRV_REQUEST_MAX_BYTES, conn->max_write); } +/** + * Let clients look up files. Always return ENOENT because we only + * care about the mountpoint itself. + */ +static void fuse_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) +{ + fuse_reply_err(req, ENOENT); +} + +/** + * Let clients get file attributes (i.e., stat() the file). + */ +static void fuse_getattr(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + struct stat statbuf; + int64_t length, allocated_blocks; + time_t now = time(NULL); + FuseExport *exp = fuse_req_userdata(req); + mode_t mode; + + length = blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + allocated_blocks = bdrv_get_allocated_file_size(blk_bs(exp->common.blk)); + if (allocated_blocks <= 0) { + allocated_blocks = DIV_ROUND_UP(length, 512); + } else { + allocated_blocks = DIV_ROUND_UP(allocated_blocks, 512); + } + + mode = S_IFREG | S_IRUSR; + if (exp->writable) { + mode |= S_IWUSR; + } + + statbuf = (struct stat) { + .st_ino = inode, + .st_mode = mode, + .st_nlink = 1, + .st_uid = getuid(), + .st_gid = getgid(), + .st_size = length, + .st_blksize = blk_bs(exp->common.blk)->bl.request_alignment, + .st_blocks = allocated_blocks, + .st_atime = now, + .st_mtime = now, + .st_ctime = now, + }; + + fuse_reply_attr(req, &statbuf, 1.); +} + +static int fuse_do_truncate(const FuseExport *exp, int64_t size, + bool req_zero_write, PreallocMode prealloc) +{ + uint64_t blk_perm, blk_shared_perm; + BdrvRequestFlags truncate_flags = 0; + int ret; + + if (req_zero_write) { + truncate_flags |= BDRV_REQ_ZERO_WRITE; + } + + blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm); + + ret = blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE, + blk_shared_perm, NULL); + if (ret < 0) { + return ret; + } + + ret = blk_truncate(exp->common.blk, size, true, prealloc, + truncate_flags, NULL); + + /* Must succeed, because we are only giving up the RESIZE permission */ + blk_set_perm(exp->common.blk, blk_perm, blk_shared_perm, &error_abort); + + return ret; +} + +/** + * Let clients set file attributes. Only resizing is supported. + */ +static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat *statbuf, + int to_set, struct fuse_file_info *fi) +{ + FuseExport *exp = fuse_req_userdata(req); + int ret; + + if (!exp->writable) { + fuse_reply_err(req, EACCES); + return; + } + + if (to_set & ~FUSE_SET_ATTR_SIZE) { + fuse_reply_err(req, ENOTSUP); + return; + } + + ret = fuse_do_truncate(exp, statbuf->st_size, true, PREALLOC_MODE_OFF); + if (ret < 0) { + fuse_reply_err(req, -ret); + return; + } + + fuse_getattr(req, inode, fi); +} + +/** + * Let clients open a file (i.e., the exported image). + */ +static void fuse_open(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + fuse_reply_open(req, fi); +} + +/** + * Handle client reads from the exported image. + */ +static void fuse_read(fuse_req_t req, fuse_ino_t inode, + size_t size, off_t offset, struct fuse_file_info *fi) +{ + FuseExport *exp = fuse_req_userdata(req); + int64_t length; + void *buf; + int ret; + + /* Limited by max_read, should not happen */ + if (size > FUSE_MAX_BOUNCE_BYTES) { + fuse_reply_err(req, EINVAL); + return; + } + + /** + * Clients will expect short reads at EOF, so we have to limit + * offset+size to the image length. + */ + length = blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + if (offset + size > length) { + size = length - offset; + } + + buf = qemu_try_blockalign(blk_bs(exp->common.blk), size); + if (!buf) { + fuse_reply_err(req, ENOMEM); + return; + } + + ret = blk_pread(exp->common.blk, offset, buf, size); + if (ret >= 0) { + fuse_reply_buf(req, buf, size); + } else { + fuse_reply_err(req, -ret); + } + + qemu_vfree(buf); +} + +/** + * Handle client writes to the exported image. + */ +static void fuse_write(fuse_req_t req, fuse_ino_t inode, const char *buf, + size_t size, off_t offset, struct fuse_file_info *fi) +{ + FuseExport *exp = fuse_req_userdata(req); + int64_t length; + int ret; + + /* Limited by max_write, should not happen */ + if (size > BDRV_REQUEST_MAX_BYTES) { + fuse_reply_err(req, EINVAL); + return; + } + + if (!exp->writable) { + fuse_reply_err(req, EACCES); + return; + } + + /** + * Clients will expect short writes at EOF, so we have to limit + * offset+size to the image length. + */ + length = blk_getlength(exp->common.blk); + if (length < 0) { + fuse_reply_err(req, -length); + return; + } + + if (offset + size > length) { + size = length - offset; + } + + ret = blk_pwrite(exp->common.blk, offset, buf, size, 0); + if (ret >= 0) { + fuse_reply_write(req, size); + } else { + fuse_reply_err(req, -ret); + } +} + +/** + * Let clients fsync the exported image. + */ +static void fuse_fsync(fuse_req_t req, fuse_ino_t inode, int datasync, + struct fuse_file_info *fi) +{ + FuseExport *exp = fuse_req_userdata(req); + int ret; + + ret = blk_flush(exp->common.blk); + fuse_reply_err(req, ret < 0 ? -ret : 0); +} + +/** + * Called before an FD to the exported image is closed. (libfuse + * notes this to be a way to return last-minute errors.) + */ +static void fuse_flush(fuse_req_t req, fuse_ino_t inode, + struct fuse_file_info *fi) +{ + fuse_fsync(req, inode, 1, fi); +} + static const struct fuse_lowlevel_ops fuse_ops = { .init = fuse_init, + .lookup = fuse_lookup, + .getattr = fuse_getattr, + .setattr = fuse_setattr, + .open = fuse_open, + .read = fuse_read, + .write = fuse_write, + .flush = fuse_flush, + .fsync = fuse_fsync, }; const BlockExportDriver blk_exp_fuse = {