static void *file_ram_alloc(RAMBlock *block, ram_addr_t memory, const char *path, Error **errp) { bool unlink_on_error = false; char *filename; char *sanitized_name; char *c; void *area = MAP_FAILED; int fd = -1; int64_t file_size; if (kvm_enabled() && !kvm_has_sync_mmu()) { error_setg(errp, "host lacks kvm mmu notifiers, -mem-path unsupported"); return NULL; } for (;;) { fd = open(path, O_RDWR); if (fd >= 0) { /* @path names an existing file, use it */ break; } if (errno == ENOENT) { /* @path names a file that doesn't exist, create it */ fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0644); if (fd >= 0) { unlink_on_error = true; break; } } else if (errno == EISDIR) { /* @path names a directory, create a file there */ /* Make name safe to use with mkstemp by replacing '/' with '_'. */ sanitized_name = g_strdup(memory_region_name(block->mr)); for (c = sanitized_name; *c != '\0'; c++) { if (*c == '/') { *c = '_'; } } filename = g_strdup_printf("%s/qemu_back_mem.%s.XXXXXX", path, sanitized_name); g_free(sanitized_name); fd = mkstemp(filename); if (fd >= 0) { unlink(filename); g_free(filename); break; } g_free(filename); } if (errno != EEXIST && errno != EINTR) { error_setg_errno(errp, errno, "can't open backing store %s for guest RAM", path); goto error; } /* * Try again on EINTR and EEXIST. The latter happens when * something else creates the file between our two open(). */ } block->page_size = qemu_fd_getpagesize(fd); block->mr->align = block->page_size; #if defined(__s390x__) if (kvm_enabled()) { block->mr->align = MAX(block->mr->align, QEMU_VMALLOC_ALIGN); } #endif file_size = get_file_size(fd); if (memory < block->page_size) { error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to " "or larger than page size 0x%zx", memory, block->page_size); goto error; } if (file_size > 0 && file_size < memory) { error_setg(errp, "backing store %s size 0x%" PRIx64 " does not match 'size' option 0x" RAM_ADDR_FMT, path, file_size, memory); goto error; } memory = ROUND_UP(memory, block->page_size); /* * ftruncate is not supported by hugetlbfs in older * hosts, so don't bother bailing out on errors. * If anything goes wrong with it under other filesystems, * mmap will fail. * * Do not truncate the non-empty backend file to avoid corrupting * the existing data in the file. Disabling shrinking is not * enough. For example, the current vNVDIMM implementation stores * the guest NVDIMM labels at the end of the backend file. If the * backend file is later extended, QEMU will not be able to find * those labels. Therefore, extending the non-empty backend file * is disabled as well. */ if (!file_size && ftruncate(fd, memory)) { perror("ftruncate"); } area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags & RAM_SHARED); if (area == MAP_FAILED) { error_setg_errno(errp, errno, "unable to map backing store for guest RAM"); goto error; } if (mem_prealloc) { os_mem_prealloc(fd, area, memory, errp); if (errp && *errp) { goto error; } } block->fd = fd; return area; error: if (area != MAP_FAILED) { qemu_ram_munmap(area, memory); } if (unlink_on_error) { unlink(path); } if (fd != -1) { close(fd); } return NULL; }
static void *file_ram_alloc(RAMBlock *block, ram_addr_t memory, const char *path, Error **errp) { bool unlink_on_error = false; char *filename; char *sanitized_name; char *c; void *area = MAP_FAILED; int fd = -1; int64_t file_size; if (kvm_enabled() && !kvm_has_sync_mmu()) { error_setg(errp, "host lacks kvm mmu notifiers, -mem-path unsupported"); return NULL; } for (;;) { fd = open(path, O_RDWR); if (fd >= 0) {   break; } if (errno == ENOENT) {   fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0644); if (fd >= 0) { unlink_on_error = true; break; } } else if (errno == EISDIR) {     sanitized_name = g_strdup(memory_region_name(block->mr)); for (c = sanitized_name; *c != '\0'; c++) { if (*c == '/') { *c = '_'; } } filename = g_strdup_printf("%s/qemu_back_mem.%s.XXXXXX", path, sanitized_name); g_free(sanitized_name); fd = mkstemp(filename); if (fd >= 0) { unlink(filename); g_free(filename); break; } g_free(filename); } if (errno != EEXIST && errno != EINTR) { error_setg_errno(errp, errno, "can't open backing store %s for guest RAM", path); goto error; }   } block->page_size = qemu_fd_getpagesize(fd); block->mr->align = block->page_size; #if defined(__s390x__) if (kvm_enabled()) { block->mr->align = MAX(block->mr->align, QEMU_VMALLOC_ALIGN); } #endif file_size = get_file_size(fd); if (memory < block->page_size) { error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to " "or larger than page size 0x%zx", memory, block->page_size); goto error; } if (file_size > 0 && file_size < memory) { error_setg(errp, "backing store %s size 0x%" PRIx64 " does not match 'size' option 0x" RAM_ADDR_FMT, path, file_size, memory); goto error; } memory = ROUND_UP(memory, block->page_size);   if (!file_size && ftruncate(fd, memory)) { perror("ftruncate"); } area = qemu_ram_mmap(fd, memory, block->mr->align, block->flags & RAM_SHARED); if (area == MAP_FAILED) { error_setg_errno(errp, errno, "unable to map backing store for guest RAM"); goto error; } if (mem_prealloc) { os_mem_prealloc(fd, area, memory, errp); if (errp && *errp) { goto error; } } block->fd = fd; return area; error: if (area != MAP_FAILED) { qemu_ram_munmap(area, memory); } if (unlink_on_error) { unlink(path); } if (fd != -1) { close(fd); } return NULL; }