Thank you for your contribution! Sashiko AI review found 5 potential issue(s) to consider: - [Medium] selftests/dmabuf-heaps: check_deps() runs before handle_build() in vmtest.sh - [Medium] selftests/dmabuf-heaps: fail instead of skip on EOPNOTSUPP in XFER_CHARGE test - [Medium] selftests/dmabuf-heaps: pidfd_alloc_supported() treats EOPNOTSUPP as supported - [Medium] selftests: dmabuf-heaps: no memory controller check in open_self_cgroupfd() - [Medium] selftests: cgroup: MEMCG_DMABUF_WAIT_RETRIES is shorter than 2s rstat FLUSH_TIME --
commit 764a620a8574ac6b7e6c57e6f71e4c743c373656 Author: Albert Esteve <[email protected]> selftests/dmabuf-heaps: Add dma-buf memcg accounting tests This commit adds selftests for dma-buf memcg accounting via charge_fd in DMA_HEAP_IOCTL_ALLOC and DMA_BUF_IOCTL_XFER_CHARGE across the dmabuf-heaps and cgroup test suites, along with a vmtest.sh runner script. > diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c > b/tools/testing/selftests/cgroup/test_memcontrol.c > index 0ed82347044ed..0b41c3c6f62c1 100644 > --- a/tools/testing/selftests/cgroup/test_memcontrol.c > +++ b/tools/testing/selftests/cgroup/test_memcontrol.c > @@ -19,10 +19,20 @@ > #include <errno.h> > #include <sys/mman.h> > > +#include <linux/dma-buf.h> > +#include <linux/dma-heap.h> > +#include <signal.h> > +#include <sys/ioctl.h> > + > +#include "../pidfd/pidfd.h" > #include "kselftest.h" > #include "cgroup_util.h" > > +#define DMA_HEAP_SYSTEM "/dev/dma_heap/system" > +#define ONE_MEG (1024 * 1024) > + > #define MEMCG_SOCKSTAT_WAIT_RETRIES 30 > +#define MEMCG_DMABUF_WAIT_RETRIES 15 [Severity: Medium] Is MEMCG_DMABUF_WAIT_RETRIES (15 retries at 100ms intervals, or 1.4 seconds before the final read) long enough to avoid races with the periodic rstat flush in test_memcg_dmabuf() and test_memcg_dmabuf_xfer_at_limit()? In mm/memcontrol.c, reading memory.stat calls mem_cgroup_flush_stats(), which only flushes rstat synchronously when stats_updates exceeds MEMCG_CHARGE_BATCH * num_online_cpus() (64 * num_online_cpus()): mm/memcontrol.c:mem_cgroup_flush_stats() if (atomic_long_read(&vmstats->stats_updates) > MEMCG_CHARGE_BATCH * num_online_cpus()) ... Charging or uncharging a ONE_MEG (1 MB) dma-buf in a fresh child cgroup updates MEMCG_DMABUF by 256 pages on 4KB-page kernels (or 16 pages on 64KB-page kernels). When num_online_cpus() >= 4 (where 256 > 64 * 4 is false) or on >4KB-page kernels, reading memory.stat skips synchronous flushing and relies on the periodic deferred work stats_flush_dwork, which runs every FLUSH_TIME (2UL * HZ, or 2.0 seconds). In test_memcg_dmabuf(), even if the first poll for ONE_MEG catches a periodic flush, that flush resets stats_updates to 0 and schedules the next stats_flush_dwork 2.0 seconds later. Immediately closing dmabuf_fd adds only 256 to stats_updates, so the subsequent 1.4-second poll for dmabuf == 0 can time out before the next 2.0-second periodic flush runs. Should MEMCG_DMABUF_WAIT_RETRIES be at least 30, matching MEMCG_SOCKSTAT_WAIT_RETRIES? > diff --git a/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c > b/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c > index 1d49df6719198..90ef14d2ecba0 100644 > --- a/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c > +++ b/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c [ ... ] > @@ -496,6 +505,218 @@ static void test_alloc_no_fd_leak_on_efault(char > *heap_name) [ ... ] > +/* > + * Probe whether the kernel honours charge_fd in DMA_HEAP_IOCTL_ALLOC. > + */ > +static bool pidfd_alloc_supported(int heap_fd) > +{ > + int devnull_fd, dmabuf_fd = -1, ret; > + > + devnull_fd = open("/dev/null", O_RDONLY); > + if (devnull_fd < 0) > + return false; > + > + ret = dmabuf_heap_alloc_pidfd(heap_fd, ONE_MEG, 0, devnull_fd, > &dmabuf_fd); > + if (dmabuf_fd >= 0) { > + close(dmabuf_fd); > + dmabuf_fd = -1; > + } > + close(devnull_fd); > + return ret < 0; > +} [Severity: Medium] What happens in pidfd_alloc_supported() when the kernel is built with CONFIG_MEMCG=n? In drivers/dma-buf/dma-heap.c, dma_heap_ioctl_allocate() passes a non-zero charge_fd to mem_cgroup_get_from_fd(): drivers/dma-buf/dma-heap.c:dma_heap_ioctl_allocate() if (heap_allocation->charge_fd) { memcg = mem_cgroup_get_from_fd(heap_allocation->charge_fd); if (IS_ERR(memcg)) return ERR_CAST(memcg); } When CONFIG_MEMCG is disabled, the stub in include/linux/memcontrol.h returns ERR_PTR(-EOPNOTSUPP): include/linux/memcontrol.h:mem_cgroup_get_from_fd() static inline struct mem_cgroup *mem_cgroup_get_from_fd(int fd) { return ERR_PTR(-EOPNOTSUPP); } Because dmabuf_heap_alloc_pidfd() returns -1 with errno == EOPNOTSUPP, returning ret < 0 causes pidfd_alloc_supported() to return true when CONFIG_MEMCG=n, and test_alloc_pidfd_self(), test_alloc_pidfd_child(), test_alloc_cgroupfd_self(), and test_xfer_charge_cgroupfd_self() then proceed and report test failures instead of skipping. Should pidfd_alloc_supported() also verify that errno != EOPNOTSUPP (or errno == EINVAL)? [ ... ] > +static int open_self_cgroupfd(void) > +{ > + char cgroup_path[PATH_MAX]; > + char buf[PATH_MAX]; > + FILE *f; > + > + f = fopen("/proc/self/cgroup", "r"); > + if (!f) > + return -1; > + > + cgroup_path[0] = '\0'; > + while (fgets(buf, sizeof(buf), f)) { > + char *p = buf; > + > + if (strncmp(p, "0::", 3) == 0) { > + p += 3; > + p[strcspn(p, "\n")] = '\0'; > + snprintf(cgroup_path, sizeof(cgroup_path), > + "/sys/fs/cgroup%s", p); > + break; > + } > + } > + fclose(f); > + > + if (!cgroup_path[0]) > + return -1; > + > + return open(cgroup_path, O_RDONLY | O_DIRECTORY); > +} > + > +/* > + * Test: allocate charging the calling process's own cgroup via a cgroupfd. > + */ > +static void test_alloc_cgroupfd_self(char *heap_name) > +{ > + int heap_fd = -1, cgroup_fd = -1, dmabuf_fd = -1, ret; > + > + heap_fd = dmabuf_heap_open(heap_name); > + > + if (!pidfd_alloc_supported(heap_fd)) { > + ksft_test_result_skip("charge_fd not supported by this > kernel\n"); > + goto out; > + } > + > + cgroup_fd = open_self_cgroupfd(); > + if (cgroup_fd < 0) { > + ksft_test_result_skip("cannot open self cgroupfd\n"); > + goto out; > + } > + > + ret = dmabuf_heap_alloc_pidfd(heap_fd, ONE_MEG, 0, cgroup_fd, > &dmabuf_fd); > + ksft_test_result(!ret, "Allocation with cgroupfd %d\n", ret); > + if (dmabuf_fd >= 0) > + close(dmabuf_fd); > + close(cgroup_fd); > +out: > + close(heap_fd); > +} [Severity: Medium] Can test_alloc_cgroupfd_self() and test_xfer_charge_cgroupfd_self() fail with ENOENT instead of skipping when the test binary is run outside vmtest.sh (for example via make run_tests or vmtest.sh -s) in a cgroup where the memory controller is not enabled? Unlike the pidfd path in mem_cgroup_get_from_fd(), which uses get_mem_cgroup_from_mm() and walks up to an online ancestor, the cgroupfd path requires the memory controller CSS to be directly enabled on the target cgroup itself: mm/memcontrol.c:mem_cgroup_get_from_fd() cgrp = cgroup_get_from_fd(fd); if (!IS_ERR(cgrp)) { rcu_read_lock(); css = cgroup_css(cgrp, &memory_cgrp_subsys); if (!css || !css_tryget_online(css)) { rcu_read_unlock(); cgroup_put(cgrp); return ERR_PTR(-ENOENT); } When dmabuf-heap runs in a leaf cgroup (such as a standard systemd user or service scope) whose parent has not enabled +memory in cgroup.subtree_control, or when booted with cgroup_disable=memory, open_self_cgroupfd() still succeeds in opening the directory, and the ioctl fails with ENOENT. Should open_self_cgroupfd() check that memory is active in that cgroup (or should these two tests skip when the ioctl fails with errno == ENOENT)? > +/* > + * Test: transfer a dma-buf's charge to self cgroup via > DMA_BUF_IOCTL_XFER_CHARGE. > + */ > +static void test_xfer_charge_cgroupfd_self(char *heap_name) > +{ > + int heap_fd = -1, cgroup_fd = -1, dmabuf_fd = -1, ret; > + struct dma_buf_transfer_charge xfer = { 0 }; > + > + heap_fd = dmabuf_heap_open(heap_name); > + > + if (!pidfd_alloc_supported(heap_fd)) { > + ksft_test_result_skip("charge_fd not supported by this > kernel\n"); > + goto out; > + } > + > + ret = dmabuf_heap_alloc(heap_fd, ONE_MEG, 0, &dmabuf_fd); > + if (ret) { > + ksft_test_result_fail("Allocation failed %d\n", ret); > + goto out; > + } > + > + cgroup_fd = open_self_cgroupfd(); > + if (cgroup_fd < 0) { > + ksft_test_result_skip("cannot open self cgroupfd\n"); > + close(dmabuf_fd); > + goto out; > + } > + > + xfer.charge_fd = cgroup_fd; > + ret = ioctl(dmabuf_fd, DMA_BUF_IOCTL_XFER_CHARGE, &xfer); > + ksft_test_result(!ret, "XFER_CHARGE to self cgroupfd %d\n", ret); [Severity: Medium] Does test_xfer_charge_cgroupfd_self() report a failure instead of skipping when main() iterates over non-system heaps in /dev/dma_heap (such as CMA heaps when CONFIG_DMABUF_HEAPS_CMA=y)? In drivers/dma-buf/dma-heap.c, dma_heap_ioctl_allocate() validates charge_fd before calling heap->ops->allocate(), so pidfd_alloc_supported() returns true for all heaps. However, in drivers/dma-buf/dma-buf.c, dma_buf_xfer_charge() checks whether the exporter enabled memcg accounting on the buffer: drivers/dma-buf/dma-buf.c:dma_buf_xfer_charge() if (!dmabuf->memcg_account) return -EOPNOTSUPP; Because only system_heap sets exp_info.memcg_account = true (while exporters such as cma_heap leave it false), ioctl(dmabuf_fd, DMA_BUF_IOCTL_XFER_CHARGE, &xfer) returns -1 with errno == EOPNOTSUPP on those heaps. Should test_xfer_charge_cgroupfd_self() call ksft_test_result_skip() when ret < 0 and errno == EOPNOTSUPP? > diff --git a/tools/testing/selftests/dmabuf-heaps/vmtest.sh > b/tools/testing/selftests/dmabuf-heaps/vmtest.sh > new file mode 100755 > index 0000000000000..3574b71ca83e8 > --- /dev/null > +++ b/tools/testing/selftests/dmabuf-heaps/vmtest.sh [ ... ] > +check_deps() { > + for dep in vng make; do > + if [[ ! -x $(command -v "${dep}") ]]; then > + echo -e "skip: dependency ${dep} not found!\n" > + exit "${KSFT_SKIP}" > + fi > + done > + > + if ${SHELL_MODE}; then > + return > + fi > + > + if [[ ! -x "${DMABUF_HEAP_TEST}" ]]; then > + printf "skip: %s not found!" "${DMABUF_HEAP_TEST}" > + printf " Please build the kselftest dmabuf-heaps target (or use > -b).\n" > + exit "${KSFT_SKIP}" > + fi > + > + if [[ ! -x "${MEMCONTROL_TEST}" ]]; then > + printf "skip: %s not found!" "${MEMCONTROL_TEST}" > + printf " Please build the kselftest cgroup target (or use > -b).\n" > + exit "${KSFT_SKIP}" > + fi > +} [ ... ] > +trap cleanup EXIT > + > +check_deps > +check_vng > +handle_build > +make_runner [Severity: Medium] If vmtest.sh is invoked with -b on a clean tree where the selftest binaries have not been built yet, won't check_deps() exit with KSFT_SKIP before handle_build() has a chance to build them? In the main flow, check_deps() runs before handle_build(), and inside check_deps() only SHELL_MODE returns early before checking for DMABUF_HEAP_TEST and MEMCONTROL_TEST. Should check_deps() also skip the binary existence checks when BUILD is true (or run after handle_build())? -- Sashiko AI review · https://sashiko.dev/#/patchset/20261027-v2_20230123_tjmercier_google_com-v3-0-78d2c4cb8...@redhat.com?part=8
