From fbdd3ff1da122c1197d2018268b5956a526363d3 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Thu, 5 Sep 2019 16:35:23 -0700 Subject: Deflake aio_test. - Most AIO tests call io_setup(nr_events = 128). sizeof(struct io_event) (128*32 = 4096). However, the actual size of the mapping created by io_setup() is determined by: (from fs/aio.c:ioctx_alloc()) /* * We keep track of the number of available ringbuffer slots, to prevent * overflow (reqs_available), and we also use percpu counters for this. * * So since up to half the slots might be on other cpu's percpu counters * and unavailable, double nr_events so userspace sees what they * expected: additionally, we move req_batch slots to/from percpu * counters at a time, so make sure that isn't 0: */ nr_events = max(nr_events, num_possible_cpus() * 4); nr_events *= 2; (from fs/aio.c:aio_setup_ring()) /* Compensate for the ring buffer's head/tail overlap entry */ nr_events += 2; /* 1 is required, 2 for good luck */ size = sizeof(struct aio_ring); size += sizeof(struct io_event) * nr_events; nr_pages = PFN_UP(size); When we mremap() only the first page of a multi-page AIO ring buffer mapping, fs/aio.c:aio_ring_mremap() updates struct kioctx::mmap_base - but struct kioctx::mmap_size is untouched, so sys_io_destroy() => kill_ioctx() vm_unmaps() the mremapped page, plus some number of pages after it. Just get the actual size of the mapping from /proc/self/maps. - Delete test case MremapOver; while it is correct that Linux will not complain if you overwrite the AIO ring buffer with another mapping, it won't actually work in the sense that AIO events will not be written to the new mapping, because Linux stores the struct pages of the ring buffer in struct kioctx::ring_pages and writes to those through kmap() rather than using userspace addresses. - Don't munmap() after mremap(MREMAP_FIXED) returns EFAULT; see new comment in factored-out test case MremapExpansion. PiperOrigin-RevId: 267482903 --- test/util/memory_util.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'test/util/memory_util.h') diff --git a/test/util/memory_util.h b/test/util/memory_util.h index 190c469b5..e189b73e8 100644 --- a/test/util/memory_util.h +++ b/test/util/memory_util.h @@ -118,6 +118,18 @@ inline PosixErrorOr MmapAnon(size_t length, int prot, int flags) { return Mmap(nullptr, length, prot, flags | MAP_ANONYMOUS, -1, 0); } +// Wrapper for mremap that returns a PosixErrorOr<>, since the return type of +// void* isn't directly compatible with SyscallSucceeds. +inline PosixErrorOr Mremap(void* old_address, size_t old_size, + size_t new_size, int flags, + void* new_address) { + void* rv = mremap(old_address, old_size, new_size, flags, new_address); + if (rv == MAP_FAILED) { + return PosixError(errno, "mremap failed"); + } + return rv; +} + // Returns true if the page containing addr is mapped. inline bool IsMapped(uintptr_t addr) { int const rv = msync(reinterpret_cast(addr & ~(kPageSize - 1)), -- cgit v1.2.3