[CRIU] [PATCH v2 3/3] aio: Restore aio ring content
Pavel Emelyanov
xemul at virtuozzo.com
Mon Mar 14 07:56:12 PDT 2016
On 03/14/2016 02:49 PM, Kirill Tkhai wrote:
> 1)Dump/restore mmaped aio ring like any other private vma entry.
> 2)Create io context, set head and tail using write to /dev/null.
> 3)Copy aio ring restored in (1) to created in (2).
> 4)Unmap temporary ring (1).
> 5)Remap (2) to address of (1).
I need better description of supported states. There are pending
requests and completed requests and criu tries not to c/r anything.
What is changed with this patch?
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
> criu/arch/ppc64/syscalls/syscall-ppc64.tbl | 1
> criu/arch/x86/syscalls/syscall_32.tbl | 1
> criu/arch/x86/syscalls/syscall_64.tbl | 1
> criu/cr-restore.c | 6 +
> criu/include/syscall-types.h | 1
> criu/include/vma.h | 5 +
> criu/pie/parasite.c | 9 --
> criu/pie/restorer.c | 166 ++++++++++++++++++++--------
> 8 files changed, 130 insertions(+), 60 deletions(-)
>
> diff --git a/criu/arch/ppc64/syscalls/syscall-ppc64.tbl b/criu/arch/ppc64/syscalls/syscall-ppc64.tbl
> index 3319379..e71a1ad 100644
> --- a/criu/arch/ppc64/syscalls/syscall-ppc64.tbl
> +++ b/criu/arch/ppc64/syscalls/syscall-ppc64.tbl
> @@ -102,4 +102,5 @@ __NR_seccomp 358 sys_seccomp (unsigned int op, unsigned int flags, const char
> __NR_memfd_create 360 sys_memfd_create (const char *name, unsigned int flags)
> __NR_io_setup 227 sys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
> __NR_io_getevents 229 sys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
> +__NR_io_submit 230 sys_io_submit (aio_context_t ctx_id, long nr, struct iocb **iocbpp)
> __NR_ipc 117 sys_ipc (unsigned int call, int first, unsigned long second, unsigned long third, const void *ptr, long fifth)
> diff --git a/criu/arch/x86/syscalls/syscall_32.tbl b/criu/arch/x86/syscalls/syscall_32.tbl
> index c527122..2b61530 100644
> --- a/criu/arch/x86/syscalls/syscall_32.tbl
> +++ b/criu/arch/x86/syscalls/syscall_32.tbl
> @@ -66,6 +66,7 @@ __NR_set_thread_area 243 sys_set_thread_area (user_desc_t *info)
> __NR_get_thread_area 244 sys_get_thread_area (user_desc_t *info)
> __NR_io_setup 245 sys_io_setup (unsigned nr_reqs, aio_context_t *ctx32p)
> __NR_io_getevents 247 sys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
> +__NR_io_submit 248 sys_io_submit (aio_context_t ctx_id, long nr, struct iocb **iocbpp)
> __NR_exit_group 252 sys_exit_group (int error_code)
> __NR_set_tid_address 258 sys_set_tid_address (int *tid_addr)
> __NR_timer_create 259 sys_timer_create (clockid_t which_clock, struct sigevent *timer_event_spec, kernel_timer_t *created_timer_id)
> diff --git a/criu/arch/x86/syscalls/syscall_64.tbl b/criu/arch/x86/syscalls/syscall_64.tbl
> index 5c32d4c..e01ea8f 100644
> --- a/criu/arch/x86/syscalls/syscall_64.tbl
> +++ b/criu/arch/x86/syscalls/syscall_64.tbl
> @@ -74,6 +74,7 @@ __NR_futex 202 sys_futex (u32 *uaddr, int op, u32 val, struct timespec *utim
> __NR_set_thread_area 205 sys_set_thread_area (user_desc_t *info)
> __NR_io_setup 206 sys_io_setup (unsigned nr_events, aio_context_t *ctx)
> __NR_io_getevents 208 sys_io_getevents (aio_context_t ctx, long min_nr, long nr, struct io_event *evs, struct timespec *tmo)
> +__NR_io_submit 209 sys_io_submit (aio_context_t ctx, long nr, struct iocb **iocbpp)
> __NR_get_thread_area 211 sys_get_thread_area (user_desc_t *info)
> __NR_set_tid_address 218 sys_set_tid_address (int *tid_addr)
> __NR_restart_syscall 219 sys_restart_syscall (void)
> diff --git a/criu/cr-restore.c b/criu/cr-restore.c
> index 30ddff9..922fa14 100644
> --- a/criu/cr-restore.c
> +++ b/criu/cr-restore.c
> @@ -316,6 +316,7 @@ static int map_private_vma(struct vma_area *vma, void **tgt_addr,
>
> size = vma_entry_len(vma->e);
> if (paddr == NULL) {
> + int flag = 0;
> /*
> * The respective memory area was NOT found in the parent.
> * Map a new one.
> @@ -323,9 +324,12 @@ static int map_private_vma(struct vma_area *vma, void **tgt_addr,
> pr_info("Map 0x%016"PRIx64"-0x%016"PRIx64" 0x%016"PRIx64" vma\n",
> vma->e->start, vma->e->end, vma->e->pgoff);
>
> + if (vma_entry_is(vma->e, VMA_AREA_AIORING))
> + flag |= MAP_ANONYMOUS;
> +
> addr = mmap(*tgt_addr, size,
> vma->e->prot | PROT_WRITE,
> - vma->e->flags | MAP_FIXED,
> + vma->e->flags | MAP_FIXED | flag,
> vma->e->fd, vma->e->pgoff);
>
> if (addr == MAP_FAILED) {
> diff --git a/criu/include/syscall-types.h b/criu/include/syscall-types.h
> index b056f6d..5b4e1aa 100644
> --- a/criu/include/syscall-types.h
> +++ b/criu/include/syscall-types.h
> @@ -31,6 +31,7 @@ struct rusage;
> struct file_handle;
> struct robust_list_head;
> struct io_event;
> +struct iocb;
> struct timespec;
>
> typedef unsigned long aio_context_t;
> diff --git a/criu/include/vma.h b/criu/include/vma.h
> index 247c5a3..ce4d5f7 100644
> --- a/criu/include/vma.h
> +++ b/criu/include/vma.h
> @@ -95,10 +95,11 @@ static inline int in_vma_area(struct vma_area *vma, unsigned long addr)
> static inline bool vma_entry_is_private(VmaEntry *entry,
> unsigned long task_size)
> {
> - return vma_entry_is(entry, VMA_AREA_REGULAR) &&
> + return (vma_entry_is(entry, VMA_AREA_REGULAR) &&
> (vma_entry_is(entry, VMA_ANON_PRIVATE) ||
> vma_entry_is(entry, VMA_FILE_PRIVATE)) &&
> - (entry->end <= task_size);
> + (entry->end <= task_size)) ||
> + vma_entry_is(entry, VMA_AREA_AIORING);
> }
>
> static inline bool vma_area_is_private(struct vma_area *vma,
> diff --git a/criu/pie/parasite.c b/criu/pie/parasite.c
> index 1df3e71..d82518e 100644
> --- a/criu/pie/parasite.c
> +++ b/criu/pie/parasite.c
> @@ -410,14 +410,7 @@ static int parasite_check_aios(struct parasite_check_aios_args *args)
> return -1;
> }
>
> - /*
> - * XXX what else can we do if there are requests
> - * in the ring?
> - */
> - if (ring->head != ring->tail) {
> - pr_err("Pending AIO requests in ring #%d\n", i);
> - return -1;
> - }
> + /* XXX: wait aio completion */
>
> args->ring[i].max_reqs = ring->nr;
> }
> diff --git a/criu/pie/restorer.c b/criu/pie/restorer.c
> index f7bde75..d19f4dc 100644
> --- a/criu/pie/restorer.c
> +++ b/criu/pie/restorer.c
> @@ -3,6 +3,7 @@
>
> #include <linux/securebits.h>
> #include <linux/capability.h>
> +#include <linux/aio_abi.h>
> #include <sys/types.h>
> #include <sys/mman.h>
> #include <sys/stat.h>
> @@ -546,6 +547,120 @@ static unsigned long restore_mapping(const VmaEntry *vma_entry)
> return addr;
> }
>
> +/*
> + * This restores aio ring header, content, head and in-kernel position
> + * of tail. To set tail, we write to /dev/null and use the fact this
> + * operation is synchronious for the device. Also, we unmap temporary
> + * anonymous area, used to store content of ring buffer during restore
> + * and mapped in map_private_vma().
> + */
> +static int restore_aio_ring(struct rst_aio_ring *raio)
> +{
> + struct aio_ring *ring = (void *)raio->addr;
> + unsigned head = ring->head;
> + unsigned tail = ring->tail;
> + struct iocb *iocb, **iocbp;
> + unsigned long ctx = 0;
> + int i, count, fd, ret;
> + char buf[1];
> +
> + ret = sys_io_setup(raio->nr_req, &ctx);
> + if (ret < 0) {
> + pr_err("Ring setup failed with %d\n", ret);
> + return -1;
> + }
> +
> + if (tail == 0 && head == 0)
> + goto populate;
> +
> + fd = sys_open("/dev/null", O_WRONLY, 0);
> + if (fd < 0) {
> + pr_err("Can't open /dev/null for aio\n");
> + return -1;
> + }
> +
> + if (tail >= head)
> + count = tail;
> + else
> + count = ring->nr - 1;
> +
> + iocb = (void *)sys_mmap(NULL, count * sizeof(struct iocb), PROT_READ|PROT_WRITE,
> + MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
> + iocbp = (void *)sys_mmap(NULL, count * sizeof(struct iocb *), PROT_READ|PROT_WRITE,
> + MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
> + if (iocb == MAP_FAILED || iocbp == MAP_FAILED) {
> + pr_err("Can't mmap aio tmp buffer\n");
> + return -1;
> + }
> +
> + for (i = 0; i < count; i++) {
> + iocbp[i] = &iocb[i];
> + iocb[i].aio_fildes = fd;
> + iocb[i].aio_buf = (unsigned long)buf;
> + iocb[i].aio_nbytes = 1;
> + iocb[i].aio_lio_opcode = IOCB_CMD_PWRITE;
> + }
> +
> + i = count;
> + do {
> + ret = sys_io_submit(ctx, i, iocbp);
> + if (ret < 0) {
> + pr_err("Can't submit %d aio iocbs: ret=%d\n", i, ret);
> + return -1;
> + }
> + i -= ret;
> +
> + if (count - i > head)
> + /*
> + * Though count is less than maximum available reqs, kernel's
> + * get_reqs_available() takes only a number of reqs, which is
> + * aliquot to kioctx::req_batch. So, set head to free a space
> + * for next io_submit().
> + *
> + * Direct set of head is equal to sys_io_getevents() call. See
> + * kernel for the details.
> + */
> + ((struct aio_ring *)ctx)->head = head;
> + } while (i);
> +
> + if (tail < head) {
> + ret = sys_io_submit(ctx, tail + 1, iocbp);
> + if (ret != tail + 1) {
> + pr_err("Can't submit %d aio iocbs more, ret=%d\n", tail + 1, ret);
> + return -1;
> + }
> + }
> +
> + sys_munmap(iocb, count * sizeof(struct iocb));
> + sys_munmap(iocbp, count * sizeof(struct iocb *));
> + sys_close(fd);
> +populate:
> + count = raio->len/sizeof(unsigned long);
> + for (i = 0; i < count; i++)
> + ((unsigned long *)ctx)[i] = ((unsigned long *)ring)[i];
> +
> + /* Unmap temporary anonymous area */
> + sys_munmap(ring, raio->len);
> +
> + /*
> + * If we failed to get the proper nr_req right and
> + * created smaller or larger ring, then this remap
> + * will (should) fail, since AIO rings has immutable
> + * size.
> + *
> + * This is not great, but anyway better than putting
> + * a ring of wrong size into correct place.
> + */
> + ctx = sys_mremap(ctx, raio->len, raio->len,
> + MREMAP_FIXED | MREMAP_MAYMOVE,
> + raio->addr);
> + if (ctx != raio->addr) {
> + pr_err("Ring remap failed with %ld\n", ctx);
> + return -1;
> + }
> + return 0;
> +}
> +
> static void rst_tcp_repair_off(struct rst_tcp_sock *rts)
> {
> int aux, ret;
> @@ -999,56 +1114,9 @@ long __export_restore_task(struct task_restore_args *args)
> * Now when all VMAs are in their places time to set
> * up AIO rings.
> */
> -
> - for (i = 0; i < args->rings_n; i++) {
> - struct rst_aio_ring *raio = &args->rings[i];
> - unsigned long ctx = 0;
> - int ret;
> -
> - ret = sys_io_setup(raio->nr_req, &ctx);
> - if (ret < 0) {
> - pr_err("Ring setup failed with %d\n", ret);
> + for (i = 0; i < args->rings_n; i++)
> + if (restore_aio_ring(&args->rings[i]) < 0)
> goto core_restore_end;
> - }
> -
> - if (ctx == raio->addr) /* Lucky bastards we are! */
> - continue;
> -
> - /*
> - * If we failed to get the proper nr_req right and
> - * created smaller or larger ring, then this remap
> - * will (should) fail, since AIO rings has immutable
> - * size.
> - *
> - * This is not great, but anyway better than putting
> - * a ring of wrong size into correct place.
> - */
> -
> - ctx = sys_mremap(ctx, raio->len, raio->len,
> - MREMAP_FIXED | MREMAP_MAYMOVE,
> - raio->addr);
> - if (ctx != raio->addr) {
> - pr_err("Ring remap failed with %ld\n", ctx);
> - goto core_restore_end;
> - }
> -
> - /*
> - * Now check that kernel not just remapped the
> - * ring into new place, but updated the internal
> - * context state respectively.
> - */
> -
> - ret = sys_io_getevents(ctx, 0, 1, NULL, NULL);
> - if (ret != 0) {
> - if (ret < 0)
> - pr_err("Kernel doesn't remap AIO rings\n");
> - else
> - pr_err("AIO context screwed up\n");
> -
> - goto core_restore_end;
> - }
> - }
> -
> /*
> * Finally restore madivse() bits
> */
>
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