[GSoC 2021] Introduce io_uring dump/restore support #1597

kkdwivedi · 2021-08-30T04:14:59Z

Currently, missing features are:

Registered files support
Registered eventfd support
Registered buffers support
Registered workqueue fd support
... and some other minor things depending on the above.

All of these depend on the eBPF iterator patches that are in https://github.com/kkdwivedi/linux/tree/criu-iter.

The following blockers exist currently:

For registered files support, the io_uring_file iterator can be used to match on files present in the fdtable of task by matching directly on the struct file pointer. To make this safe against closing of files (so that such an iteration to gather data could potentially be moved to pre_dump stage and update itself dynamically), a new file local storage map would be utilized.
For eventfd support, finding the backing fd would rely on matching the eventfd context pointer with the one stashed in f_private of the fds held open by the task. This would require pairing the io_uring iterator and task_file iterator.
Buffer registration takes reference to struct page internally, which means that the actual mapping can be destroyed after buffers are registered. This makes the task of mapping back it to a vma hard. The proposed solution to resolve is to introduce a eBPF iterator for io_uring buffers. Paired with with task_vma iterator, this should allow matching on the struct page backing the vma and the mapped buffer.
Finding the backing workqueue for an io_uring (registered using wq_fd, another io_uring) relies on matching ctx->sq_data inside the kernel, which would again rely on eBPF iterator support.

For gathering data about io_uring itself:

We can lift data like e.g. restrictions from the io_uring iteration stage itself, but there are stability issues with eBPF, so if e.g. member name is changed across kernel versions, it would require updating CRIU. The solution to this may be shipping stable eBPF iterators with the kernel (like modules) which maintain a stable output but can be modified internally across kernel versions. Right now the stopgap solution chosen is using fdinfo interface.

Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>

mihalicyn · 2021-08-30T06:14:35Z

Hi, Kumar!

Please take a look on tests failures.
Looks like on CentOS 7 we need to install liburing-devel package and use header liburing/io_uring.h from liburing.
On CentOS 8 we get 362 tests failed:

un criu dump
=[log]=> dump/zdtm/transition/fifo_loop/54/1/dump.log
------------------------ grep Error ------------------------
b'(00.010197) ----------------------------------------'
b'(00.010199)'
b'(00.010200) Collecting fds (pid: 54)'
b'(00.010201) ----------------------------------------'
b'(00.010208) Error (criu/cr-dump.c:214): pidfd_open system call not supported'
b'(00.010211) Error (criu/cr-dump.c:1326): Collect fds (pid: 54) failed with -1'
b'(00.014873) \tUnseizing 57 into 1'
b'(00.014877) \tUnseizing 58 into 1'
b'(00.014880) \tUnseizing 59 into 1'
b'(00.014883) \tUnseizing 60 into 1'
b'(00.014900) Error (criu/cr-dump.c:1834): Dumping FAILED.'

Regards,
Alex

criu/cr-dump.c

adrianreber · 2021-08-30T17:51:05Z

I started the CI tests which were not running.

kkdwivedi · 2021-08-31T07:59:54Z

This should fix everything except the 'header not found' problem for <linux/io_uring.h>.

rst0git · 2021-08-31T09:59:26Z

criu/mem.c

@@ -704,6 +709,8 @@ int prepare_mm_pid(struct pstree_item *i)
 			ret = collect_filemap(vma);
 		else if (vma_area_is(vma, VMA_AREA_SOCKET))
 			ret = collect_socket_map(vma);
+		else if (vma_area_is(vma, VMA_AREA_IO_URING))
+			ret = collect_io_uring_map(vma);


We need to make sure that CRIU continues to work with older kernel versions that don't support io_uring. Adding a kerndat check for that might help. For example, consider the case when a process tree (container) has been migrated to a system with older kernel version where io_uring is not supported.

rst0git · 2021-08-31T10:01:10Z

criu/proc_parse.c

@@ -792,6 +817,7 @@ int parse_smaps(pid_t pid, struct vm_area_list *vma_area_list, dump_filemap_t du
 		if (handle_vma(pid, vma_area, str + path_off, map_files_dir, &vfi, &prev_vfi, &vm_file_fd))
 			goto err;

+		//pr_info("dump_filemap=%p IO_URING=%d?\n", dump_filemap, (int) vma_area_is(vma_area, VMA_AREA_IO_URING));


This could be pr_debug?

rst0git · 2021-08-31T10:13:42Z

This should fix everything except the 'header not found' problem for <linux/io_uring.h>.

You can add linux/io_uring.h in criu/include/linux/.
For example, f68e5a6 adds linux/userfaultfd.h to solve a similar problem.

rst0git · 2021-09-11T20:05:05Z

criu/proc_parse.c

+	IoUringFileEntry *iofe = io_uring_get_iofe(ctx);
+	unsigned int nr;
+	pid_t pid;
+	int r;


str, r, and f are not very descriptive. Maybe we could use better variable names?

kkdwivedi · 2021-09-12T16:35:40Z

@rst0git Thanks for the review. I'll update this with your suggestions applied once I get the kernel side patches in order, which shouldn't take too long.

kkdwivedi · 2021-10-12T07:50:34Z

A prerequisite series for this and other stuff planned for later got in, now the iterators are left. After that (leaving out some specific things on CRIU side, like buffer support), this can move forward.

kkdwivedi · 2021-10-12T07:59:15Z

The iterators are in the criu-iter branch, so if someone is feeling bored, I'd appreciate review from as many people :). Note that this is feature complete , i.e. all tests part of the branch pass on BPF CI (when run locally using vmtest.sh in tools/testing/selftests/bpf). The only thing missing is bio_vec iteration for io_uring_ubuf, but that requires more thought (implement natively in the verifier, or add a helper), and I'll probably only touch that after more discussion with others. Also some stuff required to possibly do such iteration natively using a for loop (and making verifier happy about it) depends on BTF tag support, which is undergoing some change upstream for now.

Note:

If you are trying out the tests, please use latest clang to avoid any issues (Ubuntu and Fedora have nightly packages).
Use git pull --rebase to sync as this branch is force pushed/rebased onto bpf-next whenever there is a conflict.

Change made through this commit: - Include copy of flog as a seperate tree. - Modify the makefile to add and compile flog code. Signed-off-by: prakritigoyal19 <[email protected]>

CID 302713 (checkpoint-restore#1 of 1): Missing varargs init or cleanup (VARARGS) va_end was not called for argptr. Signed-off-by: Adrian Reber <[email protected]>

Separate commit for easier criu-dev <-> master transfer. Acked-by: Mike Rapoport <[email protected]> Signed-off-by: Adrian Reber <[email protected]>

Support for external net namespaces has been introduced with commit c2b21fb (criu: add support for external net namespaces). Signed-off-by: Radostin Stoyanov <[email protected]>

Currently CRIU cannot handle Checkpoint Restore operations when a device file is involved in a process, however, CRIU allows flexible extensions via special plugins but still, for certain complex devices such as a GPU, the existing hooks are not sufficient. This introduces few new hooks that will be used to support Checkpoint Restore operation with AMD GPU devices and potentially to other similar devices too. - HANDLE_DEVICE_VMA - UPDATE_VMA_MAP - RESUME_DEVICES_LATE *HANDLE_DEVICE_VMA: Hook to detect a suitable plugin to handle device file VMA with PF | IO mappings. *UPDATE_VMA_MAP: Hook to handle VMAs during a device file restore. When restoring VMAs for the device files, criu runs sys_mmap in the pie restore context but the offsets and file path within a device file may change during restore operation so it needs to be adjusted properly. *RESUME_DEVICES_LATE: Hook to do some special handling in late restore phase. During criu restore phase when a device is getting restored with the help of a plugin, some device specific operations might need to be delayed until criu finalizes the VMA placements in address space of the target process. But by the time criu finalizes this, its too late since pie phase is over and control is back to criu master process. This hook allows an external trigger to each resuming task to check whether it has a device specific operation pending such as issuing an ioctl call? Since this is called from criu master process context, supply the pid of the target process and give a chance to each plugin registered to run device specific operation if the target pid is valid. A future patch will add consumers for these plugin hooks to support AMD GPUs. Signed-off-by: Rajneesh Bhardwaj <[email protected]>

This is just a placeholder dummy plugin and will be replaced by a proper plugin that implements support for AMD GPU devices. This just facilitates the initial pull request and CI build test trigger for early code review of CRIU specific changes. Future PRs will bring in more support for amdgpu_plugin to enable CRIU with AMD ROCm. Signed-off-by: Rajneesh Bhardwaj <[email protected]>

Restore operation fails when we perform CR operation of multiple independent proceses that have device files because criu caches the ids for the device files with same mnt_ids, inode pair. This change ensures that even in case of a cached id found for a device, a unique subid is generated and returned which is used for dumping. Suggested-by: Andrei Vagin <[email protected]> Signed-off-by: Rajneesh Bhardwaj <[email protected]>

Since commit e42f5e0 ("tcp: allow to specify --tcp-close on dump"), --tcp-close option can be used when checkpointing. This option skips checkpointing established socket's state (including once established but now closed socket). However, when restoring, we still try to restore closed socket's state. As a result, a non-existent protobuf image is opened. This commit skips TCP_CLOSE socket when restoring established TCP connection and removes the redundant check for TCP_LISTEN socket as TCP_LISTEN socket cannot reach this function. Suggested-by: Andrei Vagin <[email protected]> Suggested-by: Radostin Stoyanov <[email protected]> Signed-off-by: Bui Quang Minh <[email protected]>

Signed-off-by: Bui Quang Minh <[email protected]>

The expected behavior of --tcp-close option when dumpping is to close all established tcp connections including connection that is once established but now closed. This adds an explicit description about that behavior. Signed-off-by: Bui Quang Minh <[email protected]>

Resolve the following python3 portability issues: 1) Python 3 needs explicit relative import path. 2) Coredumps are binary data, not unicode strings. Use byte strings (b"" instead of "") and open files in binary format. 3) Some functions (for example: filter) return a list in python 2, but an iterator in python 3. Port code to a common subset of python 2 and python 3 using itertool. 4) Division operator / changed meaning in Python 3. Use explicit integer division (//) where appropriate. Signed-off-by: Andrey Vyazovtsev <[email protected]>

Previous commit added support for python3 in criu-coredump. For convenience, add two files (coredump-python2 and coredump-python3) that start criu-coredump with respective python version. Edit env.sh accordingly. Signed-off-by: Andrey Vyazovtsev <[email protected]>

Signed-off-by: Radostin Stoyanov <[email protected]>

PEP8 recommends for comparisons to singletons like None to always be done with 'is' or 'is not', never the equality operators. https://python.org/dev/peps/pep-0008/#programming-recommendations Signed-off-by: Radostin Stoyanov <[email protected]>

We face that btrfs returns anonymous device in stat instead of real superblock dev for volumes, thus all btrfs volume mounts does not pass check_mountpoint_fd due to dev missmatch between stat and mountinfo. We can use special helper get_sdev_from_fd instead of stat to try to get real dev of fd for btrfs. We move check_mountpoint_fd from open_mountpoint into get_clean_fd and ns_open_mountpoint to the point where temporary mount we open fd to is still in mountinfo, thus get_sdev_from_fd would be able to find tmp mount in mountinfo. Signed-off-by: Pavel Tikhomirov <[email protected]>

All the bugs that were in the way got fixed. We can enable all tests. Signed-off-by: Nicolas Viennot <[email protected]>

Signed-off-by: Radostin Stoyanov <[email protected]>

CI badges and logo are already present in the readme file. Signed-off-by: Radostin Stoyanov <[email protected]>

Signed-off-by: Adrian Reber <[email protected]>

A couple of months (or years) ago I looked into lgtm.com for CRIU. Today on a pull request I saw result from lgtm.com for the first time and it failed. Not sure what triggered the lgtm.com message into the CRIU repository, but with the .lgtm.yml file in this commit lgtm.com can actually build CRIU. Signed-off-by: Adrian Reber <[email protected]>

This commit adds feature check support to libcriu. It already exists in the CLI and RPC and this just extends it to libcriu. This commit provides one function to do all possible feature checks in one call. The parameter to the feature check function is a structure and the user can enable which features should be checked. Using a structure makes the function extensible without the need to break the API/ABI in the future. Signed-off-by: Adrian Reber <[email protected]>

Signed-off-by: Adrian Reber <[email protected]>

When requested iovs are huge, criu needs to invoke more then one preadv()s. In this situation criu truncates memory image with offset of first preadv() and length of last one, which leads to leakage of memory image. This patch fixs truncating with right offset and length. Signed-off-by: Liu Hua <[email protected]>

This case sometimes will cause SIGILL signal in arm64 platform. <<ARM Coretex-A series Programmer's Guide for ARMv8-A>> notes: The ARM architecture does not require the hardware to ensure coherency between instruction caches and memory, even for locations of shared memory. Therefore, we need flush dcache and icache for self-modifying code. - https://developer.arm.com/documentation/den0024/a/Caches/Point-of-coherency-and-unification Signed-off-by: fu.lin <[email protected]>

This is a confusing change as it seems the original code was just wrong. GCC 12 complains with: In function ‘__conv_val’, inlined from ‘std_strtoul’ at compel/plugins/std/string.c:202:7: compel/plugins/std/string.c:154:24: error: array subscript 97 is above array bounds of ‘const char[37]’ [-Werror=array-bounds] 154 | return &conv_tab[__tolower(c)] - conv_tab; | ^~~~~~~~~~~~~~~~~~~~~~~ compel/plugins/std/string.c: In function ‘std_strtoul’: compel/plugins/std/string.c:10:19: note: while referencing ‘conv_tab’ 10 | static const char conv_tab[] = "0123456789abcdefghijklmnopqrstuvwxyz"; | ^~~~~~~~ cc1: all warnings being treated as errors Which sounds correct. The array conv_tab has just 37 elements. If I understand the code correctly we are trying to convert anything that is character between a-z and A-Z to a number for cases where the base is larger than 10. For a base 11 conversion b|B should return 11. For a base 35 conversion z|Z should return 35. This is all for a strtoul() implementation. The original code was: static const char conv_tab[] = "0123456789abcdefghijklmnopqrstuvwxyz"; return &conv_tab[__tolower(c)] - conv_tab; and that seems wrong. If conv_tab would have been some kind of hash it could have worked, but '__tolower()' will always return something larger than 97 ('a') which will always overflow the array. But maybe I just don't get that part of the code. I replaced it with return __tolower(c) - 'a' + 10; which does the right thing: 'A' = 10, 'B' = 11 ... 'Z' = 35 Signed-off-by: Adrian Reber <[email protected]>

This fixes: criu/config.c: In function ‘parse_statement’: criu/config.c:232:43: error: the comparison will always evaluate as ‘true’ for the pointer operand in ‘*(configuration + (sizetype)((long unsigned int)i * 8)) + ((sizetype)offset + 1)’ must not be NULL [-Werror=address] 232 | if (configuration[i] + offset + 1 != 0 && strchr(configuration[i] + offset, ' ')) { | ^~ Signed-off-by: Adrian Reber <[email protected]>

Parasite creation started to fail with GCC 12: On x86_64 with: ./compel/compel-host hgen -f criu/pie/restorer.built-in.o -o criu/pie/restorer-blob.h Error (compel/src/lib/handle-elf-host.c:337): Unexpected undefined symbol: `strlen'. External symbol in PIE? On aarch64 with: ld: criu/pie/restorer.o: in function `lsm_set_label': /drone/src/criu/pie/restorer.c:174: undefined reference to `strlen' Line 174 is: "for (len = 0; label[len]; len++)" Adding '-ffreestanding' to parasite compilation fixes these errors because, according to GCC developers: "strlen is a standard C function, so I don't see any bug in that being used unless you do a freestanding compilation (-nostdlib isn't that)." Signed-off-by: Adrian Reber <[email protected]>

github-actions · 2022-01-23T00:05:59Z

A friendly reminder that this PR had no activity for 30 days.

Running cross compile tests with Debian unstable sometimes fails due to missing or outdated packages. Signed-off-by: Radostin Stoyanov <[email protected]>

@Snorch

autofs.c:66:17: error: pointer 'str' may be used after 'realloc' [-Werror=use-after-free] autofs.c: In function 'check_automount': ../lib/zdtmtst.h:131:9: error: pointer 'mountpoint' may be used after 'free' [-Werror=use-after-free] 131 | test_msg("ERR: %s:%d: " format " (errno = %d (%s))\n", __FILE__, __LINE__, ##arg, errno, strerror(errno)) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ autofs.c:277:17: note: in expansion of macro 'pr_perror' 277 | pr_perror("%s: failed to close fd %d", mountpoint, p->fd); | ^~~~~~~~~ autofs.c:268:9: note: call to 'free' here 268 | free(mountpoint); | ^~~~~~~~~~~~~~~~ Fixes: checkpoint-restore#1731 v2: (@Snorch) always update `str` after successful realloc() Signed-off-by: Radostin Stoyanov <[email protected]>

Signed-off-by: Ashutosh Mehra <[email protected]>

This commit introduces basic support in CRIU to make use of eBPF kernel features to aid in the checkpoint/restore process. The immediate usecase is to provide an API to find fd to file pointer mapping, and vice-versa, for quick lookup from one file set (e.g. task, epoll, io_uring) to another. This is done by making use of eBPF iterator. This makes use of task, epoll, and io_uring file iterator features to be introduced in upcoming linux kernel versions. No dependency on clang's BPF toolchain or libbpf is taken, as we don't need those features just yet. It might be inevitable as we make more use of BPF, but for now we can tolerate just writing raw BPF assembly. To this end, also import bpf_insn.h from kernel's samples/bpf directory. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>

Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>

xinyangge-db · 2023-03-16T17:28:00Z

As the io_uring interface is getting mature, is there any plan to resume the effort in supporting io_uring in CRIU? We have a data-intensive application that is going to significantly benefit from it.

kkdwivedi force-pushed the io-uring branch from 9cb8f3c to d73671a Compare August 30, 2021 07:07

rst0git reviewed Aug 30, 2021

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kkdwivedi force-pushed the io-uring branch 2 times, most recently from 7ca36e7 to cab53ef Compare August 31, 2021 07:44

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prakritigoyal19 and others added 16 commits October 14, 2021 12:51

Add flog to CRIU

ef51ff5

Change made through this commit: - Include copy of flog as a seperate tree. - Modify the makefile to add and compile flog code. Signed-off-by: prakritigoyal19 <[email protected]>

flog: Missing varargs init or cleanup (VARARGS)

b5fcd70

CID 302713 (checkpoint-restore#1 of 1): Missing varargs init or cleanup (VARARGS) va_end was not called for argptr. Signed-off-by: Adrian Reber <[email protected]>

Run 'make indent' on 'flog/'

1a4721f

Separate commit for easier criu-dev <-> master transfer. Acked-by: Mike Rapoport <[email protected]> Signed-off-by: Adrian Reber <[email protected]>

criu(8): add --external net option

93d977c

Support for external net namespaces has been introduced with commit c2b21fb (criu: add support for external net namespaces). Signed-off-by: Radostin Stoyanov <[email protected]>

zdtm: Dumping/restoring with --tcp-close on TCP_CLOSE socket

40fc4f6

Signed-off-by: Bui Quang Minh <[email protected]>

coredump: remove unused import

e3f910f

Signed-off-by: Radostin Stoyanov <[email protected]>

coredump: sort imports

8b69c69

Signed-off-by: Radostin Stoyanov <[email protected]>

coredump: convert indentation to spaces

f0f0d7f

Signed-off-by: Radostin Stoyanov <[email protected]>

Snorch and others added 13 commits January 1, 2022 11:50

ci: test criu-image-streamer with all tests

125b32d

All the bugs that were in the way got fixed. We can enable all tests. Signed-off-by: Nicolas Viennot <[email protected]>

readme: add docker test badge

3caa619

Signed-off-by: Radostin Stoyanov <[email protected]>

contributing: remove old badges and logo

bf9a5b8

CI badges and logo are already present in the readme file. Signed-off-by: Radostin Stoyanov <[email protected]>

ci: update to latest Vagrant and Fedora images

3377245

Signed-off-by: Adrian Reber <[email protected]>

lib: added tests for feature check in libcriu

c2a12bb

Signed-off-by: Adrian Reber <[email protected]>

github-actions bot added the stale-pr label Jan 23, 2022

rst0git and others added 3 commits January 28, 2022 11:59

ci: set continue-on-error for cross-compile

985b920

Running cross compile tests with Debian unstable sometimes fails due to missing or outdated packages. Signed-off-by: Radostin Stoyanov <[email protected]>

Fix formatting in criu documentation

c2698b9

Signed-off-by: Ashutosh Mehra <[email protected]>

kkdwivedi marked this pull request as draft January 30, 2022 10:19

kkdwivedi force-pushed the io-uring branch from 7e6390f to 4da214f Compare January 30, 2022 10:19

kkdwivedi added 2 commits January 30, 2022 16:35

Introduce io_uring dump/restore support

0df5e21

Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>

kkdwivedi force-pushed the io-uring branch from 4da214f to 0df5e21 Compare January 30, 2022 11:07

github-actions bot removed the stale-pr label Apr 8, 2022

avagin force-pushed the criu-dev branch from 25d666c to a1fb2ec Compare May 13, 2022 00:57

xinyangge-db mentioned this pull request Mar 16, 2023

io_uring support in CRIU #2131

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avagin force-pushed the criu-dev branch 2 times, most recently from f392ea1 to 4d137b8 Compare June 12, 2023 06:33

avagin force-pushed the criu-dev branch from 266f150 to f5dec05 Compare October 31, 2024 06:45

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[GSoC 2021] Introduce io_uring dump/restore support #1597

[GSoC 2021] Introduce io_uring dump/restore support #1597

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[GSoC 2021] Introduce io_uring dump/restore support #1597

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