Messages in this thread | | | Subject | Re: [PATCH 2/2] f2fs: support data compression | From | Chao Yu <> | Date | Thu, 31 Oct 2019 10:21:13 +0800 |
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On 2019/10/31 1:02, Eric Biggers wrote: > On Wed, Oct 30, 2019 at 04:43:52PM +0800, Chao Yu wrote: >>>>>> static void bio_post_read_processing(struct bio_post_read_ctx *ctx) >>>>>> { >>>>>> - /* >>>>>> - * We use different work queues for decryption and for verity because >>>>>> - * verity may require reading metadata pages that need decryption, and >>>>>> - * we shouldn't recurse to the same workqueue. >>>>>> - */ >>>>> >>>>> Why is it okay (i.e., no deadlocks) to no longer use different work queues for >>>>> decryption and for verity? See the comment above which is being deleted. >>>> >>>> Could you explain more about how deadlock happen? or share me a link address if >>>> you have described that case somewhere? >>>> >>> >>> The verity work can read pages from the file which require decryption. I'm >>> concerned that it could deadlock if the work is scheduled on the same workqueue. >> >> I assume you've tried one workqueue, and suffered deadlock.. >> >>> Granted, I'm not an expert in Linux workqueues, so if you've investigated this >>> and determined that it's safe, can you explain why? >> >> I'm not familiar with workqueue... I guess it may not safe that if the work is >> scheduled to the same cpu in where verity was waiting for data? if the work is >> scheduled to other cpu, it may be safe. >> >> I can check that before splitting the workqueue for verity and decrypt/decompress. >> > > Yes this is a real problem, try 'kvm-xfstests -c f2fs/encrypt generic/579'. > The worker thread gets deadlocked in f2fs_read_merkle_tree_page() waiting for > the Merkle tree page to be decrypted. This is with the v2 compression patch; > it works fine on current mainline.
Oh, alright...
Let me split them, thanks very much for all the comments and test anyway.
Thanks,
> > INFO: task kworker/u5:0:61 blocked for more than 30 seconds. > Not tainted 5.4.0-rc1-00119-g464e31ba60d0 #13 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > kworker/u5:0 D 0 61 2 0x80004000 > Workqueue: f2fs_post_read_wq f2fs_post_read_work > Call Trace: > context_switch kernel/sched/core.c:3384 [inline] > __schedule+0x299/0x6c0 kernel/sched/core.c:4069 > schedule+0x44/0xd0 kernel/sched/core.c:4136 > io_schedule+0x11/0x40 kernel/sched/core.c:5780 > wait_on_page_bit_common mm/filemap.c:1174 [inline] > wait_on_page_bit mm/filemap.c:1223 [inline] > wait_on_page_locked include/linux/pagemap.h:527 [inline] > wait_on_page_locked include/linux/pagemap.h:524 [inline] > wait_on_page_read mm/filemap.c:2767 [inline] > do_read_cache_page+0x407/0x660 mm/filemap.c:2810 > read_cache_page+0xd/0x10 mm/filemap.c:2894 > f2fs_read_merkle_tree_page+0x2e/0x30 include/linux/pagemap.h:396 > verify_page+0x110/0x560 fs/verity/verify.c:120 > fsverity_verify_bio+0xe6/0x1a0 fs/verity/verify.c:239 > verity_work fs/f2fs/data.c:142 [inline] > f2fs_post_read_work+0x36/0x50 fs/f2fs/data.c:160 > process_one_work+0x225/0x550 kernel/workqueue.c:2269 > worker_thread+0x4b/0x3c0 kernel/workqueue.c:2415 > kthread+0x125/0x140 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > INFO: task kworker/u5:1:1140 blocked for more than 30 seconds. > Not tainted 5.4.0-rc1-00119-g464e31ba60d0 #13 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > kworker/u5:1 D 0 1140 2 0x80004000 > Workqueue: f2fs_post_read_wq f2fs_post_read_work > Call Trace: > context_switch kernel/sched/core.c:3384 [inline] > __schedule+0x299/0x6c0 kernel/sched/core.c:4069 > schedule+0x44/0xd0 kernel/sched/core.c:4136 > io_schedule+0x11/0x40 kernel/sched/core.c:5780 > wait_on_page_bit_common mm/filemap.c:1174 [inline] > wait_on_page_bit mm/filemap.c:1223 [inline] > wait_on_page_locked include/linux/pagemap.h:527 [inline] > wait_on_page_locked include/linux/pagemap.h:524 [inline] > wait_on_page_read mm/filemap.c:2767 [inline] > do_read_cache_page+0x407/0x660 mm/filemap.c:2810 > read_cache_page+0xd/0x10 mm/filemap.c:2894 > f2fs_read_merkle_tree_page+0x2e/0x30 include/linux/pagemap.h:396 > verify_page+0x110/0x560 fs/verity/verify.c:120 > fsverity_verify_bio+0xe6/0x1a0 fs/verity/verify.c:239 > verity_work fs/f2fs/data.c:142 [inline] > f2fs_post_read_work+0x36/0x50 fs/f2fs/data.c:160 > process_one_work+0x225/0x550 kernel/workqueue.c:2269 > worker_thread+0x4b/0x3c0 kernel/workqueue.c:2415 > kthread+0x125/0x140 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > Showing all locks held in the system: > 1 lock held by khungtaskd/21: > #0: ffffffff82250520 (rcu_read_lock){....}, at: rcu_lock_acquire.constprop.0+0x0/0x30 include/trace/events/lock.h:13 > 2 locks held by kworker/u5:0/61: > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline] > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline] > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240 > #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline] > #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline] > #1: ffffc90000253e50 ((work_completion)(&ctx->work)){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240 > 2 locks held by kworker/u5:1/1140: > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline] > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline] > #0: ffff88807b78eb28 ((wq_completion)f2fs_post_read_wq){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240 > #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_data kernel/workqueue.c:619 [inline] > #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline] > #1: ffffc9000174be50 ((work_completion)(&ctx->work)){+.+.}, at: process_one_work+0x1ad/0x550 kernel/workqueue.c:2240 > . >
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