This bug is in all 5.2+ kernels, fix is on the way to 5.3.0 and stable. While rare, if we can spare even one user from running into it, that'd be a good thing. Upstream discussion and patch https://lore.kernel.org/linux-btrfs/20190911145542.1125-1-fdmanana@kernel.org/T/#u Arch has applied to 5.2.14. I separately tested that it applies cleanly. https://git.archlinux.org/linux.git/commit/?h=v5.2.14-arch2&id=45fc8773f47b7cbe56caab0e14abf26d1e044e63 Call trace if this bug is hit looks like this: [49887.347053] INFO: task btrfs-transacti:1752 blocked for more than 122 seconds. [49887.347059] Not tainted 5.2.13-gentoo #2 [49887.347060] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [49887.347062] btrfs-transacti D 0 1752 2 0x80004000 [49887.347064] Call Trace: [49887.347069] ? __schedule+0x265/0x830 [49887.347071] ? bit_wait+0x50/0x50 [49887.347072] ? bit_wait+0x50/0x50 [49887.347074] schedule+0x24/0x90 [49887.347075] io_schedule+0x3c/0x60 [49887.347077] bit_wait_io+0x8/0x50 [49887.347079] __wait_on_bit+0x6c/0x80 [49887.347081] ? __lock_release.isra.29+0x155/0x2d0 [49887.347083] out_of_line_wait_on_bit+0x7b/0x80 [49887.347084] ? var_wake_function+0x20/0x20 [49887.347087] lock_extent_buffer_for_io+0x28c/0x390 [49887.347089] btree_write_cache_pages+0x18e/0x340 [49887.347091] do_writepages+0x29/0xb0 [49887.347093] ? kmem_cache_free+0x132/0x160 [49887.347095] ? convert_extent_bit+0x544/0x680 [49887.347097] filemap_fdatawrite_range+0x70/0x90 [49887.347099] btrfs_write_marked_extents+0x53/0x120 [49887.347100] btrfs_write_and_wait_transaction.isra.4+0x38/0xa0 [49887.347102] btrfs_commit_transaction+0x6bb/0x990 [49887.347103] ? start_transaction+0x33e/0x500 [49887.347105] transaction_kthread+0x139/0x15c
Email with PR to Linus including fix for 5.3.0 is here; it also mentions they intend to push it to stable. https://lore.kernel.org/linux-btrfs/cover.1568307806.git.dsterba@suse.com/T/#u The commit referenced in that PR is here (it's the same as above, but maybe the trail of breadcrumbs with this is better) https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git/commit/?h=for-5.3-rc8&id=18dfa7117a3f379862dcd3f67cadd678013bb9dd
I applied this on top of 5.3.0-rc8, compiles on x86_64 and boots fine.
FEDORA-2019-38d2e07507 has been submitted as an update to Fedora 29. https://bodhi.fedoraproject.org/updates/FEDORA-2019-38d2e07507
FEDORA-2019-e3010166bd has been submitted as an update to Fedora 30. https://bodhi.fedoraproject.org/updates/FEDORA-2019-e3010166bd
kernel-5.2.15-200.fc30, kernel-headers-5.2.15-200.fc30 has been pushed to the Fedora 30 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2019-e3010166bd
kernel-5.2.15-100.fc29, kernel-headers-5.2.15-100.fc29 has been pushed to the Fedora 29 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2019-38d2e07507
kernel-5.2.15-200.fc30, kernel-headers-5.2.15-200.fc30 has been pushed to the Fedora 30 stable repository. If problems still persist, please make note of it in this bug report.
FEDORA-2019-fa29e8d620 has been submitted as an update to Fedora 29. https://bodhi.fedoraproject.org/updates/FEDORA-2019-fa29e8d620
kernel-5.2.16-100.fc29, kernel-headers-5.2.16-100.fc29 has been pushed to the Fedora 29 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2019-fa29e8d620
FEDORA-2019-a570a92d5a has been submitted as an update to Fedora 29. https://bodhi.fedoraproject.org/updates/FEDORA-2019-a570a92d5a
kernel-5.2.17-100.fc29, kernel-headers-5.2.17-100.fc29, kernel-tools-5.2.17-100.fc29 has been pushed to the Fedora 29 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2019-a570a92d5a
kernel-5.2.17-100.fc29, kernel-headers-5.2.17-100.fc29, kernel-tools-5.2.17-100.fc29 has been pushed to the Fedora 29 stable repository. If problems still persist, please make note of it in this bug report.