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[WARNING] When running test cases with injected errors or shutdown, e.g. generic/388 or generic/475, there is a chance that the following kernel warning is triggered: BTRFS info (device dm-2): first mount of filesystem d8a19a28-3232-4809-b0df-38df83e71bff BTRFS info (device dm-2): using crc32c checksum algorithm BTRFS info (device dm-2): checking UUID tree BTRFS info (device dm-2): turning on async discard BTRFS info (device dm-2): enabling free space tree BTRFS critical (device dm-2 state E): emergency shutdown ------------[ cut here ]------------ WARNING: extent_io.c:1742 at extent_writepage_io+0x437/0x520 [btrfs], CPU#2: kworker/u43:2/651591 CPU: 2 UID: 0 PID: 651591 Comm: kworker/u43:2 Tainted: G W OE 7.0.0-rc6-custom+ #365 PREEMPT(full) 5804053f02137e627472d94b5128cc9fcb110e88 RIP: 0010:extent_writepage_io+0x437/0x520 [btrfs] Call Trace: <TASK> extent_write_cache_pages+0x2a5/0x820 [btrfs 70299925d0856939e93b17d480651713b3cbba58] btrfs_writepages+0x74/0x130 [btrfs 70299925d0856939e93b17d480651713b3cbba58] do_writepages+0xd0/0x160 __writeback_single_inode+0x42/0x340 writeback_sb_inodes+0x22d/0x580 wb_writeback+0xc6/0x360 wb_workfn+0xbd/0x470 process_one_work+0x198/0x3b0 worker_thread+0x1c8/0x330 kthread+0xee/0x120 ret_from_fork+0x2a6/0x330 ret_from_fork_asm+0x11/0x20 </TASK> ---[ end trace 0000000000000000 ]--- BTRFS error (device dm-2 state E): root 5 ino 259 folio 1323008 is marked dirty without notifying the fs BTRFS error (device dm-2 state E): failed to submit blocks, root=5 inode=259 folio=1323008 submit_bitmap=0: -117 BTRFS info (device dm-2 state E): last unmount of filesystem d8a19a28-3232-4809-b0df-38df83e71bff [CAUSE] Inside btrfs we have the following pattern in several locations, for example inside btrfs_dirty_folio(): btrfs_clear_extent_bit(&inode->io_tree, start_pos, end_of_last_block, EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, cached); ret = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block, extra_bits, cached); if (ret) return ret; However btrfs_set_extent_delalloc() can return IO errors other than -ENOMEM through the following callchain: btrfs_set_extent_delalloc() \- btrfs_find_new_delalloc_bytes() \- btrfs_get_extent() \- btrfs_lookup_file_extent() \- btrfs_search_slot() When such IO error happened, the previous btrfs_clear_extent_bit() has cleared the EXTENT_DELALLOC for the range, and we're expecting btrfs_set_extent_delalloc() to re-set EXTENT_DELALLOC. But since btrfs_set_extent_delalloc() failed before btrfs_set_extent_bit(), EXTENT_DELALLOC flag is no longer present. And if the folio range is dirty before entering btrfs_set_extent_delalloc(), we got a dirty folio but no EXTENT_DELALLOC flag now. Then we hit the folio writeback: extent_writepage() |- writepage_delalloc() | No ordered extent is created, as there is no EXTENT_DELALLOC set | for the folio range. | This also means the folio has no ordered flag set. | |- extent_writepage_io() \- if (unlikely(!folio_test_ordered(folio)) Now we hit the warning. [FIX] Introduce a new helper, btrfs_reset_extent_delalloc() to replace the currently open-coded btrfs_clear_extent_bit() + btrfs_set_extent_delalloc() combination. Instead of calling btrfs_clear_extent_bit() first, update EXTENT_DELALLOC_NEW first, as that part can fail due to metadata IO, meanwhile btrfs_clear_extent_bit() and btrfs_set_extent_bit() won't return any error but retry memory allocation until succeeded. This allows us to fail early without clearing EXTENT_DELALLOC bit, so even if that new btrfs_reset_extent_delalloc() failed before touching EXTENT_DELALLOC, the existing dirty range will still have their old EXTENT_DELALLOC flag present, thus avoid the warning. CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst