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Chao Yu
aa1be8dd64
Jan Prusakowski reported a f2fs bug as below: f2fs/007 will hang kernel during testing w/ below configs: kernel 6.12.18 (from pixel-kernel/android16-6.12) export MKFS_OPTIONS="-O encrypt -O extra_attr -O project_quota -O quota" export F2FS_MOUNT_OPTIONS="test_dummy_encryption,discard,fsync_mode=nobarrier,reserve_root=32768,checkpoint_merge,atgc" cat /proc/<umount_proc_id>/stack f2fs_wait_on_all_pages+0xa3/0x130 do_checkpoint+0x40c/0x5d0 f2fs_write_checkpoint+0x258/0x550 kill_f2fs_super+0x14f/0x190 deactivate_locked_super+0x30/0xb0 cleanup_mnt+0xba/0x150 task_work_run+0x59/0xa0 syscall_exit_to_user_mode+0x12d/0x130 do_syscall_64+0x57/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e cat /sys/kernel/debug/f2fs/status - IO_W (CP: -256, Data: 256, Flush: ( 0 0 1), Discard: ( 0 0)) cmd: 0 undiscard: 0 CP IOs reference count becomes negative. The root cause is: After4961acdd65("f2fs: fix to tag gcing flag on page during block migration"), we will tag page w/ gcing flag for raw page of cluster during its migration. However, if the inode is both encrypted and compressed, during ioc_decompress(), it will tag page w/ gcing flag, and it increase F2FS_WB_DATA reference count: - f2fs_write_multi_page - f2fs_write_raw_page - f2fs_write_single_page - do_write_page - f2fs_submit_page_write - WB_DATA_TYPE(bio_page, fio->compressed_page) : bio_page is encrypted, so mapping is NULL, and fio->compressed_page is NULL, it returns F2FS_WB_DATA - inc_page_count(.., F2FS_WB_DATA) Then, during end_io(), it decrease F2FS_WB_CP_DATA reference count: - f2fs_write_end_io - f2fs_compress_write_end_io - fscrypt_pagecache_folio : get raw page from encrypted page - WB_DATA_TYPE(&folio->page, false) : raw page has gcing flag, it returns F2FS_WB_CP_DATA - dec_page_count(.., F2FS_WB_CP_DATA) In order to fix this issue, we need to detect gcing flag in raw page in f2fs_is_cp_guaranteed(). Fixes:4961acdd65("f2fs: fix to tag gcing flag on page during block migration") Reported-by: Jan Prusakowski <jprusakowski@google.com> Signed-off-by: Chao Yu <chao@kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.