From: Chao Yu chao@kernel.org
[ Upstream commit bb5eb8a5b222fa5092f60d5555867a05ebc3bdf2 ]
------------[ cut here ]------------ WARNING: CPU: 3 PID: 579 at fs/f2fs/segment.c:2832 new_curseg+0x5e8/0x6dc pc : new_curseg+0x5e8/0x6dc Call trace: new_curseg+0x5e8/0x6dc f2fs_allocate_data_block+0xa54/0xe28 do_write_page+0x6c/0x194 f2fs_do_write_node_page+0x38/0x78 __write_node_page+0x248/0x6d4 f2fs_sync_node_pages+0x524/0x72c f2fs_write_checkpoint+0x4bc/0x9b0 __checkpoint_and_complete_reqs+0x80/0x244 issue_checkpoint_thread+0x8c/0xec kthread+0x114/0x1bc ret_from_fork+0x10/0x20
get_new_segment() detects inconsistent status in between free_segmap and free_secmap, let's record such error into super block, and bail out get_new_segment() instead of continue using the segment.
Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org ---
**YES** This commit should be backported to stable kernel trees for the following reasons: **1. Fixes Important Bug Affecting Users:** The commit addresses a kernel WARNING that can be triggered during normal filesystem operations. The call trace shows this occurs during checkpoint operations (`f2fs_write_checkpoint` → `f2fs_sync_node_pages` → `f2fs_do_write_node_page`), which are critical for data consistency. **2. Small and Contained Fix:** The changes are minimal and surgical: - In `fs/f2fs/segment.c`: Only 6 lines changed, replacing a `f2fs_bug_on()` call with proper error handling - In `include/linux/f2fs_fs.h`: Adding one new enum value for the stop checkpoint reason **3. Minimal Risk of Regression:** The change only affects the error path when corruption is detected. Instead of triggering a kernel bug, it now: - Returns `-EFSCORRUPTED` error code - Stops checkpoint with specific reason (`STOP_CP_REASON_CORRUPTED_FREE_BITMAP`) - Maintains filesystem integrity by preventing use of corrupted segments **4. Follows Established Pattern:** Similar commits (#2, #4, #5) that replace f2fs panics with graceful error handling have all been marked for backporting (Status: YES). This commit follows the exact same pattern of improving f2fs robustness. **5. Critical Subsystem Impact:** The fix touches f2fs segment management, which is fundamental to the filesystem's allocation strategy. Corruption in segment bitmaps could lead to data loss or filesystem corruption if not handled properly. **6. Clear Error Handling Improvement:** Rather than crashing the kernel when inconsistent bitmap state is detected, the fix allows the filesystem to stop checkpoint operations gracefully and record the corruption reason, which aids in debugging and recovery. The commit meets all stable tree criteria: it's an important bugfix, has minimal risk, doesn't introduce new features, and follows established patterns for similar fixes that have been successfully backported.
fs/f2fs/segment.c | 6 +++++- include/linux/f2fs_fs.h | 1 + 2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 396ef71f41e35..c45e11cb47d59 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -2836,7 +2836,11 @@ static int get_new_segment(struct f2fs_sb_info *sbi, } got_it: /* set it as dirty segment in free segmap */ - f2fs_bug_on(sbi, test_bit(segno, free_i->free_segmap)); + if (test_bit(segno, free_i->free_segmap)) { + ret = -EFSCORRUPTED; + f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_CORRUPTED_FREE_BITMAP); + goto out_unlock; + }
/* no free section in conventional zone */ if (new_sec && pinning && diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h index c24f8bc01045d..5206d63b33860 100644 --- a/include/linux/f2fs_fs.h +++ b/include/linux/f2fs_fs.h @@ -78,6 +78,7 @@ enum stop_cp_reason { STOP_CP_REASON_UPDATE_INODE, STOP_CP_REASON_FLUSH_FAIL, STOP_CP_REASON_NO_SEGMENT, + STOP_CP_REASON_CORRUPTED_FREE_BITMAP, STOP_CP_REASON_MAX, };