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([2405:201:682f:389d:2be5:a957:8629:d978]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b67acd88c77sm1292518a12.34.2025.10.11.01.32.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Oct 2025 01:32:50 -0700 (PDT) From: Deepanshu Kartikey To: heming.zhao@suse.com, joseph.qi@linux.alibaba.com, mark@fasheh.com, jlbec@evilplan.org Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, syzbot+6fdd8fa3380730a4b22c@syzkaller.appspotmail.com Subject: Re: [PATCH] ocfs2: fix stale extent map cache during COW operations Date: Sat, 11 Oct 2025 14:02:44 +0530 Message-ID: <20251011083244.822985-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Heming, Thank you for the detailed analysis and feedback. After further investigation, I discovered that the ioctl call in the reproducer (0x40406f06) is NOT FITRIM as the syzbot comment suggested. Decoding the ioctl number shows: - Type: 'o' (0x6f) - Number: 6 - This is OCFS2_IOC_MOVE_EXT (defined in fs/ocfs2/ocfs2_ioctl.h:222) So the actual call path in the reproducer is: 1. copy_file_range() - creates reflinked extent with flags=0x2 2. ioctl(OCFS2_IOC_MOVE_EXT) - calls ocfs2_move_extents() -> __ocfs2_move_extents_range() 3. write() - triggers BUG_ON Inside __ocfs2_move_extents_range(), the while loop: - Calls ocfs2_get_clusters() which caches the extent with flags=0x2 - Then calls ocfs2_move_extent() -> __ocfs2_move_extent() - __ocfs2_move_extent() at line 50 clears the refcount flag on disk: replace_rec.e_flags = ext_flags & ~OCFS2_EXT_REFCOUNTED; - But the extent cache is not invalidated This is exactly what my v2 patch fixes by adding ocfs2_extent_map_trunc() after the move operation completes. Thanks for your time! Best regards, Deepanshu