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Sat, 11 Oct 2025 05:27:55 -0700 (PDT) Message-ID: <7eb9af90-9ed0-43ec-ba8c-fb78a57ea099@suse.com> Date: Sat, 11 Oct 2025 20:27:50 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ocfs2: fix stale extent map cache during COW operations To: Deepanshu Kartikey , 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 References: <20251011083244.822985-1-kartikey406@gmail.com> From: Heming Zhao Content-Language: en-US In-Reply-To: <20251011083244.822985-1-kartikey406@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Deepanshu, Good catch! With following explanation, your patch looks good to me. Thanks, Heming On 10/11/25 16:32, Deepanshu Kartikey wrote: > 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