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(cst-prg-21-74.cust.vodafone.cz. [46.135.21.74]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e619b9c88sm14576005e9.22.2025.09.30.18.00.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Sep 2025 18:00:13 -0700 (PDT) From: Mateusz Guzik To: brauner@kernel.org Cc: viro@zeniv.linux.org.uk, jack@suse.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Mateusz Guzik Subject: [PATCH] fs: assert on ->i_count in iput_final() Date: Wed, 1 Oct 2025 03:00:10 +0200 Message-ID: <20251001010010.9967-1-mjguzik@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: quoted-printable Content-Type: text/plain; charset="utf-8" Notably make sure the count is 0 after the return from ->drop_inode(), provided we are going to drop. Inspired by suspicious games played by f2fs. Signed-off-by: Mateusz Guzik --- boots on ext4 without splats fs/inode.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/inode.c b/fs/inode.c index ec9339024ac3..fa82cb810af4 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1879,6 +1879,7 @@ static void iput_final(struct inode *inode) int drop; =20 WARN_ON(inode->i_state & I_NEW); + VFS_BUG_ON_INODE(atomic_read(&inode->i_count) !=3D 0, inode); =20 if (op->drop_inode) drop =3D op->drop_inode(inode); @@ -1893,6 +1894,12 @@ static void iput_final(struct inode *inode) return; } =20 + /* + * Re-check ->i_count in case the ->drop_inode() hooks played games. + * Note we only execute this if the verdict was to drop the inode. + */ + VFS_BUG_ON_INODE(atomic_read(&inode->i_count) !=3D 0, inode); + state =3D inode->i_state; if (!drop) { WRITE_ONCE(inode->i_state, state | I_WILL_FREE); --=20 2.34.1