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[49.186.86.168]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72057935dafsm4482206b3a.87.2024.10.27.15.26.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Oct 2024 15:26:35 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1t5BiR-006eji-2a; Mon, 28 Oct 2024 09:26:31 +1100 Date: Mon, 28 Oct 2024 09:26:31 +1100 From: Dave Chinner To: "Ritesh Harjani (IBM)" Cc: linux-ext4@vger.kernel.org, Theodore Ts'o , Jan Kara , "Darrick J . Wong" , Christoph Hellwig , John Garry , Ojaswin Mujoo , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 4/6] ext4: Warn if we ever fallback to buffered-io for DIO atomic writes Message-ID: References: <7c4779f1f0c8ead30f660a2cfbdf4d7cc08e405a.1729825985.git.ritesh.list@gmail.com> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7c4779f1f0c8ead30f660a2cfbdf4d7cc08e405a.1729825985.git.ritesh.list@gmail.com> On Fri, Oct 25, 2024 at 09:15:53AM +0530, Ritesh Harjani (IBM) wrote: > iomap will not return -ENOTBLK in case of dio atomic writes. But let's > also add a WARN_ON_ONCE and return -EIO as a safety net. > > Signed-off-by: Ritesh Harjani (IBM) > --- > fs/ext4/file.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > index f9516121a036..af6ebd0ac0d6 100644 > --- a/fs/ext4/file.c > +++ b/fs/ext4/file.c > @@ -576,8 +576,16 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from) > iomap_ops = &ext4_iomap_overwrite_ops; > ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops, > dio_flags, NULL, 0); > - if (ret == -ENOTBLK) > + if (ret == -ENOTBLK) { > ret = 0; > + /* > + * iomap will never return -ENOTBLK if write fails for atomic > + * write. But let's just add a safety net. > + */ > + if (WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC)) > + ret = -EIO; > + } Why can't the iomap code return EIO in this case for IOCB_ATOMIC? That way we don't have to put this logic into every filesystem. When/if we start supporting atomic writes for buffered IO, then it's worth pushing this out to filesystems, but right now it doesn't seem necessary... -Dave. -- Dave Chinner david@fromorbit.com