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[174.109.172.136]) by smtp.gmail.com with ESMTPSA id b34sm12983022qtc.73.2020.09.22.07.20.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Sep 2020 07:20:12 -0700 (PDT) Subject: Re: [PATCH 04/15] iomap: Call inode_dio_end() before generic_write_sync() To: Goldwyn Rodrigues , linux-fsdevel@vger.kernel.org Cc: linux-btrfs@vger.kernel.org, david@fromorbit.com, hch@lst.de, johannes.thumshirn@wdc.com, dsterba@suse.com, darrick.wong@oracle.com, Goldwyn Rodrigues References: <20200921144353.31319-1-rgoldwyn@suse.de> <20200921144353.31319-5-rgoldwyn@suse.de> From: Josef Bacik Message-ID: <20bf949a-7237-8409-4230-cddb430026a9@toxicpanda.com> Date: Tue, 22 Sep 2020 10:20:11 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <20200921144353.31319-5-rgoldwyn@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 9/21/20 10:43 AM, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > iomap complete routine can deadlock with btrfs_fallocate because of the > call to generic_write_sync(). > > P0 P1 > inode_lock() fallocate(FALLOC_FL_ZERO_RANGE) > __iomap_dio_rw() inode_lock() > > > > inode_unlock() > > inode_dio_wait() > iomap_dio_complete() > generic_write_sync() > btrfs_file_fsync() > inode_lock() > > > inode_dio_end() is used to notify the end of DIO data in order > to synchronize with truncate. Call inode_dio_end() before calling > generic_write_sync(), so filesystems can lock i_rwsem during a sync. > > --- > fs/iomap/direct-io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index d970c6bbbe11..e01f81e7b76f 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -118,6 +118,7 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio) > dio_warn_stale_pagecache(iocb->ki_filp); > } > > + inode_dio_end(file_inode(iocb->ki_filp)); > /* > * If this is a DSYNC write, make sure we push it to stable storage now > * that we've written data. > @@ -125,7 +126,6 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio) > if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC)) > ret = generic_write_sync(iocb, ret); > > - inode_dio_end(file_inode(iocb->ki_filp)); > kfree(dio); > > return ret; > Did you verify that xfs or ext4 don't rely on the inode_dio_end() happening before the generic_write_sync()? I wouldn't expect that they would, but we've already run into problems making those kind of assumptions. If it's fine you can add Reviewed-by: Josef Bacik Thanks, Josef