From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Ritesh Harjani <riteshh@linux.ibm.com>
Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, jack@suse.cz
Subject: Re: [RFC 1/2] iomap: direct-io: Move inode_dio_begin before filemap_write_and_wait_range
Date: Mon, 13 Jan 2020 13:51:59 -0800 [thread overview]
Message-ID: <20200113215159.GA8235@magnolia> (raw)
In-Reply-To: <27607a16327fe9664f32d09abe565af0d1ae56c9.1578907891.git.riteshh@linux.ibm.com>
On Mon, Jan 13, 2020 at 04:34:21PM +0530, Ritesh Harjani wrote:
> Some filesystems (e.g. ext4) need to know in it's writeback path, that
> whether DIO is in progress or not. This info may be needed to avoid the
> stale data exposure race with DIO reads.
Does XFS have this problem too?
Admittedly dio read during mmap write is probably not well supported. ;)
> Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
> ---
> fs/iomap/direct-io.c | 17 +++++++++++++----
Might want to cc fsdevel and the iomap maintainers...
--D
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 23837926c0c5..d1c159bd3854 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -468,9 +468,18 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> flags |= IOMAP_NOWAIT;
> }
>
> + /*
> + * Call inode_dio_begin() before we write out and wait for writeback to
> + * complete. This may be needed by some filesystems to prevent race
> + * like stale data exposure by DIO reads.
> + */
> + inode_dio_begin(inode);
> + /* So that i_dio_count is incremented before below operation */
> + smp_mb__after_atomic();
> +
> ret = filemap_write_and_wait_range(mapping, pos, end);
> if (ret)
> - goto out_free_dio;
> + goto out_end_dio;
>
> /*
> * Try to invalidate cache pages for the range we're direct
> @@ -488,11 +497,9 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> !inode->i_sb->s_dio_done_wq) {
> ret = sb_init_dio_done_wq(inode->i_sb);
> if (ret < 0)
> - goto out_free_dio;
> + goto out_end_dio;
> }
>
> - inode_dio_begin(inode);
> -
> blk_start_plug(&plug);
> do {
> ret = iomap_apply(inode, pos, count, flags, ops, dio,
> @@ -568,6 +575,8 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>
> return iomap_dio_complete(dio);
>
> +out_end_dio:
> + inode_dio_end(inode);
> out_free_dio:
> kfree(dio);
> return ret;
> --
> 2.21.0
>
next prev parent reply other threads:[~2020-01-13 21:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 11:04 [RFC 0/2] ext4: Fix stale data read exposure problem with DIO read/page_mkwrite Ritesh Harjani
2020-01-13 11:04 ` [RFC 1/2] iomap: direct-io: Move inode_dio_begin before filemap_write_and_wait_range Ritesh Harjani
2020-01-13 21:51 ` Darrick J. Wong [this message]
2020-01-14 9:05 ` Jan Kara
2020-01-14 16:38 ` Christoph Hellwig
2020-01-15 9:19 ` Jan Kara
2020-01-15 14:56 ` Christoph Hellwig
2020-01-14 9:12 ` Jan Kara
2020-01-14 16:37 ` Christoph Hellwig
2020-01-14 17:19 ` Jan Kara
2020-01-14 18:27 ` Christoph Hellwig
2020-01-15 9:08 ` Jan Kara
2020-01-13 11:04 ` [RFC 2/2] ext4: Fix stale data read issue with DIO read & ext4_page_mkwrite path Ritesh Harjani
2020-01-14 9:47 ` Jan Kara
2020-01-14 22:25 ` Ritesh Harjani
2020-01-14 16:39 ` [RFC 0/2] ext4: Fix stale data read exposure problem with DIO read/page_mkwrite Christoph Hellwig
2020-01-14 22:33 ` Ritesh Harjani
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