From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: viro@zeniv.linux.org.uk, Avi Kivity <avi@scylladb.com>,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/7] aio: remove the extra get_file/fput pair in io_submit_one
Date: Wed, 2 May 2018 15:04:57 -0700 [thread overview]
Message-ID: <20180502220457.GB4116@magnolia> (raw)
In-Reply-To: <20180502211448.18276-5-hch@lst.de>
On Wed, May 02, 2018 at 11:14:45PM +0200, Christoph Hellwig wrote:
> If we release the lockdep write protection token before calling into
> ->write_iter and thus never access the file pointer after an -EIOCBQUEUED
> return from ->write_iter or ->read_iter we don't need this extra
> reference.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
LGTM,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
> fs/aio.c | 25 ++++++++++++++++---------
> 1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 18507743757a..e5866e2fc331 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1515,16 +1515,19 @@ static ssize_t aio_write(struct kiocb *req, struct iocb *iocb, bool vectored,
> return ret;
> ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
> if (!ret) {
> - req->ki_flags |= IOCB_WRITE;
> - file_start_write(file);
> - ret = aio_ret(req, call_write_iter(file, req, &iter));
> /*
> - * We release freeze protection in aio_complete(). Fool lockdep
> - * by telling it the lock got released so that it doesn't
> - * complain about held lock when we return to userspace.
> + * Open-code file_start_write here to grab freeze protection,
> + * which will be released by another thread in aio_complete().
> + * Fool lockdep by telling it the lock got released so that it
> + * doesn't complain about the held lock when we return to
> + * userspace.
> */
> - if (S_ISREG(file_inode(file)->i_mode))
> + if (S_ISREG(file_inode(file)->i_mode)) {
> + __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
> __sb_writers_release(file_inode(file)->i_sb, SB_FREEZE_WRITE);
> + }
> + req->ki_flags |= IOCB_WRITE;
> + ret = aio_ret(req, call_write_iter(file, req, &iter));
> }
> kfree(iovec);
> return ret;
> @@ -1599,7 +1602,6 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> req->ki_user_iocb = user_iocb;
> req->ki_user_data = iocb->aio_data;
>
> - get_file(file);
> switch (iocb->aio_lio_opcode) {
> case IOCB_CMD_PREAD:
> ret = aio_read(&req->common, iocb, false, compat);
> @@ -1618,8 +1620,13 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> ret = -EINVAL;
> break;
> }
> - fput(file);
>
> + /*
> + * If ret is -EIOCBQUEUED, ownership of the file reference acquired
> + * above passed to the file system, which at this point might have
> + * dropped the reference, so we must be careful to not reference it
> + * once we have called into the file system.
> + */
> if (ret && ret != -EIOCBQUEUED)
> goto out_put_req;
> return 0;
> --
> 2.17.0
>
> --
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next prev parent reply other threads:[~2018-05-02 22:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-02 21:14 io_pgetevents & aio fsync V4 Christoph Hellwig
2018-05-02 21:14 ` [PATCH 1/7] aio: don't print the page size at boot time Christoph Hellwig
2018-05-02 21:14 ` [PATCH 2/7] aio: remove an outdated BUG_ON and comment in aio_complete Christoph Hellwig
2018-05-02 21:14 ` [PATCH 3/7] aio: sanitize ki_list handling Christoph Hellwig
2018-05-02 21:14 ` [PATCH 4/7] aio: remove the extra get_file/fput pair in io_submit_one Christoph Hellwig
2018-05-02 22:04 ` Darrick J. Wong [this message]
2018-05-02 21:14 ` [PATCH 5/7] aio: refactor read/write iocb setup Christoph Hellwig
2018-05-02 21:14 ` [PATCH 6/7] aio: implement IOCB_CMD_FSYNC and IOCB_CMD_FDSYNC Christoph Hellwig
2018-05-02 21:14 ` [PATCH 7/7] aio: implement io_pgetevents Christoph Hellwig
2018-05-18 8:28 ` James Hogan
2018-05-18 8:57 ` Christoph Hellwig
2018-07-04 14:21 ` Adrian Reber
2018-07-08 20:44 ` Christoph Hellwig
2018-07-09 17:20 ` Stephan Müller
2018-07-09 19:21 ` Stephan Müller
2018-07-10 12:51 ` Christoph Hellwig
2018-07-10 5:11 ` Andrei Vagin
2018-05-10 18:05 ` io_pgetevents & aio fsync V4 Al Viro
-- strict thread matches above, loose matches on Subject: below --
2018-04-15 15:01 io_pgetevents & aio fsync V3 Christoph Hellwig
2018-04-15 15:01 ` [PATCH 4/7] aio: remove the extra get_file/fput pair in io_submit_one Christoph Hellwig
2018-04-26 15:41 ` Darrick J. Wong
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