From: Bart Van Assche <bvanassche@acm.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christian Brauner <brauner@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
Kanchan Joshi <joshi.k@samsung.com>,
Jeff Layton <jlayton@kernel.org>,
Chuck Lever <chuck.lever@oracle.com>,
Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH 3/6] fs: Split fcntl_rw_hint()
Date: Thu, 1 Feb 2024 09:38:02 -0800 [thread overview]
Message-ID: <ab80ec3c-db9c-439e-8476-e4404574dfed@acm.org> (raw)
In-Reply-To: <Zbq2e7e8Ba1Df6O7@dread.disaster.area>
On 1/31/24 13:07, Dave Chinner wrote:
> On Wed, Jan 31, 2024 at 12:52:34PM -0800, Bart Van Assche wrote:
>> + inode_lock(inode);
>> + inode->i_write_hint = hint;
>> + inode_unlock(inode);
>
> What is this locking serialising against? The inode may or may not
> be locked when we access this in IO path, so why isn't this just
> WRITE_ONCE() here and READ_ONCE() in the IO paths?
How about using WRITE_ONCE()/READ_ONCE() in the fcntl implementations and
regular reads in the I/O paths? Using F_SET_RW_HINT while I/O is ongoing
is racy - there are no guarantees about how F_SET_RW_HINT will affect I/O
that has already been submitted. Hence, I think that it is acceptable to
use regular reads for i_write_hint in the I/O paths.
Thanks,
Bart.
next prev parent reply other threads:[~2024-02-01 17:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-31 20:52 [PATCH 0/6] Restore data lifetime support Bart Van Assche
2024-01-31 20:52 ` [PATCH 1/6] fs: Fix rw_hint validation Bart Van Assche
2024-01-31 20:52 ` [PATCH 2/6] fs: Verify write lifetime constants at compile time Bart Van Assche
2024-01-31 20:52 ` [PATCH 3/6] fs: Split fcntl_rw_hint() Bart Van Assche
2024-01-31 21:07 ` Dave Chinner
2024-02-01 17:38 ` Bart Van Assche [this message]
2024-01-31 20:52 ` [PATCH 4/6] fs: Move enum rw_hint into a new header file Bart Van Assche
2024-01-31 20:52 ` [PATCH 5/6] fs: Propagate write hints to the struct block_device inode Bart Van Assche
2024-01-31 20:52 ` [PATCH 6/6] block, fs: Restore the per-bio/request data lifetime fields Bart Van Assche
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