From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
darrick.wong@oracle.com, fdmanana@kernel.org, dsterba@suse.cz,
jthumshirn@suse.de, nborisov@suse.com
Subject: Re: [PATCH 4/8] iomap: Move lockdep_assert_held() to iomap_dio_rw() calls
Date: Thu, 12 Dec 2019 16:24:06 -0600 [thread overview]
Message-ID: <20191212222405.oaceuk63cme2mlkz@fiona> (raw)
In-Reply-To: <20191212095044.GD15977@infradead.org>
On 1:50 12/12, Christoph Hellwig wrote:
> On Wed, Dec 11, 2019 at 06:30:39PM -0600, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> >
> > Filesystems such as btrfs can perform direct I/O without holding the
> > inode->i_rwsem in some of the cases like writing within i_size.
>
> How is that safe?
This (inode_lock release) is only done for writes within i_size.
We only have to safeguard write against truncates, which is done by
inode_dio_wait() call in the truncate sequence (I had mistakenly removed
it in patch 8/8, I shall reinstate that). The commit that introduced this
optimization is 38851cc19adb ("Btrfs: implement unlocked dio write")
>
> > + lockdep_assert_held(&file_inode(file)->i_rwsem);
>
> Having the asserts in the callers is pointless. The assert is inside
> the iomap helper to ensure the expected calling conventions, as the
> code is written under the assumption that we have i_rwsem.
Hmm, conflicting opinions from you and Dave. Anyways, I have removed it
in individual filesystems.
--
Goldwyn
next prev parent reply other threads:[~2019-12-12 22:24 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 0:30 [PATCH 0/8 v5] btrfs direct-io using iomap Goldwyn Rodrigues
2019-12-12 0:30 ` [PATCH 1/8] fs: Export generic_file_buffered_read() Goldwyn Rodrigues
2019-12-12 9:46 ` Christoph Hellwig
2019-12-12 0:30 ` [PATCH 2/8] iomap: add a filesystem hook for direct I/O bio submission Goldwyn Rodrigues
2019-12-12 9:47 ` Christoph Hellwig
2019-12-12 0:30 ` [PATCH 3/8] btrfs: Switch to iomap_dio_rw() for dio Goldwyn Rodrigues
2019-12-12 9:49 ` Christoph Hellwig
2019-12-12 9:56 ` Johannes Thumshirn
2019-12-12 9:57 ` Christoph Hellwig
2019-12-12 10:38 ` Johannes Thumshirn
2019-12-12 19:42 ` Goldwyn Rodrigues
2019-12-12 0:30 ` [PATCH 4/8] iomap: Move lockdep_assert_held() to iomap_dio_rw() calls Goldwyn Rodrigues
2019-12-12 9:50 ` Christoph Hellwig
2019-12-12 22:24 ` Goldwyn Rodrigues [this message]
2019-12-12 22:46 ` Dave Chinner
2019-12-12 0:30 ` [PATCH 5/8] fs: Remove dio_end_io() Goldwyn Rodrigues
2019-12-12 9:50 ` Christoph Hellwig
2019-12-12 0:30 ` [PATCH 6/8] btrfs: Wait for extent bits to release page Goldwyn Rodrigues
2019-12-12 0:30 ` [PATCH 7/8] btrfs: Use iomap_end() instead of btrfs_dio_data Goldwyn Rodrigues
2019-12-12 9:52 ` Christoph Hellwig
2019-12-12 0:30 ` [PATCH 8/8] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK Goldwyn Rodrigues
2019-12-12 8:53 ` Johannes Thumshirn
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