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From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: dsterba@suse.cz, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 4/9] btrfs: Switch to iomap_dio_rw() for dio
Date: Tue, 12 May 2020 12:19:27 -0500	[thread overview]
Message-ID: <20200512171927.tk46sbriqvhasvsq@fiona> (raw)
In-Reply-To: <20200512145807.GA23409@infradead.org>

On  7:58 12/05, Christoph Hellwig wrote:
> On Sat, May 09, 2020 at 11:06:01PM -0500, Goldwyn Rodrigues wrote:
> > > > We cannot perform data reservations and release in iomap_begin() and
> > > > iomap_end() for performance and accounting issues.
> > > 
> > > So just drop "btrfs: Use ->iomap_end() instead of btrfs_dio_data"
> > > from the series and be done with it?
> > 
> > We are using current->journal_info for fdatawrite sequence hence using
> > that as a temporary pointer does not work since iomap_dio_rw() performs
> > the fdatawrite sequence.
> 
> Ok. but in that case they never really should have been separate patches.
> 

Yes, I realized it when I was dealing with this problem.

> Can someone help me to understand who consumes the reservation create by
> btrfs_delalloc_reserve_space?  Most importantly if this is done by
> something called from btrfs_dio_iomap_begin or from btrfs_submit_direct.

It is consumed in
btrfs_finish_ordered_io()->..btrfs_cow_block()->..btrfs_use_block_rsv().
So, it is a queued work from __end_write_update_ordered().

I am also understanding the way this reservation system works so I may
not be 100% correct.

More details are in the starting comments of fs/btrfs/block-rsv.c

-- 
Goldwyn

  reply	other threads:[~2020-05-12 17:19 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 21:02 [PATCH 0/9 v7] btrfs direct-io using iomap Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 1/9] fs: Export generic_file_buffered_read() Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 2/9] iomap: add a filesystem hook for direct I/O bio submission Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 3/9] iomap: Remove lockdep_assert_held() Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 4/9] btrfs: Switch to iomap_dio_rw() for dio Goldwyn Rodrigues
2020-03-27  8:10   ` Christoph Hellwig
2020-03-27 16:13     ` Goldwyn Rodrigues
2020-05-07  6:14       ` Christoph Hellwig
2020-05-07 11:37         ` David Sterba
2020-05-07 12:10           ` Christoph Hellwig
2020-05-07 13:44             ` Goldwyn Rodrigues
2020-05-08  3:14             ` Goldwyn Rodrigues
2020-05-09 13:59               ` Christoph Hellwig
2020-05-10  4:06                 ` Goldwyn Rodrigues
2020-05-12 14:58                   ` Christoph Hellwig
2020-05-12 17:19                     ` Goldwyn Rodrigues [this message]
2020-05-15 14:13                       ` Christoph Hellwig
2020-05-18 14:36                         ` Goldwyn Rodrigues
2020-05-19 20:11                         ` Goldwyn Rodrigues
2020-05-20  6:11                           ` Christoph Hellwig
2020-05-22 11:36                           ` David Sterba
2020-05-22 12:08                             ` Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 5/9] btrfs: Use ->iomap_end() instead of btrfs_dio_data Goldwyn Rodrigues
2020-03-27  8:16   ` Christoph Hellwig
2020-03-27 16:11     ` Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 6/9] fs: Remove dio_end_io() Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 7/9] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 8/9] btrfs: btrfs: split btrfs_direct_IO Goldwyn Rodrigues
2020-03-26 21:02 ` [PATCH 9/9] btrfs: unlock extents in ->iomap_end() for DIO reads Goldwyn Rodrigues
2020-03-27 15:56 ` [PATCH 0/9 v7] btrfs direct-io using iomap David Sterba

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