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From: Josef Bacik <josef@toxicpanda.com>
To: Naohiro Aota <naohiro.aota@wdc.com>
Cc: linux-btrfs@vger.kernel.org, "David Sterba" <dsterba@suse.com>,
	"Chris Mason" <clm@fb.com>, "Josef Bacik" <josef@toxicpanda.com>,
	"Qu Wenruo" <wqu@suse.com>, "Nikolay Borisov" <nborisov@suse.com>,
	linux-kernel@vger.kernel.org, "Hannes Reinecke" <hare@suse.com>,
	linux-fsdevel@vger.kernel.org,
	"Damien Le Moal" <damien.lemoal@wdc.com>,
	"Matias Bjørling" <mb@lightnvm.io>,
	"Johannes Thumshirn" <jthumshirn@suse.de>,
	"Bart Van Assche" <bvanassche@acm.org>
Subject: Re: [PATCH 17/19] btrfs: shrink delayed allocation size in HMZONED mode
Date: Thu, 13 Jun 2019 10:27:31 -0400
Message-ID: <20190613142731.mgitehmuyz2566no@MacBook-Pro-91.local> (raw)
In-Reply-To: <20190607131025.31996-18-naohiro.aota@wdc.com>

On Fri, Jun 07, 2019 at 10:10:23PM +0900, Naohiro Aota wrote:
> In a write heavy workload, the following scenario can occur:
> 
> 1. mark page #0 to page #2 (and their corresponding extent region) as dirty
>    and candidate for delayed allocation
> 
> pages    0 1 2 3 4
> dirty    o o o - -
> towrite  - - - - -
> delayed  o o o - -
> alloc
> 
> 2. extent_write_cache_pages() mark dirty pages as TOWRITE
> 
> pages    0 1 2 3 4
> dirty    o o o - -
> towrite  o o o - -
> delayed  o o o - -
> alloc
> 
> 3. Meanwhile, another write dirties page #3 and page #4
> 
> pages    0 1 2 3 4
> dirty    o o o o o
> towrite  o o o - -
> delayed  o o o o o
> alloc
> 
> 4. find_lock_delalloc_range() decide to allocate a region to write page #0
>    to page #4
> 5. but, extent_write_cache_pages() only initiate write to TOWRITE tagged
>    pages (#0 to #2)
> 
> So the above process leaves page #3 and page #4 behind. Usually, the
> periodic dirty flush kicks write IOs for page #3 and #4. However, if we try
> to mount a subvolume at this timing, mount process takes s_umount write
> lock to block the periodic flush to come in.
> 
> To deal with the problem, shrink the delayed allocation region to have only
> expected to be written pages.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  fs/btrfs/extent_io.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index c73c69e2bef4..ea582ff85c73 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3310,6 +3310,33 @@ static noinline_for_stack int writepage_delalloc(struct inode *inode,
>  			delalloc_start = delalloc_end + 1;
>  			continue;
>  		}
> +
> +		if (btrfs_fs_incompat(btrfs_sb(inode->i_sb), HMZONED) &&
> +		    (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) &&
> +		    ((delalloc_start >> PAGE_SHIFT) <
> +		     (delalloc_end >> PAGE_SHIFT))) {
> +			unsigned long i;
> +			unsigned long end_index = delalloc_end >> PAGE_SHIFT;
> +
> +			for (i = delalloc_start >> PAGE_SHIFT;
> +			     i <= end_index; i++)
> +				if (!xa_get_mark(&inode->i_mapping->i_pages, i,
> +						 PAGECACHE_TAG_TOWRITE))
> +					break;
> +
> +			if (i <= end_index) {
> +				u64 unlock_start = (u64)i << PAGE_SHIFT;
> +
> +				if (i == delalloc_start >> PAGE_SHIFT)
> +					unlock_start += PAGE_SIZE;
> +
> +				unlock_extent(tree, unlock_start, delalloc_end);
> +				__unlock_for_delalloc(inode, page, unlock_start,
> +						      delalloc_end);
> +				delalloc_end = unlock_start - 1;
> +			}
> +		}
> +

Helper please.  Really for all this hmzoned stuff I want it segregated as much
as possible so when I'm debugging or cleaning other stuff up I want to easily be
able to say "oh this is for zoned devices, it doesn't matter."  Thanks,

Josef

  reply index

Thread overview: 79+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-07 13:10 [PATCH v2 00/19] btrfs zoned block device support Naohiro Aota
2019-06-07 13:10 ` [PATCH 01/19] btrfs: introduce HMZONED feature flag Naohiro Aota
2019-06-07 13:10 ` [PATCH 02/19] btrfs: Get zone information of zoned block devices Naohiro Aota
2019-06-13 13:58   ` Josef Bacik
2019-06-18  6:04     ` Naohiro Aota
2019-06-13 13:58   ` Josef Bacik
2019-06-17 18:57   ` David Sterba
2019-06-18  6:42     ` Naohiro Aota
2019-06-27 15:11       ` David Sterba
2019-06-07 13:10 ` [PATCH 03/19] btrfs: Check and enable HMZONED mode Naohiro Aota
2019-06-13 13:57   ` Josef Bacik
2019-06-18  6:43     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 04/19] btrfs: disable fallocate in " Naohiro Aota
2019-06-07 13:10 ` [PATCH 05/19] btrfs: disable direct IO " Naohiro Aota
2019-06-13 14:00   ` Josef Bacik
2019-06-18  8:17     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 06/19] btrfs: align dev extent allocation to zone boundary Naohiro Aota
2019-06-07 13:10 ` [PATCH 07/19] btrfs: do sequential extent allocation in HMZONED mode Naohiro Aota
2019-06-13 14:07   ` Josef Bacik
2019-06-18  8:28     ` Naohiro Aota
2019-06-18 13:37       ` Josef Bacik
2019-06-17 22:30   ` David Sterba
2019-06-18  8:49     ` Naohiro Aota
2019-06-27 15:28       ` David Sterba
2019-06-07 13:10 ` [PATCH 08/19] btrfs: make unmirroed BGs readonly only if we have at least one writable BG Naohiro Aota
2019-06-13 14:09   ` Josef Bacik
2019-06-18  7:42     ` Naohiro Aota
2019-06-18 13:35       ` Josef Bacik
2019-06-07 13:10 ` [PATCH 09/19] btrfs: limit super block locations in HMZONED mode Naohiro Aota
2019-06-13 14:12   ` Josef Bacik
2019-06-18  8:51     ` Naohiro Aota
2019-06-17 22:53   ` David Sterba
2019-06-18  9:01     ` Naohiro Aota
2019-06-27 15:35       ` David Sterba
2019-06-28  3:55   ` Anand Jain
2019-06-28  6:39     ` Naohiro Aota
2019-06-28  6:52       ` Anand Jain
2019-06-07 13:10 ` [PATCH 10/19] btrfs: rename btrfs_map_bio() Naohiro Aota
2019-06-07 13:10 ` [PATCH 11/19] btrfs: introduce submit buffer Naohiro Aota
2019-06-13 14:14   ` Josef Bacik
2019-06-17  3:16     ` Damien Le Moal
2019-06-18  0:00       ` David Sterba
2019-06-18  4:04         ` Damien Le Moal
2019-06-18 13:33       ` Josef Bacik
2019-06-19 10:32         ` Damien Le Moal
2019-06-07 13:10 ` [PATCH 12/19] btrfs: expire submit buffer on timeout Naohiro Aota
2019-06-13 14:15   ` Josef Bacik
2019-06-17  3:19     ` Damien Le Moal
2019-06-07 13:10 ` [PATCH 13/19] btrfs: avoid sync IO prioritization on checksum in HMZONED mode Naohiro Aota
2019-06-13 14:17   ` Josef Bacik
2019-06-07 13:10 ` [PATCH 14/19] btrfs: redirty released extent buffers in sequential BGs Naohiro Aota
2019-06-13 14:24   ` Josef Bacik
2019-06-18  9:09     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 15/19] btrfs: reset zones of unused block groups Naohiro Aota
2019-06-07 13:10 ` [PATCH 16/19] btrfs: wait existing extents before truncating Naohiro Aota
2019-06-13 14:25   ` Josef Bacik
2019-06-07 13:10 ` [PATCH 17/19] btrfs: shrink delayed allocation size in HMZONED mode Naohiro Aota
2019-06-13 14:27   ` Josef Bacik [this message]
2019-06-07 13:10 ` [PATCH 18/19] btrfs: support dev-replace " Naohiro Aota
2019-06-13 14:33   ` Josef Bacik
2019-06-18  9:14     ` Naohiro Aota
2019-06-07 13:10 ` [PATCH 19/19] btrfs: enable to mount HMZONED incompat flag Naohiro Aota
2019-06-07 13:17 ` [PATCH 01/12] btrfs-progs: build: Check zoned block device support Naohiro Aota
2019-06-07 13:17   ` [PATCH 02/12] btrfs-progs: utils: Introduce queue_param Naohiro Aota
2019-06-07 13:17   ` [PATCH 03/12] btrfs-progs: add new HMZONED feature flag Naohiro Aota
2019-06-07 13:17   ` [PATCH 04/12] btrfs-progs: Introduce zone block device helper functions Naohiro Aota
2019-06-07 13:17   ` [PATCH 05/12] btrfs-progs: load and check zone information Naohiro Aota
2019-06-07 13:17   ` [PATCH 06/12] btrfs-progs: avoid writing super block to sequential zones Naohiro Aota
2019-06-07 13:17   ` [PATCH 07/12] btrfs-progs: support discarding zoned device Naohiro Aota
2019-06-07 13:17   ` [PATCH 08/12] btrfs-progs: volume: align chunk allocation to zones Naohiro Aota
2019-06-07 13:17   ` [PATCH 09/12] btrfs-progs: do sequential allocation Naohiro Aota
2019-06-07 13:17   ` [PATCH 10/12] btrfs-progs: mkfs: Zoned block device support Naohiro Aota
2019-06-07 13:17   ` [PATCH 11/12] btrfs-progs: device-add: support HMZONED device Naohiro Aota
2019-06-07 13:17   ` [PATCH 12/12] btrfs-progs: introduce support for dev-place " Naohiro Aota
2019-06-12 17:51 ` [PATCH v2 00/19] btrfs zoned block device support David Sterba
2019-06-13  4:59   ` Naohiro Aota
2019-06-13 13:46     ` David Sterba
2019-06-14  2:07       ` Naohiro Aota
2019-06-17  2:44       ` Damien Le Moal

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