From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 00/10] btrfs: Support for DAX devices
Date: Wed, 5 Dec 2018 21:03:08 +0800 [thread overview]
Message-ID: <1d687042-774f-e27b-7341-e5cd7a6be3d2@gmx.com> (raw)
In-Reply-To: <20181205122835.19290-1-rgoldwyn@suse.de>
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On 2018/12/5 下午8:28, Goldwyn Rodrigues wrote:
> This is a support for DAX in btrfs. I understand there have been
> previous attempts at it. However, I wanted to make sure copy-on-write
> (COW) works on dax as well.
>
> Before I present this to the FS folks I wanted to run this through the
> btrfs. Even though I wish, I cannot get it correct the first time
> around :/.. Here are some questions for which I need suggestions:
>
> Questions:
> 1. I have been unable to do checksumming for DAX devices. While
> checksumming can be done for reads and writes, it is a problem when mmap
> is involved because btrfs kernel module does not get back control after
> an mmap() writes. Any ideas are appreciated, or we would have to set
> nodatasum when dax is enabled.
I'm not familar with DAX, so it's completely possible I'm talking like
an idiot.
If btrfs_page_mkwrite() can't provide enough control, then I have a
crazy idea.
Forcing page fault for every mmap() read/write (completely disable page
cache like DIO).
So that we could get some control since we're informed to read the page
and do some hacks there.
Thanks,
Qu
>
> 2. Currently, a user can continue writing on "old" extents of an mmaped file
> after a snapshot has been created. How can we enforce writes to be directed
> to new extents after snapshots have been created? Do we keep a list of
> all mmap()s, and re-mmap them after a snapshot?
>
> Tested by creating a pmem device in RAM with "memmap=2G!4G" kernel
> command line parameter.
>
>
> [PATCH 01/10] btrfs: create a mount option for dax
> [PATCH 02/10] btrfs: basic dax read
> [PATCH 03/10] btrfs: dax: read zeros from holes
> [PATCH 04/10] Rename __endio_write_update_ordered() to
> [PATCH 05/10] btrfs: Carve out btrfs_get_extent_map_write() out of
> [PATCH 06/10] btrfs: dax write support
> [PATCH 07/10] dax: export functions for use with btrfs
> [PATCH 08/10] btrfs: dax add read mmap path
> [PATCH 09/10] btrfs: dax support for cow_page/mmap_private and shared
> [PATCH 10/10] btrfs: dax mmap write
>
> fs/btrfs/Makefile | 1
> fs/btrfs/ctree.h | 17 ++
> fs/btrfs/dax.c | 303 ++++++++++++++++++++++++++++++++++++++++++++++++++--
> fs/btrfs/file.c | 29 ++++
> fs/btrfs/inode.c | 54 +++++----
> fs/btrfs/ioctl.c | 5
> fs/btrfs/super.c | 15 ++
> fs/dax.c | 35 ++++--
> include/linux/dax.h | 16 ++
> 9 files changed, 430 insertions(+), 45 deletions(-)
>
>
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next prev parent reply other threads:[~2018-12-05 13:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-05 12:28 [PATCH 00/10] btrfs: Support for DAX devices Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 01/10] btrfs: create a mount option for dax Goldwyn Rodrigues
2018-12-05 12:42 ` Johannes Thumshirn
2018-12-05 12:43 ` Nikolay Borisov
2018-12-05 14:59 ` Adam Borowski
2018-12-05 12:28 ` [PATCH 02/10] btrfs: basic dax read Goldwyn Rodrigues
2018-12-05 13:11 ` Nikolay Borisov
2018-12-05 13:22 ` Johannes Thumshirn
2018-12-05 12:28 ` [PATCH 03/10] btrfs: dax: read zeros from holes Goldwyn Rodrigues
2018-12-05 13:26 ` Nikolay Borisov
2018-12-05 12:28 ` [PATCH 04/10] Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2018-12-05 13:35 ` Nikolay Borisov
2018-12-05 12:28 ` [PATCH 05/10] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 06/10] btrfs: dax write support Goldwyn Rodrigues
2018-12-05 13:56 ` Johannes Thumshirn
2018-12-05 12:28 ` [PATCH 07/10] dax: export functions for use with btrfs Goldwyn Rodrigues
2018-12-05 13:59 ` Johannes Thumshirn
2018-12-05 14:52 ` Christoph Hellwig
2018-12-06 11:46 ` Goldwyn Rodrigues
2018-12-12 8:07 ` Christoph Hellwig
2019-03-26 19:36 ` Dan Williams
2019-03-27 11:10 ` Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 08/10] btrfs: dax add read mmap path Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 09/10] btrfs: dax support for cow_page/mmap_private and shared Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 10/10] btrfs: dax mmap write Goldwyn Rodrigues
2018-12-05 13:03 ` Qu Wenruo [this message]
2018-12-05 21:36 ` [PATCH 00/10] btrfs: Support for DAX devices Jeff Mahoney
2018-12-05 13:57 ` Adam Borowski
2018-12-05 21:37 ` Jeff Mahoney
2018-12-06 7:40 ` Robert White
2018-12-06 10:07 ` Johannes Thumshirn
2018-12-06 11:47 ` Goldwyn Rodrigues
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