From: Josef Bacik <josef@toxicpanda.com>
To: Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v5 00/18] btrfs: add read-only support for subpage sector size
Date: Wed, 27 Jan 2021 11:17:57 -0500 [thread overview]
Message-ID: <a448ea77-957b-b7fc-c05a-29a4a13352b8@toxicpanda.com> (raw)
In-Reply-To: <20210126083402.142577-1-wqu@suse.com>
On 1/26/21 3:33 AM, Qu Wenruo wrote:
> Patches can be fetched from github:
> https://github.com/adam900710/linux/tree/subpage
> Currently the branch also contains partial RW data support (still some
> ordered extent and data csum mismatch problems)
>
> Great thanks to David/Nikolay/Josef for their effort reviewing and
> merging the preparation patches into misc-next.
>
> === What works ===
> Just from the patchset:
> - Data read
> Both regular and compressed data, with csum check.
>
> - Metadata read
>
> This means, with these patchset, 64K page systems can at least mount
> btrfs with 4K sector size read-only.
> This should provide the ability to migrate data at least.
>
> While on the github branch, there are already experimental RW supports,
> there are still ordered extent related bugs for me to fix.
> Thus only the RO part is sent for review and testing.
>
> === Patchset structure ===
> Patch 01~02: Preparation patches which don't have functional change
> Patch 03~12: Subpage metadata allocation and freeing
> Patch 13~15: Subpage metadata read path
> Patch 16~17: Subpage data read path
> Patch 18: Enable subpage RO support
>
> === Changelog ===
> v1:
> - Separate the main implementation from previous huge patchset
> Huge patchset doesn't make much sense.
>
> - Use bitmap implementation
> Now page::private will be a pointer to btrfs_subpage structure, which
> contains bitmaps for various page status.
>
> v2:
> - Use page::private as btrfs_subpage for extra info
> This replace old extent io tree based solution, which reduces latency
> and don't require memory allocation for its operations.
>
> - Cherry-pick new preparation patches from RW development
> Those new preparation patches improves the readability by their own.
>
> v3:
> - Make dummy extent buffer to follow the same subpage accessors
> Fsstress exposed several ASSERT() for dummy extent buffers.
> It turns out we need to make dummy extent buffer to own the same
> btrfs_subpage structure to make eb accessors to work properly
>
> - Two new small __process_pages_contig() related preparation patches
> One to make __process_pages_contig() to enhance the error handling
> path for locked_page, one to merge one macro.
>
> - Extent buffers refs count update
> Except try_release_extent_buffer(), all other eb uses will try to
> increase the ref count of the eb.
> For try_release_extent_buffer(), the eb refs check will happen inside
> the rcu critical section to avoid eb being freed.
>
> - Comment updates
> Addressing the comments from the mail list.
>
> v4:
> - Get rid of btrfs_subpage::tree_block_bitmap
> This is to reduce lock complexity (no need to bother extra subpage
> lock for metadata, all locks are existing locks)
> Now eb looking up mostly depends on radix tree, with small help from
> btrfs_subpage::under_alloc.
> Now I haven't experieneced metadata related problems any more during
> my local fsstress tests.
>
> - Fix a race where metadata page dirty bit can race
> Fixed in the metadata RW patchset though.
>
> - Rebased to latest misc-next branch
> With 4 patches removed, as they are already in misc-next.
>
> v5:
> - Use the updated version from David as base
> Most comment/commit message update should be kept as is.
>
> - A new separate patch to move UNMAPPED bit set timing
>
> - New comment on why we need to prealloc subpage inside a loop
> Mostly for further 16K page size support, where we can have
> eb across multiple pages.
>
> - Remove one patch which is too RW specific
> Since it introduces functional change which only makes sense for RW
> support, it's not a good idea to include it in RO support.
>
> - Error handling fixes
> Great thanks to Josef.
>
> - Refactor btrfs_subpage allocation/freeing
> Now we have btrfs_alloc_subpage() and btrfs_free_subpage() helpers to
> do all the allocation/freeing.
> It's pretty easy to convert to kmem_cache using above helpers.
> (already internally tested using kmem_cache without problem, in fact
> it's all the problems found in kmem_cache test leads to the new
> interface)
>
> - Use btrfs_subpage::eb_refs to replace old under_alloc
> This makes checking whether the page has any eb left much easier.
>
> Qu Wenruo (18):
> btrfs: merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK to
> PAGE_START_WRITEBACK
> btrfs: set UNMAPPED bit early in btrfs_clone_extent_buffer() for
> subpage support
> btrfs: introduce the skeleton of btrfs_subpage structure
> btrfs: make attach_extent_buffer_page() handle subpage case
> btrfs: make grab_extent_buffer_from_page() handle subpage case
> btrfs: support subpage for extent buffer page release
I don't have this patch in my inbox so I can't reply to it directly, but you
include refcount.h, but then use normal atomics. Please used the actual
refcount_t, as it gets us all the debugging stuff that makes finding problems
much easier. Thanks,
Josef
next prev parent reply other threads:[~2021-01-27 16:19 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 8:33 [PATCH v5 00/18] btrfs: add read-only support for subpage sector size Qu Wenruo
2021-01-26 8:33 ` [PATCH v5 01/18] btrfs: merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK to PAGE_START_WRITEBACK Qu Wenruo
2021-01-27 15:56 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 02/18] btrfs: set UNMAPPED bit early in btrfs_clone_extent_buffer() for subpage support Qu Wenruo
2021-01-27 15:56 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 03/18] btrfs: introduce the skeleton of btrfs_subpage structure Qu Wenruo
2021-01-26 8:33 ` [PATCH v5 04/18] btrfs: make attach_extent_buffer_page() handle subpage case Qu Wenruo
2021-01-27 16:01 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 05/18] btrfs: make grab_extent_buffer_from_page() " Qu Wenruo
2021-01-27 16:20 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 06/18] btrfs: support subpage for extent buffer page release Qu Wenruo
2021-01-27 16:21 ` Josef Bacik
2021-02-01 15:32 ` David Sterba
2021-01-26 8:33 ` [PATCH v5 07/18] btrfs: attach private to dummy extent buffer pages Qu Wenruo
2021-01-27 16:21 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 08/18] btrfs: introduce helpers for subpage uptodate status Qu Wenruo
2021-01-27 16:34 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 09/18] btrfs: introduce helpers for subpage error status Qu Wenruo
2021-01-27 16:34 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 10/18] btrfs: support subpage in set/clear_extent_buffer_uptodate() Qu Wenruo
2021-01-27 16:35 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 11/18] btrfs: support subpage in btrfs_clone_extent_buffer Qu Wenruo
2021-01-27 16:35 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 12/18] btrfs: support subpage in try_release_extent_buffer() Qu Wenruo
2021-01-27 16:37 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 13/18] btrfs: introduce read_extent_buffer_subpage() Qu Wenruo
2021-01-27 16:39 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 14/18] btrfs: support subpage in endio_readpage_update_page_status() Qu Wenruo
2021-01-27 16:42 ` Josef Bacik
2021-01-26 8:33 ` [PATCH v5 15/18] btrfs: introduce subpage metadata validation check Qu Wenruo
2021-01-27 16:47 ` Josef Bacik
2021-01-26 8:34 ` [PATCH v5 16/18] btrfs: introduce btrfs_subpage for data inodes Qu Wenruo
2021-01-27 16:56 ` Josef Bacik
2021-02-01 15:42 ` David Sterba
2021-01-26 8:34 ` [PATCH v5 17/18] btrfs: integrate page status update for data read path into begin/end_page_read() Qu Wenruo
2021-01-27 17:13 ` Josef Bacik
2021-02-01 15:47 ` David Sterba
2021-01-26 8:34 ` [PATCH v5 18/18] btrfs: allow RO mount of 4K sector size fs on 64K page system Qu Wenruo
2021-01-27 17:13 ` Josef Bacik
2021-02-01 15:49 ` David Sterba
2021-01-27 16:17 ` Josef Bacik [this message]
2021-01-28 0:30 ` [PATCH v5 00/18] btrfs: add read-only support for subpage sector size Qu Wenruo
2021-01-28 10:34 ` David Sterba
2021-01-28 10:51 ` Qu Wenruo
2021-02-01 14:50 ` David Sterba
2021-02-01 15:55 ` David Sterba
2021-02-02 9:21 ` [bug report] Unable to handle kernel paging request Anand Jain
2021-02-02 10:23 ` Qu Wenruo
2021-02-02 11:28 ` Anand Jain
2021-02-02 13:37 ` Anand Jain
2021-02-04 5:13 ` Qu Wenruo
2021-02-03 13:20 ` [PATCH v5 00/18] btrfs: add read-only support for subpage sector size David Sterba
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