Re: [PATCH v3 00/15] btrfs: preparation patches for subpage support

[David Sterba <dsterba@suse.cz>]

On Wed, Dec 02, 2020 at 02:47:56PM +0800, Qu Wenruo wrote:
> This is the rebased preparation branch for all patches not yet merged into
> misc-next.
> 
> It can be fetched from github (with experimental sector aligned data write
> support)
> https://github.com/adam900710/linux/tree/subpage
> 
> This patchset includes all the unmerged preparation patches for subpage
> support.
> 
> The patchset is sent without the main core for subpage support, as
> myself has proven that, big patchset bombarding won't really make
> reviewers happy, but only make the author happy (for a very short time).
> 
> Thanks for the hard work from David, there are only 15 patches unmerged.
> (With 2 new small patches to address u32 u64 problem)
> 
> Patch 01~02:	bio_offset related fixes. Make bio_offset to be u32.
> Patch 03:	Refactor metadata submission for later metadata write
> 		support.
> Patch 04~08:	Metadata related refactor.
> Patch 09~10:	Data related refactor
> Patch 11~15:	Scrub related refactor and cleanup
> 
> For the scrub patch, there was a discussion with David, about whether we
> should use sector size as the unit for metadata scrub.
> 
> His idea is, sector size should be the minimal unit for DATA, not
> metadata. This indicates there is a undefined "minimal unit" of access.
> 
> But my argument is, sector size is the minimal unit for all btrfs
> access, current btrfs has an undefined "data size", and that "data size"
> must equal to sectorsize for current btrfs implementation.
> 
> Thus for "data size" < nodesize case, we should first add support for
> "data size" > sectorsize first.
> 
> Thus I kept the scrub patch untouched, since IMHO sector size is still
> the minimal unit to access, thus iterating using sectorsize is
> completely sane.
> 
> Changelog:
> v1:
> - Separate prep patches from the huge subpage patchset
> 
> - Rebased to misc-next
> 
> - Add more commit message for patch "btrfs: extent_io: remove the
>   extent_start/extent_len for end_bio_extent_readpage()"
>   With one runtime example to explain why we are doing the same thing.
> 
> - Fix the assert_spin_lock() usage
>   What we really want is lockdep_assert_held()
> 
> - Re-iterate the reason why some extent io tests are invalid
>   This is especially important since later patches will reduce
>   extent_buffer::pages[] to bare minimal, killing the ability to
>   handle certain invalid extent buffers.
> 
> - Use sectorsize_bits for division
>   During the convert, we should only use sectorsize_bits for division,
>   this solves the hassle on 32bit system to do division.
>   But we should not use sectorsize_bits no brain, as bit shift is not
>   straight forward as multiple/division.
> 
> - Address the comments for btrfs_lookup_bio_sums() cleanup patchset
>   From naming to macro usages, all of those comments should further
>   improve the readability.
> 
> v2:
> - Remove new extent_io tree features
>   Now we won't utilize extent io tree for subpage support, thus new
>   features along with some aggressive refactor is no longer needed.
> 
> - Reduce extent_io tree operations to reduce endio time latency
>   Although extent_io tree can do a lot of things like page status, but
>   it has obvious overhead, namingly search btree.
>   So keep the original behavior by only calling extent_io operation in a
>   big extent, to reduce latency
> 
> v3:
> - Rebased to latest misc-next
>   Now only 15 patches to submit.
> 
> - Add two new patches to address u32 and u64 problems
>   The root problem is the on-disk format is abusing u64 for its length.
>   We have to draw a line between where we should convert to u32.
>   Currently for bio_offset and extent_len, we can safely use u32.
>   Just to be extra safe, added more ASSERT() for this.
> 
> - Put BTRFS_MAX_METADATA_BLOCKSIZE into uapi
>   To avoid circle including "ctree.h"
> 
> - Add more changelog for the patch enabling subpage scrub
> 
> 
> Qu Wenruo (15):
>   btrfs: rename bio_offset of extent_submit_bio_start_t to
>     opt_file_offset
>   btrfs: pass bio_offset to check_data_csum() directly
>   btrfs: inode: make btrfs_verify_data_csum() follow sector size
>   btrfs: extent_io: extract the btree page submission code into its own
>     helper function
>   btrfs: extent_io: calculate inline extent buffer page size based on
>     page size
>   btrfs: extent_io: don't allow tree block to cross page boundary for
>     subpage support
>   btrfs: extent_io: update num_extent_pages() to support subpage sized
>     extent buffer
>   btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors
>   btrfs: file-item: remove the btrfs_find_ordered_sum() call in
>     btrfs_lookup_bio_sums()
>   btrfs: file-item: refactor btrfs_lookup_bio_sums() to handle
>     out-of-order bvecs
>   btrfs: scrub: reduce the width for extent_len/stripe_len from 64 bits
>     to 32 bits
>   btrfs: scrub: always allocate one full page for one sector for RAID56
>   btrfs: scrub: support subpage tree block scrub
>   btrfs: scrub: support subpage data scrub
>   btrfs: scrub: allow scrub to work with subpage sectorsize

With a few minor fixups it's in misc-next, thanks.