| Message ID | 20210106010201.37864-1-wqu@suse.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | btrfs: add read-only support for subpage sector size | expand |
On Wed, Jan 06, 2021 at 09:01:39AM +0800, 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 > out-of-sync subpage data page status). > > Great thanks to David for his effort reviewing and merging the > preparation patches into misc-next. > Now all previously submitted preparation patches are already in > misc-next. I merged 1, 2, 3, 6 to misc-next as they're obvious and independent. The rest is up for review, I haven't looked closely on the open questions. > Qu Wenruo (22): > btrfs: extent_io: rename @offset parameter to @disk_bytenr for > submit_extent_page() Please drop "extent_io:" from any future patch subjects, they get too long already and we haven't been using this prefix consistently anyway.
On 2021/1/12 下午11:14, David Sterba wrote: > On Wed, Jan 06, 2021 at 09:01:39AM +0800, 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 >> out-of-sync subpage data page status). >> >> Great thanks to David for his effort reviewing and merging the >> preparation patches into misc-next. >> Now all previously submitted preparation patches are already in >> misc-next. > > I merged 1, 2, 3, 6 to misc-next as they're obvious and independent. > The rest is up for review, I haven't looked closely on the open > questions. I just fetched misc-next from github/kernel, and none of the branches have the patches. Maybe I should be more patient? > >> Qu Wenruo (22): >> btrfs: extent_io: rename @offset parameter to @disk_bytenr for >> submit_extent_page() > > Please drop "extent_io:" from any future patch subjects, they get too > long already and we haven't been using this prefix consistently anyway. > Got it. Thanks, Qu
Patches can be fetched from github: https://github.com/adam900710/linux/tree/subpage Currently the branch also contains partial RW data support (still some out-of-sync subpage data page status). Great thanks to David for his effort reviewing and merging the preparation patches into misc-next. Now all previously submitted preparation patches are already in 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. In the subpage branch - Metadata read write and balance Not yet full tested due to data write still has bugs need to be solved. But considering that metadata operations from previous iteration is mostly untouched, metadata read write should be pretty stable. - Baisc data balance This is new. - Data read write Only uncompressed data writes. Fsstress can survive. But still very rare data csum error, which only happens in bookend data extents (part of the data extent which is not referred by any file). This looks like something related to reflink/invalidate page and cow fixup. Still invetigating. === Needs feedback === The following design needs extra comments: - u16 bitmap As David mentioned, using u16 as bit map is not the fastest way. That's also why current bitmap code requires unsigned long (u32) as minimal unit. But using bitmap directly would double the memory usage. Thus the best way is to pack two u16 bitmap into one u32 bitmap, but that still needs extra investigation to find better practice. Anyway the skeleton should be pretty simple to expand. - Separate handling for subpage metadata Currently the metadata read and (later write path) handles subpage metadata differently. Mostly due to the page locking must be skipped for subpage metadata. I tried several times to use as many common code as possible, but every time I ended up reverting back to current code. Thankfully, for data handling we will use the same common code. - Incompatible subpage strcuture against iomap_page In btrfs we need extra bits than iomap_page. This is due to we need sector perfect write for data balance. E.g. if only one 4K sector is dirty in a 64K page, we should only write that dirty 4K back to disk, not the full 64K page. As data balance requires the new data extents to have exactly the same size as the original ones. This means, unless iomap_page get extra bits like what we're doing in btrfs for dirty, we can't merge the btrfs_subpage with iomap_page. === Patchset structure === Patch 01~03: Existing preparation patches. Mostly readability related patches found during RW development Patch 04~05: New preparation patches. Mostly related to __process_pages_contig(). Patch 06~10: Subpage handling for extent buffer allocation and freeing Patch 11~22: Subpage handling for extent buffer read path === 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. Qu Wenruo (22): btrfs: extent_io: rename @offset parameter to @disk_bytenr for submit_extent_page() btrfs: extent_io: refactor __extent_writepage_io() to improve readability btrfs: file: update comment for btrfs_dirty_pages() btrfs: extent_io: update locked page dirty/writeback/error bits in __process_pages_contig() btrfs: extent_io: merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK into PAGE_START_WRITEBACK btrfs: extent_io: introduce a helper to grab an existing extent buffer from a page btrfs: extent_io: introduce the skeleton of btrfs_subpage structure btrfs: extent_io: make attach_extent_buffer_page() to handle subpage case btrfs: extent_io: make grab_extent_buffer_from_page() to handle subpage case btrfs: extent_io: support subpage for extent buffer page release btrfs: extent_io: attach private to dummy extent buffer pages btrfs: subpage: introduce helper for subpage uptodate status btrfs: subpage: introduce helper for subpage error status btrfs: extent_io: make set/clear_extent_buffer_uptodate() to support subpage size btrfs: extent_io: make btrfs_clone_extent_buffer() to be subpage compatible btrfs: extent_io: implement try_release_extent_buffer() for subpage metadata support btrfs: extent_io: introduce read_extent_buffer_subpage() btrfs: extent_io: make endio_readpage_update_page_status() to handle subpage case btrfs: disk-io: introduce subpage metadata validation check btrfs: introduce btrfs_subpage for data inodes btrfs: integrate page status update for read path into begin/end_page_read() btrfs: allow RO mount of 4K sector size fs on 64K page system fs/btrfs/Makefile | 3 +- fs/btrfs/compression.c | 10 +- fs/btrfs/disk-io.c | 82 +++++- fs/btrfs/extent_io.c | 534 ++++++++++++++++++++++++++++-------- fs/btrfs/extent_io.h | 15 +- fs/btrfs/file.c | 35 +-- fs/btrfs/free-space-cache.c | 15 +- fs/btrfs/inode.c | 40 ++- fs/btrfs/ioctl.c | 5 +- fs/btrfs/reflink.c | 5 +- fs/btrfs/relocation.c | 12 +- fs/btrfs/subpage.c | 39 +++ fs/btrfs/subpage.h | 256 +++++++++++++++++ fs/btrfs/super.c | 7 + 14 files changed, 876 insertions(+), 182 deletions(-) create mode 100644 fs/btrfs/subpage.c create mode 100644 fs/btrfs/subpage.h