Re: [f2fs-dev] [RFC PATCH v2 0/5] f2fs: introduce inline extent mapping for inode data blocks

On 06/25, Chao Yu via Linux-f2fs-devel wrote:
> Sorry for the delay.
> 
> On 5/29/26 16:56, Yongpeng Yang wrote:
> > From: Yongpeng Yang <[email protected]>
> > 
> > Changes since v1:
> > - Introduce tracepoints for f2fs_iext_update_data_blkaddr and
> >   f2fs_iext_lookup_blkaddr to aid debugging (new patch 5/5).
> > - Bypass inline extent lookup for F2FS_GET_BLOCK_PRECACHE to ensure all
> >   mappings are loaded into the read extent cache.
> > - Unify the check for fofs exceeding direct_blocks range to use
> >   "fofs >= direct_blocks" consistently.
> > - Remove support for caching NULL_ADDR in inline extent area. If a fofs
> >   within [0, direct_blocks) is not found in inline extent, it implies
> >   NULL_ADDR. This simplifies merge and split logic.
> > - Fix f2fs_iext_enable_inline_extent to use PTR_ERR instead of -ENOMEM.
> > - Change f2fs_iext_convert_to_inline_extent return type to bool.
> > - Add benchmark data covering 4K/8K/32K/64K random read.
> > - Rename __is_extent_mergeable to __is_iextent_mergeable to avoid
> >   naming collision with extent cache code.
> > - Remove inode parameter from f2fs_iext_sanity_check (always NULL).
> > - Reduce #ifdef CONFIG_F2FS_INLINE_EXTENT nesting in node.c.
> > - Code style fixes to comply with kernel coding style.
> > 
> > This patchset introduces an inline extent mapping mechanism for f2fs.
> > Instead of storing individual block addresses in the inode's data block
> > address area (i_addr[]), this feature packs contiguous block ranges into
> > compact extent entries, significantly reducing the number of entries
> > needed and enabling faster block address lookups via binary search.
> > 
> > The inline extent format is identified by magic numbers in the inode
> > data area and is transparent to the rest of f2fs -- when the extent
> > area is full or cannot represent the mapping efficiently, it
> > automatically converts back to the direct block address format.
> > 
> > Patch 1: Preparatory refactoring -- replace raw pointer arithmetic
> >          with f2fs_data_blkaddr() to abstract block address access.
> > Patch 2: Core implementation -- data structures, extent operations
> >          (lookup, insert, merge, split, truncate), format conversion,
> >          and integration with f2fs data/node paths.
> > Patch 3: ioctl interface -- allow per-file enable/disable of inline
> >          extent format via F2FS_EXTENT_FL flag.
> > Patch 4: sysfs interface -- runtime enable/disable toggle and file
> >          extension list for automatic inline extent activation.
> > Patch 5: Tracepoints for inline extent lookup and update operations.
> > 
> > Test setup and results:
> > =======================
> > 
> > Platform: Xiaomi smartphone, UFS 4.0 storage
> > 
> >   # Enable inline extent
> >   echo 1 > /sys/fs/f2fs/<dev>/inline_extent_enable
> >   echo 'mp4' > /sys/fs/f2fs/<dev>/inline_extent_extension_list
> > 
> >   # Prepare data: write with 4K offset stride to create fragmented
> >   # extents, then overwrite sequentially so inline extent can cache
> >   # all mappings in compact form.
> >   fio --name=test --filename=data.mp4 --rw=write:4k --bs=64M \
> >       --size=8G --ioengine=libaio --direct=1
> >   sync
> >   fio --name=test --filename=data.mp4 --rw=write --bs=64M \
> >       --size=8G --ioengine=libaio --direct=1
> >   sync
> >   echo 3 > /proc/sys/vm/drop_caches
> > 
> >   # Benchmark: random buffered read, 1GB total IO
> >   fio --name=buffer-read --ioengine=libaio --rw=randread --bs=$BS \
> >       --size=8G --io_size=1G --numjobs=1 --filename=data.mp4
> > 
> > Results (random read bandwidth, MiB/s):
> > +---------------------------------------------------+
> > | BS     | baseline | inline ext | improvement      |
> > |--------+----------+------------+------------------|
> > | 4K     | 35       | 36         | +2.5%            |
> > | 8K     | 60       | 62         | +3%              |
> > | 32K    | 179      | 191        | +6.8%            |
> > | 64K    | 284      | 321        | +13%             |
> > +---------------------------------------------------+
> > 
> > The improvement comes from eliminating direct/indirect node page reads
> > during block address lookup -- all mappings are stored directly in
> > the inode page and found via O(log n) binary search.
> > 
> > Yongpeng Yang (5):
> >   f2fs: replace raw dnode pointer arithmetic with f2fs_data_blkaddr()
> >   f2fs: introduce inline extent mapping for inode data blocks
> >   f2fs: support setting inline extent flag via ioctl
> >   f2fs: add sysfs interface for inline extent management
> >   f2fs: introduce tracepoints for inline extent lookup and update
> > 
> >  fs/f2fs/Kconfig             |  18 +
> >  fs/f2fs/Makefile            |   1 +
> >  fs/f2fs/data.c              | 157 ++++++-
> >  fs/f2fs/debug.c             |   4 +
> >  fs/f2fs/dir.c               |   9 +
> >  fs/f2fs/f2fs.h              |  23 +-
> >  fs/f2fs/file.c              |  93 +++-
> >  fs/f2fs/iextent.c           | 873 ++++++++++++++++++++++++++++++++++++
> >  fs/f2fs/iextent.h           | 187 ++++++++
> >  fs/f2fs/inline.c            |   7 +
> >  fs/f2fs/namei.c             |  48 ++
> >  fs/f2fs/node.c              |  66 ++-
> >  fs/f2fs/node.h              |   4 +
> >  fs/f2fs/recovery.c          |  17 +
> >  fs/f2fs/super.c             |  13 +
> >  fs/f2fs/sysfs.c             |  52 +++
> >  include/trace/events/f2fs.h |  79 ++++
> >  17 files changed, 1635 insertions(+), 16 deletions(-)
> 
> It's quite a large number of change (including f2fs-tools change) to support
> this new feature, it causes the performance price ratio a little bit low.
> 
> About inode disk layout, as we discuss offline, maybe we can add 4 or 8 ...
> extents in i_extra_attr area of f2fs_inode structure, it can reduce the
> change line and code complex, however, not sure how will it affect the
> benefits.
> 
> To Jaegeuk, please share your thoughts on this feature.

Agreed. Can we try to add more extents simply?

> 
> Thanks,
> 
> >  create mode 100644 fs/f2fs/iextent.c
> >  create mode 100644 fs/f2fs/iextent.h
> > 
> 
> 
> 
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