f2fs: reduce memory footprint of ino management

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Currently, ino entries for APPEND_INO, UPDATE_INO, TRANS_DIR_INO, and
XATTR_DIR_INO allocate a 'struct ino_entry' slab object and attach it to
both a list and a radix tree solely for existence checks via
f2fs_exist_written_data().

Since these ino types only track binary existence status, we can embed
the information directly into radix tree value entries as a bitmap:

- The Linux radix tree/XArray supports in-place value entries via
  xa_mk_value() / xa_to_value(), which tag the least significant bit
  to store an unallocated integer value of BITS_PER_XA_VALUE bits
  (BITS_PER_LONG - 1) directly in the slot pointer.
- For each inode, (ino / BITS_PER_XA_VALUE) serves as the radix tree
  slot index, and (ino % BITS_PER_XA_VALUE) is used as the bit offset
  within the slot's bitmap.

For example, when tracking ino = 7:
- Before: Allocate a 'struct ino_entry' ({ .ino = 7 }), insert its
  pointer into the radix tree at index = 7, and link it to im->ino_list.
- After: Compute slot_index = 7 / BITS_PER_XA_VALUE (index 0) and
  bit_offset = 7 % BITS_PER_XA_VALUE (bit 7), then set bit 7 in the
  value entry via xa_mk_value(bitmap) at index 0, without allocating
  a slab object or linking to a list.

Additionally:
- In-place slot updates are performed via radix_tree_replace_slot(), and
  slots are deleted with radix_tree_delete() once the bitmap is zeroed.
- Reorder the ino list enum so ORPHAN_INO and FLUSH_INO (which still
  require struct ino_entry and list traversal) remain separated, while
  bitmap-based trees are torn down using xa_destroy().

This eliminates 'struct ino_entry' slab allocations and linked-list
tracking for these ino types, significantly reducing memory consumption.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

...

This commit is contained in:

Chao Yu 2026-08-19 09:31:07 +08:00 • committed by Jaegeuk Kim

parent 0f448bb376

commit 9a9ee7408a

2 changed files with 95 additions and 10 deletions

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99

fs/f2fs/checkpoint.c

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6

fs/f2fs/f2fs.h

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