[PATCH v3 00/14] ext4: replace ext4_es_insert_extent() when caching on-disk extents

[Zhang Yi <yi.zhang@huaweicloud.com>]

From: Zhang Yi <yi.zhang@huawei.com>

Changes since v2:
 - Rebase the codes on ext4.git dev-91ef18b567da.
 - Move the first cleanup patch in v2 to patch 08 to facilitate easier
   backporting.
 - In patch 01, correct the mismatch comments for
   EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_DATA_PARTIAL_VALID1.
 - Modify patch 06 and add 07, cleanup the commit message to avoid
   confusion, and don't always drop extent cache before splitting
   extent, instead, do this only after PARTIAL_VALID1 zeroed out or
   split extent fails.
 - In patch 08, mark zero_ex to initialized.
 - In patch 09, correct the word 'tag' to 'lable' in the commit message.
 - In patch 11, add return value check of __es_remove_extent() in
   ext4_es_cache_extent().
 - Collecting RVB tags.

   Thanks for the comments and suggestions from Jan, Ojaswin and Baokun!
   Next, it is necessary to focus on refactoring and cleaning up the
   code related to ext4_split_extent(). Ojaswin is going to take on this
   work since he has already been exploring it on his local branch.

Changes since v1:
 - Rebase the codes based on the latest linux-next 20251120.
 - Add patches 01-05, fix two stale data problems caused by
   EXT4_EXT_MAY_ZEROOUT when splitting extent.
 - Add patches 06-07, fix two stale extent status entries problems also
   caused by splitting extent.
 - Modify patches 08-10, extend __es_remove_extent() and
   ext4_es_cache_extent() to allow them to overwrite existing extents of
   the same status when caching on-disk extents, while also checking
   extents of different stauts and raising alarms to prevent misuse.
 - Add patch 13 to clear the usage of ext4_es_insert_extent(), and
   remove the TODO comment in it.

v2: https://lore.kernel.org/linux-ext4/20251121060811.1685783-1-yi.zhang@huaweicloud.com/
v1: https://lore.kernel.org/linux-ext4/20251031062905.4135909-1-yi.zhang@huaweicloud.com/

Original Description

This series addresses the optimization that Jan pointed out [1]
regarding the introduction of a sequence number to
ext4_es_insert_extent(). The proposal is to replace all instances where
the cache of on-disk extents is updated by using ext4_es_cache_extent()
instead of ext4_es_insert_extent(). This change can prevent excessive
cache invalidations caused by unnecessarily increasing the extent
sequence number when reading from the on-disk extent tree.

[1] https://lore.kernel.org/linux-ext4/ympvfypw3222g2k4xzd5pba4zhkz5jihw4td67iixvrqhuu43y@wse63ntv4s6u/

Cheers,
Yi.

Zhang Yi (14):
  ext4: subdivide EXT4_EXT_DATA_VALID1
  ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1
  ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before
    submitting I/O
  ext4: correct the mapping status if the extent has been zeroed
  ext4: don't cache extent during splitting extent
  ext4: drop extent cache after doing PARTIAL_VALID1 zeroout
  ext4: drop extent cache when splitting extent fails
  ext4: cleanup zeroout in ext4_split_extent_at()
  ext4: cleanup useless out label in __es_remove_extent()
  ext4: make __es_remove_extent() check extent status
  ext4: make ext4_es_cache_extent() support overwrite existing extents
  ext4: adjust the debug info in ext4_es_cache_extent()
  ext4: replace ext4_es_insert_extent() when caching on-disk extents
  ext4: drop the TODO comment in ext4_es_insert_extent()

 fs/ext4/extents.c        | 135 ++++++++++++++++++++++++---------------
 fs/ext4/extents_status.c | 124 ++++++++++++++++++++++++++---------
 fs/ext4/inode.c          |  18 +++---
 3 files changed, 187 insertions(+), 90 deletions(-)

-- 
2.46.1