linux-kernel - [PATCH v2 0/8] Minor cleanups and improvements to swap freeing code

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Message-Id: <20250318150614.6415-1-shikemeng@huaweicloud.com>
Date: Tue, 18 Mar 2025 23:06:06 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: akpm@...ux-foundation.org
Cc: tim.c.chen@...ux.intel.com,
	ryncsn@...il.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/8] Minor cleanups and improvements to swap freeing code

v1->v2:
-Collect RVB from Tim
-Drop patch to factor out __swap_entry_free()
-Improve changelog and add more comment.
-Avoid unneeded lock re-aquire

Hi All,
This series contains some cleanups and improvements which are made
during learning swapfile. Here is a summary of the changes:
1. Function nameing improvments.
-Use "put" instead of "free" to name functions which only do actual free
when count drops to zero.
-Use "entry" to name function only frees one swap slot. Use "entries" to
name function could may free multi swap slots within one cluster. Use
"_nr" suffix to name function which could free multi swap slots spanning
cross multi clusters.
2. Eliminate the need to set swap slot to intermediate SWAP_HAS_CACHE
value before do actual free by using swap_entry_range_free()
3. Add helpers swap_entries_put_map() and swap_entries_put_cache() as a
general-purpose routine to free swap entries within a single cluster
which will try batch-remove first and fallback to put eatch entry
indvidually with cluster lock acquired/released only once. By using 
these helpers, we could remove repeated code, levarage batch-remove in
more cases and aoivd to acquire/release cluster lock for each single
swap entry.

Kemeng Shi (8):
  mm: swap: rename __swap_[entry/entries]_free[_locked] to
    swap_[entry/entries]_put[_locked]
  mm: swap: remove unneeded VM_BUG_ON(*map != SWAP_HAS_CACHE) in
    swap_entry_range_free()
  mm: swap: use swap_entries_free() to free swap entry in
    swap_entry_put_locked()
  mm: swap: use swap_entries_free() drop last ref count in
    swap_entries_put_nr()
  mm: swap: drop last SWAP_MAP_SHMEM flag in batch in
    swap_entries_put_nr()
  mm: swap: free each cluster individually in swap_entries_put_map_nr()
  mm: swap: factor out helper to drop cache of entries within a single
    cluster
  mm: swap: replace cluster_swap_free_nr() with
    swap_entries_put_[map/cache]()

 mm/swapfile.c | 157 ++++++++++++++++++++++++--------------------------
 1 file changed, 75 insertions(+), 82 deletions(-)

-- 
2.30.0