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mm/zswap: remove SWP_SYNCHRONOUS_IO swapcache bypass workaround

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Since commit f1879e8a0c ("mm, swap: never bypass the swap cache even for
SWP_SYNCHRONOUS_IO"), all swap-in operations go through the swap cache,
including those from SWP_SYNCHRONOUS_IO devices like zram.  Which means
the workaround for swap cache bypassing introduced by commit 25cd241408
("mm: zswap: fix data loss on SWP_SYNCHRONOUS_IO devices") is no longer
needed.  Remove it, but keep the comments that are still helpful.

Link: https://lkml.kernel.org/r/20260202-zswap-syncio-cleanup-v1-1-86bb24a64521@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Suggested-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Baoquan He <bhe@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kairui Song
2026-02-02 01:47:32 +08:00
committed by Andrew Morton
parent 1c7b8d8a51
commit ae1a645def
1 changed files with 6 additions and 13 deletions
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19
mm/zswap.c
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@@ -1595,11 +1595,11 @@ int zswap_load(struct folio *folio)
{
swp_entry_t swp = folio->swap;
pgoff_t offset = swp_offset(swp);
bool swapcache = folio_test_swapcache(folio);
struct xarray *tree = swap_zswap_tree(swp);
struct zswap_entry *entry;
VM_WARN_ON_ONCE(!folio_test_locked(folio));
VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
if (zswap_never_enabled())
return -ENOENT;
@@ -1630,22 +1630,15 @@ int zswap_load(struct folio *folio)
count_objcg_events(entry->objcg, ZSWPIN, 1);
/*
* When reading into the swapcache, invalidate our entry. The
* swapcache can be the authoritative owner of the page and
* We are reading into the swapcache, invalidate zswap entry.
* The swapcache is the authoritative owner of the page and
* its mappings, and the pressure that results from having two
* in-memory copies outweighs any benefits of caching the
* compression work.
*
* (Most swapins go through the swapcache. The notable
* exception is the singleton fault on SWP_SYNCHRONOUS_IO
* files, which reads into a private page and may free it if
* the fault fails. We remain the primary owner of the entry.)
*/
if (swapcache) {
folio_mark_dirty(folio);
xa_erase(tree, offset);
zswap_entry_free(entry);
}
folio_mark_dirty(folio);
xa_erase(tree, offset);
zswap_entry_free(entry);
folio_unlock(folio);
return 0;