The patch titled
Subject: mm: zswap: function ordering: writeback
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-function-ordering-writeback.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-function-ordering-writeback.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: zswap: function ordering: writeback
Date: Mon, 29 Jan 2024 20:36:55 -0500
Shrinking needs writeback. Naturally, move the writeback code above
the shrinking code. Delete the forward decl.
Link: https://lkml.kernel.org/r/20240130014208.565554-20-hannes@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 183 +++++++++++++++++++++++++--------------------------
1 file changed, 90 insertions(+), 93 deletions(-)
--- a/mm/zswap.c~mm-zswap-function-ordering-writeback
+++ a/mm/zswap.c
@@ -276,9 +276,6 @@ static inline struct zswap_tree *swap_zs
pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
zpool_get_type((p)->zpools[0]))
-static int zswap_writeback_entry(struct zswap_entry *entry,
- swp_entry_t swpentry);
-
static bool zswap_is_full(void)
{
return totalram_pages() * zswap_max_pool_percent / 100 <
@@ -1164,6 +1161,96 @@ static void zswap_decompress(struct zswa
}
/*********************************
+* writeback code
+**********************************/
+/*
+ * Attempts to free an entry by adding a folio to the swap cache,
+ * decompressing the entry data into the folio, and issuing a
+ * bio write to write the folio back to the swap device.
+ *
+ * This can be thought of as a "resumed writeback" of the folio
+ * to the swap device. We are basically resuming the same swap
+ * writeback path that was intercepted with the zswap_store()
+ * in the first place. After the folio has been decompressed into
+ * the swap cache, the compressed version stored by zswap can be
+ * freed.
+ */
+static int zswap_writeback_entry(struct zswap_entry *entry,
+ swp_entry_t swpentry)
+{
+ struct zswap_tree *tree;
+ struct folio *folio;
+ struct mempolicy *mpol;
+ bool folio_was_allocated;
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ };
+
+ /* try to allocate swap cache folio */
+ mpol = get_task_policy(current);
+ folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
+ NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
+ if (!folio)
+ return -ENOMEM;
+
+ /*
+ * Found an existing folio, we raced with swapin or concurrent
+ * shrinker. We generally writeback cold folios from zswap, and
+ * swapin means the folio just became hot, so skip this folio.
+ * For unlikely concurrent shrinker case, it will be unlinked
+ * and freed when invalidated by the concurrent shrinker anyway.
+ */
+ if (!folio_was_allocated) {
+ folio_put(folio);
+ return -EEXIST;
+ }
+
+ /*
+ * folio is locked, and the swapcache is now secured against
+ * concurrent swapping to and from the slot. Verify that the
+ * swap entry hasn't been invalidated and recycled behind our
+ * backs (our zswap_entry reference doesn't prevent that), to
+ * avoid overwriting a new swap folio with old compressed data.
+ */
+ tree = swap_zswap_tree(swpentry);
+ spin_lock(&tree->lock);
+ if (zswap_rb_search(&tree->rbroot, swp_offset(swpentry)) != entry) {
+ spin_unlock(&tree->lock);
+ delete_from_swap_cache(folio);
+ folio_unlock(folio);
+ folio_put(folio);
+ return -ENOMEM;
+ }
+
+ /* Safe to deref entry after the entry is verified above. */
+ zswap_entry_get(entry);
+ spin_unlock(&tree->lock);
+
+ zswap_decompress(entry, &folio->page);
+
+ count_vm_event(ZSWPWB);
+ if (entry->objcg)
+ count_objcg_event(entry->objcg, ZSWPWB);
+
+ spin_lock(&tree->lock);
+ zswap_invalidate_entry(tree, entry);
+ zswap_entry_put(entry);
+ spin_unlock(&tree->lock);
+
+ /* folio is up to date */
+ folio_mark_uptodate(folio);
+
+ /* move it to the tail of the inactive list after end_writeback */
+ folio_set_reclaim(folio);
+
+ /* start writeback */
+ __swap_writepage(folio, &wbc);
+ folio_put(folio);
+
+ return 0;
+}
+
+/*********************************
* shrinker functions
**********************************/
static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_one *l,
@@ -1419,96 +1506,6 @@ resched:
zswap_pool_put(pool);
}
-/*********************************
-* writeback code
-**********************************/
-/*
- * Attempts to free an entry by adding a folio to the swap cache,
- * decompressing the entry data into the folio, and issuing a
- * bio write to write the folio back to the swap device.
- *
- * This can be thought of as a "resumed writeback" of the folio
- * to the swap device. We are basically resuming the same swap
- * writeback path that was intercepted with the zswap_store()
- * in the first place. After the folio has been decompressed into
- * the swap cache, the compressed version stored by zswap can be
- * freed.
- */
-static int zswap_writeback_entry(struct zswap_entry *entry,
- swp_entry_t swpentry)
-{
- struct zswap_tree *tree;
- struct folio *folio;
- struct mempolicy *mpol;
- bool folio_was_allocated;
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- };
-
- /* try to allocate swap cache folio */
- mpol = get_task_policy(current);
- folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
- NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
- if (!folio)
- return -ENOMEM;
-
- /*
- * Found an existing folio, we raced with swapin or concurrent
- * shrinker. We generally writeback cold folios from zswap, and
- * swapin means the folio just became hot, so skip this folio.
- * For unlikely concurrent shrinker case, it will be unlinked
- * and freed when invalidated by the concurrent shrinker anyway.
- */
- if (!folio_was_allocated) {
- folio_put(folio);
- return -EEXIST;
- }
-
- /*
- * folio is locked, and the swapcache is now secured against
- * concurrent swapping to and from the slot. Verify that the
- * swap entry hasn't been invalidated and recycled behind our
- * backs (our zswap_entry reference doesn't prevent that), to
- * avoid overwriting a new swap folio with old compressed data.
- */
- tree = swap_zswap_tree(swpentry);
- spin_lock(&tree->lock);
- if (zswap_rb_search(&tree->rbroot, swp_offset(swpentry)) != entry) {
- spin_unlock(&tree->lock);
- delete_from_swap_cache(folio);
- folio_unlock(folio);
- folio_put(folio);
- return -ENOMEM;
- }
-
- /* Safe to deref entry after the entry is verified above. */
- zswap_entry_get(entry);
- spin_unlock(&tree->lock);
-
- zswap_decompress(entry, &folio->page);
-
- count_vm_event(ZSWPWB);
- if (entry->objcg)
- count_objcg_event(entry->objcg, ZSWPWB);
-
- spin_lock(&tree->lock);
- zswap_invalidate_entry(tree, entry);
- zswap_entry_put(entry);
- spin_unlock(&tree->lock);
-
- /* folio is up to date */
- folio_mark_uptodate(folio);
-
- /* move it to the tail of the inactive list after end_writeback */
- folio_set_reclaim(folio);
-
- /* start writeback */
- __swap_writepage(folio, &wbc);
- folio_put(folio);
-
- return 0;
-}
-
static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
{
unsigned long *page;
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
mm-zswap-fix-objcg-use-after-free-in-entry-destruction.patch
mm-zswap-rename-zswap_free_entry-to-zswap_entry_free.patch
mm-zswap-inline-and-remove-zswap_entry_find_get.patch
mm-zswap-move-zswap_invalidate_entry-to-related-functions.patch
mm-zswap-warn-when-referencing-a-dead-entry.patch
mm-zswap-clean-up-zswap_entry_put.patch
mm-zswap-rename-__zswap_load-to-zswap_decompress.patch
mm-zswap-break-out-zwap_compress.patch
mm-zswap-further-cleanup-zswap_store.patch
mm-zswap-simplify-zswap_invalidate.patch
mm-zswap-function-ordering-pool-alloc-free.patch
mm-zswap-function-ordering-pool-refcounting.patch
mm-zswap-function-ordering-zswap_pools.patch
mm-zswap-function-ordering-pool-params.patch
mm-zswap-function-ordering-public-lru-api.patch
mm-zswap-function-ordering-move-entry-sections-out-of-lru-section.patch
mm-zswap-function-ordering-move-entry-section-out-of-tree-section.patch
mm-zswap-function-ordering-compress-decompress-functions.patch
mm-zswap-function-ordering-per-cpu-compression-infra.patch
mm-zswap-function-ordering-writeback.patch
mm-zswap-function-ordering-shrink_memcg_cb.patch
