mm: zswap: function ordering: writeback
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@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Cc: Chengming Zhou <zhouchengming@bytedance.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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mm/zswap.c
183
mm/zswap.c
@ -276,9 +276,6 @@ static inline struct zswap_tree *swap_zswap_tree(swp_entry_t swp)
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pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
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zpool_get_type((p)->zpools[0]))
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static int zswap_writeback_entry(struct zswap_entry *entry,
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swp_entry_t swpentry);
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static bool zswap_is_full(void)
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{
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return totalram_pages() * zswap_max_pool_percent / 100 <
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@ -1163,6 +1160,96 @@ static void zswap_decompress(struct zswap_entry *entry, struct page *page)
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zpool_unmap_handle(zpool, entry->handle);
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}
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/*********************************
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* writeback code
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**********************************/
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/*
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* Attempts to free an entry by adding a folio to the swap cache,
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* decompressing the entry data into the folio, and issuing a
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* bio write to write the folio back to the swap device.
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*
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* This can be thought of as a "resumed writeback" of the folio
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* to the swap device. We are basically resuming the same swap
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* writeback path that was intercepted with the zswap_store()
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* in the first place. After the folio has been decompressed into
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* the swap cache, the compressed version stored by zswap can be
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* freed.
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*/
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static int zswap_writeback_entry(struct zswap_entry *entry,
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swp_entry_t swpentry)
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{
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struct zswap_tree *tree;
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struct folio *folio;
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struct mempolicy *mpol;
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bool folio_was_allocated;
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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};
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/* try to allocate swap cache folio */
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mpol = get_task_policy(current);
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folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
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NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
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if (!folio)
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return -ENOMEM;
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/*
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* Found an existing folio, we raced with swapin or concurrent
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* shrinker. We generally writeback cold folios from zswap, and
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* swapin means the folio just became hot, so skip this folio.
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* For unlikely concurrent shrinker case, it will be unlinked
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* and freed when invalidated by the concurrent shrinker anyway.
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*/
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if (!folio_was_allocated) {
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folio_put(folio);
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return -EEXIST;
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}
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/*
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* folio is locked, and the swapcache is now secured against
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* concurrent swapping to and from the slot. Verify that the
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* swap entry hasn't been invalidated and recycled behind our
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* backs (our zswap_entry reference doesn't prevent that), to
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* avoid overwriting a new swap folio with old compressed data.
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*/
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tree = swap_zswap_tree(swpentry);
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spin_lock(&tree->lock);
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if (zswap_rb_search(&tree->rbroot, swp_offset(swpentry)) != entry) {
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spin_unlock(&tree->lock);
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delete_from_swap_cache(folio);
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folio_unlock(folio);
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folio_put(folio);
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return -ENOMEM;
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}
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/* Safe to deref entry after the entry is verified above. */
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zswap_entry_get(entry);
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spin_unlock(&tree->lock);
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zswap_decompress(entry, &folio->page);
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count_vm_event(ZSWPWB);
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if (entry->objcg)
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count_objcg_event(entry->objcg, ZSWPWB);
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spin_lock(&tree->lock);
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zswap_invalidate_entry(tree, entry);
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zswap_entry_put(entry);
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spin_unlock(&tree->lock);
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/* folio is up to date */
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folio_mark_uptodate(folio);
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/* move it to the tail of the inactive list after end_writeback */
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folio_set_reclaim(folio);
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/* start writeback */
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__swap_writepage(folio, &wbc);
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folio_put(folio);
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return 0;
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}
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/*********************************
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* shrinker functions
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**********************************/
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@ -1419,96 +1506,6 @@ resched:
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zswap_pool_put(pool);
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}
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/*********************************
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* writeback code
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**********************************/
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/*
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* Attempts to free an entry by adding a folio to the swap cache,
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* decompressing the entry data into the folio, and issuing a
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* bio write to write the folio back to the swap device.
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*
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* This can be thought of as a "resumed writeback" of the folio
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* to the swap device. We are basically resuming the same swap
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* writeback path that was intercepted with the zswap_store()
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* in the first place. After the folio has been decompressed into
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* the swap cache, the compressed version stored by zswap can be
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* freed.
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*/
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static int zswap_writeback_entry(struct zswap_entry *entry,
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swp_entry_t swpentry)
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{
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struct zswap_tree *tree;
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struct folio *folio;
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struct mempolicy *mpol;
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bool folio_was_allocated;
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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};
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/* try to allocate swap cache folio */
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mpol = get_task_policy(current);
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folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
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NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
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if (!folio)
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return -ENOMEM;
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/*
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* Found an existing folio, we raced with swapin or concurrent
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* shrinker. We generally writeback cold folios from zswap, and
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* swapin means the folio just became hot, so skip this folio.
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* For unlikely concurrent shrinker case, it will be unlinked
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* and freed when invalidated by the concurrent shrinker anyway.
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*/
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if (!folio_was_allocated) {
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folio_put(folio);
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return -EEXIST;
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}
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/*
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* folio is locked, and the swapcache is now secured against
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* concurrent swapping to and from the slot. Verify that the
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* swap entry hasn't been invalidated and recycled behind our
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* backs (our zswap_entry reference doesn't prevent that), to
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* avoid overwriting a new swap folio with old compressed data.
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*/
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tree = swap_zswap_tree(swpentry);
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spin_lock(&tree->lock);
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if (zswap_rb_search(&tree->rbroot, swp_offset(swpentry)) != entry) {
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spin_unlock(&tree->lock);
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delete_from_swap_cache(folio);
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folio_unlock(folio);
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folio_put(folio);
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return -ENOMEM;
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}
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/* Safe to deref entry after the entry is verified above. */
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zswap_entry_get(entry);
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spin_unlock(&tree->lock);
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zswap_decompress(entry, &folio->page);
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count_vm_event(ZSWPWB);
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if (entry->objcg)
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count_objcg_event(entry->objcg, ZSWPWB);
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spin_lock(&tree->lock);
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zswap_invalidate_entry(tree, entry);
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zswap_entry_put(entry);
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spin_unlock(&tree->lock);
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/* folio is up to date */
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folio_mark_uptodate(folio);
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/* move it to the tail of the inactive list after end_writeback */
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folio_set_reclaim(folio);
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/* start writeback */
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__swap_writepage(folio, &wbc);
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folio_put(folio);
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return 0;
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}
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static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
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{
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unsigned long *page;
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