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Message-Id: <20241127225324.6770-3-kanchana.p.sridhar@intel.com>
Date: Wed, 27 Nov 2024 14:53:24 -0800
From: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
To: linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
hannes@...xchg.org,
yosryahmed@...gle.com,
nphamcs@...il.com,
chengming.zhou@...ux.dev,
usamaarif642@...il.com,
ryan.roberts@....com,
21cnbao@...il.com,
akpm@...ux-foundation.org
Cc: wajdi.k.feghali@...el.com,
vinodh.gopal@...el.com,
kanchana.p.sridhar@...el.com
Subject: [PATCH v1 2/2] mm: zswap: zswap_store_pages() simplifications for batching.
In order to set up zswap_store_pages() to enable a clean batching
implementation in [1], this patch implements the following changes:
1) Addition of zswap_alloc_entries() which will allocate zswap entries for
all pages in the specified range for the folio, upfront. If this fails,
we return an error status to zswap_store().
2) Addition of zswap_compress_pages() that calls zswap_compress() for each
page, and returns false if any zswap_compress() fails, so
zswap_store_page() can cleanup resources allocated and return an error
status to zswap_store().
3) A "store_pages_failed" label that is a catch-all for all failure points
in zswap_store_pages(). This facilitates cleaner error handling within
zswap_store_pages(), which will become important for IAA compress
batching in [1].
[1]: https://patchwork.kernel.org/project/linux-mm/list/?series=911935
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
---
mm/zswap.c | 93 +++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 71 insertions(+), 22 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index b09d1023e775..db80c66e2205 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1409,9 +1409,56 @@ static void shrink_worker(struct work_struct *w)
* main API
**********************************/
+static bool zswap_compress_pages(struct page *pages[],
+ struct zswap_entry *entries[],
+ u8 nr_pages,
+ struct zswap_pool *pool)
+{
+ u8 i;
+
+ for (i = 0; i < nr_pages; ++i) {
+ if (!zswap_compress(pages[i], entries[i], pool))
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Allocate @nr zswap entries for storing @nr pages in a folio.
+ * If any one of the entry allocation fails, delete all entries allocated
+ * thus far, and return false.
+ * If @nr entries are successfully allocated, set each entry's "handle"
+ * to "ERR_PTR(-EINVAL)" to denote that the handle has not yet been allocated.
+ */
+static bool zswap_alloc_entries(struct zswap_entry *entries[], int node_id, u8 nr)
+{
+ u8 i;
+
+ for (i = 0; i < nr; ++i) {
+ entries[i] = zswap_entry_cache_alloc(GFP_KERNEL, node_id);
+ if (!entries[i]) {
+ u8 j;
+
+ zswap_reject_kmemcache_fail++;
+ for (j = 0; j < i; ++j)
+ zswap_entry_cache_free(entries[j]);
+ return false;
+ }
+
+ entries[i]->handle = (unsigned long)ERR_PTR(-EINVAL);
+ }
+
+ return true;
+}
+
/*
* Store multiple pages in @folio, starting from the page at index @si up to
* and including the page at index @ei.
+ * The error handling from all failure points is handled by the
+ * "store_pages_failed" label, based on the initial ERR_PTR(-EINVAL) value for
+ * the zswap_entry's handle set by zswap_alloc_entries(), and the fact that the
+ * entry's handle is subsequently modified only upon a successful zpool_malloc().
*/
static ssize_t zswap_store_pages(struct folio *folio,
long si,
@@ -1419,26 +1466,25 @@ static ssize_t zswap_store_pages(struct folio *folio,
struct obj_cgroup *objcg,
struct zswap_pool *pool)
{
- struct page *page;
- swp_entry_t page_swpentry;
- struct zswap_entry *entry, *old;
+ struct zswap_entry *entries[SWAP_CRYPTO_BATCH_SIZE], *old;
+ struct page *pages[SWAP_CRYPTO_BATCH_SIZE];
size_t compressed_bytes = 0;
u8 nr_pages = ei - si + 1;
u8 i;
- for (i = 0; i < nr_pages; ++i) {
- page = folio_page(folio, si + i);
- page_swpentry = page_swap_entry(page);
+ /* allocate entries */
+ if (!zswap_alloc_entries(entries, folio_nid(folio), nr_pages))
+ return -EINVAL;
- /* allocate entry */
- entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page));
- if (!entry) {
- zswap_reject_kmemcache_fail++;
- return -EINVAL;
- }
+ for (i = 0; i < nr_pages; ++i)
+ pages[i] = folio_page(folio, si + i);
- if (!zswap_compress(page, entry, pool))
- goto compress_failed;
+ if (!zswap_compress_pages(pages, entries, nr_pages, pool))
+ goto store_pages_failed;
+
+ for (i = 0; i < nr_pages; ++i) {
+ swp_entry_t page_swpentry = page_swap_entry(pages[i]);
+ struct zswap_entry *entry = entries[i];
old = xa_store(swap_zswap_tree(page_swpentry),
swp_offset(page_swpentry),
@@ -1448,7 +1494,7 @@ static ssize_t zswap_store_pages(struct folio *folio,
WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n", err);
zswap_reject_alloc_fail++;
- goto store_failed;
+ goto store_pages_failed;
}
/*
@@ -1489,16 +1535,19 @@ static ssize_t zswap_store_pages(struct folio *folio,
}
compressed_bytes += entry->length;
- continue;
-
-store_failed:
- zpool_free(pool->zpool, entry->handle);
-compress_failed:
- zswap_entry_cache_free(entry);
- return -EINVAL;
}
return compressed_bytes;
+
+store_pages_failed:
+ for (i = 0; i < nr_pages; ++i) {
+ if (!IS_ERR_VALUE(entries[i]->handle))
+ zpool_free(pool->zpool, entries[i]->handle);
+
+ zswap_entry_cache_free(entries[i]);
+ }
+
+ return -EINVAL;
}
bool zswap_store(struct folio *folio)
--
2.27.0
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