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Message-Id: <a41138ecc857ef13e7c5ffa0174321e9e2c9970a.1723434324.git.baolin.wang@linux.alibaba.com>
Date: Mon, 12 Aug 2024 15:42:07 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
hughd@...gle.com
Cc: willy@...radead.org,
david@...hat.com,
wangkefeng.wang@...wei.com,
chrisl@...nel.org,
ying.huang@...el.com,
21cnbao@...il.com,
ryan.roberts@....com,
shy828301@...il.com,
ziy@...dia.com,
ioworker0@...il.com,
da.gomez@...sung.com,
p.raghav@...sung.com,
baolin.wang@...ux.alibaba.com,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v5 6/9] mm: shmem: support large folio allocation for shmem_replace_folio()
To support large folio swapin for shmem in the following patches, add
large folio allocation for the new replacement folio in shmem_replace_folio().
Moreover large folios occupy N consecutive entries in the swap cache
instead of using multi-index entries like the page cache, therefore
we should replace each consecutive entries in the swap cache instead
of using the shmem_replace_entry().
As well as updating statistics and folio reference count using the number
of pages in the folio.
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
mm/shmem.c | 54 +++++++++++++++++++++++++++++++-----------------------
1 file changed, 31 insertions(+), 23 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index f6bab42180ea..d94f02ad7bd1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1889,28 +1889,24 @@ static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
- struct folio *old, *new;
- struct address_space *swap_mapping;
- swp_entry_t entry;
- pgoff_t swap_index;
- int error;
-
- old = *foliop;
- entry = old->swap;
- swap_index = swap_cache_index(entry);
- swap_mapping = swap_address_space(entry);
+ struct folio *new, *old = *foliop;
+ swp_entry_t entry = old->swap;
+ struct address_space *swap_mapping = swap_address_space(entry);
+ pgoff_t swap_index = swap_cache_index(entry);
+ XA_STATE(xas, &swap_mapping->i_pages, swap_index);
+ int nr_pages = folio_nr_pages(old);
+ int error = 0, i;
/*
* We have arrived here because our zones are constrained, so don't
* limit chance of success by further cpuset and node constraints.
*/
gfp &= ~GFP_CONSTRAINT_MASK;
- VM_BUG_ON_FOLIO(folio_test_large(old), old);
- new = shmem_alloc_folio(gfp, 0, info, index);
+ new = shmem_alloc_folio(gfp, folio_order(old), info, index);
if (!new)
return -ENOMEM;
- folio_get(new);
+ folio_ref_add(new, nr_pages);
folio_copy(new, old);
flush_dcache_folio(new);
@@ -1920,18 +1916,25 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
new->swap = entry;
folio_set_swapcache(new);
- /*
- * Our caller will very soon move newpage out of swapcache, but it's
- * a nice clean interface for us to replace oldpage by newpage there.
- */
+ /* Swap cache still stores N entries instead of a high-order entry */
xa_lock_irq(&swap_mapping->i_pages);
- error = shmem_replace_entry(swap_mapping, swap_index, old, new);
+ for (i = 0; i < nr_pages; i++) {
+ void *item = xas_load(&xas);
+
+ if (item != old) {
+ error = -ENOENT;
+ break;
+ }
+
+ xas_store(&xas, new);
+ xas_next(&xas);
+ }
if (!error) {
mem_cgroup_replace_folio(old, new);
- __lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1);
- __lruvec_stat_mod_folio(new, NR_SHMEM, 1);
- __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1);
- __lruvec_stat_mod_folio(old, NR_SHMEM, -1);
+ __lruvec_stat_mod_folio(new, NR_FILE_PAGES, nr_pages);
+ __lruvec_stat_mod_folio(new, NR_SHMEM, nr_pages);
+ __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -nr_pages);
+ __lruvec_stat_mod_folio(old, NR_SHMEM, -nr_pages);
}
xa_unlock_irq(&swap_mapping->i_pages);
@@ -1951,7 +1954,12 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
old->private = NULL;
folio_unlock(old);
- folio_put_refs(old, 2);
+ /*
+ * The old folio are removed from swap cache, drop the 'nr_pages'
+ * reference, as well as one temporary reference getting from swap
+ * cache.
+ */
+ folio_put_refs(old, nr_pages + 1);
return error;
}
--
2.39.3
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