mm/swapfile.c | 78 +++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 67 insertions(+), 11 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 35cb58373493..25c3f98fa8d5 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -156,6 +156,25 @@ static bool swap_is_has_cache(struct swap_info_struct *si,
return true;
}
+static bool swap_is_last_map(struct swap_info_struct *si,
+ unsigned long offset, int nr_pages,
+ bool *has_cache)
Please use double tabs for indenting parameters on 2nd line on
new/changed code:
unsigned long offset, int nr_pages, bool *has_cache)
Results in less churn when renaming functions and we can frequently
avoid some lines.
+{
+ unsigned char *map = si->swap_map + offset;
+ unsigned char *map_end = map + nr_pages;
+ bool cached = false;
+
+ do {
+ if ((*map & ~SWAP_HAS_CACHE) != 1)
+ return false;
+ if (*map & SWAP_HAS_CACHE)
+ cached = true;
+ } while (++map < map_end);
+
+ *has_cache = cached;
+ return true;
+}
+
/*
* returns number of pages in the folio that backs the swap entry. If positive,
* the folio was reclaimed. If negative, the folio was not reclaimed. If 0, no
@@ -1469,6 +1488,53 @@ static unsigned char __swap_entry_free(struct swap_info_struct *si,
return usage;
}
+static bool __swap_entries_free(struct swap_info_struct *si,
+ swp_entry_t entry, int nr)
Dito.
+{
+ unsigned long offset = swp_offset(entry);
+ unsigned int type = swp_type(entry);
+ struct swap_cluster_info *ci;
+ bool has_cache = false;
+ unsigned char count;
+ bool can_batch;
+ int i;
+
+ if (nr <= 1 || swap_count(data_race(si->swap_map[offset])) != 1)
+ goto fallback;
+ /* cross into another cluster */
+ if (nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER)
+ goto fallback;
+
+ ci = lock_cluster_or_swap_info(si, offset);
+ can_batch = swap_is_last_map(si, offset, nr, &has_cache);
+ if (can_batch) {
+ for (i = 0; i < nr; i++)
+ WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE);
+ }
+ unlock_cluster_or_swap_info(si, ci);
+
+ if (!can_batch)
+ goto fallback;
I'd avoid "can_batch" and just do:
ci = lock_cluster_or_swap_info(si, offset);
if (!swap_is_last_map(si, offset, nr, &has_cache)) {
unlock_cluster_or_swap_info(si, ci);
goto fallback;
}
for (i = 0; i < nr; i++)
WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE);
unlock_cluster_or_swap_info(si, ci);
+ if (!has_cache) {
+ spin_lock(&si->lock);
I'm no expert on that code, but we might drop the cluster lock the take
the swap_info lock and then retake the cluster lock. I assume there are
no races we are worrying about here, right?
+ swap_entry_range_free(si, entry, nr);
+ spin_unlock(&si->lock);
+ }
+ return has_cache;
+
+fallback:
+ for (i = 0; i < nr; i++) {
One space too much before the "<".
+ if (data_race(si->swap_map[offset + i])) {
+ count = __swap_entry_free(si, swp_entry(type, offset + i));
+ if (count == SWAP_HAS_CACHE)
+ has_cache = true;
+ } else {
+ WARN_ON_ONCE(1);
+ }
+ }
+ return has_cache;
+}
+
--
Cheers,
David / dhildenb
