[PATCH -V6 02/21] swap: Add __swap_duplicate_locked()

Huang Ying
2018-10-10T07:27:48Z

The part of __swap_duplicate() with lock held is separated into a new
function __swap_duplicate_locked(). Because we will add more logic
about the PMD swap mapping into __swap_duplicate() and keep the most
PTE swap mapping related logic in __swap_duplicate_locked().

Just mechanical code refactoring, there is no any functional change in
this patch.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
---
mm/swapfile.c | 63 +++++++++++++++++++++++++++++++++--------------------------
1 file changed, 35 insertions(+), 28 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 97a1bd1a7c9a..6a570ef00fa7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3436,32 +3436,12 @@ void si_swapinfo(struct sysinfo *val)
spin_unlock(&swap_lock);
}

-/*
- * Verify that a swap entry is valid and increment its swap map count.
- *
- * Returns error code in following case.
- * - success -> 0
- * - swp_entry is invalid -> EINVAL
- * - swp_entry is migration entry -> EINVAL
- * - swap-cache reference is requested but there is already one. -> EEXIST
- * - swap-cache reference is requested but the entry is not used. -> ENOENT
- * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
- */
-static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
+static int __swap_duplicate_locked(struct swap_info_struct *p,
+ unsigned long offset, unsigned char usage)
{
- struct swap_info_struct *p;
- struct swap_cluster_info *ci;
- unsigned long offset;
unsigned char count;
unsigned char has_cache;
- int err = -EINVAL;
-
- p = get_swap_device(entry);
- if (!p)
- goto out;
-
- offset = swp_offset(entry);
- ci = lock_cluster_or_swap_info(p, offset);
+ int err = 0;

count = p->swap_map[offset];

@@ -3471,12 +3451,11 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
*/
if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
err = -ENOENT;
- goto unlock_out;
+ goto out;
}

has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
- err = 0;

if (usage == SWAP_HAS_CACHE) {

@@ -3503,11 +3482,39 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)

p->swap_map[offset] = count | has_cache;

-unlock_out:
+out:
+ return err;
+}
+
+/*
+ * Verify that a swap entry is valid and increment its swap map count.
+ *
+ * Returns error code in following case.
+ * - success -> 0
+ * - swp_entry is invalid -> EINVAL
+ * - swp_entry is migration entry -> EINVAL
+ * - swap-cache reference is requested but there is already one. -> EEXIST
+ * - swap-cache reference is requested but the entry is not used. -> ENOENT
+ * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
+ */
+static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
+{
+ struct swap_info_struct *p;
+ struct swap_cluster_info *ci;
+ unsigned long offset;
+ int err = -EINVAL;
+
+ p = get_swap_device(entry);
+ if (!p)
+ goto out;
+
+ offset = swp_offset(entry);
+ ci = lock_cluster_or_swap_info(p, offset);
+ err = __swap_duplicate_locked(p, offset, usage);
unlock_cluster_or_swap_info(p, ci);
+
+ put_swap_device(p);
out:
- if (p)
- put_swap_device(p);
return err;
}

--
2.16.4