From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm: swap: add comments to lock_cluster_or_swap_info()
Patch series "swap: THP optimizing refactoring", v4.
Now the THP (Transparent Huge Page) swap optimizing is implemented in the
way like below,
#ifdef CONFIG_THP_SWAP
huge_function(...)
{
}
#else
normal_function(...)
{
}
#endif
general_function(...)
{
if (huge)
return thp_function(...);
else
return normal_function(...);
}
As pointed out by Dave Hansen, this will,
1. Created a new, wholly untested code path for huge page
2. Created two places to patch bugs
3. Are not reusing code when possible
This patchset is to address these problems via merging huge/normal code
path/functions if possible.
One concern is that this may cause code size to dilate when
!CONFIG_TRANSPARENT_HUGEPAGE. The data shows that most refactoring will
only cause quite slight code size increase.
This patch (of 8):
To improve code readability.
Link: http://lkml.kernel.org/r/20180720071845.17920-2-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Suggested-and-acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/mm/swapfile.c~swap-add-comments-to-lock_cluster_or_swap_info
+++ a/mm/swapfile.c
@@ -296,13 +296,18 @@ static inline void unlock_cluster(struct
spin_unlock(&ci->lock);
}
+/*
+ * Determine the locking method in use for this device. Return
+ * swap_cluster_info if SSD-style cluster-based locking is in place.
+ */
static inline struct swap_cluster_info *lock_cluster_or_swap_info(
- struct swap_info_struct *si,
- unsigned long offset)
+ struct swap_info_struct *si, unsigned long offset)
{
struct swap_cluster_info *ci;
+ /* Try to use fine-grained SSD-style locking if available: */
ci = lock_cluster(si, offset);
+ /* Otherwise, fall back to traditional, coarse locking: */
if (!ci)
spin_lock(&si->lock);
_
