[RFCv2 1/3] mm: Don't hide spin_lock in swap_info_get internal

Minchan Kim
2014-06-20T06:48:00Z

Now, swap_info_get hides lock holding by doing it internally
but releasing the lock so caller should release the lock.
Normally, it's not a good pattern and I need to handle lock
from caller in next patchset.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/swapfile.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 8798b2e0ac59..ec2ce926ea5f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -740,7 +740,6 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
goto bad_offset;
if (!p->swap_map[offset])
goto bad_free;
- spin_lock(&p->lock);
return p;

bad_free:
@@ -835,6 +834,7 @@ void swap_free(swp_entry_t entry)

p = swap_info_get(entry);
if (p) {
+ spin_lock(&p->lock);
swap_entry_free(p, entry, 1);
spin_unlock(&p->lock);
}
@@ -849,6 +849,7 @@ void swapcache_free(swp_entry_t entry)

p = swap_info_get(entry);
if (p) {
+ spin_lock(&p->lock);
swap_entry_free(p, entry, SWAP_HAS_CACHE);
spin_unlock(&p->lock);
}
@@ -868,6 +869,7 @@ int page_swapcount(struct page *page)
entry.val = page_private(page);
p = swap_info_get(entry);
if (p) {
+ spin_lock(&p->lock);
count = swap_count(p->swap_map[swp_offset(entry)]);
spin_unlock(&p->lock);
}
@@ -950,6 +952,7 @@ int free_swap_and_cache(swp_entry_t entry)

p = swap_info_get(entry);
if (p) {
+ spin_lock(&p->lock);
if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
page = find_get_page(swap_address_space(entry),
entry.val);
@@ -2763,6 +2766,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
goto outer;
}

+ spin_lock(&si->lock);
offset = swp_offset(entry);
count = si->swap_map[offset] & ~SWAP_HAS_CACHE;

--
2.0.0