Cc-ing Uros,
On (25/01/27 12:58), Andrew Morton wrote:
[..]
> -static int zram_slot_trylock(struct zram *zram, u32 index)
> +static int zram_slot_write_trylock(struct zram *zram, u32 index)
> {
> - return spin_trylock(&zram->table[index].lock);
> + int old;
> +
> + old = atomic_cmpxchg(&zram->table[index].lock, ZRAM_ENTRY_UNLOCKED,
> + ZRAM_ENTRY_WRLOCKED);
> + return old == ZRAM_ENTRY_UNLOCKED;
> }
>
> -static void zram_slot_lock(struct zram *zram, u32 index)
> +static void zram_slot_write_lock(struct zram *zram, u32 index)
> {
> - spin_lock(&zram->table[index].lock);
> + atomic_t *lock = &zram->table[index].lock;
> + int old;
> +
> + while (1) {
> + old = atomic_cmpxchg(lock, ZRAM_ENTRY_UNLOCKED,
> + ZRAM_ENTRY_WRLOCKED);
> + if (old == ZRAM_ENTRY_UNLOCKED)
> + return;
> +
> + cond_resched();
> + }
> }
>
> -static void zram_slot_unlock(struct zram *zram, u32 index)
> +static void zram_slot_write_unlock(struct zram *zram, u32 index)
> {
> - spin_unlock(&zram->table[index].lock);
> + atomic_set(&zram->table[index].lock, ZRAM_ENTRY_UNLOCKED);
> +}
> +
> +static void zram_slot_read_lock(struct zram *zram, u32 index)
> +{
> + atomic_t *lock = &zram->table[index].lock;
> + int old;
> +
> + while (1) {
> + old = atomic_read(lock);
> + if (old == ZRAM_ENTRY_WRLOCKED) {
> + cond_resched();
> + continue;
> + }
> +
> + if (atomic_cmpxchg(lock, old, old + 1) == old)
> + return;
> +
> + cond_resched();
> + }
> +}
> +
> +static void zram_slot_read_unlock(struct zram *zram, u32 index)
> +{
> + atomic_dec(&zram->table[index].lock);
> }
Hello Andrew,
I think I want to make these look as close to zsmalloc implementation
as possible.
A simple patch below. No functional changes. (also renamed
zram_slot_write_trylock() to zram_slot_try_write_lock() which is a
more common naming convention for functions of that sort.)
Would you prefer a complete re-spin of the series, with these changes
squashed, or a "fixup" patch?
---
drivers/block/zram/zram_drv.c | 41 +++++++++++++++--------------------
1 file changed, 17 insertions(+), 24 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d73e8374e9cc..9622fcad2115 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -59,28 +59,26 @@ static void zram_free_page(struct zram *zram, size_t index);
static int zram_read_from_zspool(struct zram *zram, struct page *page,
u32 index);
-static int zram_slot_write_trylock(struct zram *zram, u32 index)
+static bool zram_slot_try_write_lock(struct zram *zram, u32 index)
{
- int old;
+ atomic_t *lock = &zram->table[index].lock;
+ int old = ZRAM_ENTRY_UNLOCKED;
- old = atomic_cmpxchg(&zram->table[index].lock, ZRAM_ENTRY_UNLOCKED,
- ZRAM_ENTRY_WRLOCKED);
- return old == ZRAM_ENTRY_UNLOCKED;
+ return atomic_try_cmpxchg(lock, &old, ZRAM_ENTRY_WRLOCKED);
}
static void zram_slot_write_lock(struct zram *zram, u32 index)
{
atomic_t *lock = &zram->table[index].lock;
- int old;
-
- while (1) {
- old = atomic_cmpxchg(lock, ZRAM_ENTRY_UNLOCKED,
- ZRAM_ENTRY_WRLOCKED);
- if (old == ZRAM_ENTRY_UNLOCKED)
- return;
+ int old = atomic_read(lock);
- cond_resched();
- }
+ do {
+ if (old != ZRAM_ENTRY_UNLOCKED) {
+ cond_resched();
+ old = atomic_read(lock);
+ continue;
+ }
+ } while (!atomic_try_cmpxchg(lock, &old, ZRAM_ENTRY_WRLOCKED));
}
static void zram_slot_write_unlock(struct zram *zram, u32 index)
@@ -91,20 +89,15 @@ static void zram_slot_write_unlock(struct zram *zram, u32 index)
static void zram_slot_read_lock(struct zram *zram, u32 index)
{
atomic_t *lock = &zram->table[index].lock;
- int old;
+ int old = atomic_read(lock);
- while (1) {
- old = atomic_read(lock);
+ do {
if (old == ZRAM_ENTRY_WRLOCKED) {
cond_resched();
+ old = atomic_read(lock);
continue;
}
-
- if (atomic_cmpxchg(lock, old, old + 1) == old)
- return;
-
- cond_resched();
- }
+ } while (!atomic_try_cmpxchg(lock, &old, old + 1));
}
static void zram_slot_read_unlock(struct zram *zram, u32 index)
@@ -2315,7 +2308,7 @@ static void zram_slot_free_notify(struct block_device *bdev,
zram = bdev->bd_disk->private_data;
atomic64_inc(&zram->stats.notify_free);
- if (!zram_slot_write_trylock(zram, index)) {
+ if (!zram_slot_try_write_lock(zram, index)) {
atomic64_inc(&zram->stats.miss_free);
return;
}
--
2.48.1.262.g85cc9f2d1e-goog
