zram: drop wb_limit_lock

We don't need wb_limit_lock.  Writeback limit setters take an exclusive
write zram init_lock, while wb_limit modifications happen only from a
single task and under zram read init_lock.  No concurrent wb_limit
modifications are possible (we permit only one post-processing task at a
time).  Add lockdep assertions to wb_limit mutators.

While at it, fixup coding styles.

Link: https://lkml.kernel.org/r/20251122074029.3948921-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Yuwen Chen <ywen.chen@foxmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8dd733707a40db50ae7c744e5f580a530f5d903f..8064972256031f07df6cdd2edd804160a57cb000 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -532,9 +532,7 @@ static ssize_t writeback_limit_enable_store(struct device *dev,
                return ret;
 
        down_write(&zram->init_lock);
-       spin_lock(&zram->wb_limit_lock);
        zram->wb_limit_enable = val;
-       spin_unlock(&zram->wb_limit_lock);
        up_write(&zram->init_lock);
        ret = len;
 
@@ -549,9 +547,7 @@ static ssize_t writeback_limit_enable_show(struct device *dev,
        struct zram *zram = dev_to_zram(dev);
 
        down_read(&zram->init_lock);
-       spin_lock(&zram->wb_limit_lock);
        val = zram->wb_limit_enable;
-       spin_unlock(&zram->wb_limit_lock);
        up_read(&zram->init_lock);
 
        return sysfs_emit(buf, "%d\n", val);
@@ -569,9 +565,7 @@ static ssize_t writeback_limit_store(struct device *dev,
                return ret;
 
        down_write(&zram->init_lock);
-       spin_lock(&zram->wb_limit_lock);
        zram->bd_wb_limit = val;
-       spin_unlock(&zram->wb_limit_lock);
        up_write(&zram->init_lock);
        ret = len;
 
@@ -579,15 +573,13 @@ static ssize_t writeback_limit_store(struct device *dev,
 }
 
 static ssize_t writeback_limit_show(struct device *dev,
-               struct device_attribute *attr, char *buf)
+                                   struct device_attribute *attr, char *buf)
 {
        u64 val;
        struct zram *zram = dev_to_zram(dev);
 
        down_read(&zram->init_lock);
-       spin_lock(&zram->wb_limit_lock);
        val = zram->bd_wb_limit;
-       spin_unlock(&zram->wb_limit_lock);
        up_read(&zram->init_lock);
 
        return sysfs_emit(buf, "%llu\n", val);
@@ -869,18 +861,18 @@ release_wb_ctl:
 
 static void zram_account_writeback_rollback(struct zram *zram)
 {
-       spin_lock(&zram->wb_limit_lock);
+       lockdep_assert_held_read(&zram->init_lock);
+
        if (zram->wb_limit_enable)
                zram->bd_wb_limit +=  1UL << (PAGE_SHIFT - 12);
-       spin_unlock(&zram->wb_limit_lock);
 }
 
 static void zram_account_writeback_submit(struct zram *zram)
 {
-       spin_lock(&zram->wb_limit_lock);
+       lockdep_assert_held_read(&zram->init_lock);
+
        if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
                zram->bd_wb_limit -=  1UL << (PAGE_SHIFT - 12);
-       spin_unlock(&zram->wb_limit_lock);
 }
 
 static int zram_writeback_complete(struct zram *zram, struct zram_wb_req *req)
@@ -1005,13 +997,10 @@ static int zram_writeback_slots(struct zram *zram,
        u32 index = 0;
 
        while ((pps = select_pp_slot(ctl))) {
-               spin_lock(&zram->wb_limit_lock);
                if (zram->wb_limit_enable && !zram->bd_wb_limit) {
-                       spin_unlock(&zram->wb_limit_lock);
                        ret = -EIO;
                        break;
                }
-               spin_unlock(&zram->wb_limit_lock);
 
                while (!req) {
                        req = zram_select_idle_req(wb_ctl);
@@ -2962,7 +2951,6 @@ static int zram_add(void)
        init_rwsem(&zram->init_lock);
 #ifdef CONFIG_ZRAM_WRITEBACK
        zram->wb_batch_size = 32;
-       spin_lock_init(&zram->wb_limit_lock);
 #endif
 
        /* gendisk structure */

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 1a647f42c1a48056d032e9dd841ba36a9e95ef14..c6d94501376c643f5752c4798cd9dd8386629590 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -127,7 +127,6 @@ struct zram {
        bool claim; /* Protected by disk->open_mutex */
 #ifdef CONFIG_ZRAM_WRITEBACK
        struct file *backing_dev;
-       spinlock_t wb_limit_lock;
        bool wb_limit_enable;
        u32 wb_batch_size;
        u64 bd_wb_limit;