zram: add free space management in backing device

With backing device, zram needs management of free space of backing
device.

This patch adds bitmap logic to manage free space which is very naive.
However, it would be simple enough as considering uncompressible pages's
frequenty in zram.

Link: http://lkml.kernel.org/r/1498459987-24562-6-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 81eb81f17ef9d227388937c41b4306a2df486c97..fcdbbb1e77458ed3840564b4e5eefbb7c46fdcbf 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -292,6 +292,9 @@ static void reset_bdev(struct zram *zram)
        zram->backing_dev = NULL;
        zram->old_block_size = 0;
        zram->bdev = NULL;
+
+       kvfree(zram->bitmap);
+       zram->bitmap = NULL;
 }
 
 static ssize_t backing_dev_show(struct device *dev,
@@ -330,7 +333,8 @@ static ssize_t backing_dev_store(struct device *dev,
        struct file *backing_dev = NULL;
        struct inode *inode;
        struct address_space *mapping;
-       unsigned int old_block_size = 0;
+       unsigned int bitmap_sz, old_block_size = 0;
+       unsigned long nr_pages, *bitmap = NULL;
        struct block_device *bdev = NULL;
        int err;
        struct zram *zram = dev_to_zram(dev);
@@ -369,16 +373,27 @@ static ssize_t backing_dev_store(struct device *dev,
        if (err < 0)
                goto out;
 
+       nr_pages = i_size_read(inode) >> PAGE_SHIFT;
+       bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long);
+       bitmap = kvzalloc(bitmap_sz, GFP_KERNEL);
+       if (!bitmap) {
+               err = -ENOMEM;
+               goto out;
+       }
+
        old_block_size = block_size(bdev);
        err = set_blocksize(bdev, PAGE_SIZE);
        if (err)
                goto out;
 
        reset_bdev(zram);
+       spin_lock_init(&zram->bitmap_lock);
 
        zram->old_block_size = old_block_size;
        zram->bdev = bdev;
        zram->backing_dev = backing_dev;
+       zram->bitmap = bitmap;
+       zram->nr_pages = nr_pages;
        up_write(&zram->init_lock);
 
        pr_info("setup backing device %s\n", file_name);
@@ -386,6 +401,9 @@ static ssize_t backing_dev_store(struct device *dev,
 
        return len;
 out:
+       if (bitmap)
+               kvfree(bitmap);
+
        if (bdev)
                blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 
@@ -399,6 +417,34 @@ out:
        return err;
 }
 
+static unsigned long get_entry_bdev(struct zram *zram)
+{
+       unsigned long entry;
+
+       spin_lock(&zram->bitmap_lock);
+       /* skip 0 bit to confuse zram.handle = 0 */
+       entry = find_next_zero_bit(zram->bitmap, zram->nr_pages, 1);
+       if (entry == zram->nr_pages) {
+               spin_unlock(&zram->bitmap_lock);
+               return 0;
+       }
+
+       set_bit(entry, zram->bitmap);
+       spin_unlock(&zram->bitmap_lock);
+
+       return entry;
+}
+
+static void put_entry_bdev(struct zram *zram, unsigned long entry)
+{
+       int was_set;
+
+       spin_lock(&zram->bitmap_lock);
+       was_set = test_and_clear_bit(entry, zram->bitmap);
+       spin_unlock(&zram->bitmap_lock);
+       WARN_ON_ONCE(!was_set);
+}
+
 #else
 static bool zram_wb_enabled(struct zram *zram) { return false; }
 static inline void reset_bdev(struct zram *zram) {};

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 113a41118918c0e9f0e3dfa9c3e4c55a76e87e82..707aec0a2681d6a4f5124770f8fb5c8764ead329 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -119,6 +119,9 @@ struct zram {
        struct file *backing_dev;
        struct block_device *bdev;
        unsigned int old_block_size;
+       unsigned long *bitmap;
+       unsigned long nr_pages;
+       spinlock_t bitmap_lock;
 #endif
 };
 #endif