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Date: Mon, 12 Jun 2017 14:02:47 +0900
From: Minchan Kim <minchan@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Juneho Choi <juno.choi@....com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
kernel-team <kernel-team@....com>,
Minchan Kim <minchan@...nel.org>
Subject: [RFC 3/7] zram: add interface to specify backing device
For writeback feature, user should set up backing device before
the zram working. This patch enables the interface via
/sys/block/zramX/backing_dev.
Currently, it supports block device only but it could be enhanced
for file as well.
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
drivers/block/zram/zram_drv.c | 163 ++++++++++++++++++++++++++++++++++++++++++
drivers/block/zram/zram_drv.h | 5 ++
2 files changed, 168 insertions(+)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index a0c304b..dcb6f83 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -271,6 +271,163 @@ static ssize_t mem_used_max_store(struct device *dev,
return len;
}
+#ifdef CONFIG_ZRAM_WRITEBACK
+static bool zram_wb_enabled(struct zram *zram)
+{
+ return zram->backing_dev;
+}
+
+static void reset_bdev(struct zram *zram)
+{
+ struct inode *inode;
+ struct address_space *mapping;
+ struct block_device *bdev;
+
+ if (!zram_wb_enabled(zram))
+ return;
+
+ mapping = zram->backing_dev->f_mapping;
+ inode = mapping->host;
+ bdev = I_BDEV(inode);
+
+ if (zram->old_block_size)
+ set_blocksize(bdev, zram->old_block_size);
+ blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+ /* hope filp_close flush all of IO */
+ filp_close(zram->backing_dev, NULL);
+ zram->backing_dev = NULL;
+ zram->old_block_size = 0;
+ zram->bdev = NULL;
+}
+
+static ssize_t backing_dev_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct zram *zram = dev_to_zram(dev);
+ struct file *file = zram->backing_dev;
+ char *p;
+ ssize_t ret;
+
+ down_read(&zram->init_lock);
+ if (!zram_wb_enabled(zram)) {
+ memcpy(buf, "none\n", 5);
+ up_read(&zram->init_lock);
+ return 5;
+ }
+
+ p = file_path(file, buf, PAGE_SIZE - 1);
+ if (IS_ERR(p)) {
+ ret = PTR_ERR(p);
+ goto out;
+ }
+
+ ret = strlen(p);
+ memmove(buf, p, ret);
+ buf[ret++] = '\n';
+out:
+ up_read(&zram->init_lock);
+ return ret;
+}
+
+static ssize_t backing_dev_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ char *file_name;
+ struct filename *name = NULL;
+ struct file *backing_dev = NULL;
+ struct inode *inode;
+ struct address_space *mapping;
+ unsigned int old_block_size = 0;
+ struct block_device *bdev = NULL;
+ int err;
+ size_t sz;
+ struct zram *zram = dev_to_zram(dev);
+
+ file_name = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!file_name)
+ return -ENOMEM;
+
+ down_write(&zram->init_lock);
+ if (init_done(zram)) {
+ pr_info("Can't setup backing device for initialized device\n");
+ err = -EBUSY;
+ goto out;
+ }
+
+ strlcpy(file_name, buf, len);
+ /* ignore trailing newline */
+ sz = strlen(file_name);
+ if (sz > 0 && file_name[sz - 1] == '\n')
+ file_name[sz - 1] = 0x00;
+
+ name = getname_kernel(file_name);
+ if (IS_ERR(name)) {
+ err = PTR_ERR(name);
+ name = NULL;
+ goto out;
+ }
+
+ backing_dev = file_open_name(name, O_RDWR|O_LARGEFILE, 0);
+ if (IS_ERR(backing_dev)) {
+ err = PTR_ERR(backing_dev);
+ backing_dev = NULL;
+ goto out;
+ }
+
+ mapping = backing_dev->f_mapping;
+ inode = mapping->host;
+
+ /* Support only block device in this moment */
+ if (!S_ISBLK(inode->i_mode)) {
+ err = -ENOTBLK;
+ goto out;
+ }
+
+ bdev = bdgrab(I_BDEV(inode));
+ err = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram);
+ if (err < 0)
+ goto out;
+
+ old_block_size = block_size(bdev);
+ err = set_blocksize(bdev, PAGE_SIZE);
+ if (err)
+ goto out;
+
+ reset_bdev(zram);
+
+ zram->old_block_size = old_block_size;
+ zram->bdev = bdev;
+ zram->backing_dev = backing_dev;
+ up_write(&zram->init_lock);
+
+ pr_info("setup backing device %s\n", file_name);
+
+ putname(name);
+ kfree(file_name);
+
+ return len;
+out:
+ if (bdev)
+ blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+
+ if (backing_dev)
+ filp_close(backing_dev, NULL);
+
+ if (name)
+ putname(name);
+ up_write(&zram->init_lock);
+
+ kfree(file_name);
+
+ return err;
+}
+
+#else
+static bool zram_wb_enabled(struct zram *zram) { return false; }
+static void reset_bdev(struct zram *zram) {};
+#endif
+
+
/*
* We switched to per-cpu streams and this attr is not needed anymore.
* However, we will keep it around for some time, because:
@@ -1198,6 +1355,9 @@ static DEVICE_ATTR_RW(use_dedup);
#else
static DEVICE_ATTR_RO(use_dedup);
#endif
+#ifdef CONFIG_ZRAM_WRITEBACK
+static DEVICE_ATTR_RW(backing_dev);
+#endif
static struct attribute *zram_disk_attrs[] = {
&dev_attr_disksize.attr,
@@ -1209,6 +1369,9 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_max_comp_streams.attr,
&dev_attr_comp_algorithm.attr,
&dev_attr_use_dedup.attr,
+#ifdef CONFIG_ZRAM_WRITEBACK
+ &dev_attr_backing_dev.attr,
+#endif
&dev_attr_io_stat.attr,
&dev_attr_mm_stat.attr,
&dev_attr_debug_stat.attr,
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 8ccfdcd..5193bcb 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -136,6 +136,11 @@ struct zram {
*/
bool claim; /* Protected by bdev->bd_mutex */
bool use_dedup;
+#ifdef CONFIG_ZRAM_WRITEBACK
+ struct file *backing_dev;
+ struct block_device *bdev;
+ unsigned int old_block_size;
+#endif
};
static inline bool zram_dedup_enabled(struct zram *zram)
--
2.7.4
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