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 <[email protected]> --- 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
