From 6566d1a32bf725a4fa9119f16270505451ad01ac Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Thu, 25 Jun 2015 15:00:24 -0700 Subject: zram: add dynamic device add/remove functionality We currently don't support on-demand device creation. The one and only way to have N zram devices is to specify num_devices module parameter (default value: 1). IOW if, for some reason, at some point, user wants to have N + 1 devies he/she must umount all the existing devices, unload the module, load the module passing num_devices equals to N + 1. And do this again, if needed. This patch introduces zram control sysfs class, which has two sysfs attrs: - hot_add -- add a new zram device - hot_remove -- remove a specific (device_id) zram device hot_add sysfs attr is read-only and has only automatic device id assignment mode (as requested by Minchan Kim). read operation performed on this attr creates a new zram device and returns back its device_id or error status. Usage example: # add a new specific zram device cat /sys/class/zram-control/hot_add 2 # remove a specific zram device echo 4 > /sys/class/zram-control/hot_remove Returning zram_add() error code back to user (-ENOMEM in this case) cat /sys/class/zram-control/hot_add cat: /sys/class/zram-control/hot_add: Cannot allocate memory NOTE, there might be users who already depend on the fact that at least zram0 device gets always created by zram_init(). Preserve this behavior. [minchan@kernel.org: use zram->claim to avoid lockdep splat] Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zram_drv.c | 100 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 97 insertions(+), 3 deletions(-) (limited to 'drivers/block/zram') diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 6a3b36d5bad6..830f0eb501fa 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -29,10 +29,14 @@ #include #include #include +#include #include "zram_drv.h" static DEFINE_IDR(zram_index_idr); +/* idr index must be protected */ +static DEFINE_MUTEX(zram_index_mutex); + static int zram_major; static const char *default_compressor = "lzo"; @@ -1273,24 +1277,104 @@ out_free_dev: return ret; } -static void zram_remove(struct zram *zram) +static int zram_remove(struct zram *zram) { - pr_info("Removed device: %s\n", zram->disk->disk_name); + struct block_device *bdev; + + bdev = bdget_disk(zram->disk, 0); + if (!bdev) + return -ENOMEM; + + mutex_lock(&bdev->bd_mutex); + if (bdev->bd_openers || zram->claim) { + mutex_unlock(&bdev->bd_mutex); + bdput(bdev); + return -EBUSY; + } + + zram->claim = true; + mutex_unlock(&bdev->bd_mutex); + /* * Remove sysfs first, so no one will perform a disksize - * store while we destroy the devices + * store while we destroy the devices. This also helps during + * hot_remove -- zram_reset_device() is the last holder of + * ->init_lock, no later/concurrent disksize_store() or any + * other sysfs handlers are possible. */ sysfs_remove_group(&disk_to_dev(zram->disk)->kobj, &zram_disk_attr_group); + /* Make sure all the pending I/O are finished */ + fsync_bdev(bdev); zram_reset_device(zram); + bdput(bdev); + + pr_info("Removed device: %s\n", zram->disk->disk_name); + idr_remove(&zram_index_idr, zram->disk->first_minor); blk_cleanup_queue(zram->disk->queue); del_gendisk(zram->disk); put_disk(zram->disk); kfree(zram); + return 0; +} + +/* zram-control sysfs attributes */ +static ssize_t hot_add_show(struct class *class, + struct class_attribute *attr, + char *buf) +{ + int ret; + + mutex_lock(&zram_index_mutex); + ret = zram_add(); + mutex_unlock(&zram_index_mutex); + + if (ret < 0) + return ret; + return scnprintf(buf, PAGE_SIZE, "%d\n", ret); +} + +static ssize_t hot_remove_store(struct class *class, + struct class_attribute *attr, + const char *buf, + size_t count) +{ + struct zram *zram; + int ret, dev_id; + + /* dev_id is gendisk->first_minor, which is `int' */ + ret = kstrtoint(buf, 10, &dev_id); + if (ret) + return ret; + if (dev_id < 0) + return -EINVAL; + + mutex_lock(&zram_index_mutex); + + zram = idr_find(&zram_index_idr, dev_id); + if (zram) + ret = zram_remove(zram); + else + ret = -ENODEV; + + mutex_unlock(&zram_index_mutex); + return ret ? ret : count; } +static struct class_attribute zram_control_class_attrs[] = { + __ATTR_RO(hot_add), + __ATTR_WO(hot_remove), + __ATTR_NULL, +}; + +static struct class zram_control_class = { + .name = "zram-control", + .owner = THIS_MODULE, + .class_attrs = zram_control_class_attrs, +}; + static int zram_remove_cb(int id, void *ptr, void *data) { zram_remove(ptr); @@ -1299,6 +1383,7 @@ static int zram_remove_cb(int id, void *ptr, void *data) static void destroy_devices(void) { + class_unregister(&zram_control_class); idr_for_each(&zram_index_idr, &zram_remove_cb, NULL); idr_destroy(&zram_index_idr); unregister_blkdev(zram_major, "zram"); @@ -1308,14 +1393,23 @@ static int __init zram_init(void) { int ret; + ret = class_register(&zram_control_class); + if (ret) { + pr_warn("Unable to register zram-control class\n"); + return ret; + } + zram_major = register_blkdev(0, "zram"); if (zram_major <= 0) { pr_warn("Unable to get major number\n"); + class_unregister(&zram_control_class); return -EBUSY; } while (num_devices != 0) { + mutex_lock(&zram_index_mutex); ret = zram_add(); + mutex_unlock(&zram_index_mutex); if (ret < 0) goto out_error; num_devices--; -- cgit v1.2.3