Messages in this thread Patch in this message | | | From | Sergey Senozhatsky <> | Subject | [PATCHv3 9/9] zram: add dynamic device add/remove functionality | Date | Mon, 27 Apr 2015 22:21:51 +0900 |
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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: - zram_add -- add a new zram device - zram_remove -- remove a specific (device_id) zram device
zram_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/zram_add 2
# remove a specific zram device echo 4 > /sys/class/zram-control/zram_remove
Returning zram_add() error code back to user (-ENOMEM in this case)
cat /sys/class/zram-control/zram_add cat: /sys/class/zram-control/zram_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.
Reported-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> --- Documentation/blockdev/zram.txt | 23 +++++++- drivers/block/zram/zram_drv.c | 120 +++++++++++++++++++++++++++++++++------- 2 files changed, 120 insertions(+), 23 deletions(-)
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 65e9430..fc686d4 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -99,7 +99,24 @@ size of the disk when not in use so a huge zram is wasteful. mkfs.ext4 /dev/zram1 mount /dev/zram1 /tmp -7) Stats: +7) Add/remove zram devices + +zram provides a control interface, which enables dynamic (on-demand) device +addition and removal. + +In order to add a new /dev/zramX device, perform read operation on zram_add +attribute. This will return either new device's device id (meaning that you +can use /dev/zram<id>) or error code. + +Example: + cat /sys/class/zram-control/zram_add + 1 + +To remove the existing /dev/zramX device (where X is a device id) +execute + echo X > /sys/class/zram-control/zram_remove + +8) Stats: Per-device statistics are exported as various nodes under /sys/block/zram<id>/ A brief description of exported device attritbutes. For more details please @@ -174,11 +191,11 @@ line of text and contains the following stats separated by whitespace: zero_pages num_migrated -8) Deactivate: +9) Deactivate: swapoff /dev/zram0 umount /dev/zram1 -9) Reset: +10) Reset: Write any positive value to 'reset' sysfs node echo 1 > /sys/block/zram0/reset echo 1 > /sys/block/zram1/reset diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 3df4394..fa530aa 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -29,10 +29,14 @@ #include <linux/vmalloc.h> #include <linux/err.h> #include <linux/idr.h> +#include <linux/sysfs.h> #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"; @@ -1068,26 +1072,23 @@ static ssize_t reset_store(struct device *dev, struct zram *zram; struct block_device *bdev; + ret = kstrtou16(buf, 10, &do_reset); + if (ret) + return ret; + + if (!do_reset) + return -EINVAL; + zram = dev_to_zram(dev); bdev = bdget_disk(zram->disk, 0); - if (!bdev) return -ENOMEM; mutex_lock(&bdev->bd_mutex); /* Do not reset an active device! */ if (bdev->bd_openers) { - ret = -EBUSY; - goto out; - } - - ret = kstrtou16(buf, 10, &do_reset); - if (ret) - goto out; - - if (!do_reset) { - ret = -EINVAL; - goto out; + mutex_unlock(&bdev->bd_mutex); + return -EBUSY; } /* Make sure all pending I/O is finished */ @@ -1099,11 +1100,6 @@ static ssize_t reset_store(struct device *dev, bdput(bdev); return len; - -out: - mutex_unlock(&bdev->bd_mutex); - bdput(bdev); - return ret; } static const struct block_device_operations zram_devops = { @@ -1256,24 +1252,98 @@ 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) { + mutex_unlock(&bdev->bd_mutex); + return -EBUSY; + } + /* * 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 + * zram_remove() -- device_reset() is the last holder of + * ->init_lock. */ sysfs_remove_group(&disk_to_dev(zram->disk)->kobj, &zram_disk_attr_group); + /* Make sure all pending I/O is finished */ + fsync_bdev(bdev); zram_reset_device(zram); + mutex_unlock(&bdev->bd_mutex); + + 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 module control sysfs attributes */ +static ssize_t zram_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 zram_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 || 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(zram_add), + __ATTR_WO(zram_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); @@ -1282,6 +1352,7 @@ 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"); @@ -1291,14 +1362,23 @@ 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--; -- 2.4.0.rc3.3.g6eb1401
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