From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756400AbbCCMt5 (ORCPT ); Tue, 3 Mar 2015 07:49:57 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:45860 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932117AbbCCMtx (ORCPT ); Tue, 3 Mar 2015 07:49:53 -0500 From: Sergey Senozhatsky To: Andrew Morton , Minchan Kim Cc: Nitin Gupta , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCH 5/8] zram: add dynamic device add/remove functionality Date: Tue, 3 Mar 2015 21:49:47 +0900 Message-Id: <1425386990-6339-6-git-send-email-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.3.1.167.g7f4ba4b In-Reply-To: <1425386990-6339-1-git-send-email-sergey.senozhatsky@gmail.com> References: <1425386990-6339-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce zram-control sysfs class, which has two sysfs attrs: - zram_add -- add a new specific (device_id) zram device - zram_remove -- remove a specific (device_id) zram device Usage example: # add a new specific zram device echo 4 > /sys/class/zram-control/zram_add # remove a specific zram device echo 4 > /sys/class/zram-control/zram_remove There is no automatic device_id generation, so user is expected to provide one. NOTE, there might be users who already depend on the fact that at least zram0 device gets always created by zram_init(). Thus, due to compatibility reasons, along with requested device_id (f.e. 5) zram0 will also be created. Signed-off-by: Sergey Senozhatsky --- Documentation/ABI/testing/sysfs-class-zram | 23 ++++++ Documentation/blockdev/zram.txt | 23 +++++- drivers/block/zram/zram_drv.c | 120 +++++++++++++++++++++++++++++ 3 files changed, 162 insertions(+), 4 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-class-zram diff --git a/Documentation/ABI/testing/sysfs-class-zram b/Documentation/ABI/testing/sysfs-class-zram new file mode 100644 index 0000000..99b2a1e --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-zram @@ -0,0 +1,23 @@ +What: /sys/class/zram-control/ +Date: March 2015 +KernelVersion: 4.1 +Contact: Sergey Senozhatsky +Description: + The zram-control/ class sub-directory belongs to zram + device class + +What: /sys/class/zram-control/zram_add +Date: March 2015 +KernelVersion: 4.1 +Contact: Sergey Senozhatsky +Description: + Add a specific /dev/zramX device, where X is a device_id + provided by user + + What: /sys/class/zram-control/zram_add +Date: March 2015 +KernelVersion: 4.1 +Contact: Sergey Senozhatsky +Description: + Remove a specific /dev/zramX device, where X is a device_id + provided by user diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 7fcf9c6..4b140fa 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -19,7 +19,9 @@ Following shows a typical sequence of steps for using zram. 1) Load Module: modprobe zram num_devices=4 This creates 4 devices: /dev/zram{0,1,2,3} - (num_devices parameter is optional. Default: 1) + +num_devices parameter is optional and tells zram how many devices should be +pre-created. Default: 1. 2) Set max number of compression streams Compression backend may use up to max_comp_streams compression streams, @@ -97,7 +99,20 @@ 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 (where X is a unique device id) +execute + echo X > /sys/class/zram-control/zram_add + +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/ disksize @@ -113,11 +128,11 @@ size of the disk when not in use so a huge zram is wasteful. mem_used_total mem_used_max -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 bab8b20..a457e16 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -33,16 +33,23 @@ #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"; /* Module params (documentation at end) */ static unsigned int num_devices = 1; +#define ZRAM_CTL_ADD 1 +#define ZRAM_CTL_REMOVE 2 + #define ZRAM_ATTR_RO(name) \ static ssize_t name##_show(struct device *d, \ struct device_attribute *attr, char *b) \ @@ -1173,6 +1180,109 @@ static void zram_remove(struct zram *zram) kfree(zram); } +/* lookup if there is any device pointer that match the given device_id. + * return device pointer if so, or ERR_PTR() otherwise. */ +static struct zram *zram_lookup(int dev_id) +{ + struct zram *zram; + + zram = idr_find(&zram_index_idr, dev_id); + if (zram) + return zram; + return ERR_PTR(-ENODEV); +} + +/* common zram-control add/remove handler */ +static int zram_control(int cmd, const char *buf) +{ + struct zram *zram; + int ret = -ENOSYS, err, dev_id; + + /* dev_id is gendisk->first_minor, which is `int' */ + ret = kstrtoint(buf, 10, &dev_id); + if (ret || dev_id < 0) + return ret; + + mutex_lock(&zram_index_mutex); + zram = zram_lookup(dev_id); + + switch (cmd) { + case ZRAM_CTL_ADD: + if (!IS_ERR(zram)) { + ret = -EEXIST; + break; + } + ret = zram_add(dev_id); + break; + case ZRAM_CTL_REMOVE: + if (IS_ERR(zram)) { + ret = PTR_ERR(zram); + break; + } + + /* First, make ->disksize device attr RO, closing + * ZRAM_CTL_REMOVE vs disksize_store() race window */ + ret = sysfs_chmod_file(&disk_to_dev(zram->disk)->kobj, + &dev_attr_disksize.attr, S_IRUGO); + if (ret) + break; + + ret = zram_reset_device(zram); + if (ret == 0) { + /* ->disksize is RO and there are no ->bd_openers */ + zram_remove(zram); + break; + } + + /* If there are still device bd_openers, try to make ->disksize + * RW again and return. even if we fail to make ->disksize RW, + * user still has RW ->reset attr. so it's possible to destroy + * that device */ + err = sysfs_chmod_file(&disk_to_dev(zram->disk)->kobj, + &dev_attr_disksize.attr, + S_IWUSR | S_IRUGO); + if (err) + ret = err; + break; + } + mutex_unlock(&zram_index_mutex); + + return ret; +} + +/* zram module control sysfs attributes */ +static ssize_t zram_add_store(struct class *class, + struct class_attribute *attr, + const char *buf, + size_t count) +{ + int ret = zram_control(ZRAM_CTL_ADD, buf); + + return ret ? ret : count; +} + +static ssize_t zram_remove_store(struct class *class, + struct class_attribute *attr, + const char *buf, + size_t count) +{ + int ret = zram_control(ZRAM_CTL_REMOVE, buf); + + return ret ? ret : count; +} + +static struct class_attribute zram_control_class_attrs[] = { + __ATTR_WO(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_exit_cb(int id, void *ptr, void *data) { zram_remove(ptr); @@ -1181,6 +1291,7 @@ static int zram_exit_cb(int id, void *ptr, void *data) static void destroy_devices(void) { + class_unregister(&zram_control_class); idr_for_each(&zram_index_idr, &zram_exit_cb, NULL); idr_destroy(&zram_index_idr); unregister_blkdev(zram_major, "zram"); @@ -1197,14 +1308,23 @@ static int __init zram_init(void) return -EINVAL; } + 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; } for (dev_id = 0; dev_id < num_devices; dev_id++) { + mutex_lock(&zram_index_mutex); ret = zram_add(dev_id); + mutex_unlock(&zram_index_mutex); if (ret != 0) goto out_error; } -- 2.3.1.167.g7f4ba4b