Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932817AbaGQOGD (ORCPT ); Thu, 17 Jul 2014 10:06:03 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:49998 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756649AbaGQOGA (ORCPT ); Thu, 17 Jul 2014 10:06:00 -0400 Date: Thu, 17 Jul 2014 23:04:40 +0900 From: Sergey Senozhatsky To: Timofey Titovets Cc: minchan@kernel.org, Sergey Senozhatsky , linux-kernel@vger.kernel.org, Andrew Morton , Jerome Marchand , Nitin Gupta Subject: Re: [PATCH v2] zram: auto add/del devices on demand Message-ID: <20140717140440.GA1275@swordfish> References: <53C7C131.1060306@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53C7C131.1060306@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (07/17/14 15:27), Timofey Titovets wrote: > This add supporting of autochange count of zram devices on demand, like loop > devices; > This working by following rules: > - Always save minimum devices count specified by num_device (can be > specified while kernel module loading) > - if last device already using add new device; > - if last and prelast devices is free - delete last zram device; > > Signed-off-by: Timofey Titovets > > From v1 -> v2: > Delete useless variable 'ret', added documentation for explain new zram > behaviour > > Please pull from: > https://github.com/Nefelim4ag/linux.git > --- > Tested on 3.15.5-2-ARCH, can be applied on any kernel version > after this patch 'zram: add LZ4 compression support' - https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=6e76668e415adf799839f0ab205142ad7002d260 > --- > diff --git a/Documentation/blockdev/zram.txt > b/Documentation/blockdev/zram.txt > index 0595c3f..7f5c921 100644 > --- a/Documentation/blockdev/zram.txt > +++ b/Documentation/blockdev/zram.txt > @@ -18,9 +18,19 @@ 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} > + This pre creates 4 devices: /dev/zram{0,1,2,3} > (num_devices parameter is optional. Default: 1) > > + Kernel dynamically changes number of zram devices by demand > + (between num_devices and 31) > + If set disk size(4) for last device > + kernel automatically adds new zram device > + If last two devices have zero disk size after reset(8), > + kernel will destroy last device > + > + Summing up all features, comes one simple rule: > + "The last zram device is always free for use" I can't understand what is the real benefit? > 2) Set max number of compression streams > Compression backend may use up to max_comp_streams compression streams, > thus allowing up to max_comp_streams concurrent compression operations. > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 089e72c..9b2fc89 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -42,6 +42,10 @@ static const char *default_compressor = "lzo"; > > /* Module params (documentation at end) */ > static unsigned int num_devices = 1; > +static unsigned int last_created_dev = 1; > + > +static void zram_add_dev(void); > +static void zram_del_dev(void); > #define ZRAM_ATTR_RO(name) \ > static ssize_t zram_attr_##name##_show(struct device *d, \ > @@ -168,6 +172,7 @@ static ssize_t comp_algorithm_store(struct device *dev, > struct device_attribute *attr, const char *buf, size_t len) > { > struct zram *zram = dev_to_zram(dev); > + > down_write(&zram->init_lock); > if (init_done(zram)) { > up_write(&zram->init_lock); > @@ -239,6 +244,7 @@ static struct zram_meta *zram_meta_alloc(u64 disksize) > { > size_t num_pages; > struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL); > + > if (!meta) > goto out; > > @@ -374,6 +380,7 @@ static int zram_bvec_read(struct zram *zram, struct > bio_vec *bvec, > struct page *page; > unsigned char *user_mem, *uncmem = NULL; > struct zram_meta *meta = zram->meta; > + > page = bvec->bv_page; > > read_lock(&meta->tb_lock); > @@ -607,6 +614,7 @@ static void zram_reset_device(struct zram *zram, bool > reset_capacity) > /* Free all pages that are still in this zram device */ > for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) { > unsigned long handle = meta->table[index].handle; > + > if (!handle) > continue; > > @@ -668,6 +676,7 @@ static ssize_t disksize_store(struct device *dev, > set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); > revalidate_disk(zram->disk); > up_write(&zram->init_lock); > + zram_add_dev(); > return len; > > out_destroy_comp: > @@ -712,6 +721,7 @@ static ssize_t reset_store(struct device *dev, > bdput(bdev); > > zram_reset_device(zram, true); > + zram_del_dev(); > return len; > > out: > @@ -954,6 +964,41 @@ static void destroy_device(struct zram *zram) > blk_cleanup_queue(zram->queue); > } > > +/* remove last free device, if last and prelast dev a free */ > +static void zram_del_dev(void) > +{ > + if (last_created_dev < num_devices) > + return; > + > + if (zram_devices[last_created_dev].disksize == 0 && > + zram_devices[last_created_dev-1].disksize == 0 > + ) { racy? > + destroy_device(&zram_devices[last_created_dev]); > + last_created_dev--; > + pr_info("Deleted zram%u device\n", last_created_dev); > + } > +} > + > +/* Auto add empty zram device, if last device in use */ > +static void zram_add_dev(void) > +{ > + if (last_created_dev+1 > max_num_devices) { > + pr_warn("Can't add zram%u, max device number reached\n", > + num_devices); > + return; > + } racy? > + if (&zram_devices[last_created_dev].disksize > 0) { > + last_created_dev++; > + if (create_device(&zram_devices[last_created_dev], last_created_dev)) { > + destroy_device(&zram_devices[last_created_dev]); > + last_created_dev--; racy? -ss > + return; > + } > + pr_info("Created zram%u device\n", last_created_dev); > + } > +} > + > static int __init zram_init(void) > { > int ret, dev_id; > @@ -972,18 +1017,20 @@ static int __init zram_init(void) > goto out; > } > > - /* Allocate the device array and initialize each one */ > - zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL); > + /* Allocate the device array */ > + zram_devices = kcalloc(max_num_devices, sizeof(struct zram), GFP_KERNEL); > if (!zram_devices) { > ret = -ENOMEM; > goto unregister; > } > > + /* Initialise zram{0..num_devices} */ > for (dev_id = 0; dev_id < num_devices; dev_id++) { > ret = create_device(&zram_devices[dev_id], dev_id); > if (ret) > goto free_devices; > } > + last_created_dev = num_devices-1; > > pr_info("Created %u device(s) ...\n", num_devices); > > @@ -1004,7 +1051,7 @@ static void __exit zram_exit(void) > int i; > struct zram *zram; > > - for (i = 0; i < num_devices; i++) { > + for (i = 0; i < last_created_dev+1; i++) { > zram = &zram_devices[i]; > > destroy_device(zram); > @@ -1025,7 +1072,7 @@ module_init(zram_init); > module_exit(zram_exit); > > module_param(num_devices, uint, 0); > -MODULE_PARM_DESC(num_devices, "Number of zram devices"); > +MODULE_PARM_DESC(num_devices, "Number of pre created zram devices"); > > MODULE_LICENSE("Dual BSD/GPL"); > MODULE_AUTHOR("Nitin Gupta "); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/