Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934517AbaGQP1I (ORCPT ); Thu, 17 Jul 2014 11:27:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19740 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933680AbaGQP1F (ORCPT ); Thu, 17 Jul 2014 11:27:05 -0400 Message-ID: <53C7EB3E.5070204@redhat.com> Date: Thu, 17 Jul 2014 17:26:54 +0200 From: Jerome Marchand User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Timofey Titovets , Sergey Senozhatsky CC: minchan@kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Nitin Gupta Subject: Re: [PATCH v2] zram: auto add/del devices on demand References: <53C7C131.1060306@gmail.com> <20140717140440.GA1275@swordfish> <53C7E530.2010503@gmail.com> In-Reply-To: <53C7E530.2010503@gmail.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/17/2014 05:01 PM, Timofey Titovets wrote: > > > On 07/17/2014 05:04 PM, Sergey Senozhatsky wrote: >> 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 >>> "); >>> > > I can't understand what do you mean on "racy?" Racy as in "race condition". > if you mind random empty lines in code, I've just checked code by > checkpatch.pl and fixed warnings. > > I'll try to explain, why I wrote a patch: zram, as a loop device, > is a virtual device, not physical, and i think that adding new free > devices automatically (like loop) is useful and expected behavior > (for virtual device). I don't know much about loop devices. How are they dynamically added/deleted? Is that the same mechanism as your patch implement? That may be a matter of taste, but I personally find that behaviour rather awkward. Jerome > > By default, zram creates only one device, and if I need to use two > devices (for example), my actions lead to module?s reloading: 1. > umount busy device 2. lose my data. Yes, I can backup it, and > restore, but this is also useless, if I can do it more beautiful 3. > unload module 4. load module again with new num devices parameter > or make it parametre "permanent" by creating file in modprobe.d > > This is handwork and such behavior is uncomfortable. > > if number of devices is dynamically changeable, I can skip this > actions and save my time and energy instead of wasting on these > activities. -- 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/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTx+s4AAoJEHTzHJCtsuoClfkIAKYfuhWQWSvSD9XPQUD0R7HI kW6865EWpNZjWR5WVYng48dvYwPV+2YGKJE1a+FyIwa06jjDO+Gm/FnOcnUhUcDz NFjTSBa1CIbh1hXU5uiI6u3BNw66BDjaprVe6x1tcW96y7T7Po+IWdf5+N7GMCtf 9H14KOCd20X5FsvPz70UkkpkLQZK1UdzmQ+1KYPb+bC3ACgTsuxs9Wxs1Tzn+tP/ DDvbZRd4FAcGZsC88U2gyuNAhoVYXVqzokukeV7hRlsSCFibwEOQzoZl/xljyICK Xv+uuMupmAVWv9CrlYexqT/HFoDOhAs7uRM2sgza39apUdQfkGg0vIw+9GV7+Q0= =Bxhk -----END PGP SIGNATURE----- -- 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/