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Message-ID: <53C7DADC.3060508@redhat.com>
Date: Thu, 17 Jul 2014 16:17:00 +0200
From: Jerome Marchand <jmarchan@...hat.com>
To: Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Timofey Titovets <nefelim4ag@...il.com>
CC: minchan@...nel.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Nitin Gupta <ngupta@...are.org>
Subject: Re: [PATCH v2] zram: auto add/del devices on demand
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 07/17/2014 04:04 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 <nefelim4ag@...il.com>
>>
>> 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?
Looks like it:
$ cat conctest.sh
#! /bin/sh
modprobe zram
while true; do
for i in `seq 1 10`; do
echo 10485760 > /sys/block/zram0/disksize&
echo 1 > /sys/block/zram0/reset&
done
done
$ sudo ./conctest.sh
[ 51.535387] ------------[ cut here ]------------
[ 51.536305] WARNING: CPU: 0 PID: 840 at fs/kernfs/dir.c:1209
kernfs_remove_by_name_ns+0x95/0xa0()
[ 51.537908] kernfs: can not remove 'max_comp_streams', no directory
[ 51.539089] Modules linked in: zram lz4_compress xt_conntrack
cfg80211 rfkill ebtable_nat ebtable_broute bridge stp llc
ebtable_filter ebtables ip6_tables iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
iptable_security iptable_raw ppdev crct10dif_pclmul crc32_pclmul
crc32c_intel joydev ghash_clmulni_intel microcode serio_raw pcspkr
virtio_balloon virtio_console parport_pc pvpanic virtio_net parport
floppy i2c_piix4 nfsd auth_rpcgss nfs_acl lockd sunrpc qxl
drm_kms_helper ttm virtio_blk drm virtio_pci virtio_ring virtio
ata_generic pata_acpi
[ 51.550844] CPU: 0 PID: 840 Comm: conc_init.sh Tainted: G D W
3.16.0-rc5-memacct-next-20140715+ #146
[ 51.552606] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 51.553691] 0000000000000009 ffff880078343d20 ffffffff8172d344
ffff880078343d68
[ 51.555412] ffff880078343d58 ffffffff8108ad1d 0000000000000000
ffffffffa0320242
[ 51.557811] ffffffffa0321058 0000000000000002 ffff880078343f50
ffff880078343db8
[ 51.559580] Call Trace:
[ 51.560139] [<ffffffff8172d344>] dump_stack+0x45/0x56
[ 51.561161] [<ffffffff8108ad1d>] warn_slowpath_common+0x7d/0xa0
[ 51.562333] [<ffffffff8108ad8c>] warn_slowpath_fmt+0x4c/0x50
[ 51.563445] [<ffffffff81218196>] ? evict+0x106/0x170
[ 51.564432] [<ffffffff81275695>] kernfs_remove_by_name_ns+0x95/0xa0
[ 51.565627] [<ffffffff81277ee9>] remove_files.isra.1+0x39/0x70
[ 51.566753] [<ffffffff812781f4>] sysfs_remove_group+0x44/0xa0
[ 51.567870] [<ffffffffa031e058>] destroy_device.isra.17+0x28/0x50
[zram]
[ 51.569089] [<ffffffffa031e5d0>] reset_store+0x100/0x140 [zram]
[ 51.570197] [<ffffffff8146c3e8>] dev_attr_store+0x18/0x30
[ 51.571247] [<ffffffff81276fd4>] sysfs_kf_write+0x44/0x60
[ 51.572201] [<ffffffff812768d7>] kernfs_fop_write+0xe7/0x170
[ 51.573283] [<ffffffff811fbcf7>] vfs_write+0xb7/0x1f0
[ 51.574143] [<ffffffff811fc8a9>] SyS_write+0x49/0xb0
[ 51.574976] [<ffffffff8112e724>] ? __audit_syscall_entry+0xb4/0x110
[ 51.576213] [<ffffffff817362a9>] system_call_fastpath+0x16/0x1b
[ 51.577422] ---[ end trace cdb79035dad379f3 ]---
[ 51.578401] ------------[ cut here ]------------
[ 51.579354] WARNING: CPU: 0 PID: 840 at fs/kernfs/dir.c:1209
kernfs_remove_by_name_ns+0x95/0xa0()
[ 51.580966] kernfs: can not remove 'comp_algorithm', no directory
[ 51.582108] Modules linked in: zram lz4_compress xt_conntrack
cfg80211 rfkill ebtable_nat ebtable_broute bridge stp llc
ebtable_filter ebtables ip6_tables iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
iptable_security iptable_raw ppdev crct10dif_pclmul crc32_pclmul
crc32c_intel joydev ghash_clmulni_intel microcode serio_raw pcspkr
virtio_balloon virtio_console parport_pc pvpanic virtio_net parport
floppy i2c_piix4 nfsd auth_rpcgss nfs_acl lockd sunrpc qxl
drm_kms_helper ttm virtio_blk drm virtio_pci virtio_ring virtio
ata_generic pata_acpi
[ 51.597177] CPU: 0 PID: 840 Comm: conc_init.sh Tainted: G D W
3.16.0-rc5-memacct-next-20140715+ #146
[ 51.598549] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 51.599661] 0000000000000009 ffff880078343d20 ffffffff8172d344
ffff880078343d68
[ 51.601519] ffff880078343d58 ffffffff8108ad1d 0000000000000000
ffffffffa0320233
[ 51.603362] ffffffffa0321058 0000000000000002 ffff880078343f50
ffff880078343db8
[ 51.604913] Call Trace:
[ 51.605444] [<ffffffff8172d344>] dump_stack+0x45/0x56
[ 51.606537] [<ffffffff8108ad1d>] warn_slowpath_common+0x7d/0xa0
[ 51.607507] [<ffffffff8108ad8c>] warn_slowpath_fmt+0x4c/0x50
[ 51.608582] [<ffffffff81218196>] ? evict+0x106/0x170
[ 51.609423] [<ffffffff81275695>] kernfs_remove_by_name_ns+0x95/0xa0
[ 51.610436] [<ffffffff81277ee9>] remove_files.isra.1+0x39/0x70
[ 51.611408] [<ffffffff812781f4>] sysfs_remove_group+0x44/0xa0
[ 51.612431] [<ffffffffa031e058>] destroy_device.isra.17+0x28/0x50
[zram]
[ 51.613214] [<ffffffffa031e5d0>] reset_store+0x100/0x140 [zram]
[ 51.613928] [<ffffffff8146c3e8>] dev_attr_store+0x18/0x30
[ 51.614634] [<ffffffff81276fd4>] sysfs_kf_write+0x44/0x60
[ 51.615387] [<ffffffff812768d7>] kernfs_fop_write+0xe7/0x170
[ 51.616246] [<ffffffff811fbcf7>] vfs_write+0xb7/0x1f0
[ 51.619107] [<ffffffff811fc8a9>] SyS_write+0x49/0xb0
[ 51.620063] [<ffffffff8112e724>] ? __audit_syscall_entry+0xb4/0x110
[ 51.622071] [<ffffffff817362a9>] system_call_fastpath+0x16/0x1b
[ 51.623256] ---[ end trace cdb79035dad379f4 ]---
And lots more of similar messages.
Jerome
>
>
> -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
>> <ngupta@...are.org>");
>>
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