Re: [PATCH v2] zram: auto add/del devices on demand

[Timofey Titovets]

On 07/17/2014 06:19 PM, Timofey Titovets wrote:
> On 07/17/2014 05:17 PM, Jerome Marchand wrote:
> > 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
>
> Thanks for catching, i try fix it and resend patch.

I check loop device logic, and loop device not destroy automatically, 
only creating on demand.

If i delete automatically destroy logic function from my patch, for 
working like loop
(also loop create new device only if all device in use) and without 
destroy function my patch pass your concurrency test.
Because we can't catch case when device created and destroyed in same time.


It have meaning to rework patch, for save only auto add logic and make 
it working like loop (if all device in use -> add new)?

I also have until to setup zram devices (written on C++), like losetup 
for loop devices, and i think if patch for kernel will be adopted.
I can port my util from C++ to C and try add to util-linux, for having 
generic solution to setup zram devices, instead of several tens of 
utilities for all distros).

I just think what all in linux can have generic, simple, fast and useful 
solution, and if i can make something more useful, i must do it.

Thanks,
Timofey.
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