Re: [PATCH] zram: Using GFP_ATOMIC instead of GFP_KERNEL to allocate bitmap memory in backing_dev_store

[Dongyun Liu]

On 2023/12/1 23:39, Sergey Senozhatsky wrote:
> On (23/11/30 23:20), Dongyun Liu wrote:
> > INFO: task init:331 blocked for more than 120 seconds.  "echo 0 >
> > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:init   state:D stack:    0 pid:    1 ppid:     0 flags:0x04000000
> > Call trace:
> >    __switch_to+0x244/0x4e4
> >    __schedule+0x5bc/0xc48
> >    schedule+0x80/0x164
> >    rwsem_down_read_slowpath+0x4fc/0xf9c
> >    __down_read+0x140/0x188
> >    down_read+0x14/0x24
> >    try_wakeup_wbd_thread+0x78/0x1ec [zram]
> >    __zram_bvec_write+0x720/0x878 [zram]
> >    zram_bvec_rw+0xa8/0x234 [zram]
> >    zram_submit_bio+0x16c/0x268 [zram]
> >    submit_bio_noacct+0x128/0x3c8
> >    submit_bio+0x1cc/0x3d0
> >    __swap_writepage+0x5c4/0xd4c
> >    swap_writepage+0x130/0x158
> >    pageout+0x1f4/0x478
> >    shrink_page_list+0x9b4/0x1eb8
> >    shrink_inactive_list+0x2f4/0xaa8
> >    shrink_lruvec+0x184/0x340
> >    shrink_node_memcgs+0x84/0x3a0
> >    shrink_node+0x2c4/0x6c4
> >    shrink_zones+0x16c/0x29c
> >    do_try_to_free_pages+0xe4/0x2b4
> >    try_to_free_pages+0x388/0x7b4
> >    __alloc_pages_direct_reclaim+0x88/0x278
> >    __alloc_pages_slowpath+0x4ec/0xf6c
> >    __alloc_pages_nodemask+0x1f4/0x3dc
> >    kmalloc_order+0x54/0x338
> >    kmalloc_order_trace+0x34/0x1bc
> >    __kmalloc+0x5e8/0x9c0
> >    kvmalloc_node+0xa8/0x264
> >    backing_dev_store+0x1a4/0x818 [zram]
> >    dev_attr_store+0x38/0x8c
> >    sysfs_kf_write+0x64/0xc4
>
> Hmm, I'm not really following this backtrace. Backing device
> configuration is only possible on un-initialized zram device.
> If it's uninitialized, then why is it being used for swapout
> later in the call stack?

Uh, at this moment, zram has finished initializing and is
working. The backing device is an optional zram-based feature.
I think it can be created later.