Messages in this thread | | | Subject | Re: [PATCH 1/4] erofs: fix setting up pcluster for temporary pages | From | Vladimir Zapolskiy <> | Date | Fri, 30 Oct 2020 15:32:55 +0200 |
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Hi Gao Xiang,
On 10/30/20 2:47 PM, Gao Xiang wrote: > Hi Vladimir, > > On Fri, Oct 30, 2020 at 02:20:31PM +0200, Vladimir Zapolskiy wrote: >> Hello Gao Xiang, >> >> On 10/22/20 5:57 PM, Gao Xiang via Linux-erofs wrote: >>> From: Gao Xiang <hsiangkao@redhat.com> >>> >>> pcluster should be only set up for all managed pages instead of >>> temporary pages. Since it currently uses page->mapping to identify, >>> the impact is minor for now. >>> >>> Fixes: 5ddcee1f3a1c ("erofs: get rid of __stagingpage_alloc helper") >>> Cc: <stable@vger.kernel.org> # 5.5+ >>> Signed-off-by: Gao Xiang <hsiangkao@redhat.com> >> >> I was looking exactly at this problem recently, my change is one-to-one >> to your fix, thus I can provide a tag: >> >> Tested-by: Vladimir Zapolskiy <vladimir@tuxera.com> > > Many thanks for confirming this! > I found this when I was killing magical stagingpage page->mapping, > it's somewhat late :-) >
sure, for me it was an exciting immersion into the filesystem code :)
>> >> >> The fixed problem is minor, but the kernel log becomes polluted, if >> a page allocation debug option is enabled: >> >> % md5sum ~/erofs/testfile >> BUG: Bad page state in process kworker/u9:0 pfn:687de >> page:0000000057b8bcb4 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x687de >> flags: 0x4000000000002000(private) >> raw: 4000000000002000 dead000000000100 dead000000000122 0000000000000000 >> raw: 0000000000000000 ffff888066758690 00000000ffffffff 0000000000000000 >> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set >> Modules linked in: >> CPU: 1 PID: 602 Comm: kworker/u9:0 Not tainted 5.9.1 #2 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 >> Workqueue: erofs_unzipd z_erofs_decompressqueue_work >> Call Trace: >> dump_stack+0x84/0xba >> bad_page.cold+0xac/0xb1 >> check_free_page_bad+0xb0/0xc0 >> free_pcp_prepare+0x2c8/0x2d0 >> free_unref_page+0x18/0xf0 >> put_pages_list+0x11a/0x120 >> z_erofs_decompressqueue_work+0xc9/0x110 >> ? z_erofs_decompress_pcluster.isra.0+0xf10/0xf10 >> ? read_word_at_a_time+0x12/0x20 >> ? strscpy+0xc7/0x1a0 >> process_one_work+0x30c/0x730 >> worker_thread+0x91/0x640 >> ? __kasan_check_read+0x11/0x20 >> ? rescuer_thread+0x8a0/0x8a0 >> kthread+0x1dd/0x200 >> ? kthread_unpark+0xa0/0xa0 >> ret_from_fork+0x1f/0x30 >> Disabling lock debugging due to kernel taint > > Yeah, I can make a pull-request to Linus if you need this to be in master > now, or I can post it for v5.11-rc1 since 5.4 LTS isn't effected (and it > would be only a print problem with debugging option.) >
As for myself I don't utterly need this fix on the master branch ASAP, however it might be reasonable to get it included right into the next v5.10 release, because I believe it'll be an LTS. Eventually it's up to you to make a decision, from my side I won't urge you, the fixed issue is obviously a non-critical one.
Thank you for the original fix and taking my opinion into consideration :)
-- Best wishes, Vladimir
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