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@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx> # 5.5+
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
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@xxxxxxxxxx>
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
