On 2021/12/8 6:10, Jaegeuk Kim wrote:
On 12/07, Matthew Wilcox wrote:
On Tue, Dec 07, 2021 at 01:39:06PM -0800, Jaegeuk Kim wrote:
On 12/07, Matthew Wilcox wrote:
Call Trace:
<TASK>
folio_mark_dirty+0x136/0x270 mm/page-writeback.c:2639
if (likely(mapping)) {
...
if (folio_test_reclaim(folio))
folio_clear_reclaim(folio);
return mapping->a_ops->set_page_dirty(&folio->page);
how do we get to a NULL ->set_page_dirty for a metadata page's
mapping->a_ops? This is definitely an f2fs expert question.
I can't find anything in f2fs, since that page was got by f2fs_grab_meta_page
along with grab_cache_page() that we never unlocked it.
40 struct page *f2fs_grab_meta_page(struct f2fs_sb_info *sbi, pgoff_t index)
41 {
42 struct address_space *mapping = META_MAPPING(sbi);
43 struct page *page;
44 repeat:
45 page = f2fs_grab_cache_page(mapping, index, false);
-> grab_cache_page(mapping, index);
46 if (!page) {
47 cond_resched();
48 goto repeat;
49 }
50 f2fs_wait_on_page_writeback(page, META, true, true);
51 if (!PageUptodate(page))
52 SetPageUptodate(page);
53 return page;
54 }
Suspecting something in folio wrt folio_mapping()?
81 bool set_page_dirty(struct page *page)
82 {
83 return folio_mark_dirty(page_folio(page));
84 }
... huh? How could folio_mapping() be getting this wrong?
Dunno.
page_folio() does the same thing as compound_head() -- as far as I know
you don't use compound pages for f2fs metadata, so this basically just
casts the page to a struct folio.
folio_mapping() is just like the old page_mapping() (see commit
2f52578f9c64). Unless you've done something like set the swapcache
bit on your metadata page, it's just going to return folio->mapping
(ie the same as page->mapping).
Hmm, I've never seen this call stack before, so simply started to suspect
folio.
I'm afraid this is a f2fs bug... :(
folio wasn't merged at the first report time (5.14-rc2).
https://syzkaller.appspot.com/bug?extid=07ff38c9c93ca170de07
I doubt the direct reason of panic may be the same as the one of bug
reported in bugzilla:
https://bugzilla.kernel.org/show_bug.cgi?id=215231
However, I still can't figure out why meta_inode's a_ops will change
to f2fs_meta_aops.
Thanks,
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