Messages in this thread | | | Date | Mon, 11 Oct 2021 11:22:14 +0800 | Subject | Re: [PATCH v4 2/2] mm, thp: bail out early in collapse_file for writeback page | From | Rongwei Wang <> |
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On 10/11/21 11:08 AM, Matthew Wilcox wrote: > On Mon, Oct 11, 2021 at 10:22:41AM +0800, Rongwei Wang wrote: >> Currently collapse_file does not explicitly check PG_writeback, instead, >> page_has_private and try_to_release_page are used to filter writeback >> pages. This does not work for xfs with blocksize equal to or larger >> than pagesize, because in such case xfs has no page->private. >> >> This makes collapse_file bail out early for writeback page. Otherwise, >> xfs end_page_writeback will panic as follows. >> >> Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") > > This is the wrong Fixes line. This same bug exists earlier than this. > Your testing may not show it before then, but if you mmap something > that isn't an executable, you can provoke it. It should be: > > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") > > (unless there's something I'm missing?) Hi, Matthew I forget the Patch #2 fix the bug that is different with Patch #1. I will update this.
Thanks for your remind! > > Also, this should surely have a Cc: stable@vger.kernel.org in the > tags section? It's a user-visible bug, we want it backported. OK, Thanks! > >> Suggested-by: Yang Shi <shy828301@gmail.com> >> Signed-off-by: Xu Yu <xuyu@linux.alibaba.com> >> Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com> >> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> >> Reviewed-by: Yang Shi <shy828301@gmail.com> >> --- >> mm/khugepaged.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 045cc579f724..48de4e1b0783 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -1763,6 +1763,10 @@ static void collapse_file(struct mm_struct *mm, >> filemap_flush(mapping); >> result = SCAN_FAIL; >> goto xa_unlocked; >> + } else if (PageWriteback(page)) { >> + xas_unlock_irq(&xas); >> + result = SCAN_FAIL; >> + goto xa_unlocked; >> } else if (trylock_page(page)) { >> get_page(page); >> xas_unlock_irq(&xas); >> @@ -1798,7 +1802,8 @@ static void collapse_file(struct mm_struct *mm, >> goto out_unlock; >> } >> >> - if (!is_shmem && PageDirty(page)) { >> + if (!is_shmem && (PageDirty(page) || >> + PageWriteback(page))) { >> /* >> * khugepaged only works on read-only fd, so this >> * page is dirty because it hasn't been flushed >> -- >> 2.27.0 >>
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