linux-ext4 - [Bug 201631] WARNING: CPU: 11 PID: 29593 at fs/ext4/inode.c:3927 .ext4_set_page

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Date:   Mon, 04 Feb 2019 06:37:07 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...r.kernel.org
Subject: [Bug 201631] WARNING: CPU: 11 PID: 29593 at fs/ext4/inode.c:3927
 .ext4_set_page_dirty+0x70/0xb0

https://bugzilla.kernel.org/show_bug.cgi?id=201631

--- Comment #63 from Aneesh Kumar KV (aneesh.kumar@...ux.ibm.com) ---
(In reply to Jan Kara from comment #62)
> Erhard, thanks for the results! They are very weird but pretty clear:
> cleaned state is 0x10 so page_vma_mapped_walk() called from page_mkclean()
> has bailed out somewhere between:
> 
>         if (bh)
>                 bh->b_cleaned_state |= 16;
> restart:
>         pgd = pgd_offset(mm, pvmw->address);
>         if (!pgd_present(*pgd))
>                 return false;
>         p4d = p4d_offset(pgd, pvmw->address);
>         if (!p4d_present(*p4d))
>                 return false;
>         pud = pud_offset(p4d, pvmw->address);
>         if (!pud_present(*pud))
>                 return false;
>         if (bh)
>                 bh->b_cleaned_state |= 32;
> 
> I really don't understand how any of these tests could fail when later
> unmap_page_range() has found the pte. But I somehow suspect commit 
> da7ad366b497f5 "powerpc/mm/book3s: Update pmd_present to look at
> _PAGE_PRESENT bit" could be related since it was introduced in the window
> where the problems started happening and it touches relevant code.
> 
> Aneesh, what needs to be reverted so that we can test that this commit is
> indeed the problematic one? I suppose:
> 
> da7ad366b497 "powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT
> bit"
> f1981b5b302f "powerpc/mm/hugetlb/book3s: add _PAGE_PRESENT to hugepd
> pointer."
> ae28f17b5eeb "powerpc/mm/book3s: Check for pmd_large instead of
> pmd_trans_huge"
> 75646c480fde "arch/powerpc/mm/hash: validate the pte entries before handling
> the hash fault"
> 8890e03380d3 "powerpc/mm/thp: update pmd_trans_huge to check for pmd_present"
> a0820ff33451 "powerpc/mm:book3s: Enable THP migration support"



We can revert the first and the last patch. I am attaching the patches this got
the revert failures fixed.

-aneesh

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