From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org,
"Thomas Hellstrom" <thellstrom@vmware.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Matthew Wilcox" <willy@infradead.org>,
"Will Deacon" <will.deacon@arm.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Rik van Riel" <riel@surriel.com>,
"Minchan Kim" <minchan@kernel.org>,
"Michal Hocko" <mhocko@suse.com>,
"Huang Ying" <ying.huang@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>
Subject: Re: [PATCH v3 1/7] mm: Remove BUG_ON mmap_sem not held from xxx_trans_huge_lock()
Date: Thu, 3 Oct 2019 13:32:09 +0200 [thread overview]
Message-ID: <aa671279-c874-aedd-667f-e3a604bb0d67@shipmail.org> (raw)
In-Reply-To: <20191003110232.mltuantcw5pcrybo@box>
Hi, Kirill,
On 10/3/19 1:02 PM, Kirill A. Shutemov wrote:
> On Wed, Oct 02, 2019 at 03:47:24PM +0200, Thomas Hellström (VMware) wrote:
>> From: Thomas Hellstrom <thellstrom@vmware.com>
>>
>> The caller needs to make sure that the vma is not torn down during the
>> lock operation and can also use the i_mmap_rwsem for file-backed vmas.
>> Remove the BUG_ON. We could, as an alternative, add a test that either
>> vma->vm_mm->mmap_sem or vma->vm_file->f_mapping->i_mmap_rwsem are held.
>>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Rik van Riel <riel@surriel.com>
>> Cc: Minchan Kim <minchan@kernel.org>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Huang Ying <ying.huang@intel.com>
>> Cc: Jérôme Glisse <jglisse@redhat.com>
>> Cc: Kirill A. Shutemov <kirill@shutemov.name>
>> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> The patch looks good to me:
>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>
> But I looked at usage at pagewalk.c and it is inconsitent. The walker
> takes ptl before calling ->pud_entry(), but not for ->pmd_entry().
>
> It should be fixed: do not take the lock before ->pud_entry(). The
> callback must take care of it.
>
> Looks like we have single ->pud_entry() implementation the whole kernel.
> It should be trivial to fix.
>
> Could you do this?
>
I could probably fix that. There are some comments in the patch
introducing that code as to why it was done that way, though, but I
don't remember offhand what the arguments were.
But there seems to be more races WRT puds. See my next email. Perhaps
this should be fixed as part of a larger audit of the huge_pud code?
/Thomas
next prev parent reply other threads:[~2019-10-03 11:32 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 13:47 [PATCH v3 0/7] Emulated coherent graphics memory take 2 Thomas Hellström (VMware)
2019-10-02 13:47 ` [PATCH v3 1/7] mm: Remove BUG_ON mmap_sem not held from xxx_trans_huge_lock() Thomas Hellström (VMware)
2019-10-03 11:02 ` Kirill A. Shutemov
2019-10-03 11:32 ` Thomas Hellström (VMware) [this message]
2019-10-02 13:47 ` [PATCH v3 2/7] mm: Add a walk_page_mapping() function to the pagewalk code Thomas Hellström (VMware)
2019-10-02 17:52 ` Linus Torvalds
2019-10-03 11:17 ` Kirill A. Shutemov
2019-10-03 11:32 ` Thomas Hellström (VMware)
2019-10-04 12:37 ` Kirill A. Shutemov
2019-10-04 12:58 ` Thomas Hellström (VMware)
2019-10-04 13:24 ` Kirill A. Shutemov
2019-10-02 13:47 ` [PATCH v3 3/7] mm: Add write-protect and clean utilities for address space ranges Thomas Hellström (VMware)
2019-10-02 18:06 ` Linus Torvalds
2019-10-02 18:13 ` Matthew Wilcox
2019-10-02 19:09 ` Thomas Hellström (VMware)
2019-10-02 20:27 ` Linus Torvalds
2019-10-03 7:56 ` Thomas Hellstrom
2019-10-03 16:55 ` Linus Torvalds
2019-10-03 18:03 ` Thomas Hellström (VMware)
2019-10-03 18:11 ` Linus Torvalds
2019-10-02 13:47 ` [PATCH v3 4/7] drm/vmwgfx: Implement an infrastructure for write-coherent resources Thomas Hellström (VMware)
2019-10-02 13:47 ` [PATCH v3 5/7] drm/vmwgfx: Use an RBtree instead of linked list for MOB resources Thomas Hellström (VMware)
2019-10-02 13:47 ` [PATCH v3 6/7] drm/vmwgfx: Implement an infrastructure for read-coherent resources Thomas Hellström (VMware)
2019-10-02 13:47 ` [PATCH v3 7/7] drm/vmwgfx: Add surface dirty-tracking callbacks Thomas Hellström (VMware)
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