The patch titled
Subject: mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled
has been added to the -mm tree. Its filename is
mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
Subject: mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled
Previously, we noticed the one rpma example was failed[1] since
36f30e486d, where it will use ODP feature to do RDMA WRITE between fsdax
files.
After digging into the code, we found hmm_vma_handle_pte() will still
return EFAULT even though all the its requesting flags has been fulfilled.
That's because a DAX page will be marked as (_PAGE_SPECIAL | PAGE_DEVMAP)
by pte_mkdevmap().
[1]: https://github.com/pmem/rpma/issues/1142
Link: https://lkml.kernel.org/r/20210830094232.203029-1-lizhijian@xxxxxxxxxxxxxx
Fixes: 405506274922 ("mm/hmm: add missing call to hmm_pte_need_fault in HMM_PFN_SPECIAL handling")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hmm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/hmm.c~mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled
+++ a/mm/hmm.c
@@ -295,10 +295,13 @@ static int hmm_vma_handle_pte(struct mm_
goto fault;
/*
+ * Bypass devmap pte such as DAX page when all pfn requested
+ * flags(pfn_req_flags) are fulfilled.
* Since each architecture defines a struct page for the zero page, just
* fall through and treat it like a normal page.
*/
- if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
+ if (pte_special(pte) && !pte_devmap(pte) &&
+ !is_zero_pfn(pte_pfn(pte))) {
if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
pte_unmap(ptep);
return -EFAULT;
_
Patches currently in -mm which might be from lizhijian@xxxxxxxxxxxxxx are
mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled.patch
