The patch titled
Subject: mm/memory.c: allow different return codes for copy_nonpresent_pte()
has been added to the -mm tree. Its filename is
mm-memoryc-allow-different-return-codes-for-copy_nonpresent_pte.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memoryc-allow-different-return-codes-for-copy_nonpresent_pte.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memoryc-allow-different-return-codes-for-copy_nonpresent_pte.patch
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------------------------------------------------------
From: Alistair Popple <apopple@xxxxxxxxxx>
Subject: mm/memory.c: allow different return codes for copy_nonpresent_pte()
Currently if copy_nonpresent_pte() returns a non-zero value it is assumed
to be a swap entry which requires further processing outside the loop in
copy_pte_range() after dropping locks. This prevents other values being
returned to signal conditions such as failure which a subsequent change
requires.
Instead make copy_nonpresent_pte() return an error code if further
processing is required and read the value for the swap entry in the main
loop under the ptl.
Link: https://lkml.kernel.org/r/20210616105937.23201-7-apopple@xxxxxxxxxx
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
--- a/mm/memory.c~mm-memoryc-allow-different-return-codes-for-copy_nonpresent_pte
+++ a/mm/memory.c
@@ -717,7 +717,7 @@ copy_nonpresent_pte(struct mm_struct *ds
if (likely(!non_swap_entry(entry))) {
if (swap_duplicate(entry) < 0)
- return entry.val;
+ return -EIO;
/* make sure dst_mm is on swapoff's mmlist. */
if (unlikely(list_empty(&dst_mm->mmlist))) {
@@ -973,12 +973,14 @@ again:
continue;
}
if (unlikely(!pte_present(*src_pte))) {
- entry.val = copy_nonpresent_pte(dst_mm, src_mm,
- dst_pte, src_pte,
- dst_vma, src_vma,
- addr, rss);
- if (entry.val)
+ ret = copy_nonpresent_pte(dst_mm, src_mm,
+ dst_pte, src_pte,
+ dst_vma, src_vma,
+ addr, rss);
+ if (ret == -EIO) {
+ entry = pte_to_swp_entry(*src_pte);
break;
+ }
progress += 8;
continue;
}
@@ -1011,20 +1013,24 @@ again:
pte_unmap_unlock(orig_dst_pte, dst_ptl);
cond_resched();
- if (entry.val) {
+ if (ret == -EIO) {
+ VM_WARN_ON_ONCE(!entry.val);
if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) {
ret = -ENOMEM;
goto out;
}
entry.val = 0;
- } else if (ret) {
- WARN_ON_ONCE(ret != -EAGAIN);
+ } else if (ret == -EAGAIN) {
prealloc = page_copy_prealloc(src_mm, src_vma, addr);
if (!prealloc)
return -ENOMEM;
- /* We've captured and resolved the error. Reset, try again. */
- ret = 0;
+ } else if (ret) {
+ VM_WARN_ON_ONCE(1);
}
+
+ /* We've captured and resolved the error. Reset, try again. */
+ ret = 0;
+
if (addr != end)
goto again;
out:
_
Patches currently in -mm which might be from apopple@xxxxxxxxxx are
mm-remove-special-swap-entry-functions.patch
mm-swapops-rework-swap-entry-manipulation-code.patch
mm-rmap-split-try_to_munlock-from-try_to_unmap.patch
mm-rmap-split-migration-into-its-own-function.patch
mm-rename-migrate_pgmap_owner.patch
mm-memoryc-allow-different-return-codes-for-copy_nonpresent_pte.patch
mm-device-exclusive-memory-access.patch
mm-selftests-for-exclusive-device-memory.patch
nouveau-svm-refactor-nouveau_range_fault.patch
nouveau-svm-implement-atomic-svm-access.patch
