The patch titled
Subject: mm-add-mremap_dontunmap-to-mremap-v7
has been added to the -mm tree. Its filename is
mm-add-mremap_dontunmap-to-mremap-v7.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-mremap_dontunmap-to-mremap-v7.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-mremap_dontunmap-to-mremap-v7.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: Brian Geffon <bgeffon@xxxxxxxxxx>
Subject: mm-add-mremap_dontunmap-to-mremap-v7
Don't allow resizing VMA as part of MREMAP_DONTUNMAP. There is no clear
use case at the moment and it can be added later as it simplifies the
implementation for now.
Link: http://lkml.kernel.org/r/20200221174248.244748-1-bgeffon@xxxxxxxxxx
Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx>
Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx>
Tested-by: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>
Cc: "Michael S . Tsirkin" <mst@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Sonny Rao <sonnyrao@xxxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Jesse Barnes <jsbarnes@xxxxxxxxxx>
Cc: Nathan Chancellor <natechancellor@xxxxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mremap.c | 33 ++++++++++-----------------------
1 file changed, 10 insertions(+), 23 deletions(-)
--- a/mm/mremap.c~mm-add-mremap_dontunmap-to-mremap-v7
+++ a/mm/mremap.c
@@ -416,24 +416,10 @@ static unsigned long move_vma(struct vm_
vm_acct_memory(vma_pages(new_vma));
}
- /*
- * locked_vm accounting: if the mapping remained the same size
- * it will have just moved and we don't need to touch locked_vm
- * because we skip the do_unmap. If the mapping shrunk before
- * being moved then the do_unmap on that portion will have
- * adjusted vm_locked. Only if the mapping grows do we need to
- * do something special; the reason is locked_vm only accounts
- * for old_len, but we're now adding new_len - old_len locked
- * bytes to the new mapping.
- */
- if (vm_flags & VM_LOCKED && new_len > old_len) {
- mm->locked_vm += (new_len - old_len) >> PAGE_SHIFT;
- *locked = true;
- }
-
/* We always clear VM_LOCKED[ONFAULT] on the old vma */
vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+ /* Because we won't unmap we don't need to touch locked_vm */
goto out;
}
@@ -588,13 +574,9 @@ static unsigned long mremap_to(unsigned
goto out;
}
- /*
- * MREMAP_DONTUNMAP expands by new_len - (new_len - old_len), we will
- * check that we can expand by new_len and vma_to_resize will handle
- * the vma growing which is (new_len - old_len).
- */
+ /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
if (flags & MREMAP_DONTUNMAP &&
- !may_expand_vm(mm, vma->vm_flags, new_len >> PAGE_SHIFT)) {
+ !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
ret = -ENOMEM;
goto out;
}
@@ -670,10 +652,15 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
return ret;
- /* MREMAP_DONTUNMAP is always a move */
- if (flags & MREMAP_DONTUNMAP && !(flags & MREMAP_MAYMOVE))
+ /*
+ * MREMAP_DONTUNMAP is always a move and it does not allow resizing
+ * in the process.
+ */
+ if (flags & MREMAP_DONTUNMAP &&
+ (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
return ret;
+
if (offset_in_page(addr))
return ret;
_
Patches currently in -mm which might be from bgeffon@xxxxxxxxxx are
mm-add-mremap_dontunmap-to-mremap.patch
mm-add-mremap_dontunmap-to-mremap-v6.patch
mm-add-mremap_dontunmap-to-mremap-v7.patch
selftest-add-mremap_dontunmap-selftest.patch
selftest-add-mremap_dontunmap-selftest-v7.patch
