On 13.02.25 19:17, Lorenzo Stoakes wrote:
There is no reason to disallow guard regions in file-backed mappings -
readahead and fault-around both function correctly in the presence of PTE
markers, equally other operations relating to memory-mapped files function
correctly.
Additionally, read-only mappings if introducing guard-regions, only
restrict the mapping further, which means there is no violation of any
access rights by permitting this to be so.
Removing this restriction allows for read-only mapped files (such as
executable files) correctly which would otherwise not be permitted.
Signed-off-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
---
mm/madvise.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index 6ecead476a80..e01e93e179a8 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1051,13 +1051,7 @@ static bool is_valid_guard_vma(struct vm_area_struct
*vma, bool allow_locked)
if (!allow_locked)
disallowed |= VM_LOCKED;
- if (!vma_is_anonymous(vma))
- return false;
-
- if ((vma->vm_flags & (VM_MAYWRITE | disallowed)) != VM_MAYWRITE)
- return false;
-
- return true;
+ return !(vma->vm_flags & disallowed);
}
static bool is_guard_pte_marker(pte_t ptent)
Acked-by: David Hildenbrand <da...@redhat.com>
I assume these markers cannot completely prevent us from allocating
pages/folios for these underlying file/pageache ranges of these markers
in case of shmem during page faults, right?
--
Cheers,
David / dhildenb
