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.stoakes@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 david@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?