diff options
| author | David Hildenbrand <david@redhat.com> | 2023-01-02 17:08:54 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-18 17:12:56 -0800 |
| commit | fc4f4be9b5271e43eeb4c675d190fa9734de9ea3 (patch) | |
| tree | fbdc88b711df8a850345a8539784b29e84d7c920 /mm/nommu.c | |
| parent | da0618c146ca0e1412173a8a229dd737a73b1a4f (diff) | |
mm/nommu: factor out check for NOMMU shared mappings into is_nommu_shared_mapping()
Patch series "mm/nommu: don't use VM_MAYSHARE for MAP_PRIVATE mappings".
Trying to reduce the confusion around VM_SHARED and VM_MAYSHARE first
requires !CONFIG_MMU to stop using VM_MAYSHARE for MAP_PRIVATE mappings.
CONFIG_MMU only sets VM_MAYSHARE for MAP_SHARED mappings.
This paves the way for further VM_MAYSHARE and VM_SHARED cleanups: for
example, renaming VM_MAYSHARED to VM_MAP_SHARED to make it cleaner what is
actually means.
Let's first get the weird case out of the way and not use VM_MAYSHARE in
MAP_PRIVATE mappings, using a new VM_MAYOVERLAY flag instead.
This patch (of 3):
We want to stop using VM_MAYSHARE in private mappings to pave the way for
clarifying the semantics of VM_MAYSHARE vs. VM_SHARED and reduce the
confusion. While CONFIG_MMU uses VM_MAYSHARE to represent MAP_SHARED,
!CONFIG_MMU also sets VM_MAYSHARE for selected R/O private file mappings
that are an effective overlay of a file mapping.
Let's factor out all relevant VM_MAYSHARE checks in !CONFIG_MMU code into
is_nommu_shared_mapping() first.
Note that whenever VM_SHARED is set, VM_MAYSHARE must be set as well
(unless there is a serious BUG). So there is not need to test for
VM_SHARED manually.
No functional change intended.
Link: https://lkml.kernel.org/r/20230102160856.500584-1-david@redhat.com
Link: https://lkml.kernel.org/r/20230102160856.500584-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/nommu.c')
| -rw-r--r-- | mm/nommu.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 5b83938ecb67..1671ebbecb8d 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -958,9 +958,10 @@ static int do_mmap_private(struct vm_area_struct *vma, */ if (capabilities & NOMMU_MAP_DIRECT) { ret = call_mmap(vma->vm_file, vma); + /* shouldn't return success if we're not sharing */ + if (WARN_ON_ONCE(!is_nommu_shared_mapping(vma->vm_flags))) + ret = -ENOSYS; if (ret == 0) { - /* shouldn't return success if we're not sharing */ - BUG_ON(!(vma->vm_flags & VM_MAYSHARE)); vma->vm_region->vm_top = vma->vm_region->vm_end; return 0; } @@ -1106,7 +1107,7 @@ unsigned long do_mmap(struct file *file, * these cases, sharing is handled in the driver or filesystem rather * than here */ - if (vm_flags & VM_MAYSHARE) { + if (is_nommu_shared_mapping(vm_flags)) { struct vm_region *pregion; unsigned long pglen, rpglen, pgend, rpgend, start; @@ -1116,7 +1117,7 @@ unsigned long do_mmap(struct file *file, for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) { pregion = rb_entry(rb, struct vm_region, vm_rb); - if (!(pregion->vm_flags & VM_MAYSHARE)) + if (!is_nommu_shared_mapping(pregion->vm_flags)) continue; /* search for overlapping mappings on the same file */ @@ -1600,7 +1601,7 @@ static unsigned long do_mremap(unsigned long addr, if (vma->vm_end != vma->vm_start + old_len) return (unsigned long) -EFAULT; - if (vma->vm_flags & VM_MAYSHARE) + if (is_nommu_shared_mapping(vma->vm_flags)) return (unsigned long) -EPERM; if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start) |