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authorLorenzo Stoakes <lstoakes@gmail.com>2023-10-11 18:04:28 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-10-18 14:34:18 -0700
commit94d7d923395129b9248777e575c877e40007f9dc (patch)
treeaa2290d2d5da3c9be8a8eb9fb7d1a8acc63cca80 /mm/mprotect.c
parent3657fdc2451abf135c2d20949acf57d78cc50338 (diff)
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mm: abstract the vma_merge()/split_vma() pattern for mprotect() et al.
mprotect() and other functions which change VMA parameters over a range each employ a pattern of:- 1. Attempt to merge the range with adjacent VMAs. 2. If this fails, and the range spans a subset of the VMA, split it accordingly. This is open-coded and duplicated in each case. Also in each case most of the parameters passed to vma_merge() remain the same. Create a new function, vma_modify(), which abstracts this operation, accepting only those parameters which can be changed. To avoid the mess of invoking each function call with unnecessary parameters, create inline wrapper functions for each of the modify operations, parameterised only by what is required to perform the action. We can also significantly simplify the logic - by returning the VMA if we split (or merged VMA if we do not) we no longer need specific handling for merge/split cases in any of the call sites. Note that the userfaultfd_release() case works even though it does not split VMAs - since start is set to vma->vm_start and end is set to vma->vm_end, the split logic does not trigger. In addition, since we calculate pgoff to be equal to vma->vm_pgoff + (start - vma->vm_start) >> PAGE_SHIFT, and start - vma->vm_start will be 0 in this instance, this invocation will remain unchanged. We eliminate a VM_WARN_ON() in mprotect_fixup() as this simply asserts that vma_merge() correctly ensures that flags remain the same, something that is already checked in is_mergeable_vma() and elsewhere, and in any case is not specific to mprotect(). Link: https://lkml.kernel.org/r/0dfa9368f37199a423674bf0ee312e8ea0619044.1697043508.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/mprotect.c')
-rw-r--r--mm/mprotect.c29
1 files changed, 4 insertions, 25 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 03e2cec3e669..f1dc8f8c84ef 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -581,7 +581,6 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
long nrpages = (end - start) >> PAGE_SHIFT;
unsigned int mm_cp_flags = 0;
unsigned long charged = 0;
- pgoff_t pgoff;
int error;
if (newflags == oldflags) {
@@ -631,34 +630,14 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
newflags &= ~VM_ACCOUNT;
}
- /*
- * First try to merge with previous and/or next vma.
- */
- pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
- *pprev = vma_merge(vmi, mm, *pprev, start, end, newflags,
- vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
- vma->vm_userfaultfd_ctx, anon_vma_name(vma));
- if (*pprev) {
- vma = *pprev;
- VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
- goto success;
+ vma = vma_modify_flags(vmi, *pprev, vma, start, end, newflags);
+ if (IS_ERR(vma)) {
+ error = PTR_ERR(vma);
+ goto fail;
}
*pprev = vma;
- if (start != vma->vm_start) {
- error = split_vma(vmi, vma, start, 1);
- if (error)
- goto fail;
- }
-
- if (end != vma->vm_end) {
- error = split_vma(vmi, vma, end, 0);
- if (error)
- goto fail;
- }
-
-success:
/*
* vm_flags and vm_page_prot are protected by the mmap_lock
* held in write mode.