[PATCH v3 37/48] mmap: Clean up mmap_region() unrolling

Liam Howlett
2023-01-17T02:40:32Z

Move logic of unrolling to the error path as apposed to duplicating it
within the function body. This reduces the potential of missing an
update to one path when making changes.

Cc: Li Zetao <lizetao1@huawei.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
mm/mmap.c | 45 ++++++++++++++++++---------------------------
1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index cc53f638187b..01988db478e1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2600,12 +2600,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
* Expansion is handled above, merging is handled below.
* Drivers should not alter the address of the VMA.
*/
- if (WARN_ON((addr != vma->vm_start))) {
- error = -EINVAL;
+ error = -EINVAL;
+ if (WARN_ON((addr != vma->vm_start)))
goto close_and_free_vma;
- }
- vma_iter_set(&vmi, addr);

+ vma_iter_set(&vmi, addr);
/*
* If vm_flags changed after call_mmap(), we should try merge
* vma again as we may succeed this time.
@@ -2642,25 +2641,13 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
}

/* Allow architectures to sanity-check the vm_flags */
- if (!arch_validate_flags(vma->vm_flags)) {
- error = -EINVAL;
- if (file)
- goto close_and_free_vma;
- else if (vma->vm_file)
- goto unmap_and_free_vma;
- else
- goto free_vma;
- }
+ error = -EINVAL;
+ if (!arch_validate_flags(vma->vm_flags))
+ goto close_and_free_vma;

- if (vma_iter_prealloc(&vmi, vma)) {
- error = -ENOMEM;
- if (file)
- goto close_and_free_vma;
- else if (vma->vm_file)
- goto unmap_and_free_vma;
- else
- goto free_vma;
- }
+ error = -ENOMEM;
+ if (vma_iter_prealloc(&vmi, vma))
+ goto close_and_free_vma;

if (vma->vm_file)
i_mmap_lock_write(vma->vm_file->f_mapping);
@@ -2719,14 +2706,18 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
return addr;

close_and_free_vma:
- if (vma->vm_ops && vma->vm_ops->close)
+ if (file && vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
+
+ if (file || vma->vm_file) {
unmap_and_free_vma:
- fput(vma->vm_file);
- vma->vm_file = NULL;
+ fput(vma->vm_file);
+ vma->vm_file = NULL;

- /* Undo any partial mapping done by a device driver. */
- unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, vma->vm_end);
+ /* Undo any partial mapping done by a device driver. */
+ unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start,
+ vma->vm_end);
+ }
if (file && (vm_flags & VM_SHARED))
mapping_unmap_writable(file->f_mapping);
free_vma:
--
2.35.1