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mm: Update do_vmi_align_munmap() return semantics

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Since do_vmi_align_munmap() will always honor the downgrade request on
the success, the callers no longer have to deal with confusing return
codes.  Since all callers that request downgrade actually want the lock
to be dropped, change the downgrade to an unlock request.

Note that the lock still needs to be held in read mode during the page
table clean up to avoid races with a map request.

Update do_vmi_align_munmap() to return 0 for success.  Clean up the
callers and comments to always expect the unlock to be honored on the
success path.  The error path will always leave the lock untouched.

As part of the cleanup, the wrapper function do_vmi_munmap() and callers
to the wrapper are also updated.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/linux-mm/20230629191414.1215929-1-willy@infradead.org/
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Liam R. Howlett
2023-06-29 22:28:16 -04:00
committed by Linus Torvalds
parent e4bd84c069
commit 408579cd62
3 changed files with 56 additions and 68 deletions
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4
include/linux/mm.h
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@@ -3177,7 +3177,7 @@ extern unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long pgoff, unsigned long *populate, struct list_head *uf);
extern int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
unsigned long start, size_t len, struct list_head *uf,
bool downgrade);
bool unlock);
extern int do_munmap(struct mm_struct *, unsigned long, size_t,
struct list_head *uf);
extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior);
@@ -3185,7 +3185,7 @@ extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in,
#ifdef CONFIG_MMU
extern int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
unsigned long start, unsigned long end,
struct list_head *uf, bool downgrade);
struct list_head *uf, bool unlock);
extern int __mm_populate(unsigned long addr, unsigned long len,
int ignore_errors);
static inline void mm_populate(unsigned long addr, unsigned long len)