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mm/mmap.c: make vma_merge() comment more easy to understand

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Case 1/6, 2/7 and 3/8 have the same pattern and we handle them in the
same logic.

Rearrange the comment to make it a little easy for audience to
understand.

Link: http://lkml.kernel.org/r/20191030012445.16944-1-richardw.yang@linux.intel.com
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Wei Yang 2019-11-30 17:57:39 -08:00 committed by Linus Torvalds
parent 35e3d566df
commit 5d42ab293f
1 changed files with 12 additions and 9 deletions
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21
mm/mmap.c
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@ -1091,15 +1091,18 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
* the area passed down from mprotect_fixup, never extending beyond one
* vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
*
* AAAA AAAA AAAA AAAA
* PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN PPPPNNNNXXXX
* cannot merge might become might become might become
* PPNNNNNNNNNN PPPPPPPPPPNN PPPPPPPPPPPP 6 or
* mmap, brk or case 4 below case 5 below PPPPPPPPXXXX 7 or
* mremap move: PPPPXXXXXXXX 8
* AAAA
* PPPP NNNN PPPPPPPPPPPP PPPPPPPPNNNN PPPPNNNNNNNN
* might become case 1 below case 2 below case 3 below
* AAAA AAAA AAAA
* PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN
* cannot merge might become might become
* PPNNNNNNNNNN PPPPPPPPPPNN
* mmap, brk or case 4 below case 5 below
* mremap move:
* AAAA AAAA
* PPPP NNNN PPPPNNNNXXXX
* might become might become
* PPPPPPPPPPPP 1 or PPPPPPPPPPPP 6 or
* PPPPPPPPNNNN 2 or PPPPPPPPXXXX 7 or
* PPPPNNNNNNNN 3 PPPPXXXXXXXX 8
*
* It is important for case 8 that the vma NNNN overlapping the
* region AAAA is never going to extended over XXXX. Instead XXXX must