Messages in this thread | | | Date | Mon, 08 Aug 2005 12:47:02 -0700 | From | Prasanna Meda <> | Subject | Re: [PATCH] fix madvise vma merging |
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Hugh Dickins wrote:
> On Fri, 5 Aug 2005, Prasanna Meda wrote: > > Hugh Dickins wrote: > > > > > 2. Correct initial value of prev when starting part way into a vma: as > > > in sys_mprotect and do_mlock, it needs to be set to vma in this case > > > (vma_merge handles only that minimum of cases shown in its comments). > > > > Acknowledge corrections 1 and 3 readily. Treated vma_merge > > as block box that can handle all cases. Motivation for pointless > > case 3 is to skip holes and did not notice that has been covered. > > Thanks for corrections. > > And thanks for the confirmations. > > > Correction 2 is tricky. Sometimes it merges similar to case 3, > > misses a needed split, where after the fix we can get case 4 > > merge. If that is what you are saying, we are in agreement. > > Otherwise, can you explain the real problem? > > I probably am saying what you are saying there, > but it's hard for me to understand it that way. > > Missing out the "start > vma->vm_start" adjustment of prev introduces > additional (but redundant: non-canonical) cases not considered at all > by vma_merge, now entered with a "prev" which is remote and surely > irrelevant to merging. "misses a needed split", yes, I saw that; > indeed my test ended up taking the "cases 3, 8" path, when, given > the right prev, it should have been handled as a "case 4". >
Ok, we both are on the same page. Your obseravtions are same. Thanks a lot for the code review and finding corner cases.
-Prasanna.
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