folly: MemoryMapping: madvise: round the end to lower bound
folly: MemoryMapping: madvise: round the end to lower bound

Test Plan: n/a

Reviewed By: ott@fb.com

Subscribers: ott, folly-diffs@, yfeldblum, tudort, chalfant

FB internal diff: D2100535

Tasks: 4421175

Signature: t1:2100535:1432674713:6f5f40a8462851b2b8972c68d34ae23aaf1e9340

shaobz/folly,bobegir/folly,kernelim/folly,brunomorishita/folly,wildinto/folly,constantine001/folly,sonnyhu/folly,bsampath/folly,bikong2/folly,xzmagic/folly,arg0/folly,sakishum/folly,raphaelamorim/folly,theiver9827/folly,bowlofstew/folly,nickhen/folly,alexst07/folly,leolujuyi/folly,bikong2/folly,doctaweeks/folly,loversInJapan/folly,gaoyingie/folly,kernelim/folly,CJstar/folly,stonegithubs/folly,Orvid/folly,raphaelamorim/folly,leolujuyi/folly,leolujuyi/folly,PoisonBOx/folly,floxard/folly,floxard/folly,stonegithubs/folly,reddit/folly,yangjin-unique/folly,reddit/folly,renyinew/folly,reddit/folly,yangjin-unique/folly,SammyK/folly,brunomorishita/folly,gavioto/folly,floxard/folly,CJstar/folly,tempbottle/folly,cole14/folly,guker/folly,floxard/folly,gavioto/folly,doctaweeks/folly,bowlofstew/folly,KSreeHarsha/folly,PoisonBOx/folly,SeanRBurton/folly,PoisonBOx/folly,bowlofstew/folly,SeanRBurton/folly,tomhughes/folly,stonegithubs/folly,lifei/folly,renyinew/folly,juniway/folly,raphaelamorim/folly,stonegithubs/folly,bowlofstew/folly,yangjin-unique/folly,sonnyhu/folly,tomhughes/folly,facebook/folly,lifei/folly,leolujuyi/folly,yangjin-unique/folly,bsampath/folly,shaobz/folly,constantine001/folly,zhiweicai/folly,cole14/folly,bobegir/folly,clearlylin/folly,brunomorishita/folly,Orvid/folly,alexst07/folly,fw1121/folly,constantine001/folly,hongliangzhao/folly,lifei/folly,sonnyhu/folly,constantine001/folly,theiver9827/folly,cole14/folly,kernelim/folly,CJstar/folly,tomhughes/folly,gavioto/folly,SammyK/folly,tempbottle/folly,SeanRBurton/folly,reddit/folly,PPC64/folly,Hincoin/folly,sonnyhu/folly,juniway/folly,SeanRBurton/folly,rklabs/folly,SammyK/folly,SeanRBurton/folly,tomhughes/folly,kernelim/folly,Eagle-X/folly,upsoft/folly,nickhen/folly,gaoyingie/folly,cole14/folly,colemancda/folly,upsoft/folly,mqeizi/folly,Orvid/folly,wildinto/folly,KSreeHarsha/folly,yangjin-unique/folly,tomhughes/folly,upsoft/folly,arg0/folly,doctaweeks/folly,renyinew/folly,theiver9827/folly,gaoyingie/folly,juniway/folly,PPC64/folly,gavioto/folly,gaoyingie/folly,constantine001/folly,bobegir/folly,mqeizi/folly,fw1121/folly,shaobz/folly,raphaelamorim/folly,loversInJapan/folly,xzmagic/folly,project-zerus/folly,doctaweeks/folly,Orvid/folly,project-zerus/folly,hongliangzhao/folly,leolujuyi/folly,xzmagic/folly,loversInJapan/folly,sakishum/folly,upsoft/folly,clearlylin/folly,chjp2046/folly,fw1121/folly,zhiweicai/folly,Hincoin/folly,hongliangzhao/folly,chjp2046/folly,arg0/folly,guker/folly,facebook/folly,clearlylin/folly,Hincoin/folly,colemancda/folly,gavioto/folly,CJstar/folly,alexst07/folly,charsyam/folly,bikong2/folly,kernelim/folly,charsyam/folly,KSreeHarsha/folly,CJstar/folly,mqeizi/folly,arg0/folly,cole14/folly,wildinto/folly,stonegithubs/folly,Orvid/folly,guker/folly,bobegir/folly,juniway/folly,facebook/folly,gaoyingie/folly,facebook/folly,guker/folly,project-zerus/folly,SammyK/folly,upsoft/folly,colemancda/folly,lifei/folly,rklabs/folly,sakishum/folly,Hincoin/folly,bsampath/folly,Hincoin/folly,chjp2046/folly,PPC64/folly,shaobz/folly,Eagle-X/folly,Eagle-X/folly,bikong2/folly,renyinew/folly,rklabs/folly,doctaweeks/folly,renyinew/folly,theiver9827/folly,loversInJapan/folly,bobegir/folly,Eagle-X/folly,brunomorishita/folly,raphaelamorim/folly,bsampath/folly,reddit/folly,fw1121/folly,Eagle-X/folly,nickhen/folly,tempbottle/folly,SammyK/folly,alexst07/folly,zhiweicai/folly,fw1121/folly,lifei/folly,sakishum/folly,loversInJapan/folly,zhiweicai/folly,shaobz/folly,zhiweicai/folly,charsyam/folly,facebook/folly,sakishum/folly,chjp2046/folly,alexst07/folly,theiver9827/folly,clearlylin/folly,mqeizi/folly,hongliangzhao/folly,nickhen/folly,wildinto/folly,guker/folly,PoisonBOx/folly,KSreeHarsha/folly,tempbottle/folly,bsampath/folly,chjp2046/folly,PPC64/folly,PoisonBOx/folly,bikong2/folly,rklabs/folly,arg0/folly,rklabs/folly,nickhen/folly,mqeizi/folly,xzmagic/folly,PPC64/folly,colemancda/folly,colemancda/folly,project-zerus/folly,clearlylin/folly,juniway/folly,project-zerus/folly,KSreeHarsha/folly,charsyam/folly,tempbottle/folly,xzmagic/folly,floxard/folly,hongliangzhao/folly,bowlofstew/folly,wildinto/folly,sonnyhu/folly,brunomorishita/folly