D 2026-07-31T21:12:47.156
T +comment b224ffeb401fb1be0b32078a4175a6f67eac6d956ae7cfbffefde5d09504fcf1 logstore:\sopenReadOnly\sscans\sheader-only;\sverified_on_open\sis\sgone\n\nThe\sspeedup\sreaches\sproduction.\sopenReadOnly\sis\sthe\spath\severy\sCLI\sverb\ntakes\s--\sRepository.open\sfalls\sback\sto\sit,\sand\sRepository.logStore,\sthe\ncontent\schannel\sbehind\scat,\sartifact,\scheckout\sand\ssync,\scalls\sit\swith\sno\ncache\sin\sfront.\sIt\sscanned\severy\spayload\sbyte\son\severy\sinvocation:\n\n\s\s10k\sframes\s\s42\sMB\s\s\s\s42.2ms\s->\s10.3ms\n\s\s10k\sframes\s410\sMB\s\s\s298.0ms\s->\s12.3ms\n\s\s100k\sframes\s416\sMB\s\s511.9ms\s->\s115.4ms\n\s\s100\sframes\s419\sMB\s\s\s321.4ms\s->\s\s0.10ms\n\nOpen\scost\sis\snow\sa\sfunction\sof\sframe\scount,\snot\srepository\ssize.\n\nverified_on_open\swas\sthe\sflag\sopenReadOnly\sset\sto\stell\sreadFrameAt\sthat\nthe\sscan\shad\salready\schecked\severy\sframe,\sso\sreads\scould\sskip\stheir\sown\ncrc.\sWith\sno\sscan\sdoing\sthat,\sthe\sexemption\shad\snothing\sleft\sto\srest\son\nand\sthe\sflag\sis\sdeleted.\sreadFrameAt\snow\scrc-checks\sunconditionally:\sit\sis\nthe\sonly\sthing\sstanding\sbetween\sa\srotted\spayload\sand\sa\scaller\sthat\nbelieves\sit,\sand\srestoring\sany\sskip\sthere\smeans\srestoring\sthe\sscan.\n\nDetection\sis\srelocated,\snot\sremoved.\sA\spayload\sbitflip\sno\slonger\svoids\sthe\nopen\s--\sthe\srest\sof\sthe\srepository\sstays\susable\s--\sand\ssurfaces\sthe\sfirst\ntime\sanyone\sreads\sthose\sbytes:\s"zit\scat"\sand\s"zit\sartifact"\sboth\srefuse\nwith\s'repository\sis\scorrupt',\sand\s"zit\sverify"\snames\sthe\sartifact\sand\sthe\noffset.\sThat\sverb\sshipped\sfirst\sfor\sexactly\sthis\sreason.\n\nopenForVerify\sis\sdeleted.\sIt\sexisted\sbecause\sopenReadOnly\sboth\saborted\son\na\sdamaged\sstore\sand\sgranted\sread-time\strust,\sneither\sof\swhich\sverify\scould\naccept;\sboth\sproperties\sare\sgone,\sit\sbecame\sbyte-identical\sto\nopenReadOnly,\sand\sits\sown\sdoc\scomment\ssaid\sto\sremove\sit\sin\sthis\scommit.\n\nThe\sDST\sprove-it-can-fail\sarm\sis\sinverted\srather\sthan\sdeleted.\sIt\sasserted\nthat\sopenReadOnly\sWOULD\sserve\slatent\srot\ssilently,\sacross\sa\sseed\srange\nwhere\sat\sleast\sone\scorpus\slands\sa\spayload\srot\son\sa\sraw\sframe\swhose\sheader\nsurvived.\sThat\shazard\sis\sgone,\sso\sthe\ssame\srange\snow\sasserts\sthe\sopposite:\nthe\sread\spath\snever\sserves\srot\sas\ssuccess.\strust_on_read\sgoes\swith\sit\s--\nthere\sare\sno\slonger\stwo\spaths\sto\sselect\sbetween.\sLosing\sthe\seager\swhole-log\nscan\scost\snothing\shere,\sbecause\sper-read\sverification\sis\swhat\swas\scatching\nthis\sall\salong.\n\nNet\s-40\slines.\n\nVerified:\sfmt\sclean,\stest\s2327/2327,\sgate,\se2e\s671/671,\sdst\s6\sseeds\sx\s1000\nsteps.\sThe\sSlice\s1\stripwire\s--\sthe\sassertion\sthat\sopenReadOnly\sstill\nrejected\seagerly,\swritten\sto\sfail\sif\sthe\sflag\swas\sdeleted\swithout\san\sfsck\nverb\s--\sfired\son\sthis\scommit,\swhich\sis\sthe\sone\sit\swas\saimed\sat.\n
U dmestas
Z 8a42832434a832f96f3867ff57966a22