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99cbd70f0b
beyond the end of disk. r298900 added code to prevent this. Some BIOSes cause significant delays if asked to read past end-of-disk. We never trusted the BIOS to accurately report the sectorsize of disks before and this set of changes. Unfortuately they interact badly with the infamous >2TB wraparound bugs. We have a number of relatively-recent machines in the FreeBSD.org cluster where the BIOS reports 3TB disks as 1TB. With pre-r298900 they work just fine. After r298900 they stop working if the boot environment attempts to access anything outside the first 1TB on the disk. 'ZFS: I/O error, all block copies unavailable' etc. It affects both UFS and ZFS if they try to boot from large volumes. This change replaces the blind trust of the BIOS end-of-disk reporting with a read-ahead clip to prevent reads crossing the of end-of-disk boundary. Since 2^32 (2TB) size reporting truncation is not uncommon, the clipping is done on 2TB aliases of the reported end-of-disk. ie: a 3TB disk reported as 1TB has readahead clipped at 1TB, 3TB, 5TB, ... as one of them is likely to be the real end-of-disk. This should make the loader on these broken machines behave the same as traditional pre-r298900 loader behavior, without disabling read-ahead. PR: 212139 Discussed with: tsoome, allanjude |
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| .. | ||
| boot0 | ||
| boot0sio | ||
| boot2 | ||
| btx | ||
| cdboot | ||
| common | ||
| gptboot | ||
| gptzfsboot | ||
| kgzldr | ||
| libfirewire | ||
| libi386 | ||
| loader | ||
| mbr | ||
| pmbr | ||
| pxeldr | ||
| zfsboot | ||
| zfsloader | ||
| Makefile | ||
| Makefile.inc | ||