gaspersic/go-ethereum
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consensus/ethash: avoid runtime errors due to OOD on mmap writes (#23799)

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When we map a file for generating the DAG, we do a simple truncate to e.g. 1Gb. This is fine, even if we have nowhere near 1Gb disk available, as the actual file doesn't take up the full 1Gb, merely a few bytes. When we start generating into it, however, it eventually crashes with a unexpected fault address .

This change fixes it (on linux systems) by using the Fallocate syscall, which preallocates suffcient space on disk to avoid that situation. 


Co-authored-by: Felix Lange <fjl@twurst.com>
This commit is contained in:
Martin Holst Swende
2021-11-02 11:33:54 +01:00
committed by GitHub
parent 2e8b58f076
commit 178debe435
3 changed files with 76 additions and 2 deletions
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7
consensus/ethash/ethash.go
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@ -136,13 +136,16 @@ func memoryMapAndGenerate(path string, size uint64, lock bool, generator func(bu
if err != nil {
return nil, nil, nil, err
}
if err = dump.Truncate(int64(len(dumpMagic))*4 + int64(size)); err != nil {
if err = ensureSize(dump, int64(len(dumpMagic))*4+int64(size)); err != nil {
dump.Close()
os.Remove(temp)
return nil, nil, nil, err
}
// Memory map the file for writing and fill it with the generator
mem, buffer, err := memoryMapFile(dump, true)
if err != nil {
dump.Close()
os.Remove(temp)
return nil, nil, nil, err
}
copy(buffer, dumpMagic)
@ -358,7 +361,7 @@ func (d *dataset) generate(dir string, limit int, lock bool, test bool) {
if err != nil {
logger.Error("Failed to generate mapped ethash dataset", "err", err)
d.dataset = make([]uint32, dsize/2)
d.dataset = make([]uint32, dsize/4)
generateDataset(d.dataset, d.epoch, cache)
}
// Iterate over all previous instances and delete old ones