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context: move prealloc dedupe to a separate Task

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A prealloc extent reference can be deduped immediately and asynchronously.
There is no need to slow down extent scanning to do it.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2020-10-28 13:55:26 -04:00
parent 1e7dbc6f97
commit b49d458792
1 changed files with 23 additions and 13 deletions
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16
src/bees-context.cc
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@ -337,20 +337,30 @@ BeesContext::scan_one_extent(const BeesFileRange &bfr, const Extent &e)
if (e.flags() & Extent::PREALLOC) {
// Prealloc is all zero and we replace it with a hole.
// No special handling is required here. Nuke it and move on.
Task(
"dedup_prealloc",
[m_ctx, bfr, e]() {
BEESLOGINFO("prealloc extent " << e);
// Must not extend past EOF
auto extent_size = min(e.end(), bfr.file_size()) - e.begin();
BeesFileRange prealloc_bfr(m_ctx->tmpfile()->make_hole(extent_size));
BeesRangePair brp(prealloc_bfr, bfr);
// Must hold tmpfile until dedupe is done
auto tmpfile = m_ctx->tmpfile();
BeesFileRange prealloc_bfr(tmpfile->make_hole(extent_size));
// Apparently they can both extend past EOF
BeesFileRange copy_bfr(bfr.fd(), e.begin(), e.begin() + extent_size);
BeesRangePair brp(prealloc_bfr, copy_bfr);
// Raw dedup here - nothing else to do with this extent, nothing to merge with
if (m_ctx->dedup(brp)) {
BEESCOUNT(dedup_prealloc_hit);
BEESCOUNTADD(dedup_prealloc_bytes, e.size());
return bfr;
// return bfr;
} else {
BEESCOUNT(dedup_prealloc_miss);
}
}
).run();
return bfr; // if dedup success, which we now blindly assume
}
// OK we need to read extent now
readahead(bfr.fd(), bfr.begin(), bfr.size());