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bees: post-kernel-5.7 toxic extent handling

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Toxic extents are mostly gone in kernel 5.7 and later.  Increase the
timeout for toxic extent handling to reduce false positives, and remove
persistenly stored toxic hashes from the hash table.

Toxic hashes are still stored nonpersistently to help mitigate problems
due to any remaining kernel bugs.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2021-05-28 02:13:33 -04:00
parent 43d38ca536
commit 7a197e2f33
2 changed files with 29 additions and 1 deletions
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28
src/bees-hash.cc
View File

@ -452,6 +452,34 @@ BeesHashTable::fetch_missing_extent_by_index(uint64_t extent_index)
readahead(m_fd, dirty_extent_offset + dirty_extent_size, dirty_extent_size);
}
});
Cell *cell = m_extent_ptr[extent_index ].p_buckets[0].p_cells;
Cell *cell_end = m_extent_ptr[extent_index + 1].p_buckets[0].p_cells;
size_t toxic_cleared_count = 0;
set<BeesHashTable::Cell> seen_it(cell, cell_end);
while (cell < cell_end) {
if (cell->e_addr & BeesAddress::c_toxic_mask) {
++toxic_cleared_count;
cell->e_addr &= ~BeesAddress::c_toxic_mask;
// Clearing the toxic bit might mean we now have a duplicate.
// This could be due to a race between two
// inserts, one finds the extent toxic while the
// other does not. That's arguably a bug elsewhere,
// but we should rewrite the whole extent lookup/insert
// loop, not spend time fixing code that will be
// thrown out later anyway.
// If there is a cell that is identical to this one
// except for the toxic bit, then we don't need this one.
if (seen_it.count(*cell)) {
cell->e_addr = 0;
cell->e_hash = 0;
}
}
++cell;
}
if (toxic_cleared_count) {
BEESLOGDEBUG("Cleared " << toxic_cleared_count << " hashes while fetching hash table extent " << extent_index);
}
}
void

2
src/bees.h
View File

@ -93,7 +93,7 @@ const double BEES_DEFAULT_THREAD_FACTOR = 1.0;
const double BEES_TOO_LONG = 5.0;
// Avoid any extent where LOGICAL_INO takes this much kernel CPU time
const double BEES_TOXIC_SYS_DURATION = 0.1;
const double BEES_TOXIC_SYS_DURATION = 5.0;
// Maximum number of refs to a single extent before we have other problems
// If we have more than 10K refs to an extent, adding another will save 0.01% space