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bees: use MultiLocker to serialize dedupe and logical_ino

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In current kernels there is a bug which leads to an infinite loop in
add_all_parents().  The bug is triggered by one thread running dedupe
while another runs logical_ino.

Work around this by ensuring that bees process never runs dedupe and
logical_ino ioctls at the same time.  Any number of either can run
at the same time, but not one of both.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2022-11-16 23:46:14 -05:00
parent 4a4a2de89f
commit a2e1887c52
2 changed files with 21 additions and 11 deletions
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31
src/bees-context.cc
View File

@ -207,11 +207,6 @@ BeesContext::dedup(const BeesRangePair &brp_in)
BeesAddress first_addr(brp.first.fd(), brp.first.begin());
BeesAddress second_addr(brp.second.fd(), brp.second.begin());
BEESLOGINFO("dedup: src " << pretty(brp.first.size()) << " [" << to_hex(brp.first.begin()) << ".." << to_hex(brp.first.end()) << "] {" << first_addr << "} " << name_fd(brp.first.fd()) << "\n"
<< " dst " << pretty(brp.second.size()) << " [" << to_hex(brp.second.begin()) << ".." << to_hex(brp.second.end()) << "] {" << second_addr << "} " << name_fd(brp.second.fd()));
BEESNOTE("dedup: src " << pretty(brp.first.size()) << " [" << to_hex(brp.first.begin()) << ".." << to_hex(brp.first.end()) << "] {" << first_addr << "} " << name_fd(brp.first.fd()) << "\n"
<< " dst " << pretty(brp.second.size()) << " [" << to_hex(brp.second.begin()) << ".." << to_hex(brp.second.end()) << "] {" << second_addr << "} " << name_fd(brp.second.fd()));
if (first_addr.get_physical_or_zero() == second_addr.get_physical_or_zero()) {
BEESLOGTRACE("equal physical addresses in dedup");
BEESCOUNT(bug_dedup_same_physical);
@ -222,7 +217,16 @@ BeesContext::dedup(const BeesRangePair &brp_in)
BEESCOUNT(dedup_try);
Timer dedup_timer;
bool rv = btrfs_extent_same(brp.first.fd(), brp.first.begin(), brp.first.size(), brp.second.fd(), brp.second.begin());
BEESNOTE("waiting to dedup " << brp);
const auto lock = MultiLocker::get_lock("dedupe");
BEESLOGINFO("dedup: src " << pretty(brp.first.size()) << " [" << to_hex(brp.first.begin()) << ".." << to_hex(brp.first.end()) << "] {" << first_addr << "} " << name_fd(brp.first.fd()) << "\n"
<< " dst " << pretty(brp.second.size()) << " [" << to_hex(brp.second.begin()) << ".." << to_hex(brp.second.end()) << "] {" << second_addr << "} " << name_fd(brp.second.fd()));
BEESNOTE("dedup: src " << pretty(brp.first.size()) << " [" << to_hex(brp.first.begin()) << ".." << to_hex(brp.first.end()) << "] {" << first_addr << "} " << name_fd(brp.first.fd()) << "\n"
<< " dst " << pretty(brp.second.size()) << " [" << to_hex(brp.second.begin()) << ".." << to_hex(brp.second.end()) << "] {" << second_addr << "} " << name_fd(brp.second.fd()));
const bool rv = btrfs_extent_same(brp.first.fd(), brp.first.begin(), brp.first.size(), brp.second.fd(), brp.second.begin());
BEESCOUNTADD(dedup_ms, dedup_timer.age() * 1000);
if (rv) {
@ -849,16 +853,21 @@ BeesContext::resolve_addr_uncached(BeesAddress addr)
// Wait for the balance to finish before we run LOGICAL_INO
wait_for_balance();
BtrfsIoctlLogicalInoArgs log_ino(addr.get_physical_or_zero());
// Time how long this takes
Timer resolve_timer;
BtrfsIoctlLogicalInoArgs log_ino(addr.get_physical_or_zero());
// Get this thread's system CPU usage
struct rusage usage_before;
DIE_IF_MINUS_ONE(getrusage(RUSAGE_THREAD, &usage_before));
{
BEESNOTE("waiting to resolve addr " << addr << " with LOGICAL_INO");
const auto lock = MultiLocker::get_lock("logical_ino");
// Get this thread's system CPU usage
DIE_IF_MINUS_ONE(getrusage(RUSAGE_THREAD, &usage_before));
// Restart timer now that we're no longer waiting for lock
resolve_timer.reset();
BEESTOOLONG("Resolving addr " << addr << " in " << root_path() << " refs " << log_ino.m_iors.size());
BEESNOTE("resolving addr " << addr << " with LOGICAL_INO");
if (log_ino.do_ioctl_nothrow(root_fd())) {

1
src/bees.h
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@ -8,6 +8,7 @@
#include "crucible/fd.h"
#include "crucible/fs.h"
#include "crucible/lockset.h"
#include "crucible/multilock.h"
#include "crucible/pool.h"
#include "crucible/progress.h"
#include "crucible/time.h"