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roots: rework btrfs send workaround using btrfs-tree

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Drop the cache since we no longer have to open a file every time we
check a subvol's status.

Also stop counting workaround events at the root level twice.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2021-12-01 14:43:08 -05:00
parent 4d59939b07
commit f98599407f
2 changed files with 16 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
src/bees-roots.cc
View File

@ -1,5 +1,6 @@
#include "bees.h"
#include "crucible/btrfs-tree.h"
#include "crucible/cache.h"
#include "crucible/ntoa.h"
#include "crucible/string.h"
@ -199,35 +200,14 @@ BeesRoots::transid_min()
uint64_t
BeesRoots::transid_max_nocache()
{
uint64_t rv = 0;
BEESNOTE("Calculating transid_max");
BEESTRACE("Calculating transid_max");
// We look for the root of the extent tree and read its transid.
// Should run in O(1) time and be fairly reliable.
BtrfsIoctlSearchKey sk;
sk.tree_id = BTRFS_ROOT_TREE_OBJECTID;
sk.min_type = sk.max_type = BTRFS_ROOT_ITEM_KEY;
sk.min_objectid = sk.max_objectid = BTRFS_EXTENT_TREE_OBJECTID;
while (true) {
sk.nr_items = 4;
BEESTRACE("transid_max search sk " << sk);
sk.do_ioctl(m_ctx->root_fd());
if (sk.m_result.empty()) {
break;
}
// We are just looking for the highest transid on the filesystem.
// We don't care which object it comes from.
for (auto i : sk.m_result) {
sk.next_min(i, BTRFS_ROOT_ITEM_KEY);
if (i.transid > rv) {
rv = i.transid;
}
}
}
const auto bti = m_root_fetcher.root(BTRFS_EXTENT_TREE_OBJECTID);
BEESTRACE("extracting transid from " << bti);
const auto rv = bti.transid();
// transid must be greater than zero, or we did something very wrong
THROW_CHECK1(runtime_error, rv, rv > 0);
@ -376,7 +356,6 @@ void
BeesRoots::clear_caches()
{
m_ctx->fd_cache()->clear();
m_root_ro_cache.clear();
}
void
@ -563,14 +542,11 @@ BeesRoots::state_load()
BeesRoots::BeesRoots(shared_ptr<BeesContext> ctx) :
m_ctx(ctx),
m_root_fetcher(ctx->root_fd()),
m_crawl_state_file(ctx->home_fd(), crawl_state_filename()),
m_crawl_thread("crawl_transid"),
m_writeback_thread("crawl_writeback")
{
m_root_ro_cache.func([&](uint64_t root) -> bool {
return is_root_ro_nocache(root);
});
m_root_ro_cache.max_size(BEES_ROOT_FD_CACHE_SIZE);
}
void
@ -730,32 +706,22 @@ BeesRoots::open_root(uint64_t rootid)
return m_ctx->fd_cache()->open_root(rootid);
}
bool
BeesRoots::is_root_ro_nocache(uint64_t root)
{
BEESTRACE("checking subvol flags on root " << root);
Fd root_fd = open_root(root);
BEESTRACE("checking subvol flags on root " << root << " path " << name_fd(root_fd));
uint64_t flags = 0;
DIE_IF_NON_ZERO(ioctl(root_fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags));
if (flags & BTRFS_SUBVOL_RDONLY) {
BEESLOGDEBUG("WORKAROUND: Avoiding RO root " << root);
BEESCOUNT(root_workaround_btrfs_send);
return true;
}
return false;
}
bool
BeesRoots::is_root_ro(uint64_t root)
{
// If we are not implementing the workaround there is no need for cache
// If we are not working around btrfs send, all roots are rw to us
if (!m_workaround_btrfs_send) {
return false;
}
return m_root_ro_cache(root);
BEESTRACE("checking subvol flags on root " << root);
const auto item = m_root_fetcher.root(root);
// If we can't access the subvol's root item...guess it's ro?
if (!item || item.root_flags() & BTRFS_ROOT_SUBVOL_RDONLY) {
return true;
}
return false;
}
uint64_t

4
src/bees.h
View File

@ -1,6 +1,7 @@
#ifndef BEES_H
#define BEES_H
#include "crucible/btrfs-tree.h"
#include "crucible/cache.h"
#include "crucible/chatter.h"
#include "crucible/error.h"
@ -533,6 +534,7 @@ public:
class BeesRoots : public enable_shared_from_this<BeesRoots> {
shared_ptr<BeesContext> m_ctx;
BtrfsRootFetcher m_root_fetcher;
BeesStringFile m_crawl_state_file;
map<uint64_t, shared_ptr<BeesCrawl>> m_root_crawl_map;
mutex m_mutex;
@ -545,7 +547,6 @@ class BeesRoots : public enable_shared_from_this<BeesRoots> {
size_t m_transid_factor = BEES_TRANSID_FACTOR;
Task m_crawl_task;
bool m_workaround_btrfs_send = false;
LRUCache<bool, uint64_t> m_root_ro_cache;
mutex m_tmpfiles_mutex;
map<BeesFileId, Fd> m_tmpfiles;
@ -558,7 +559,6 @@ class BeesRoots : public enable_shared_from_this<BeesRoots> {
void insert_root(const BeesCrawlState &bcs);
Fd open_root_nocache(uint64_t root);
Fd open_root_ino_nocache(uint64_t root, uint64_t ino);
bool is_root_ro_nocache(uint64_t root);
uint64_t transid_min();
uint64_t transid_max();
uint64_t transid_max_nocache();