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Merge pull request #13826 from xokdvium/sqlite-zfs-hack

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SQLite: fsync db.sqlite-shm before opening the database
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Robert Hensing 2025-08-26 00:05:40 +02:00 • committed by GitHub
commit c1e2396d58
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26
src/libstore/sqlite.cc
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@ -4,6 +4,10 @@
#include "nix/util/url.hh"
#include "nix/util/signals.hh"
#ifdef __linux__
# include <sys/vfs.h>
#endif
#include <sqlite3.h>
#include <atomic>
@ -60,6 +64,28 @@ static void traceSQL(void * x, const char * sql)
SQLite::SQLite(const std::filesystem::path & path, SQLiteOpenMode mode)
{
// Work around a ZFS issue where SQLite's truncate() call on
// db.sqlite-shm can randomly take up to a few seconds. See
// https://github.com/openzfs/zfs/issues/14290#issuecomment-3074672917.
// Remove this workaround when a fix is widely installed, perhaps 2027? Candidate:
// https://github.com/search?q=repo%3Aopenzfs%2Fzfs+%22Linux%3A+zfs_putpage%3A+complete+async+page+writeback+immediately%22&type=commits
#ifdef __linux__
try {
auto shmFile = path;
shmFile += "-shm";
AutoCloseFD fd = open(shmFile.string().c_str(), O_RDWR | O_CLOEXEC);
if (fd) {
struct statfs fs;
if (fstatfs(fd.get(), &fs))
throw SysError("statfs() on '%s'", shmFile);
if (fs.f_type == /* ZFS_SUPER_MAGIC */ 801189825 && fdatasync(fd.get()) != 0)
throw SysError("fsync() on '%s'", shmFile);
}
} catch (...) {
throw;
}
#endif
// useSQLiteWAL also indicates what virtual file system we need. Using
// `unix-dotfile` is needed on NFS file systems and on Windows' Subsystem
// for Linux (WSL) where useSQLiteWAL should be false by default.