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// SPDX-License-Identifier: GPL-3.0-or-later
#include "systemd-internals.h"
// ----------------------------------------------------------------------------
// fstat64 overloading to speed up libsystemd
// https://github.com/systemd/systemd/pull/29261
#include <dlfcn.h>
#include <sys/stat.h>
#define FSTAT_CACHE_MAX 1024
struct fdstat64_cache_entry {
bool enabled;
bool updated;
int err_no;
struct stat64 stat;
int ret;
size_t cached_count;
size_t session;
};
struct fdstat64_cache_entry fstat64_cache[FSTAT_CACHE_MAX] = {0 };
__thread size_t fstat_thread_calls = 0;
__thread size_t fstat_thread_cached_responses = 0;
static __thread bool enable_thread_fstat = false;
static __thread size_t fstat_caching_thread_session = 0;
static size_t fstat_caching_global_session = 0;
void fstat_cache_enable_on_thread(void) {
fstat_caching_thread_session = __atomic_add_fetch(&fstat_caching_global_session, 1, __ATOMIC_ACQUIRE);
enable_thread_fstat = true;
}
void fstat_cache_disable_on_thread(void) {
fstat_caching_thread_session = __atomic_add_fetch(&fstat_caching_global_session, 1, __ATOMIC_RELEASE);
enable_thread_fstat = false;
}
int fstat64(int fd, struct stat64 *buf) {
static int (*real_fstat)(int, struct stat64 *) = NULL;
if (!real_fstat)
real_fstat = dlsym(RTLD_NEXT, "fstat64");
fstat_thread_calls++;
if(fd >= 0 && fd < FSTAT_CACHE_MAX) {
if(enable_thread_fstat && fstat64_cache[fd].session != fstat_caching_thread_session) {
fstat64_cache[fd].session = fstat_caching_thread_session;
fstat64_cache[fd].enabled = true;
fstat64_cache[fd].updated = false;
}
if(fstat64_cache[fd].enabled && fstat64_cache[fd].updated && fstat64_cache[fd].session == fstat_caching_thread_session) {
fstat_thread_cached_responses++;
errno = fstat64_cache[fd].err_no;
*buf = fstat64_cache[fd].stat;
fstat64_cache[fd].cached_count++;
return fstat64_cache[fd].ret;
}
}
int ret = real_fstat(fd, buf);
if(fd >= 0 && fd < FSTAT_CACHE_MAX && fstat64_cache[fd].enabled && fstat64_cache[fd].session == fstat_caching_thread_session) {
fstat64_cache[fd].ret = ret;
fstat64_cache[fd].updated = true;
fstat64_cache[fd].err_no = errno;
fstat64_cache[fd].stat = *buf;
}
return ret;
}
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