11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
142 lines
4.1 KiB
C
142 lines
4.1 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/file.h>
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#include <sys/stat.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fs-util.h"
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#include "lockfile-util.h"
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#include "macro.h"
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#include "path-util.h"
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int make_lock_file(const char *p, int operation, LockFile *ret) {
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_cleanup_close_ int fd = -1;
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_cleanup_free_ char *t = NULL;
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int r;
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/*
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* We use UNPOSIX locks if they are available. They have nice
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* semantics, and are mostly compatible with NFS. However,
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* they are only available on new kernels. When we detect we
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* are running on an older kernel, then we fall back to good
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* old BSD locks. They also have nice semantics, but are
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* slightly problematic on NFS, where they are upgraded to
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* POSIX locks, even though locally they are orthogonal to
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* POSIX locks.
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*/
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t = strdup(p);
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if (!t)
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return -ENOMEM;
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for (;;) {
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struct flock fl = {
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.l_type = (operation & ~LOCK_NB) == LOCK_EX ? F_WRLCK : F_RDLCK,
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.l_whence = SEEK_SET,
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};
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struct stat st;
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fd = open(p, O_CREAT|O_RDWR|O_NOFOLLOW|O_CLOEXEC|O_NOCTTY, 0600);
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if (fd < 0)
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return -errno;
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r = fcntl(fd, (operation & LOCK_NB) ? F_OFD_SETLK : F_OFD_SETLKW, &fl);
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if (r < 0) {
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/* If the kernel is too old, use good old BSD locks */
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if (errno == EINVAL)
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r = flock(fd, operation);
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if (r < 0)
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return errno == EAGAIN ? -EBUSY : -errno;
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}
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/* If we acquired the lock, let's check if the file
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* still exists in the file system. If not, then the
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* previous exclusive owner removed it and then closed
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* it. In such a case our acquired lock is worthless,
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* hence try again. */
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r = fstat(fd, &st);
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if (r < 0)
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return -errno;
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if (st.st_nlink > 0)
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break;
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fd = safe_close(fd);
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}
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ret->path = t;
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ret->fd = fd;
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ret->operation = operation;
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fd = -1;
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t = NULL;
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return r;
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}
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int make_lock_file_for(const char *p, int operation, LockFile *ret) {
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const char *fn;
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char *t;
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assert(p);
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assert(ret);
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fn = basename(p);
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if (!filename_is_valid(fn))
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return -EINVAL;
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t = newa(char, strlen(p) + 2 + 4 + 1);
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stpcpy(stpcpy(stpcpy(mempcpy(t, p, fn - p), ".#"), fn), ".lck");
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return make_lock_file(t, operation, ret);
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}
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void release_lock_file(LockFile *f) {
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int r;
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if (!f)
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return;
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if (f->path) {
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/* If we are the exclusive owner we can safely delete
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* the lock file itself. If we are not the exclusive
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* owner, we can try becoming it. */
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if (f->fd >= 0 &&
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(f->operation & ~LOCK_NB) == LOCK_SH) {
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static const struct flock fl = {
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.l_type = F_WRLCK,
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.l_whence = SEEK_SET,
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};
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r = fcntl(f->fd, F_OFD_SETLK, &fl);
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if (r < 0 && errno == EINVAL)
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r = flock(f->fd, LOCK_EX|LOCK_NB);
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if (r >= 0)
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f->operation = LOCK_EX|LOCK_NB;
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}
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if ((f->operation & ~LOCK_NB) == LOCK_EX)
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unlink_noerrno(f->path);
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f->path = mfree(f->path);
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}
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f->fd = safe_close(f->fd);
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f->operation = 0;
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}
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