0c69794138
These lines are generally out-of-date, incomplete and unnecessary. With SPDX and git repository much more accurate and fine grained information about licensing and authorship is available, hence let's drop the per-file copyright notice. Of course, removing copyright lines of others is problematic, hence this commit only removes my own lines and leaves all others untouched. It might be nicer if sooner or later those could go away too, making git the only and accurate source of authorship information.
137 lines
4 KiB
C
137 lines
4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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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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