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common: Enhance dotlock, so that we can have a CLI util. 

* common/dotlock.h (DOTLOCK_LOCK_BY_PARENT, DOTLOCK_LOCKED): New.
* common/dotlock.c [HAVE_POSIX_SYSTEM]: Include <dirent.h>.
(dotlock_get_process_id, dotlock_detect_tname): New.
(dotlock_create_unix): Handle the case when no_write option is
specified.  Not creating the lock file, but detect the the file of
tname.
(dotlock_create) [HAVE_POSIX_SYSTEM]: Add support of
DOTLOCK_LOCK_BY_PARENT and DOTLOCK_LOCKED for dotlock CLI util.
(dotlock_take_unix): Support the case of DOTLOCK_LOCK_BY_PARENT.

--

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2023-12-19 15:59:41 +09:00
parent 1c5584c395
commit 6b4fd3a5da
No known key found for this signature in database
GPG Key ID: 640114AF89DE6054
2 changed files with 138 additions and 11 deletions
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144
common/dotlock.c
View File

@ -291,6 +291,7 @@
# include <sys/types.h>
# include <sys/stat.h>
# include <sys/utsname.h>
# include <dirent.h>
#endif
#include <sys/types.h>
#include <sys/time.h>
@ -393,6 +394,8 @@ struct dotlock_handle
unsigned int locked:1; /* Lock status. */
unsigned int disable:1; /* If true, locking is disabled. */
unsigned int use_o_excl:1; /* Use open (O_EXCL) for locking. */
unsigned int by_parent:1; /* Parent does the locking. */
unsigned int no_write:1; /* No write to the lockfile. */
int extra_fd; /* A place for the caller to store an FD. */
@ -679,6 +682,80 @@ use_hardlinks_p (const char *tname)
#ifdef HAVE_POSIX_SYSTEM
static int
dotlock_get_process_id (dotlock_t h)
{
return h->by_parent? (int)getppid(): (int)getpid();
}
static int
dotlock_detect_tname (dotlock_t h)
{
struct stat sb;
DIR *dir;
char *dirname;
char *basename;
struct dirent *d;
int r;
if (stat (h->lockname, &sb))
return -1;
basename = make_basename (h->lockname, NULL);
dirname = make_dirname (h->lockname);
dir = opendir (dirname);
if (dir == NULL)
{
xfree (basename);
xfree (dirname);
return -1;
}
while ((d = readdir (dir)))
if (sb.st_ino == d->d_ino && strcmp (d->d_name, basename))
break;
if (d)
{
int len = strlen (h->tname);
int dlen = strlen (d->d_name);
const char *tname_path;
if (dlen > len)
{
xfree (basename);
xfree (dirname);
return -1;
}
strcpy (stpcpy (stpcpy (h->tname, dirname), DIRSEP_S), d->d_name);
h->use_o_excl = 0;
tname_path = strchr (h->tname + strlen (dirname) + 2, '.');
if (!tname_path)
{
xfree (basename);
xfree (dirname);
return -1;
}
h->nodename_off = tname_path - h->tname + 1;
}
else
h->use_o_excl = 1;
r = closedir (dir);
if (r)
{
xfree (basename);
xfree (dirname);
return r;
}
xfree (basename);
xfree (dirname);
return 0;
}
/* Locking core for Unix. It used a temporary file and the link
system call to make locking an atomic operation. */
static dotlock_t
@ -691,8 +768,10 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
int dirpartlen;
struct utsname utsbuf;
size_t tnamelen;
int pid;
snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid() );
pid = dotlock_get_process_id (h);
snprintf (pidstr, sizeof pidstr, "%10d\n", pid);
/* Create a temporary file. */
if ( uname ( &utsbuf ) )
@ -726,10 +805,17 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
}
h->nodename_len = strlen (nodename);
if (h->no_write)
{
memset (h->tname, '_', tnamelen);
h->tname[tnamelen] = 0;
goto skip_write;
}
snprintf (h->tname, tnamelen, "%.*s/.#lk%p.", dirpartlen, dirpart, h );
h->nodename_off = strlen (h->tname);
snprintf (h->tname+h->nodename_off, tnamelen - h->nodename_off,
"%s.%d", nodename, (int)getpid ());
"%s.%d", nodename, pid);
do
{
@ -792,6 +878,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
goto write_failed;
}
skip_write:
h->lockname = xtrymalloc (strlen (file_to_lock) + 6 );
if (!h->lockname)
{
@ -807,6 +894,20 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
strcpy (stpcpy (h->lockname, file_to_lock), EXTSEP_S "lock");
UNLOCK_all_lockfiles ();
if (h->no_write)
{
if (dotlock_detect_tname (h) < 0)
{
xfree (h->lockname);
xfree (h->tname);
xfree (h);
my_set_errno (EACCES);
return NULL;
}
h->locked = 1;
}
return h;
write_failed:
@ -914,10 +1015,15 @@ dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
POSIX systems a temporary file ".#lk.<hostname>.pid[.threadid] is
used.
The only defined FLAG bit is DOTLOCK_PREPARE_CREATE, which only
allocates the handle and requires a further call to
dotlock_finish_create. This can be used to set a callback between
these calls.
FLAGS may include DOTLOCK_PREPARE_CREATE bit, which only allocates
the handle and requires a further call to dotlock_finish_create.
This can be used to set a callback between these calls.
FLAGS may include DOTLOCK_LOCK_BY_PARENT bit, when it's the parent
process controlling the lock. This is used by dotlock util.
FLAGS may include DOTLOCK_LOCKED bit, when it should not create the
lockfile, but to unlock. This is used by dotlock util.
The function returns an new handle which needs to be released using
destroy_dotlock but gets also released at the termination of the
@ -929,8 +1035,13 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
{
static int initialized;
dotlock_t h;
#ifndef HAVE_DOSISH_SYSTEM
int by_parent = 0;
int no_write = 0;
#endif
if ( !initialized )
if ( !(flags & DOTLOCK_LOCK_BY_PARENT)
&& !initialized )
{
atexit (dotlock_remove_lockfiles);
initialized = 1;
@ -939,6 +1050,14 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
if ( !file_to_lock )
return NULL; /* Only initialization was requested. */
#ifndef HAVE_DOSISH_SYSTEM
if ((flags & DOTLOCK_LOCK_BY_PARENT) || (flags & DOTLOCK_LOCKED))
{
by_parent = !!(flags & DOTLOCK_LOCK_BY_PARENT);
no_write = !!(flags & DOTLOCK_LOCKED);
flags &= ~(DOTLOCK_LOCK_BY_PARENT | DOTLOCK_LOCKED);
}
#endif
if ((flags & ~DOTLOCK_PREPARE_CREATE))
{
my_set_errno (EINVAL);
@ -949,6 +1068,10 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
if (!h)
return NULL;
h->extra_fd = -1;
#ifndef HAVE_DOSISH_SYSTEM
h->by_parent = by_parent;
h->no_write = no_write;
#endif
if (never_lock)
{
@ -1181,7 +1304,8 @@ dotlock_take_unix (dotlock_t h, long timeout)
{
char pidstr[16];
snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid());
snprintf (pidstr, sizeof pidstr, "%10d\n",
dotlock_get_process_id (h));
if (write (fd, pidstr, 11 ) == 11
&& write (fd, h->tname + h->nodename_off,h->nodename_len)
== h->nodename_len
@ -1251,7 +1375,7 @@ dotlock_take_unix (dotlock_t h, long timeout)
my_info_0 ("lockfile disappeared\n");
goto again;
}
else if ( (pid == getpid() && same_node)
else if ( (pid == dotlock_get_process_id (h) && same_node && !h->by_parent)
|| (same_node && kill (pid, 0) && errno == ESRCH) )
{
/* Stale lockfile is detected. */
@ -1460,7 +1584,7 @@ dotlock_release_unix (dotlock_t h)
my_set_errno (saveerrno);
return -1;
}
if ( pid != getpid() || !same_node )
if ( pid != dotlock_get_process_id (h) || !same_node )
{
my_error_1 ("release_dotlock: not our lock (pid=%d)\n", pid);
if (h->info_cb)

5
common/dotlock.h
View File

@ -108,7 +108,10 @@ enum dotlock_reasons
DOTLOCK_WAITING /* Waiting for the lock - may be terminated. */
};
#define DOTLOCK_PREPARE_CREATE (1<<5) /* Require dotlock_finish_create. */
/* Flags for dotlock_create. */
#define DOTLOCK_PREPARE_CREATE (1U << 5) /* Require dotlock_finish_create. */
#define DOTLOCK_LOCK_BY_PARENT (1U << 6) /* Used by dotlock util. */
#define DOTLOCK_LOCKED (1U << 7) /* Used by dotlock util. */
void dotlock_disable (void);
dotlock_t dotlock_create (const char *file_to_lock, unsigned int flags);