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Commit c37ec8e5 c37ec8e53426fee3e6b19cdc3d16f29c117bd6a4 by Sergey Poznyakoff
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Reorganized. Default locking type is DOTLOCK. 

If the mailbox to be locked is not writable for the user,
locking type changes to NULL (no locking at all). If the
directory where the mailbox resides is not writable, the
locking type switches to KERNEL.
1 parent 6dc2d96f
Inline Side-by-side
Showing 1 changed file with 294 additions and 185 deletions
......@@ -29,6 +29,7 @@
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <utime.h>
#include <sys/param.h>
......@@ -50,16 +51,25 @@ struct _locker
int refcnt;
char *file;
int flags;
int expire_time;
int retries;
int retry_sleep;
union lock_data {
struct {
char *dotlock;
char *nfslock;
} dot;
int flags;
struct {
char *name;
} external;
int expire_time;
int retries;
int retry_sleep;
char *external;
struct {
int fd;
} kernel;
} data;
};
/* Assert that we're managing the refcnt and fd correctly, either
......@@ -68,10 +78,14 @@ struct _locker
*/
#define INVARIANT(l) assert((l)->refcnt >= 0);
static void expire_stale_lock (locker_t lock);
static int stat_check (const char *file, int fd, int links);
static int check_file_permissions (const char *file);
static int lock_external(locker_t l, int lock);
static void expire_stale_lock __P((locker_t lock));
static int stat_check __P((const char *file, int fd, int links));
static int check_file_permissions __P((const char *file));
static int lock_external __P((locker_t l, int lock));
static int _locker_lock_dotlock __P((locker_t lock));
static int _locker_unlock_dotlock __P((locker_t lock));
static int _locker_lock_kernel __P((locker_t lock));
static int _locker_unlock_kernel __P((locker_t lock));
int
locker_create (locker_t *plocker, const char *filename, int flags)
......@@ -81,7 +95,7 @@ locker_create (locker_t *plocker, const char *filename, int flags)
if (plocker == NULL)
return MU_ERR_OUT_PTR_NULL;
if(filename == NULL)
if (filename == NULL)
return EINVAL;
l = calloc (1, sizeof (*l));
......@@ -89,24 +103,13 @@ locker_create (locker_t *plocker, const char *filename, int flags)
return ENOMEM;
/* Should make l->file be the resulting of following the symlinks. */
l->file = strdup(filename);
l->file = strdup (filename);
if (l->file == NULL)
{
free (l);
return ENOMEM;
}
l->dotlock = malloc(strlen(l->file) + 5 /*strlen(".lock")*/ + 1);
if(!l->dotlock)
{
free (l->file);
free (l);
return ENOMEM;
}
sprintf(l->dotlock, "%s.lock", l->file);
if (strcmp (filename, "/dev/null") == 0)
l->flags = MU_LOCKER_NULL;
else if (flags)
......@@ -118,13 +121,28 @@ locker_create (locker_t *plocker, const char *filename, int flags)
l->retries = MU_LOCKER_RETRIES;
l->retry_sleep = MU_LOCKER_RETRY_SLEEP;
if(flags & MU_LOCKER_EXTERNAL)
/* Initialize locker-type-specific data */
if (flags & MU_LOCKER_EXTERNAL)
{
if (!(l->data.external.name = strdup (MU_LOCKER_EXTERNAL_PROGRAM)))
{
locker_destroy (&l);
return ENOMEM;
}
}
else if (!(flags & MU_LOCKER_KERNEL))
{
if(!(l->external = strdup(MU_LOCKER_EXTERNAL_PROGRAM)))
l->data.dot.dotlock = malloc (strlen (l->file)
+ 5 /*strlen(".lock")*/ + 1);
if (!l->data.dot.dotlock)
{
locker_destroy(&l);
free (l->file);
free (l);
return ENOMEM;
}
sprintf (l->data.dot.dotlock, "%s.lock", l->file);
}
INVARIANT(l);
......@@ -135,14 +153,29 @@ locker_create (locker_t *plocker, const char *filename, int flags)
}
void
_locker_destroy_private (locker_t locker)
{
if (locker)
{
if (locker->flags & MU_LOCKER_EXTERNAL)
free (locker->data.external.name);
else if (locker->flags & MU_LOCKER_KERNEL)
/* nothing */;
else
{
free (locker->data.dot.dotlock);
free (locker->data.dot.nfslock);
}
}
}
void
locker_destroy (locker_t *plocker)
{
if (plocker && *plocker)
{
_locker_destroy_private (*plocker);
free ((*plocker)->file);
free ((*plocker)->dotlock);
free ((*plocker)->nfslock);
free ((*plocker)->external);
free (*plocker);
*plocker = NULL;
}
......@@ -164,7 +197,7 @@ locker_set_expire_time (locker_t locker, int etime)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(etime <= 0)
if (etime <= 0)
return EINVAL;
locker->expire_time = etime;
......@@ -178,7 +211,7 @@ locker_set_retries (locker_t locker, int retries)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(retries <= 0)
if (retries <= 0)
return EINVAL;
locker->retries = retries;
......@@ -192,7 +225,7 @@ locker_set_retry_sleep (locker_t locker, int retry_sleep)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(retry_sleep <= 0)
if (retry_sleep <= 0)
return EINVAL;
locker->retry_sleep = retry_sleep;
......@@ -207,22 +240,25 @@ locker_set_external (locker_t locker, const char* program)
if (!locker)
return MU_ERR_LOCKER_NULL;
if (!(locker->flags & MU_LOCKER_EXTERNAL))
return EINVAL;
/* program can be NULL */
if(program != 0)
if (program != 0)
{
p = strdup(program);
if(!p)
p = strdup (program);
if (!p)
return ENOMEM;
}
free(locker->external);
locker->external = p;
free (locker->data.external.name);
locker->data.external.name = p;
return 0;
}
int locker_get_flags (locker_t locker, int *flags)
int
locker_get_flags (locker_t locker, int *flags)
{
if (!locker)
return MU_ERR_LOCKER_NULL;
......@@ -241,7 +277,7 @@ locker_get_expire_time (locker_t locker, int *ptime)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(!ptime)
if (!ptime)
return EINVAL;
*ptime = locker->expire_time;
......@@ -255,7 +291,7 @@ locker_get_retries (locker_t locker, int *retries)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(!retries)
if (!retries)
return EINVAL;
*retries = locker->retries;
......@@ -269,7 +305,7 @@ locker_get_retry_sleep (locker_t locker, int *retry_sleep)
if (!locker)
return MU_ERR_LOCKER_NULL;
if(!retry_sleep)
if (!retry_sleep)
return EINVAL;
*retry_sleep = locker->retry_sleep;
......@@ -280,8 +316,7 @@ locker_get_retry_sleep (locker_t locker, int *retry_sleep)
int
locker_lock (locker_t lock)
{
int err = 0;
int fd = -1;
int rc;
int retries = 1;
if (lock == NULL)
......@@ -298,141 +333,65 @@ locker_lock (locker_t lock)
return 0;
}
/* Do the lock with an external program, if requested. */
if (lock->flags & MU_LOCKER_EXTERNAL)
if (access (lock->file, W_OK))
{
return lock_external(lock, 1);
/* There is no use trying to lock the file if we are not
allowed to write to it */
_locker_destroy_private (lock);
lock->flags |= MU_LOCKER_NULL;
return 0;
}
/* Check we are trying to lock a regular file, with a link count
of 1, that we have permission to read, etc., or don't lock it. */
if((err = check_file_permissions(lock->file)))
return err;
if (lock->flags & MU_LOCKER_RETRY)
{
retries = lock->retries;
}
if ((rc = check_file_permissions(lock->file)))
return rc;
while (retries--)
{
/* cleanup after last loop */
close (fd);
fd = -1;
if (lock->nfslock)
/* Do the lock with an external program, if requested. */
if (lock->flags & MU_LOCKER_EXTERNAL)
return lock_external (lock, 1);
else if (!(lock->flags & MU_LOCKER_KERNEL))
{
unlink (lock->nfslock);
free (lock->nfslock);
lock->nfslock = 0;
}
char *tmp, *p;
expire_stale_lock (lock);
/* build the NFS hitching-post to the lock file */
{
char host[MAXHOSTNAMELEN + 1] = "localhost";
char pid[11]; /* 10 is strlen(2^32 = 4294967296) */
char now[11];
size_t sz = 0;
gethostname (host, sizeof (host));
host[MAXHOSTNAMELEN] = 0;
snprintf (pid, sizeof (pid), "%d", getpid ());
pid[sizeof (pid) - 1] = 0;
snprintf (now, sizeof (now), "%d", time (0));
now[sizeof (now) - 1] = 0;
sz = strlen (lock->file) + 1 /* "." */ +
strlen (pid) + 1 /* "." */ +
strlen (now) + 1 /* "." */ +
strlen (host) + 1;
lock->nfslock = malloc (sz);
if (!lock->nfslock)
tmp = strdup (lock->file);
if (!tmp)
return ENOMEM;
snprintf (lock->nfslock, sz, "%s.%s.%s.%s", lock->file, pid, now,
host);
lock->nfslock[sz - 1] = 0;
}
strcpy (tmp, lock->file);
p = strrchr (tmp, '/');
/* A '/' must be present, if not we'll coredump, and that's
correct! */
*p = 0;
fd = open (lock->nfslock, O_WRONLY | O_CREAT | O_EXCL, LOCKFILE_ATTR);
if (fd == -1)
if (access (tmp, W_OK))
{
if (errno == EEXIST)
continue; /* Try with another lockfile name. */
else
return errno;
/* Fallback to kernel locking */
_locker_destroy_private (lock);
lock->flags |= MU_LOCKER_KERNEL;
}
close (fd);
fd = -1;
/* Try to link to the lockfile. */
if (link (lock->nfslock, lock->dotlock) == -1)
{
err = errno;
if (err != EEXIST)
break; /* fatal */
free (tmp);
}
else
{
if ((fd = open (lock->dotlock, O_RDONLY)) == -1)
if (lock->flags & MU_LOCKER_RETRY)
{
err = errno;
break; /* fatal, we just made it, we should be able to open! */
retries = lock->retries;
}
err = stat_check (lock->nfslock, fd, 2);
if (err == 0)
while (retries--)
{
/* We got the lock! */
break;
}
if (lock->flags & MU_LOCKER_KERNEL)
rc = _locker_lock_kernel (lock);
else
{
unlink (lock->dotlock);
unlink (lock->nfslock);
/* If there was something invalid about the file/fd, return
a more descriptive code. */
if (err == EINVAL)
err = MU_ERR_LOCK_BAD_LOCK;
break;
}
}
if (retries)
rc = _locker_lock_dotlock (lock);
if (rc == EAGAIN && retries)
sleep (lock->retry_sleep);
else if (rc)
return rc;
else /* rc == 0 */
break;
}
unlink (lock->nfslock);
/* EEXIST means somebody else has the lock, anything else is an
error. */
if (err == EEXIST)
err = MU_ERR_LOCK_CONFLICT;
if (err)
return err;
/* If no errors, we have the lock. */
assert (lock->refcnt == 0);
if (lock->flags & MU_LOCKER_PID)
{
char buf[16];
sprintf (buf, "%ld", (long) getpid ());
write (fd, buf, strlen (buf));
}
close(fd);
lock->refcnt = 1;
return 0;
......@@ -447,8 +406,8 @@ locker_touchlock (locker_t lock)
if (lock->flags == MU_LOCKER_NULL)
return 0;
if(lock->refcnt > 0)
return utime (lock->dotlock, NULL);
if (lock->refcnt > 0)
return utime (lock->data.dot.dotlock, NULL);
return MU_ERR_LOCK_NOT_HELD;
}
......@@ -456,7 +415,7 @@ locker_touchlock (locker_t lock)
int
locker_unlock (locker_t lock)
{
int err = 0;
int rc = 0;
if (!lock)
return MU_ERR_LOCKER_NULL;
......@@ -469,9 +428,7 @@ locker_unlock (locker_t lock)
/* Do the lock with an external program, if requested. */
if (lock->flags & MU_LOCKER_EXTERNAL)
{
return lock_external (lock, 0);
}
if (lock->refcnt > 1)
{
......@@ -479,25 +436,18 @@ locker_unlock (locker_t lock)
return 0;
}
if ((err = check_file_permissions (lock->file)))
return err;
if (unlink (lock->dotlock) == -1)
{
err = errno;
if (err == ENOENT)
{
lock->refcnt = 0;
err = MU_ERR_LOCK_NOT_HELD;
return err;
}
if ((rc = check_file_permissions (lock->file)))
return rc;
return err;
}
if (lock->flags & MU_LOCKER_KERNEL)
rc = _locker_unlock_kernel (lock);
else
rc = _locker_unlock_dotlock (lock);
if (rc == 0)
lock->refcnt = 0;
return 0;
return rc;
}
int
......@@ -513,7 +463,7 @@ locker_remove_lock (locker_t lock)
/* Force the reference count to 1 to unlock the file. */
lock->refcnt = 1;
err = locker_unlock(lock);
err = locker_unlock (lock);
return err;
}
......@@ -523,7 +473,7 @@ static void
expire_stale_lock (locker_t lock)
{
int stale = 0;
int fd = open (lock->dotlock, O_RDONLY);
int fd = open (lock->data.dot.dotlock, O_RDONLY);
if (fd == -1)
return;
......@@ -547,6 +497,7 @@ expire_stale_lock (locker_t lock)
stale = 1; /* Corrupted file, remove the lock. */
}
}
/* Check to see if the lock expired. */
if (lock->flags & MU_LOCKER_TIME)
{
......@@ -560,7 +511,7 @@ expire_stale_lock (locker_t lock)
close (fd);
if (stale)
unlink (lock->dotlock);
unlink (lock->data.dot.dotlock);
}
static int
......@@ -571,11 +522,11 @@ stat_check (const char *file, int fd, int links)
int err = 0;
int localfd = -1;
if(fd == -1)
if (fd == -1)
{
localfd = open(file, O_RDONLY);
if(localfd == -1)
if (localfd == -1)
return errno;
fd = localfd;
}
......@@ -603,8 +554,8 @@ stat_check (const char *file, int fd, int links)
#undef CHK
}
if(localfd != -1)
close(localfd);
if (localfd != -1)
close (localfd);
return err;
}
......@@ -616,7 +567,7 @@ check_file_permissions (const char *file)
int err = 0;
if ((fd = open (file, O_RDONLY)) == -1)
return errno;
return errno == ENOENT ? 0 : errno;
err = stat_check (file, fd, 1);
close (fd);
......@@ -631,6 +582,161 @@ check_file_permissions (const char *file)
return 0;
}
/* Locker-specific lock/unlock functions */
int
_locker_lock_dotlock (locker_t lock)
{
char host[MAXHOSTNAMELEN + 1] = "localhost";
char pid[11]; /* 10 is strlen(2^32 = 4294967296) */
char now[11];
size_t sz = 0;
int err = 0;
int fd;
if (lock->data.dot.nfslock)
{
unlink (lock->data.dot.nfslock);
free (lock->data.dot.nfslock);
lock->data.dot.nfslock = 0;
}
expire_stale_lock (lock);
/* build the NFS hitching-post to the lock file */
gethostname (host, sizeof (host));
host[MAXHOSTNAMELEN] = 0;
snprintf (now, sizeof (now), "%d", time (0));
now[sizeof (now) - 1] = 0;
snprintf (pid, sizeof (pid), "%d", getpid ());
pid[sizeof (pid) - 1] = 0;
sz = strlen (lock->file) + 1 /* "." */
+ strlen (pid) + 1 /* "." */
+ strlen (now) + 1 /* "." */
+ strlen (host) + 1;
lock->data.dot.nfslock = malloc (sz);
if (!lock->data.dot.nfslock)
return ENOMEM;
snprintf (lock->data.dot.nfslock, sz, "%s.%s.%s.%s", lock->file, pid, now,
host);
fd = open (lock->data.dot.nfslock,
O_WRONLY | O_CREAT | O_EXCL, LOCKFILE_ATTR);
if (fd == -1)
{
if (errno == EEXIST)
return EAGAIN;
else
return errno;
}
close (fd);
/* Try to link to the lockfile. */
if (link (lock->data.dot.nfslock, lock->data.dot.dotlock) == -1)
{
if (errno == EEXIST)
return MU_ERR_LOCK_CONFLICT;
return errno;
}
if ((fd = open (lock->data.dot.dotlock, O_RDONLY)) == -1)
return errno;
err = stat_check (lock->data.dot.nfslock, fd, 2);
if (err)
{
if (err == EINVAL)
return MU_ERR_LOCK_BAD_LOCK;
return errno;
}
unlink (lock->data.dot.nfslock);
/* If no errors, we have the lock. */
assert (lock->refcnt == 0);
if (lock->flags & MU_LOCKER_PID)
{
char buf[16];
sprintf (buf, "%ld", (long) getpid ());
write (fd, buf, strlen (buf));
}
close(fd);
return 0;
}
int
_locker_unlock_dotlock (locker_t lock)
{
if (unlink (lock->data.dot.dotlock) == -1)
{
int err = errno;
if (err == ENOENT)
{
lock->refcnt = 0;
err = MU_ERR_LOCK_NOT_HELD;
return err;
}
return err;
}
return 0;
}
int
_locker_lock_kernel (locker_t lock)
{
int fd;
struct flock fl;
fd = open (lock->file, O_RDWR);
if (fd == -1)
return errno;
lock->data.kernel.fd = fd;
fl.l_type = F_WRLCK;
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 0; /* Lock entire file */
if (fcntl (fd, F_SETLK, &fl))
{
#ifdef EACCESS
if (errno == EACCESS)
return EAGAIN;
#endif
if (errno == EAGAIN)
return EAGAIN;
return errno;
}
return 0;
}
int
_locker_unlock_kernel (locker_t lock)
{
struct flock fl;
fl.l_type = F_UNLCK;
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 0; /* Unlock entire file */
if (fcntl (lock->data.kernel.fd, F_SETLK, &fl))
{
#ifdef EACCESS
if (errno == EACCESS)
return EAGAIN;
#endif
if (errno == EAGAIN)
return EAGAIN;
return errno;
}
close (lock->data.kernel.fd);
return 0;
}
/*
Estimate 1 decimal digit per 3 bits, + 1 for round off.
*/
......@@ -651,7 +757,8 @@ lock_external (locker_t l, int lock)
assert (lock == !l->refcnt);
/* lock is true, refcnt is 0 or lock is false and refcnt is 1 */
av[ac++] = l->external ? l->external : MU_LOCKER_EXTERNAL_PROGRAM;
av[ac++] = l->data.external.name ?
l->data.external.name : MU_LOCKER_EXTERNAL_PROGRAM;
if (l->flags & MU_LOCKER_TIME)
{
......@@ -659,12 +766,14 @@ lock_external (locker_t l, int lock)
aforce[sizeof (aforce) - 1] = 0;
av[ac++] = aforce;
}
if (l->flags & MU_LOCKER_RETRY)
{
snprintf (aretry, sizeof (aretry), "-r%d", l->retries);
aretry[sizeof (aretry) - 1] = 0;
av[ac++] = aretry;
}
if (lock == 0)
{
av[ac++] = "-u";
......