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Subjectlocks.c: removal of semaphores
From

Here's a slightly modified version of Andrew's patch: the version he
sent me on Sunday contained an incomplete merge of my fix to
locks_remove_posix(), meaning that the host server was not being
notified that posix locks were cleared in the call to close().

The following patch contains his patch + the above correction +
removal of the now-redundant BKLs in fl_notify & friends. It's been
tested. Amongst other things, we now pass all the Connectathon tests.

Remaining issues on NFS locking: just the lock reclaiming fixes, which
as I said earlier are non-critical for purposes of the 2.4.0 release.


fs/locks.c

- Remove semaphore file_lock_sem, and revert to BKL locking in
order to fix various races and deadlocks.

- locks_delete_lock() should not call file->f_op->lock(). The
latter notifies the *server*, hence calling it from routines like
posix_lock_file() while merging/unmerging locks in our internal
representation of the locks is a bug.

- A new function locks_unlock_delete() takes care of the special
case when we're freeing all locks upon close().

- Straighten out lock notification. Don't bother waking up task
when we have a notify function. Don't wake up task in
posix_unblock_lock().


fs/lockd/clntlock.c
- Remove semaphore file_lock_sem. We're now protected by the BKL.

fs/lockd/clntproc, fs/lockd/svclock.c
- Remove redundant BKL. The caller already holds it.

Cheers,
Trond


diff -u --recursive --new-file linux-2.4.0-test10/fs/lockd/clntlock.c linux-2.4.0-lockd/fs/lockd/clntlock.c
--- linux-2.4.0-test10/fs/lockd/clntlock.c Mon Oct 16 21:58:51 2000
+++ linux-2.4.0-lockd/fs/lockd/clntlock.c Tue Nov 7 02:24:01 2000
@@ -168,7 +168,6 @@
* reclaim is in progress */
lock_kernel();
lockd_up();
- down(&file_lock_sem);

/* First, reclaim all locks that have been granted previously. */
restart:
@@ -181,12 +180,11 @@
fl->fl_u.nfs_fl.state != host->h_state &&
(fl->fl_u.nfs_fl.flags & NFS_LCK_GRANTED)) {
fl->fl_u.nfs_fl.flags &= ~ NFS_LCK_GRANTED;
- nlmclnt_reclaim(host, fl);
+ nlmclnt_reclaim(host, fl); /* This sleeps */
goto restart;
}
tmp = tmp->next;
}
- up(&file_lock_sem);

host->h_reclaiming = 0;
wake_up(&host->h_gracewait);
diff -u --recursive --new-file linux-2.4.0-test10/fs/lockd/clntproc.c linux-2.4.0-lockd/fs/lockd/clntproc.c
--- linux-2.4.0-test10/fs/lockd/clntproc.c Mon Oct 30 23:41:41 2000
+++ linux-2.4.0-lockd/fs/lockd/clntproc.c Tue Nov 7 00:35:39 2000
@@ -407,19 +407,15 @@
static
void nlmclnt_insert_lock_callback(struct file_lock *fl)
{
- lock_kernel();
nlm_get_host(fl->fl_u.nfs_fl.host);
- unlock_kernel();
}
static
void nlmclnt_remove_lock_callback(struct file_lock *fl)
{
- lock_kernel();
if (fl->fl_u.nfs_fl.host) {
nlm_release_host(fl->fl_u.nfs_fl.host);
fl->fl_u.nfs_fl.host = NULL;
}
- unlock_kernel();
}

/*
diff -u --recursive --new-file linux-2.4.0-test10/fs/lockd/svclock.c linux-2.4.0-lockd/fs/lockd/svclock.c
--- linux-2.4.0-test10/fs/lockd/svclock.c Tue Nov 7 00:38:57 2000
+++ linux-2.4.0-lockd/fs/lockd/svclock.c Tue Nov 7 00:37:13 2000
@@ -468,16 +468,13 @@

dprintk("lockd: VFS unblock notification for block %p\n", fl);
posix_unblock_lock(fl);
- lock_kernel();
for (bp = &nlm_blocked; (block = *bp); bp = &block->b_next) {
if (nlm_compare_locks(&block->b_call.a_args.lock.fl, fl)) {
nlmsvc_insert_block(block, 0);
svc_wake_up(block->b_daemon);
- unlock_kernel();
return;
}
}
- unlock_kernel();

printk(KERN_WARNING "lockd: notification for unknown block!\n");
}
diff -u --recursive --new-file linux-2.4.0-test10/fs/locks.c linux-2.4.0-lockd/fs/locks.c
--- linux-2.4.0-test10/fs/locks.c Fri Oct 13 21:12:18 2000
+++ linux-2.4.0-lockd/fs/locks.c Tue Nov 7 02:31:05 2000
@@ -125,11 +125,6 @@
#include <asm/semaphore.h>
#include <asm/uaccess.h>

-DECLARE_MUTEX(file_lock_sem);
-
-#define acquire_fl_sem() down(&file_lock_sem)
-#define release_fl_sem() up(&file_lock_sem)
-
int leases_enable = 1;
int lease_break_time = 45;

@@ -428,6 +423,15 @@
list_add(&waiter->fl_link, &blocked_list);
}

+static inline
+void locks_notify_blocked(struct file_lock *waiter)
+{
+ if (waiter->fl_notify)
+ waiter->fl_notify(waiter);
+ else
+ wake_up(&waiter->fl_wait);
+}
+
/* Wake up processes blocked waiting for blocker.
* If told to wait then schedule the processes until the block list
* is empty, otherwise empty the block list ourselves.
@@ -436,11 +440,9 @@
{
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter = list_entry(blocker->fl_block.next, struct file_lock, fl_block);
- /* N.B. Is it possible for the notify function to block?? */
- if (waiter->fl_notify)
- waiter->fl_notify(waiter);
- wake_up(&waiter->fl_wait);
+
if (wait) {
+ locks_notify_blocked(waiter);
/* Let the blocked process remove waiter from the
* block list when it gets scheduled.
*/
@@ -451,6 +453,7 @@
* time it wakes up blocker won't exist any more.
*/
locks_delete_block(waiter);
+ locks_notify_blocked(waiter);
}
}
}
@@ -477,7 +480,6 @@
*/
static void locks_delete_lock(struct file_lock **thisfl_p, unsigned int wait)
{
- int (*lock)(struct file *, int, struct file_lock *);
struct file_lock *fl = *thisfl_p;

*thisfl_p = fl->fl_next;
@@ -488,7 +490,7 @@

fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
if (fl->fl_fasync != NULL){
- printk("locks_delete_lock: fasync == %p\n", fl->fl_fasync);
+ printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
fl->fl_fasync = NULL;
}

@@ -496,12 +498,24 @@
fl->fl_remove(fl);

locks_wake_up_blocks(fl, wait);
- lock = fl->fl_file->f_op->lock;
- if (lock) {
+ locks_free_lock(fl);
+}
+
+/*
+ * Call back client filesystem in order to get it to unregister a lock,
+ * then delete lock. Essentially useful only in locks_remove_*().
+ * Note: this must be called with the semaphore already held!
+ */
+static inline void locks_unlock_delete(struct file_lock **thisfl_p)
+{
+ struct file_lock *fl = *thisfl_p;
+ int (*lock)(struct file *, int, struct file_lock *);
+
+ if ((lock = fl->fl_file->f_op->lock) != NULL) {
fl->fl_type = F_UNLCK;
lock(fl->fl_file, F_SETLK, fl);
}
- locks_free_lock(fl);
+ locks_delete_lock(thisfl_p, 0);
}

/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
@@ -562,22 +576,19 @@
return (locks_conflict(caller_fl, sys_fl));
}

-int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, struct semaphore *sem, int timeout)
+static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
{
int result = 0;
- wait_queue_t wait;
- init_waitqueue_entry(&wait, current);
+ DECLARE_WAITQUEUE(wait, current);

- __add_wait_queue(fl_wait, &wait);
current->state = TASK_INTERRUPTIBLE;
- up(sem);
+ add_wait_queue(fl_wait, &wait);
if (timeout == 0)
schedule();
else
result = schedule_timeout(timeout);
if (signal_pending(current))
result = -ERESTARTSYS;
- down(sem);
remove_wait_queue(fl_wait, &wait);
current->state = TASK_RUNNING;
return result;
@@ -587,7 +598,7 @@
{
int result;
locks_insert_block(blocker, waiter);
- result = interruptible_sleep_on_locked(&waiter->fl_wait, &file_lock_sem, 0);
+ result = interruptible_sleep_on_locked(&waiter->fl_wait, 0);
locks_delete_block(waiter);
return result;
}
@@ -596,7 +607,7 @@
{
int result;
locks_insert_block(blocker, waiter);
- result = interruptible_sleep_on_locked(&waiter->fl_wait, &file_lock_sem, time);
+ result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
locks_delete_block(waiter);
return result;
}
@@ -606,14 +617,14 @@
{
struct file_lock *cfl;

- acquire_fl_sem();
+ lock_kernel();
for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
if (!(cfl->fl_flags & FL_POSIX))
continue;
if (posix_locks_conflict(cfl, fl))
break;
}
- release_fl_sem();
+ unlock_kernel();

return (cfl);
}
@@ -668,14 +679,14 @@
/*
* Search the lock list for this inode for any POSIX locks.
*/
- acquire_fl_sem();
+ lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!(fl->fl_flags & FL_POSIX))
continue;
if (fl->fl_owner != owner)
break;
}
- release_fl_sem();
+ unlock_kernel();
return fl ? -EAGAIN : 0;
}

@@ -696,7 +707,7 @@
new_fl->fl_end = offset + count - 1;

error = 0;
- acquire_fl_sem();
+ lock_kernel();

repeat:
/* Search the lock list for this inode for locks that conflict with
@@ -729,7 +740,7 @@
}
}
locks_free_lock(new_fl);
- release_fl_sem();
+ unlock_kernel();
return error;
}

@@ -847,7 +858,7 @@
if (!(new_fl && new_fl2))
goto out;

- acquire_fl_sem();
+ lock_kernel();
if (caller->fl_type != F_UNLCK) {
repeat:
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
@@ -951,7 +962,7 @@
* as the change in lock type might satisfy
* their needs.
*/
- locks_wake_up_blocks(fl, 0);
+ locks_wake_up_blocks(fl, 0); /* This cannot schedule()! */
fl->fl_start = caller->fl_start;
fl->fl_end = caller->fl_end;
fl->fl_type = caller->fl_type;
@@ -992,7 +1003,7 @@
locks_wake_up_blocks(left, 0);
}
out:
- release_fl_sem();
+ unlock_kernel();
/*
* Free any unused locks.
*/
@@ -1038,7 +1049,7 @@

alloc_err = lease_alloc(NULL, 0, &new_fl);

- acquire_fl_sem();
+ lock_kernel();
flock = inode->i_flock;
if (flock->fl_type & F_INPROGRESS) {
if ((mode & O_NONBLOCK)
@@ -1107,7 +1118,7 @@
}

out:
- release_fl_sem();
+ unlock_kernel();
if (!alloc_err)
locks_free_lock(new_fl);
return error;
@@ -1210,7 +1221,7 @@

before = &inode->i_flock;

- acquire_fl_sem();
+ lock_kernel();

while ((fl = *before) != NULL) {
if (fl->fl_flags != FL_LEASE)
@@ -1261,7 +1272,7 @@
filp->f_owner.uid = current->uid;
filp->f_owner.euid = current->euid;
out_unlock:
- release_fl_sem();
+ unlock_kernel();
return error;
}

@@ -1307,10 +1318,10 @@
&& !(filp->f_mode & 3))
goto out_putf;

- acquire_fl_sem();
+ lock_kernel();
error = flock_lock_file(filp, type,
(cmd & (LOCK_UN | LOCK_NB)) ? 0 : 1);
- release_fl_sem();
+ unlock_kernel();

out_putf:
fput(filp);
@@ -1643,16 +1654,16 @@
*/
return;
}
- acquire_fl_sem();
+ lock_kernel();
before = &inode->i_flock;
while ((fl = *before) != NULL) {
if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner) {
- locks_delete_lock(before, 0);
+ locks_unlock_delete(before);
continue;
}
before = &fl->fl_next;
}
- release_fl_sem();
+ unlock_kernel();
}

/*
@@ -1667,7 +1678,7 @@
if (!inode->i_flock)
return;

- acquire_fl_sem();
+ lock_kernel();
before = &inode->i_flock;

while ((fl = *before) != NULL) {
@@ -1678,7 +1689,7 @@
}
before = &fl->fl_next;
}
- release_fl_sem();
+ unlock_kernel();
}

/**
@@ -1691,9 +1702,7 @@
void
posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
{
- acquire_fl_sem();
locks_insert_block(blocker, waiter);
- release_fl_sem();
}

/**
@@ -1705,12 +1714,8 @@
void
posix_unblock_lock(struct file_lock *waiter)
{
- acquire_fl_sem();
- if (!list_empty(&waiter->fl_block)) {
+ if (!list_empty(&waiter->fl_block))
locks_delete_block(waiter);
- wake_up(&waiter->fl_wait);
- }
- release_fl_sem();
}

static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
@@ -1801,7 +1806,7 @@
off_t pos = 0;
int i = 0;

- acquire_fl_sem();
+ lock_kernel();
list_for_each(tmp, &file_lock_list) {
struct list_head *btmp;
struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
@@ -1822,7 +1827,7 @@
}
}
done:
- release_fl_sem();
+ unlock_kernel();
*start = buffer;
if(q-buffer < length)
return (q-buffer);
@@ -1847,7 +1852,7 @@
{
struct file_lock *fl;
int result = 1;
- acquire_fl_sem();
+ lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (fl->fl_flags == FL_POSIX) {
if (fl->fl_type == F_RDLCK)
@@ -1864,7 +1869,7 @@
result = 0;
break;
}
- release_fl_sem();
+ unlock_kernel();
return result;
}

@@ -1885,7 +1890,7 @@
{
struct file_lock *fl;
int result = 1;
- acquire_fl_sem();
+ lock_kernel();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (fl->fl_flags == FL_POSIX) {
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
@@ -1900,7 +1905,7 @@
result = 0;
break;
}
- release_fl_sem();
+ unlock_kernel();
return result;
}
#endif
diff -u --recursive --new-file linux-2.4.0-test10/include/linux/fs.h linux-2.4.0-lockd/include/linux/fs.h
--- linux-2.4.0-test10/include/linux/fs.h Tue Oct 31 20:18:05 2000
+++ linux-2.4.0-lockd/include/linux/fs.h Tue Nov 7 00:51:43 2000
@@ -546,7 +546,6 @@
#endif

extern struct list_head file_lock_list;
-extern struct semaphore file_lock_sem;

#include <linux/fcntl.h>

diff -u --recursive --new-file linux-2.4.0-test10/kernel/ksyms.c linux-2.4.0-lockd/kernel/ksyms.c
--- linux-2.4.0-test10/kernel/ksyms.c Mon Oct 30 19:50:27 2000
+++ linux-2.4.0-lockd/kernel/ksyms.c Tue Nov 7 00:32:44 2000
@@ -215,7 +215,6 @@
EXPORT_SYMBOL(page_hash_bits);
EXPORT_SYMBOL(page_hash_table);
EXPORT_SYMBOL(file_lock_list);
-EXPORT_SYMBOL(file_lock_sem);
EXPORT_SYMBOL(locks_init_lock);
EXPORT_SYMBOL(locks_copy_lock);
EXPORT_SYMBOL(posix_lock_file);
-
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