fs/locks.c: prepare for BKL removal
This prepares the removal of the big kernel lock from the
file locking code. We still use the BKL as long as fs/lockd
uses it and ceph might sleep, but we can flip the definition
to a private spinlock as soon as that's done.
All users outside of fs/lockd get converted to use
lock_flocks() instead of lock_kernel() where appropriate.
Based on an earlier patch to use a spinlock from Matthew
Wilcox, who has attempted this a few times before, the
earliest patch from over 10 years ago turned it into
a semaphore, which ended up being slower than the BKL
and was subsequently reverted.
Someone should do some serious performance testing when
this becomes a spinlock, since this has caused problems
before. Using a spinlock should be at least as good
as the BKL in theory, but who knows...
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Sage Weil <sage@newdream.net>
Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
diff --git a/fs/locks.c b/fs/locks.c
index ab24d49..8b2b6ad 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -143,6 +143,22 @@
static LIST_HEAD(file_lock_list);
static LIST_HEAD(blocked_list);
+/*
+ * Protects the two list heads above, plus the inode->i_flock list
+ * FIXME: should use a spinlock, once lockd and ceph are ready.
+ */
+void lock_flocks(void)
+{
+ lock_kernel();
+}
+EXPORT_SYMBOL_GPL(lock_flocks);
+
+void unlock_flocks(void)
+{
+ unlock_kernel();
+}
+EXPORT_SYMBOL_GPL(unlock_flocks);
+
static struct kmem_cache *filelock_cache __read_mostly;
/* Allocate an empty lock structure. */
@@ -511,9 +527,9 @@
*/
static void locks_delete_block(struct file_lock *waiter)
{
- lock_kernel();
+ lock_flocks();
__locks_delete_block(waiter);
- unlock_kernel();
+ unlock_flocks();
}
/* Insert waiter into blocker's block list.
@@ -644,7 +660,7 @@
{
struct file_lock *cfl;
- lock_kernel();
+ lock_flocks();
for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
continue;
@@ -657,7 +673,7 @@
fl->fl_pid = pid_vnr(cfl->fl_nspid);
} else
fl->fl_type = F_UNLCK;
- unlock_kernel();
+ unlock_flocks();
return;
}
EXPORT_SYMBOL(posix_test_lock);
@@ -730,18 +746,16 @@
int error = 0;
int found = 0;
- lock_kernel();
+ if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
+ new_fl = locks_alloc_lock();
+ if (!new_fl)
+ return -ENOMEM;
+ }
+
+ lock_flocks();
if (request->fl_flags & FL_ACCESS)
goto find_conflict;
- if (request->fl_type != F_UNLCK) {
- error = -ENOMEM;
- new_fl = locks_alloc_lock();
- if (new_fl == NULL)
- goto out;
- error = 0;
- }
-
for_each_lock(inode, before) {
struct file_lock *fl = *before;
if (IS_POSIX(fl))
@@ -767,8 +781,11 @@
* If a higher-priority process was blocked on the old file lock,
* give it the opportunity to lock the file.
*/
- if (found)
+ if (found) {
+ unlock_flocks();
cond_resched();
+ lock_flocks();
+ }
find_conflict:
for_each_lock(inode, before) {
@@ -794,7 +811,7 @@
error = 0;
out:
- unlock_kernel();
+ unlock_flocks();
if (new_fl)
locks_free_lock(new_fl);
return error;
@@ -823,7 +840,7 @@
new_fl2 = locks_alloc_lock();
}
- lock_kernel();
+ lock_flocks();
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
fl = *before;
@@ -991,7 +1008,7 @@
locks_wake_up_blocks(left);
}
out:
- unlock_kernel();
+ unlock_flocks();
/*
* Free any unused locks.
*/
@@ -1066,14 +1083,14 @@
/*
* Search the lock list for this inode for any POSIX locks.
*/
- lock_kernel();
+ lock_flocks();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!IS_POSIX(fl))
continue;
if (fl->fl_owner != owner)
break;
}
- unlock_kernel();
+ unlock_flocks();
return fl ? -EAGAIN : 0;
}
@@ -1186,7 +1203,7 @@
new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
- lock_kernel();
+ lock_flocks();
time_out_leases(inode);
@@ -1247,8 +1264,10 @@
break_time++;
}
locks_insert_block(flock, new_fl);
+ unlock_flocks();
error = wait_event_interruptible_timeout(new_fl->fl_wait,
!new_fl->fl_next, break_time);
+ lock_flocks();
__locks_delete_block(new_fl);
if (error >= 0) {
if (error == 0)
@@ -1263,7 +1282,7 @@
}
out:
- unlock_kernel();
+ unlock_flocks();
if (!IS_ERR(new_fl))
locks_free_lock(new_fl);
return error;
@@ -1319,7 +1338,7 @@
struct file_lock *fl;
int type = F_UNLCK;
- lock_kernel();
+ lock_flocks();
time_out_leases(filp->f_path.dentry->d_inode);
for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
fl = fl->fl_next) {
@@ -1328,7 +1347,7 @@
break;
}
}
- unlock_kernel();
+ unlock_flocks();
return type;
}
@@ -1341,7 +1360,7 @@
* The (input) flp->fl_lmops->fl_break function is required
* by break_lease().
*
- * Called with kernel lock held.
+ * Called with file_lock_lock held.
*/
int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
{
@@ -1436,7 +1455,15 @@
}
EXPORT_SYMBOL(generic_setlease);
- /**
+static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
+{
+ if (filp->f_op && filp->f_op->setlease)
+ return filp->f_op->setlease(filp, arg, lease);
+ else
+ return generic_setlease(filp, arg, lease);
+}
+
+/**
* vfs_setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
@@ -1467,12 +1494,9 @@
{
int error;
- lock_kernel();
- if (filp->f_op && filp->f_op->setlease)
- error = filp->f_op->setlease(filp, arg, lease);
- else
- error = generic_setlease(filp, arg, lease);
- unlock_kernel();
+ lock_flocks();
+ error = __vfs_setlease(filp, arg, lease);
+ unlock_flocks();
return error;
}
@@ -1499,9 +1523,9 @@
if (error)
return error;
- lock_kernel();
+ lock_flocks();
- error = vfs_setlease(filp, arg, &flp);
+ error = __vfs_setlease(filp, arg, &flp);
if (error || arg == F_UNLCK)
goto out_unlock;
@@ -1516,7 +1540,7 @@
error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
out_unlock:
- unlock_kernel();
+ unlock_flocks();
return error;
}
@@ -2020,7 +2044,7 @@
fl.fl_ops->fl_release_private(&fl);
}
- lock_kernel();
+ lock_flocks();
before = &inode->i_flock;
while ((fl = *before) != NULL) {
@@ -2038,7 +2062,7 @@
}
before = &fl->fl_next;
}
- unlock_kernel();
+ unlock_flocks();
}
/**
@@ -2053,12 +2077,12 @@
{
int status = 0;
- lock_kernel();
+ lock_flocks();
if (waiter->fl_next)
__locks_delete_block(waiter);
else
status = -ENOENT;
- unlock_kernel();
+ unlock_flocks();
return status;
}
@@ -2172,7 +2196,7 @@
static void *locks_start(struct seq_file *f, loff_t *pos)
{
- lock_kernel();
+ lock_flocks();
f->private = (void *)1;
return seq_list_start(&file_lock_list, *pos);
}
@@ -2184,7 +2208,7 @@
static void locks_stop(struct seq_file *f, void *v)
{
- unlock_kernel();
+ unlock_flocks();
}
static const struct seq_operations locks_seq_operations = {
@@ -2231,7 +2255,7 @@
{
struct file_lock *fl;
int result = 1;
- lock_kernel();
+ lock_flocks();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if (fl->fl_type == F_RDLCK)
@@ -2248,7 +2272,7 @@
result = 0;
break;
}
- unlock_kernel();
+ unlock_flocks();
return result;
}
@@ -2271,7 +2295,7 @@
{
struct file_lock *fl;
int result = 1;
- lock_kernel();
+ lock_flocks();
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
@@ -2286,7 +2310,7 @@
result = 0;
break;
}
- unlock_kernel();
+ unlock_flocks();
return result;
}