--- /dev/null
+/* AFS file locking support
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include "internal.h"
+
+#define AFS_LOCK_GRANTED 0
+#define AFS_LOCK_PENDING 1
+
+static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
+static void afs_fl_release_private(struct file_lock *fl);
+
+static struct workqueue_struct *afs_lock_manager;
+static DEFINE_MUTEX(afs_lock_manager_mutex);
+
+static const struct file_lock_operations afs_lock_ops = {
+ .fl_copy_lock = afs_fl_copy_lock,
+ .fl_release_private = afs_fl_release_private,
+};
+
+/*
+ * initialise the lock manager thread if it isn't already running
+ */
+static int afs_init_lock_manager(void)
+{
+ int ret;
+
+ ret = 0;
+ if (!afs_lock_manager) {
+ mutex_lock(&afs_lock_manager_mutex);
+ if (!afs_lock_manager) {
+ afs_lock_manager =
+ create_singlethread_workqueue("kafs_lockd");
+ if (!afs_lock_manager)
+ ret = -ENOMEM;
+ }
+ mutex_unlock(&afs_lock_manager_mutex);
+ }
+ return ret;
+}
+
+/*
+ * destroy the lock manager thread if it's running
+ */
+void __exit afs_kill_lock_manager(void)
+{
+ if (afs_lock_manager)
+ destroy_workqueue(afs_lock_manager);
+}
+
+/*
+ * if the callback is broken on this vnode, then the lock may now be available
+ */
+void afs_lock_may_be_available(struct afs_vnode *vnode)
+{
+ _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
+
+ queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
+}
+
+/*
+ * the lock will time out in 5 minutes unless we extend it, so schedule
+ * extension in a bit less than that time
+ */
+static void afs_schedule_lock_extension(struct afs_vnode *vnode)
+{
+ queue_delayed_work(afs_lock_manager, &vnode->lock_work,
+ AFS_LOCKWAIT * HZ / 2);
+}
+
+/*
+ * grant one or more locks (readlocks are allowed to jump the queue if the
+ * first lock in the queue is itself a readlock)
+ * - the caller must hold the vnode lock
+ */
+static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
+{
+ struct file_lock *p, *_p;
+
+ list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
+ if (fl->fl_type == F_RDLCK) {
+ list_for_each_entry_safe(p, _p, &vnode->pending_locks,
+ fl_u.afs.link) {
+ if (p->fl_type == F_RDLCK) {
+ p->fl_u.afs.state = AFS_LOCK_GRANTED;
+ list_move_tail(&p->fl_u.afs.link,
+ &vnode->granted_locks);
+ wake_up(&p->fl_wait);
+ }
+ }
+ }
+}
+
+/*
+ * do work for a lock, including:
+ * - probing for a lock we're waiting on but didn't get immediately
+ * - extending a lock that's close to timing out
+ */
+void afs_lock_work(struct work_struct *work)
+{
+ struct afs_vnode *vnode =
+ container_of(work, struct afs_vnode, lock_work.work);
+ struct file_lock *fl;
+ afs_lock_type_t type;
+ struct key *key;
+ int ret;
+
+ _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
+
+ spin_lock(&vnode->lock);
+
+ if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
+ _debug("unlock");
+ spin_unlock(&vnode->lock);
+
+ /* attempt to release the server lock; if it fails, we just
+ * wait 5 minutes and it'll time out anyway */
+ ret = afs_vnode_release_lock(vnode, vnode->unlock_key);
+ if (ret < 0)
+ printk(KERN_WARNING "AFS:"
+ " Failed to release lock on {%x:%x} error %d\n",
+ vnode->fid.vid, vnode->fid.vnode, ret);
+
+ spin_lock(&vnode->lock);
+ key_put(vnode->unlock_key);
+ vnode->unlock_key = NULL;
+ clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
+ }
+
+ /* if we've got a lock, then it must be time to extend that lock as AFS
+ * locks time out after 5 minutes */
+ if (!list_empty(&vnode->granted_locks)) {
+ _debug("extend");
+
+ if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
+ BUG();
+ fl = list_entry(vnode->granted_locks.next,
+ struct file_lock, fl_u.afs.link);
+ key = key_get(fl->fl_file->private_data);
+ spin_unlock(&vnode->lock);
+
+ ret = afs_vnode_extend_lock(vnode, key);
+ clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
+ key_put(key);
+ switch (ret) {
+ case 0:
+ afs_schedule_lock_extension(vnode);
+ break;
+ default:
+ /* ummm... we failed to extend the lock - retry
+ * extension shortly */
+ printk(KERN_WARNING "AFS:"
+ " Failed to extend lock on {%x:%x} error %d\n",
+ vnode->fid.vid, vnode->fid.vnode, ret);
+ queue_delayed_work(afs_lock_manager, &vnode->lock_work,
+ HZ * 10);
+ break;
+ }
+ _leave(" [extend]");
+ return;
+ }
+
+ /* if we don't have a granted lock, then we must've been called back by
+ * the server, and so if might be possible to get a lock we're
+ * currently waiting for */
+ if (!list_empty(&vnode->pending_locks)) {
+ _debug("get");
+
+ if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
+ BUG();
+ fl = list_entry(vnode->pending_locks.next,
+ struct file_lock, fl_u.afs.link);
+ key = key_get(fl->fl_file->private_data);
+ type = (fl->fl_type == F_RDLCK) ?
+ AFS_LOCK_READ : AFS_LOCK_WRITE;
+ spin_unlock(&vnode->lock);
+
+ ret = afs_vnode_set_lock(vnode, key, type);
+ clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
+ switch (ret) {
+ case -EWOULDBLOCK:
+ _debug("blocked");
+ break;
+ case 0:
+ _debug("acquired");
+ if (type == AFS_LOCK_READ)
+ set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
+ else
+ set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
+ ret = AFS_LOCK_GRANTED;
+ default:
+ spin_lock(&vnode->lock);
+ /* the pending lock may have been withdrawn due to a
+ * signal */
+ if (list_entry(vnode->pending_locks.next,
+ struct file_lock, fl_u.afs.link) == fl) {
+ fl->fl_u.afs.state = ret;
+ if (ret == AFS_LOCK_GRANTED)
+ afs_grant_locks(vnode, fl);
+ else
+ list_del_init(&fl->fl_u.afs.link);
+ wake_up(&fl->fl_wait);
+ spin_unlock(&vnode->lock);
+ } else {
+ _debug("withdrawn");
+ clear_bit(AFS_VNODE_READLOCKED, &vnode->flags);
+ clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
+ spin_unlock(&vnode->lock);
+ afs_vnode_release_lock(vnode, key);
+ if (!list_empty(&vnode->pending_locks))
+ afs_lock_may_be_available(vnode);
+ }
+ break;
+ }
+ key_put(key);
+ _leave(" [pend]");
+ return;
+ }
+
+ /* looks like the lock request was withdrawn on a signal */
+ spin_unlock(&vnode->lock);
+ _leave(" [no locks]");
+}
+
+/*
+ * pass responsibility for the unlocking of a vnode on the server to the
+ * manager thread, lest a pending signal in the calling thread interrupt
+ * AF_RXRPC
+ * - the caller must hold the vnode lock
+ */
+static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
+{
+ cancel_delayed_work(&vnode->lock_work);
+ if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) &&
+ !test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags))
+ BUG();
+ if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags))
+ BUG();
+ vnode->unlock_key = key_get(key);
+ afs_lock_may_be_available(vnode);
+}
+
+/*
+ * request a lock on a file on the server
+ */
+static int afs_do_setlk(struct file *file, struct file_lock *fl)
+{
+ struct inode *inode = file_inode(file);
+ struct afs_vnode *vnode = AFS_FS_I(inode);
+ afs_lock_type_t type;
+ struct key *key = file->private_data;
+ int ret;
+
+ _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
+
+ /* only whole-file locks are supported */
+ if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
+ return -EINVAL;
+
+ ret = afs_init_lock_manager();
+ if (ret < 0)
+ return ret;
+
+ fl->fl_ops = &afs_lock_ops;
+ INIT_LIST_HEAD(&fl->fl_u.afs.link);
+ fl->fl_u.afs.state = AFS_LOCK_PENDING;
+
+ type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
+
+ spin_lock(&inode->i_lock);
+
+ /* make sure we've got a callback on this file and that our view of the
+ * data version is up to date */
+ ret = afs_vnode_fetch_status(vnode, NULL, key);
+ if (ret < 0)
+ goto error;
+
+ if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
+ ret = -EAGAIN;
+ goto error;
+ }
+
+ spin_lock(&vnode->lock);
+
+ /* if we've already got a readlock on the server then we can instantly
+ * grant another readlock, irrespective of whether there are any
+ * pending writelocks */
+ if (type == AFS_LOCK_READ &&
+ vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
+ _debug("instant readlock");
+ ASSERTCMP(vnode->flags &
+ ((1 << AFS_VNODE_LOCKING) |
+ (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
+ ASSERT(!list_empty(&vnode->granted_locks));
+ goto sharing_existing_lock;
+ }
+
+ /* if there's no-one else with a lock on this vnode, then we need to
+ * ask the server for a lock */
+ if (list_empty(&vnode->pending_locks) &&
+ list_empty(&vnode->granted_locks)) {
+ _debug("not locked");
+ ASSERTCMP(vnode->flags &
+ ((1 << AFS_VNODE_LOCKING) |
+ (1 << AFS_VNODE_READLOCKED) |
+ (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
+ list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
+ set_bit(AFS_VNODE_LOCKING, &vnode->flags);
+ spin_unlock(&vnode->lock);
+
+ ret = afs_vnode_set_lock(vnode, key, type);
+ clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
+ switch (ret) {
+ case 0:
+ _debug("acquired");
+ goto acquired_server_lock;
+ case -EWOULDBLOCK:
+ _debug("would block");
+ spin_lock(&vnode->lock);
+ ASSERT(list_empty(&vnode->granted_locks));
+ ASSERTCMP(vnode->pending_locks.next, ==,
+ &fl->fl_u.afs.link);
+ goto wait;
+ default:
+ spin_lock(&vnode->lock);
+ list_del_init(&fl->fl_u.afs.link);
+ spin_unlock(&vnode->lock);
+ goto error;
+ }
+ }
+
+ /* otherwise, we need to wait for a local lock to become available */
+ _debug("wait local");
+ list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
+wait:
+ if (!(fl->fl_flags & FL_SLEEP)) {
+ _debug("noblock");
+ ret = -EAGAIN;
+ goto abort_attempt;
+ }
+ spin_unlock(&vnode->lock);
+
+ /* now we need to sleep and wait for the lock manager thread to get the
+ * lock from the server */
+ _debug("sleep");
+ ret = wait_event_interruptible(fl->fl_wait,
+ fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
+ if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
+ ret = fl->fl_u.afs.state;
+ if (ret < 0)
+ goto error;
+ spin_lock(&vnode->lock);
+ goto given_lock;
+ }
+
+ /* we were interrupted, but someone may still be in the throes of
+ * giving us the lock */
+ _debug("intr");
+ ASSERTCMP(ret, ==, -ERESTARTSYS);
+
+ spin_lock(&vnode->lock);
+ if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
+ ret = fl->fl_u.afs.state;
+ if (ret < 0) {
+ spin_unlock(&vnode->lock);
+ goto error;
+ }
+ goto given_lock;
+ }
+
+abort_attempt:
+ /* we aren't going to get the lock, either because we're unwilling to
+ * wait, or because some signal happened */
+ _debug("abort");
+ if (list_empty(&vnode->granted_locks) &&
+ vnode->pending_locks.next == &fl->fl_u.afs.link) {
+ if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
+ /* kick the next pending lock into having a go */
+ list_del_init(&fl->fl_u.afs.link);
+ afs_lock_may_be_available(vnode);
+ }
+ } else {
+ list_del_init(&fl->fl_u.afs.link);
+ }
+ spin_unlock(&vnode->lock);
+ goto error;
+
+acquired_server_lock:
+ /* we've acquired a server lock, but it needs to be renewed after 5
+ * mins */
+ spin_lock(&vnode->lock);
+ afs_schedule_lock_extension(vnode);
+ if (type == AFS_LOCK_READ)
+ set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
+ else
+ set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
+sharing_existing_lock:
+ /* the lock has been granted as far as we're concerned... */
+ fl->fl_u.afs.state = AFS_LOCK_GRANTED;
+ list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
+given_lock:
+ /* ... but we do still need to get the VFS's blessing */
+ ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
+ ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
+ (1 << AFS_VNODE_WRITELOCKED))) != 0);
+ ret = posix_lock_file(file, fl, NULL);
+ if (ret < 0)
+ goto vfs_rejected_lock;
+ spin_unlock(&vnode->lock);
+
+ /* again, make sure we've got a callback on this file and, again, make
+ * sure that our view of the data version is up to date (we ignore
+ * errors incurred here and deal with the consequences elsewhere) */
+ afs_vnode_fetch_status(vnode, NULL, key);
+
+error:
+ spin_unlock(&inode->i_lock);
+ _leave(" = %d", ret);
+ return ret;
+
+vfs_rejected_lock:
+ /* the VFS rejected the lock we just obtained, so we have to discard
+ * what we just got */
+ _debug("vfs refused %d", ret);
+ list_del_init(&fl->fl_u.afs.link);
+ if (list_empty(&vnode->granted_locks))
+ afs_defer_unlock(vnode, key);
+ goto abort_attempt;
+}
+
+/*
+ * unlock on a file on the server
+ */
+static int afs_do_unlk(struct file *file, struct file_lock *fl)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
+ struct key *key = file->private_data;
+ int ret;
+
+ _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
+
+ /* only whole-file unlocks are supported */
+ if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
+ return -EINVAL;
+
+ fl->fl_ops = &afs_lock_ops;
+ INIT_LIST_HEAD(&fl->fl_u.afs.link);
+ fl->fl_u.afs.state = AFS_LOCK_PENDING;
+
+ spin_lock(&vnode->lock);
+ ret = posix_lock_file(file, fl, NULL);
+ if (ret < 0) {
+ spin_unlock(&vnode->lock);
+ _leave(" = %d [vfs]", ret);
+ return ret;
+ }
+
+ /* discard the server lock only if all granted locks are gone */
+ if (list_empty(&vnode->granted_locks))
+ afs_defer_unlock(vnode, key);
+ spin_unlock(&vnode->lock);
+ _leave(" = 0");
+ return 0;
+}
+
+/*
+ * return information about a lock we currently hold, if indeed we hold one
+ */
+static int afs_do_getlk(struct file *file, struct file_lock *fl)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
+ struct key *key = file->private_data;
+ int ret, lock_count;
+
+ _enter("");
+
+ fl->fl_type = F_UNLCK;
+
+ mutex_lock(&vnode->vfs_inode.i_mutex);
+
+ /* check local lock records first */
+ ret = 0;
+ posix_test_lock(file, fl);
+ if (fl->fl_type == F_UNLCK) {
+ /* no local locks; consult the server */
+ ret = afs_vnode_fetch_status(vnode, NULL, key);
+ if (ret < 0)
+ goto error;
+ lock_count = vnode->status.lock_count;
+ if (lock_count) {
+ if (lock_count > 0)
+ fl->fl_type = F_RDLCK;
+ else
+ fl->fl_type = F_WRLCK;
+ fl->fl_start = 0;
+ fl->fl_end = OFFSET_MAX;
+ }
+ }
+
+error:
+ mutex_unlock(&vnode->vfs_inode.i_mutex);
+ _leave(" = %d [%hd]", ret, fl->fl_type);
+ return ret;
+}
+
+/*
+ * manage POSIX locks on a file
+ */
+int afs_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+ _enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
+ vnode->fid.vid, vnode->fid.vnode, cmd,
+ fl->fl_type, fl->fl_flags,
+ (long long) fl->fl_start, (long long) fl->fl_end);
+
+ /* AFS doesn't support mandatory locks */
+ if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
+ return -ENOLCK;
+
+ if (IS_GETLK(cmd))
+ return afs_do_getlk(file, fl);
+ if (fl->fl_type == F_UNLCK)
+ return afs_do_unlk(file, fl);
+ return afs_do_setlk(file, fl);
+}
+
+/*
+ * manage FLOCK locks on a file
+ */
+int afs_flock(struct file *file, int cmd, struct file_lock *fl)
+{
+ struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+ _enter("{%x:%u},%d,{t=%x,fl=%x}",
+ vnode->fid.vid, vnode->fid.vnode, cmd,
+ fl->fl_type, fl->fl_flags);
+
+ /*
+ * No BSD flocks over NFS allowed.
+ * Note: we could try to fake a POSIX lock request here by
+ * using ((u32) filp | 0x80000000) or some such as the pid.
+ * Not sure whether that would be unique, though, or whether
+ * that would break in other places.
+ */
+ if (!(fl->fl_flags & FL_FLOCK))
+ return -ENOLCK;
+
+ /* we're simulating flock() locks using posix locks on the server */
+ if (fl->fl_type == F_UNLCK)
+ return afs_do_unlk(file, fl);
+ return afs_do_setlk(file, fl);
+}
+
+/*
+ * the POSIX lock management core VFS code copies the lock record and adds the
+ * copy into its own list, so we need to add that copy to the vnode's lock
+ * queue in the same place as the original (which will be deleted shortly
+ * after)
+ */
+static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
+{
+ _enter("");
+
+ list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
+}
+
+/*
+ * need to remove this lock from the vnode queue when it's removed from the
+ * VFS's list
+ */
+static void afs_fl_release_private(struct file_lock *fl)
+{
+ _enter("");
+
+ list_del_init(&fl->fl_u.afs.link);
+}
Code Review / kvmfornfv.git / blobdiff