mirror of https://gitee.com/openkylin/linux.git
afs: Further fix file locking
Further fix the file locking in the afs filesystem client in a number of
ways, including:
(1) Don't submit the operation to obtain a lock from the server in a work
queue context, but rather do it in the process context of whoever
issued the requesting system call.
(2) The owner of the file_lock struct at the front of the pending_locks
queue now owns right to talk to the server.
(3) Write locks can be instantly granted if they don't overlap with any
other locks *and* we have a write lock on the server.
(4) In the event of an authentication/permission error, all other matching
pending locks requests are also immediately aborted.
(5) Properly use VFS core locks_lock_file_wait() to distribute the server
lock amongst local client locks, including waiting for the lock to
become available.
Test with:
sqlite3 /afs/.../scratch/billings.sqlite <<EOF
CREATE TABLE hosts (
hostname varchar(80),
shorthost varchar(80),
room varchar(30),
building varchar(30),
PRIMARY KEY(shorthost)
);
EOF
With the version of sqlite3 that I have, this should fail consistently with
EAGAIN, whether or not the program is straced (which introduces some delays
between lock syscalls).
Fixes: 0fafdc9f88 ("afs: Fix file locking")
Reported-by: Jonathan Billings <jsbillin@umich.edu>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
parent
68ce801ffd
commit
4be5975aea
396
fs/afs/flock.c
396
fs/afs/flock.c
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@ -13,9 +13,11 @@
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#define AFS_LOCK_GRANTED 0
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#define AFS_LOCK_PENDING 1
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#define AFS_LOCK_YOUR_TRY 2
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struct workqueue_struct *afs_lock_manager;
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static void afs_next_locker(struct afs_vnode *vnode, int error);
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static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
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static void afs_fl_release_private(struct file_lock *fl);
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@ -24,6 +26,12 @@ static const struct file_lock_operations afs_lock_ops = {
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.fl_release_private = afs_fl_release_private,
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};
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static inline void afs_set_lock_state(struct afs_vnode *vnode, enum afs_lock_state state)
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{
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_debug("STATE %u -> %u", vnode->lock_state, state);
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vnode->lock_state = state;
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}
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/*
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* if the callback is broken on this vnode, then the lock may now be available
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*/
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@ -31,7 +39,13 @@ void afs_lock_may_be_available(struct afs_vnode *vnode)
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{
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_enter("{%llx:%llu}", vnode->fid.vid, vnode->fid.vnode);
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queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
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if (vnode->lock_state != AFS_VNODE_LOCK_WAITING_FOR_CB)
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return;
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spin_lock(&vnode->lock);
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if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
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afs_next_locker(vnode, 0);
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spin_unlock(&vnode->lock);
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}
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/*
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@ -75,24 +89,67 @@ void afs_lock_op_done(struct afs_call *call)
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* first lock in the queue is itself a readlock)
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* - the caller must hold the vnode lock
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*/
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static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl)
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static void afs_grant_locks(struct afs_vnode *vnode)
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{
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struct file_lock *p, *_p;
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bool exclusive = (vnode->lock_type == AFS_LOCK_WRITE);
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list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
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if (fl->fl_type == F_RDLCK) {
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list_for_each_entry_safe(p, _p, &vnode->pending_locks,
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fl_u.afs.link) {
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if (p->fl_type == F_RDLCK) {
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p->fl_u.afs.state = AFS_LOCK_GRANTED;
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list_move_tail(&p->fl_u.afs.link,
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&vnode->granted_locks);
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wake_up(&p->fl_wait);
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}
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}
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list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
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if (!exclusive && p->fl_type == F_WRLCK)
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continue;
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list_move_tail(&p->fl_u.afs.link, &vnode->granted_locks);
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p->fl_u.afs.state = AFS_LOCK_GRANTED;
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wake_up(&p->fl_wait);
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}
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}
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/*
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* If an error is specified, reject every pending lock that matches the
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* authentication and type of the lock we failed to get. If there are any
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* remaining lockers, try to wake up one of them to have a go.
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*/
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static void afs_next_locker(struct afs_vnode *vnode, int error)
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{
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struct file_lock *p, *_p, *next = NULL;
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struct key *key = vnode->lock_key;
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unsigned int fl_type = F_RDLCK;
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_enter("");
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if (vnode->lock_type == AFS_LOCK_WRITE)
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fl_type = F_WRLCK;
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list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
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if (error &&
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p->fl_type == fl_type &&
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afs_file_key(p->fl_file) == key) {
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list_del_init(&p->fl_u.afs.link);
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p->fl_u.afs.state = error;
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wake_up(&p->fl_wait);
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}
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/* Select the next locker to hand off to. */
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if (next &&
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(next->fl_type == F_WRLCK || p->fl_type == F_RDLCK))
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continue;
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next = p;
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}
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vnode->lock_key = NULL;
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key_put(key);
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if (next) {
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
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next->fl_u.afs.state = AFS_LOCK_YOUR_TRY;
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wake_up(&next->fl_wait);
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} else {
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_NONE);
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}
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_leave("");
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}
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/*
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* Get a lock on a file
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*/
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@ -196,8 +253,6 @@ void afs_lock_work(struct work_struct *work)
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{
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struct afs_vnode *vnode =
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container_of(work, struct afs_vnode, lock_work.work);
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struct file_lock *fl, *next;
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afs_lock_type_t type;
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struct key *key;
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int ret;
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@ -210,7 +265,7 @@ void afs_lock_work(struct work_struct *work)
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switch (vnode->lock_state) {
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case AFS_VNODE_LOCK_NEED_UNLOCK:
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_debug("unlock");
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vnode->lock_state = AFS_VNODE_LOCK_UNLOCKING;
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_UNLOCKING);
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spin_unlock(&vnode->lock);
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/* attempt to release the server lock; if it fails, we just
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@ -222,22 +277,9 @@ void afs_lock_work(struct work_struct *work)
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vnode->fid.vid, vnode->fid.vnode, ret);
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spin_lock(&vnode->lock);
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key_put(vnode->lock_key);
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vnode->lock_key = NULL;
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vnode->lock_state = AFS_VNODE_LOCK_NONE;
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if (list_empty(&vnode->pending_locks)) {
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spin_unlock(&vnode->lock);
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return;
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}
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/* The new front of the queue now owns the state variables. */
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next = list_entry(vnode->pending_locks.next,
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struct file_lock, fl_u.afs.link);
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vnode->lock_key = key_get(afs_file_key(next->fl_file));
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vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
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vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
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goto again;
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afs_next_locker(vnode, 0);
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spin_unlock(&vnode->lock);
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return;
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/* If we've already got a lock, then it must be time to extend that
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* lock as AFS locks time out after 5 minutes.
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@ -248,7 +290,7 @@ void afs_lock_work(struct work_struct *work)
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ASSERT(!list_empty(&vnode->granted_locks));
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key = key_get(vnode->lock_key);
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vnode->lock_state = AFS_VNODE_LOCK_EXTENDING;
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_EXTENDING);
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spin_unlock(&vnode->lock);
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ret = afs_extend_lock(vnode, key); /* RPC */
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@ -262,72 +304,26 @@ void afs_lock_work(struct work_struct *work)
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if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
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goto again;
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vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
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if (ret == 0)
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afs_schedule_lock_extension(vnode);
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else
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if (ret != 0)
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queue_delayed_work(afs_lock_manager, &vnode->lock_work,
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HZ * 10);
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spin_unlock(&vnode->lock);
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_leave(" [ext]");
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return;
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/* If we don't have a granted lock, then we must've been called
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* back by the server, and so if might be possible to get a
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* lock we're currently waiting for.
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*/
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/* If we're waiting for a callback to indicate lock release, we can't
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* actually rely on this, so need to recheck at regular intervals. The
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* problem is that the server might not notify us if the lock just
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* expires (say because a client died) rather than being explicitly
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* released.
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*/
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case AFS_VNODE_LOCK_WAITING_FOR_CB:
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_debug("get");
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key = key_get(vnode->lock_key);
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type = vnode->lock_type;
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vnode->lock_state = AFS_VNODE_LOCK_SETTING;
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_debug("retry");
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afs_next_locker(vnode, 0);
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spin_unlock(&vnode->lock);
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ret = afs_set_lock(vnode, key, type); /* RPC */
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key_put(key);
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spin_lock(&vnode->lock);
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switch (ret) {
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case -EWOULDBLOCK:
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_debug("blocked");
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break;
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case 0:
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_debug("acquired");
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vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
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/* Fall through */
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default:
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/* Pass the lock or the error onto the first locker in
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* the list - if they're looking for this type of lock.
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* If they're not, we assume that whoever asked for it
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* took a signal.
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*/
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if (list_empty(&vnode->pending_locks)) {
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_debug("withdrawn");
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vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
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goto again;
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}
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fl = list_entry(vnode->pending_locks.next,
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struct file_lock, fl_u.afs.link);
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type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
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if (vnode->lock_type != type) {
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_debug("changed");
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vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
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goto again;
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}
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fl->fl_u.afs.state = ret;
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if (ret == 0)
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afs_grant_locks(vnode, fl);
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else
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list_del_init(&fl->fl_u.afs.link);
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wake_up(&fl->fl_wait);
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spin_unlock(&vnode->lock);
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_leave(" [granted]");
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return;
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}
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return;
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default:
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/* Looks like a lock request was withdrawn. */
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@ -345,14 +341,15 @@ void afs_lock_work(struct work_struct *work)
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*/
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static void afs_defer_unlock(struct afs_vnode *vnode)
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{
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_enter("");
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_enter("%u", vnode->lock_state);
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if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
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vnode->lock_state == AFS_VNODE_LOCK_EXTENDING) {
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if (list_empty(&vnode->granted_locks) &&
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(vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
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vnode->lock_state == AFS_VNODE_LOCK_EXTENDING)) {
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cancel_delayed_work(&vnode->lock_work);
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vnode->lock_state = AFS_VNODE_LOCK_NEED_UNLOCK;
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afs_lock_may_be_available(vnode);
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_NEED_UNLOCK);
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queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
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}
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}
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@ -401,50 +398,6 @@ static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key,
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return 0;
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}
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/*
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* Remove the front runner from the pending queue.
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* - The caller must hold vnode->lock.
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*/
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static void afs_dequeue_lock(struct afs_vnode *vnode, struct file_lock *fl)
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{
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struct file_lock *next;
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_enter("");
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/* ->lock_type, ->lock_key and ->lock_state only belong to this
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* file_lock if we're at the front of the pending queue or if we have
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* the lock granted or if the lock_state is NEED_UNLOCK or UNLOCKING.
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*/
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if (vnode->granted_locks.next == &fl->fl_u.afs.link &&
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vnode->granted_locks.prev == &fl->fl_u.afs.link) {
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list_del_init(&fl->fl_u.afs.link);
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afs_defer_unlock(vnode);
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return;
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}
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if (!list_empty(&vnode->granted_locks) ||
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vnode->pending_locks.next != &fl->fl_u.afs.link) {
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list_del_init(&fl->fl_u.afs.link);
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return;
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}
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list_del_init(&fl->fl_u.afs.link);
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key_put(vnode->lock_key);
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vnode->lock_key = NULL;
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vnode->lock_state = AFS_VNODE_LOCK_NONE;
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if (list_empty(&vnode->pending_locks))
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return;
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/* The new front of the queue now owns the state variables. */
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next = list_entry(vnode->pending_locks.next,
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struct file_lock, fl_u.afs.link);
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vnode->lock_key = key_get(afs_file_key(next->fl_file));
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vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
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vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
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afs_lock_may_be_available(vnode);
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}
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/*
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* request a lock on a file on the server
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*/
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@ -469,44 +422,66 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
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return ret;
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spin_lock(&vnode->lock);
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/* If we've already got a readlock on the server then we instantly
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* grant another readlock, irrespective of whether there are any
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* pending writelocks.
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*/
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if (type == AFS_LOCK_READ &&
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vnode->lock_state == AFS_VNODE_LOCK_GRANTED &&
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vnode->lock_type == AFS_LOCK_READ) {
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_debug("instant readlock");
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ASSERT(!list_empty(&vnode->granted_locks));
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goto share_existing_lock;
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}
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list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
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/* If we've already got a lock on the server then try to move to having
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* the VFS grant the requested lock. Note that this means that other
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* clients may get starved out.
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*/
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_debug("try %u", vnode->lock_state);
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if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED) {
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if (type == AFS_LOCK_READ) {
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_debug("instant readlock");
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list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
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fl->fl_u.afs.state = AFS_LOCK_GRANTED;
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goto vnode_is_locked_u;
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}
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if (vnode->lock_type == AFS_LOCK_WRITE) {
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_debug("instant writelock");
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list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
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fl->fl_u.afs.state = AFS_LOCK_GRANTED;
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goto vnode_is_locked_u;
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}
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}
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if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
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goto need_to_wait;
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try_to_lock:
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/* We don't have a lock on this vnode and we aren't currently waiting
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* for one either, so ask the server for a lock.
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*
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* Note that we need to be careful if we get interrupted by a signal
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* after dispatching the request as we may still get the lock, even
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* though we don't wait for the reply (it's not too bad a problem - the
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* lock will expire in 10 mins anyway).
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* lock will expire in 5 mins anyway).
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*/
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_debug("not locked");
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vnode->lock_key = key_get(key);
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vnode->lock_type = type;
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vnode->lock_state = AFS_VNODE_LOCK_SETTING;
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afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
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spin_unlock(&vnode->lock);
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ret = afs_set_lock(vnode, key, type); /* RPC */
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spin_lock(&vnode->lock);
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switch (ret) {
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case -EKEYREJECTED:
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case -EKEYEXPIRED:
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case -EKEYREVOKED:
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case -EPERM:
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case -EACCES:
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fl->fl_u.afs.state = ret;
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list_del_init(&fl->fl_u.afs.link);
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afs_next_locker(vnode, ret);
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goto error_unlock;
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default:
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goto abort_attempt;
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fl->fl_u.afs.state = ret;
|
||||
list_del_init(&fl->fl_u.afs.link);
|
||||
afs_next_locker(vnode, 0);
|
||||
goto error_unlock;
|
||||
|
||||
case -EWOULDBLOCK:
|
||||
/* The server doesn't have a lock-waiting queue, so the client
|
||||
|
|
@ -516,29 +491,23 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
|
|||
_debug("would block");
|
||||
ASSERT(list_empty(&vnode->granted_locks));
|
||||
ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link);
|
||||
vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
|
||||
goto need_to_wait;
|
||||
goto lock_is_contended;
|
||||
|
||||
case 0:
|
||||
_debug("acquired");
|
||||
break;
|
||||
afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
|
||||
afs_grant_locks(vnode);
|
||||
goto vnode_is_locked_u;
|
||||
}
|
||||
|
||||
/* we've acquired a server lock, but it needs to be renewed after 5
|
||||
* mins */
|
||||
vnode->lock_state = AFS_VNODE_LOCK_GRANTED;
|
||||
afs_schedule_lock_extension(vnode);
|
||||
|
||||
share_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 */
|
||||
vnode_is_locked_u:
|
||||
spin_unlock(&vnode->lock);
|
||||
vnode_is_locked:
|
||||
/* the lock has been granted by the server... */
|
||||
ASSERTCMP(fl->fl_u.afs.state, ==, AFS_LOCK_GRANTED);
|
||||
|
||||
ret = posix_lock_file(file, fl, NULL);
|
||||
/* ... but the VFS still needs to distribute access on this client. */
|
||||
ret = locks_lock_file_wait(file, fl);
|
||||
if (ret < 0)
|
||||
goto vfs_rejected_lock;
|
||||
|
||||
|
|
@ -550,38 +519,61 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
|
|||
_leave(" = 0");
|
||||
return 0;
|
||||
|
||||
lock_is_contended:
|
||||
if (!(fl->fl_flags & FL_SLEEP)) {
|
||||
list_del_init(&fl->fl_u.afs.link);
|
||||
afs_next_locker(vnode, 0);
|
||||
ret = -EAGAIN;
|
||||
goto error_unlock;
|
||||
}
|
||||
|
||||
afs_set_lock_state(vnode, AFS_VNODE_LOCK_WAITING_FOR_CB);
|
||||
queue_delayed_work(afs_lock_manager, &vnode->lock_work, HZ * 5);
|
||||
|
||||
need_to_wait:
|
||||
/* We're going to have to wait. Either this client doesn't have a lock
|
||||
* on the server yet and we need to wait for a callback to occur, or
|
||||
* the client does have a lock on the server, but it belongs to some
|
||||
* other process(es) and is incompatible with the lock we want.
|
||||
* the client does have a lock on the server, but it's shared and we
|
||||
* need an exclusive lock.
|
||||
*/
|
||||
ret = -EAGAIN;
|
||||
if (fl->fl_flags & FL_SLEEP) {
|
||||
spin_unlock(&vnode->lock);
|
||||
spin_unlock(&vnode->lock);
|
||||
|
||||
_debug("sleep");
|
||||
ret = wait_event_interruptible(fl->fl_wait,
|
||||
fl->fl_u.afs.state != AFS_LOCK_PENDING);
|
||||
_debug("sleep");
|
||||
ret = wait_event_interruptible(fl->fl_wait,
|
||||
fl->fl_u.afs.state != AFS_LOCK_PENDING);
|
||||
_debug("wait = %d", ret);
|
||||
|
||||
if (fl->fl_u.afs.state >= 0 && fl->fl_u.afs.state != AFS_LOCK_GRANTED) {
|
||||
spin_lock(&vnode->lock);
|
||||
|
||||
switch (fl->fl_u.afs.state) {
|
||||
case AFS_LOCK_YOUR_TRY:
|
||||
fl->fl_u.afs.state = AFS_LOCK_PENDING;
|
||||
goto try_to_lock;
|
||||
case AFS_LOCK_PENDING:
|
||||
if (ret > 0) {
|
||||
/* We need to retry the lock. We may not be
|
||||
* notified by the server if it just expired
|
||||
* rather than being released.
|
||||
*/
|
||||
ASSERTCMP(vnode->lock_state, ==, AFS_VNODE_LOCK_WAITING_FOR_CB);
|
||||
afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
|
||||
fl->fl_u.afs.state = AFS_LOCK_PENDING;
|
||||
goto try_to_lock;
|
||||
}
|
||||
goto error_unlock;
|
||||
case AFS_LOCK_GRANTED:
|
||||
default:
|
||||
break;
|
||||
}
|
||||
|
||||
spin_unlock(&vnode->lock);
|
||||
}
|
||||
|
||||
if (fl->fl_u.afs.state == AFS_LOCK_GRANTED)
|
||||
goto given_lock;
|
||||
if (fl->fl_u.afs.state < 0)
|
||||
ret = fl->fl_u.afs.state;
|
||||
|
||||
abort_attempt:
|
||||
/* we aren't going to get the lock, either because we're unwilling to
|
||||
* wait, or because some signal happened */
|
||||
_debug("abort");
|
||||
afs_dequeue_lock(vnode, fl);
|
||||
|
||||
error_unlock:
|
||||
spin_unlock(&vnode->lock);
|
||||
_leave(" = %d", ret);
|
||||
return ret;
|
||||
goto vnode_is_locked;
|
||||
ret = fl->fl_u.afs.state;
|
||||
goto error;
|
||||
|
||||
vfs_rejected_lock:
|
||||
/* The VFS rejected the lock we just obtained, so we have to discard
|
||||
|
|
@ -591,9 +583,13 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
|
|||
_debug("vfs refused %d", ret);
|
||||
spin_lock(&vnode->lock);
|
||||
list_del_init(&fl->fl_u.afs.link);
|
||||
if (list_empty(&vnode->granted_locks))
|
||||
afs_defer_unlock(vnode);
|
||||
goto error_unlock;
|
||||
afs_defer_unlock(vnode);
|
||||
|
||||
error_unlock:
|
||||
spin_unlock(&vnode->lock);
|
||||
error:
|
||||
_leave(" = %d", ret);
|
||||
return ret;
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
@ -609,7 +605,7 @@ static int afs_do_unlk(struct file *file, struct file_lock *fl)
|
|||
/* Flush all pending writes before doing anything with locks. */
|
||||
vfs_fsync(file, 0);
|
||||
|
||||
ret = posix_lock_file(file, fl, NULL);
|
||||
ret = locks_lock_file_wait(file, fl);
|
||||
_leave(" = %d [%u]", ret, vnode->lock_state);
|
||||
return ret;
|
||||
}
|
||||
|
|
@ -731,7 +727,11 @@ static void afs_fl_release_private(struct file_lock *fl)
|
|||
_enter("");
|
||||
|
||||
spin_lock(&vnode->lock);
|
||||
afs_dequeue_lock(vnode, fl);
|
||||
|
||||
list_del_init(&fl->fl_u.afs.link);
|
||||
if (list_empty(&vnode->granted_locks))
|
||||
afs_defer_unlock(vnode);
|
||||
|
||||
_debug("state %u for %p", vnode->lock_state, vnode);
|
||||
spin_unlock(&vnode->lock);
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue