patch-2.1.32 linux/fs/lockd/svclock.c

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diff -u --recursive --new-file v2.1.31/linux/fs/lockd/svclock.c linux/fs/lockd/svclock.c
@@ -0,0 +1,620 @@
+/*
+ * linux/fs/lockd/svclock.c
+ *
+ * Handling of server-side locks, mostly of the blocked variety.
+ * This is the ugliest part of lockd because we tread on very thin ice.
+ * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
+ * IMNSHO introducing the grant callback into the NLM protocol was one
+ * of the worst ideas Sun ever had. Except maybe for the idea of doing
+ * NFS file locking at all.
+ *
+ * I'm trying hard to avoid race conditions by protecting most accesses
+ * to a file's list of blocked locks through a semaphore. The global
+ * list of blocked locks is not protected in this fashion however.
+ * Therefore, some functions (such as the RPC callback for the async grant
+ * call) move blocked locks towards the head of the list *while some other
+ * process might be traversing it*. This should not be a problem in
+ * practice, because this will only cause functions traversing the list
+ * to visit some blocks twice.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/svc.h>
+#include <linux/lockd/nlm.h>
+#include <linux/lockd/lockd.h>
+
+
+#define NLMDBG_FACILITY		NLMDBG_SVCLOCK
+
+static void	nlmsvc_insert_block(struct nlm_block *block, unsigned long);
+static int	nlmsvc_remove_block(struct nlm_block *block);
+static void	nlmsvc_grant_callback(struct rpc_task *task);
+static void	nlmsvc_notify_blocked(struct file_lock *);
+
+/*
+ * The list of blocked locks to retry
+ */
+static struct nlm_block *	nlm_blocked = NULL;
+
+/*
+ * Insert a blocked lock into the global list
+ */
+static void
+nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
+{
+	struct nlm_block **bp, *b;
+
+	dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
+	if (block->b_queued)
+		nlmsvc_remove_block(block);
+	for (bp = &nlm_blocked; (b = *bp); bp = &b->b_next)
+		if (when < b->b_when)
+			break;
+
+	block->b_queued = 1;
+	block->b_when = when;
+	block->b_next = b;
+	*bp = block;
+}
+
+/*
+ * Remove a block from the global list
+ */
+static int
+nlmsvc_remove_block(struct nlm_block *block)
+{
+	struct nlm_block **bp, *b;
+
+	if (!block->b_queued)
+		return 1;
+	for (bp = &nlm_blocked; (b = *bp); bp = &b->b_next) {
+		if (b == block) {
+			*bp = block->b_next;
+			block->b_queued = 0;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Find a block for a given lock and optionally remove it from
+ * the list.
+ */
+static struct nlm_block *
+nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove)
+{
+	struct nlm_block	**head, *block;
+	struct file_lock	*fl;
+
+	dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %ld-%ld ty=%d\n",
+				file, lock->fl.fl_pid, lock->fl.fl_start,
+				lock->fl.fl_end, lock->fl.fl_type);
+	for (head = &nlm_blocked; (block = *head); head = &block->b_next) {
+		fl = &block->b_call.a_args.lock.fl;
+		dprintk("       check f=%p pd=%d %ld-%ld ty=%d\n",
+				block->b_file, fl->fl_pid, fl->fl_start,
+				fl->fl_end, fl->fl_type);
+		if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
+			if (remove)
+				*head = block->b_next;
+			return block;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Find a block with a given NLM cookie.
+ */
+static inline struct nlm_block *
+nlmsvc_find_block(u32 cookie)
+{
+	struct nlm_block *block;
+
+	for (block = nlm_blocked; block; block = block->b_next) {
+		if (block->b_call.a_args.cookie == cookie)
+			break;
+	}
+
+	return block;
+}
+
+/*
+ * Create a block and initialize it.
+ *
+ * Note: we explicitly set the cookie of the grant reply to that of
+ * the blocked lock request. The spec explicitly mentions that the client
+ * should _not_ rely on the callback containing the same cookie as the
+ * request, but (as I found out later) that's because some implementations
+ * do just this. Never mind the standards comittees, they support our
+ * logging industries.
+ */
+static inline struct nlm_block *
+nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
+				struct nlm_lock *lock, u32 cookie)
+{
+	struct nlm_block	*block;
+	struct nlm_host		*host;
+	struct nlm_rqst		*call;
+
+	/* Create host handle for callback */
+	host = nlmclnt_lookup_host(&rqstp->rq_addr,
+				rqstp->rq_prot, rqstp->rq_vers);
+	if (host == NULL)
+		return NULL;
+
+	/* Allocate memory for block, and initialize arguments */
+	if (!(block = (struct nlm_block *) kmalloc(sizeof(*block), GFP_KERNEL)))
+		goto failed;
+	memset(block, 0, sizeof(*block));
+
+	/* Set notifier function for VFS, and init args */
+	lock->fl.fl_notify = nlmsvc_notify_blocked;
+	if (!nlmclnt_setgrantargs(&block->b_call, lock)) {
+		kfree(block);
+		goto failed;
+	}
+	block->b_call.a_args.cookie = cookie;	/* see above */
+
+	dprintk("lockd: created block %p...\n", block);
+
+	/* Create and initialize the block */
+	block->b_daemon = rqstp->rq_server;
+	block->b_host   = host;
+	block->b_file   = file;
+
+	/* Add to file's list of blocks */
+	block->b_fnext  = file->f_blocks;
+	file->f_blocks  = block;
+
+	/* Set up RPC arguments for callback */
+	call = &block->b_call;
+	call->a_host    = host;
+	call->a_flags   = RPC_TASK_ASYNC;
+
+	return block;
+
+failed:
+	nlm_release_host(host);
+	return NULL;
+}
+
+/*
+ * Delete a block. If the lock was cancelled or the grant callback
+ * failed, unlock is set to 1.
+ * It is the caller's responsibility to check whether the file
+ * can be closed hereafter.
+ */
+static void
+nlmsvc_delete_block(struct nlm_block *block, int unlock)
+{
+	struct file_lock	*fl = &block->b_call.a_args.lock.fl;
+	struct nlm_file		*file = block->b_file;
+	struct nlm_block	**bp;
+
+	dprintk("lockd: deleting block %p...\n", block);
+
+	/* Remove block from list */
+	nlmsvc_remove_block(block);
+
+	/* If granted, unlock it, else remove from inode block list */
+	if (unlock && block->b_granted) {
+		dprintk("lockd: deleting granted lock\n");
+		fl->fl_type = F_UNLCK;
+		posix_lock_file(&block->b_file->f_file, fl, 0);
+		block->b_granted = 0;
+	} else {
+		dprintk("lockd: unblocking blocked lock\n");
+		posix_unblock_lock(fl);
+	}
+
+	/* If the block is in the middle of a GRANT callback,
+	 * don't kill it yet. */
+	if (block->b_incall) {
+		nlmsvc_insert_block(block, NLM_NEVER);
+		block->b_done = 1;
+		return;
+	}
+
+	/* Remove block from file's list of blocks */
+	for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
+		if (*bp == block) {
+			*bp = block->b_fnext;
+			break;
+		}
+	}
+
+	if (block->b_host)
+		nlm_release_host(block->b_host);
+	nlmclnt_freegrantargs(&block->b_call);
+	kfree(block);
+}
+
+/*
+ * Loop over all blocks and perform the action specified.
+ * (NLM_ACT_CHECK handled by nlmsvc_inspect_file).
+ */
+int
+nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
+{
+	struct nlm_block	*block, *next;
+
+	down(&file->f_sema);
+	for (block = file->f_blocks; block; block = next) {
+		next = block->b_fnext;
+		if (action == NLM_ACT_MARK)
+			block->b_host->h_inuse = 1;
+		else if (action == NLM_ACT_UNLOCK) {
+			if (host == NULL || host == block->b_host)
+				nlmsvc_delete_block(block, 1);
+		}
+	}
+	up(&file->f_sema);
+	return 0;
+}
+
+/*
+ * Attempt to establish a lock, and if it can't be granted, block it
+ * if required.
+ */
+u32
+nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
+			struct nlm_lock *lock, int wait, u32 cookie)
+{
+	struct file_lock	*conflock;
+	struct nlm_block	*block;
+	int			error;
+
+	dprintk("lockd: nlmsvc_lock(%04x/%ld, ty=%d, pi=%d, %ld-%ld, bl=%d)\n",
+				file->f_file.f_inode->i_dev,
+				file->f_file.f_inode->i_ino,
+				lock->fl.fl_type, lock->fl.fl_pid,
+				lock->fl.fl_start,
+				lock->fl.fl_end,
+				wait);
+
+	/* Lock file against concurrent access */
+	down(&file->f_sema);
+
+	/* Get existing block (in case client is busy-waiting) */
+	block = nlmsvc_lookup_block(file, lock, 0);
+
+	lock->fl.fl_flags |= FL_LOCKD;
+
+again:
+	if (!(conflock = posix_test_lock(&file->f_file, &lock->fl))) {
+		error = posix_lock_file(&file->f_file, &lock->fl, 0);
+
+		if (block)
+			nlmsvc_delete_block(block, 0);
+		up(&file->f_sema);
+
+		dprintk("lockd: posix_lock_file returned %d\n", -error);
+		switch(-error) {
+		case 0:
+			return nlm_granted;
+		case EDEADLK:			/* no applicable NLM status */
+		case EAGAIN:
+			return nlm_lck_denied;
+		default:			/* includes ENOLCK */
+			return nlm_lck_denied_nolocks;
+		}
+	}
+
+	if (!wait) {
+		up(&file->f_sema);
+		return nlm_lck_denied;
+	}
+
+	/* If we don't have a block, create and initialize it. Then
+	 * retry because we may have slept in kmalloc. */
+	if (block == NULL) {
+		dprintk("lockd: blocking on this lock (allocating).\n");
+		if (!(block = nlmsvc_create_block(rqstp, file, lock, cookie)))
+			return nlm_lck_denied_nolocks;
+		goto again;
+	}
+
+	/* Append to list of blocked */
+	nlmsvc_insert_block(block, NLM_NEVER);
+
+	/* Now add block to block list of the conflicting lock */
+	dprintk("lockd: blocking on this lock.\n");
+	posix_block_lock(conflock, &block->b_call.a_args.lock.fl);
+
+	up(&file->f_sema);
+	return nlm_lck_blocked;
+}
+
+/*
+ * Test for presence of a conflicting lock.
+ */
+u32
+nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
+				       struct nlm_lock *conflock)
+{
+	struct file_lock	*fl;
+
+	dprintk("lockd: nlmsvc_testlock(%04x/%ld, ty=%d, %ld-%ld)\n",
+				file->f_file.f_inode->i_dev,
+				file->f_file.f_inode->i_ino,
+				lock->fl.fl_type,
+				lock->fl.fl_start,
+				lock->fl.fl_end);
+
+	if ((fl = posix_test_lock(&file->f_file, &lock->fl)) != NULL) {
+		dprintk("lockd: conflicting lock(ty=%d, %ld-%ld)\n",
+				fl->fl_type, fl->fl_start, fl->fl_end);
+		conflock->caller = "somehost";	/* FIXME */
+		conflock->oh.len = 0;		/* don't return OH info */
+		conflock->fl = *fl;
+		return nlm_lck_denied;
+	}
+
+	return nlm_granted;
+}
+
+/*
+ * Remove a lock.
+ * This implies a CANCEL call: We send a GRANT_MSG, the client replies
+ * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
+ * afterwards. In this case the block will still be there, and hence
+ * must be removed.
+ */
+u32
+nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
+{
+	int	error;
+
+	dprintk("lockd: nlmsvc_unlock(%04x/%ld, pi=%d, %ld-%ld)\n",
+				file->f_file.f_inode->i_dev,
+				file->f_file.f_inode->i_ino,
+				lock->fl.fl_pid,
+				lock->fl.fl_start,
+				lock->fl.fl_end);
+
+	/* First, cancel any lock that might be there */
+	nlmsvc_cancel_blocked(file, lock);
+
+	lock->fl.fl_type = F_UNLCK;
+	error = posix_lock_file(&file->f_file, &lock->fl, 0);
+
+	return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
+}
+
+/*
+ * Cancel a previously blocked request.
+ *
+ * A cancel request always overrides any grant that may currently
+ * be in progress.
+ * The calling procedure must check whether the file can be closed.
+ */
+u32
+nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
+{
+	struct nlm_block	*block;
+
+	dprintk("lockd: nlmsvc_cancel(%04x/%ld, pi=%d, %ld-%ld)\n",
+				file->f_file.f_inode->i_dev,
+				file->f_file.f_inode->i_ino,
+				lock->fl.fl_pid,
+				lock->fl.fl_start,
+				lock->fl.fl_end);
+
+	down(&file->f_sema);
+	if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL)
+		nlmsvc_delete_block(block, 1);
+	up(&file->f_sema);
+	return nlm_granted;
+}
+
+/*
+ * Unblock a blocked lock request. This is a callback invoked from the
+ * VFS layer when a lock on which we blocked is removed.
+ *
+ * This function doesn't grant the blocked lock instantly, but rather moves
+ * the block to the head of nlm_blocked where it can be picked up by lockd.
+ */
+static void
+nlmsvc_notify_blocked(struct file_lock *fl)
+{
+	struct nlm_block	**bp, *block;
+
+	dprintk("lockd: VFS unblock notification for block %p\n", fl);
+	posix_unblock_lock(fl);
+	for (bp = &nlm_blocked; (block = *bp); bp = &block->b_next) {
+		if (&block->b_call.a_args.lock.fl == fl) {
+			svc_wake_up(block->b_daemon);
+			nlmsvc_insert_block(block, 0);
+			return;
+		}
+	}
+
+	printk(KERN_WARNING "lockd: notification for unknown block!\n");
+}
+
+/*
+ * Try to claim a lock that was previously blocked.
+ *
+ * Note that we use both the RPC_GRANTED_MSG call _and_ an async
+ * RPC thread when notifying the client. This seems like overkill...
+ * Here's why:
+ *  -	we don't want to use a synchronous RPC thread, otherwise
+ *	we might find ourselves hanging on a dead portmapper.
+ *  -	Some lockd implementations (e.g. HP) don't react to
+ *	RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
+ */
+static void
+nlmsvc_grant_blocked(struct nlm_block *block)
+{
+	struct nlm_file		*file = block->b_file;
+	struct nlm_lock		*lock = &block->b_call.a_args.lock;
+	struct file_lock	*conflock;
+	int			error;
+
+	dprintk("lockd: grant blocked lock %p\n", block);
+
+	/* First thing is lock the file */
+	down(&file->f_sema);
+
+	/* Unlink block request from list */
+	nlmsvc_remove_block(block);
+
+	/* If b_granted is true this means we've been here before.
+	 * Just retry the grant callback, possibly refreshing the RPC
+	 * binding */
+	if (block->b_granted) {
+		nlm_rebind_host(block->b_host);
+		goto callback;
+	}
+
+	/* Try the lock operation again */
+	if ((conflock = posix_test_lock(&file->f_file, &lock->fl)) != NULL) {
+		/* Bummer, we blocked again */
+		dprintk("lockd: lock still blocked\n");
+		nlmsvc_insert_block(block, NLM_NEVER);
+		posix_block_lock(conflock, &lock->fl);
+		up(&file->f_sema);
+		return;
+	}
+
+	/* Alright, no conflicting lock. Now lock it for real. If the
+	 * following yields an error, this is most probably due to low
+	 * memory. Retry the lock in a few seconds.
+	 */
+	if ((error = posix_lock_file(&file->f_file, &lock->fl, 0)) < 0) {
+		printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
+				-error, __FUNCTION__);
+		nlmsvc_insert_block(block, jiffies + 10 * HZ);
+		up(&file->f_sema);
+		return;
+	}
+
+callback:
+	/* Lock was granted by VFS. */
+	dprintk("lockd: GRANTing blocked lock.\n");
+	block->b_granted = 1;
+	block->b_incall  = 1;
+
+	/* Schedule next grant callback in 30 seconds */
+	nlmsvc_insert_block(block, jiffies + 30 * HZ);
+
+	/* Call the client */
+	nlmclnt_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
+						nlmsvc_grant_callback);
+	up(&file->f_sema);
+}
+
+/*
+ * This is the callback from the RPC layer when the NLM_GRANTED_MSG
+ * RPC call has succeeded or timed out.
+ * Like all RPC callbacks, it is invoked by the rpciod process, so it
+ * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
+ * chain once more in order to have it removed by lockd itself (which can
+ * then sleep on the file semaphore without disrupting e.g. the nfs client).
+ */
+static void
+nlmsvc_grant_callback(struct rpc_task *task)
+{
+	struct nlm_rqst		*call = (struct nlm_rqst *) task->tk_calldata;
+	struct nlm_block	*block;
+	unsigned long		timeout;
+
+	dprintk("lockd: GRANT_MSG RPC callback\n");
+	if (!(block = nlmsvc_find_block(call->a_args.cookie))) {
+		dprintk("lockd: no block for cookie %x\n", call->a_args.cookie);
+		return;
+	}
+
+	/* Technically, we should down the file semaphore here. Since we
+	 * move the block towards the head of the queue only, no harm
+	 * can be done, though. */
+	if (task->tk_status < 0) {
+		/* RPC error: Re-insert for retransmission */
+		timeout = jiffies + 10 * HZ;
+	} else if (block->b_done) {
+		/* Block already removed, kill it for real */
+		timeout = 0;
+	} else {
+		/* Call was successful, now wait for client callback */
+		timeout = jiffies + 60 * HZ;
+	}
+	nlmsvc_insert_block(block, timeout);
+	svc_wake_up(block->b_daemon);
+	block->b_incall = 0;
+
+	nlm_release_host(call->a_host);
+	rpc_release_task(task);
+}
+
+/*
+ * We received a GRANT_RES callback. Try to find the corresponding
+ * block.
+ */
+void
+nlmsvc_grant_reply(u32 cookie, u32 status)
+{
+	struct nlm_block	*block;
+	struct nlm_file		*file;
+
+	if (!(block = nlmsvc_find_block(cookie)))
+		return;
+	file = block->b_file;
+
+	file->f_count++;
+	down(&file->f_sema);
+	if ((block = nlmsvc_find_block(cookie)) != NULL) {
+		if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
+			/* Try again in a couple of seconds */
+			nlmsvc_insert_block(block, jiffies + 10 * HZ);
+			block = NULL;
+		} else {
+			/* Lock is now held by client, or has been rejected.
+			 * In both cases, the block should be removed. */
+			file->f_count++;
+			up(&file->f_sema);
+			if (status == NLM_LCK_GRANTED)
+				nlmsvc_delete_block(block, 0);
+			else
+				nlmsvc_delete_block(block, 1);
+		}
+	}
+	if (!block)
+		up(&file->f_sema);
+	nlm_release_file(file);
+}
+
+/*
+ * Retry all blocked locks that have been notified. This is where lockd
+ * picks up locks that can be granted, or grant notifications that must
+ * be retransmitted.
+ */
+unsigned long
+nlmsvc_retry_blocked(void)
+{
+	struct nlm_block	*block;
+
+	dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
+			nlm_blocked,
+			nlm_blocked? nlm_blocked->b_when : 0);
+	while ((block = nlm_blocked) && block->b_when < jiffies) {
+		dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
+			block, block->b_when, block->b_done);
+		if (block->b_done)
+			nlmsvc_delete_block(block, 0);
+		else
+			nlmsvc_grant_blocked(block);
+	}
+
+	if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
+		return block->b_when;
+	return 0;
+}
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