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727 lines
19 KiB
727 lines
19 KiB
/*
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* linux/fs/lockd/svclock.c
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*
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* Handling of server-side locks, mostly of the blocked variety.
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* This is the ugliest part of lockd because we tread on very thin ice.
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* GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
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* IMNSHO introducing the grant callback into the NLM protocol was one
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* of the worst ideas Sun ever had. Except maybe for the idea of doing
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* NFS file locking at all.
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*
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* I'm trying hard to avoid race conditions by protecting most accesses
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* to a file's list of blocked locks through a semaphore. The global
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* list of blocked locks is not protected in this fashion however.
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* Therefore, some functions (such as the RPC callback for the async grant
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* call) move blocked locks towards the head of the list *while some other
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* process might be traversing it*. This should not be a problem in
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* practice, because this will only cause functions traversing the list
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* to visit some blocks twice.
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*
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* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
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*/
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#include <linux/config.h>
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/smp_lock.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/sunrpc/svc.h>
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#include <linux/lockd/nlm.h>
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#include <linux/lockd/lockd.h>
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#define NLMDBG_FACILITY NLMDBG_SVCLOCK
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#ifdef CONFIG_LOCKD_V4
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#define nlm_deadlock nlm4_deadlock
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#else
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#define nlm_deadlock nlm_lck_denied
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#endif
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static void nlmsvc_release_block(struct nlm_block *block);
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static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
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static int nlmsvc_remove_block(struct nlm_block *block);
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static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
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static void nlmsvc_freegrantargs(struct nlm_rqst *call);
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static const struct rpc_call_ops nlmsvc_grant_ops;
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/*
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* The list of blocked locks to retry
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*/
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static struct nlm_block * nlm_blocked;
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/*
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* Insert a blocked lock into the global list
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*/
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static void
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nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
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{
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struct nlm_block **bp, *b;
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dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
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kref_get(&block->b_count);
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if (block->b_queued)
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nlmsvc_remove_block(block);
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bp = &nlm_blocked;
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if (when != NLM_NEVER) {
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if ((when += jiffies) == NLM_NEVER)
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when ++;
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while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER)
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bp = &b->b_next;
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} else
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while ((b = *bp) != 0)
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bp = &b->b_next;
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block->b_queued = 1;
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block->b_when = when;
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block->b_next = b;
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*bp = block;
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}
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/*
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* Remove a block from the global list
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*/
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static int
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nlmsvc_remove_block(struct nlm_block *block)
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{
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struct nlm_block **bp, *b;
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if (!block->b_queued)
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return 1;
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for (bp = &nlm_blocked; (b = *bp) != 0; bp = &b->b_next) {
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if (b == block) {
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*bp = block->b_next;
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block->b_queued = 0;
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nlmsvc_release_block(block);
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return 1;
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}
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}
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return 0;
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}
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/*
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* Find a block for a given lock
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*/
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static struct nlm_block *
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nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
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{
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struct nlm_block **head, *block;
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struct file_lock *fl;
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dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
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file, lock->fl.fl_pid,
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(long long)lock->fl.fl_start,
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(long long)lock->fl.fl_end, lock->fl.fl_type);
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for (head = &nlm_blocked; (block = *head) != 0; head = &block->b_next) {
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fl = &block->b_call->a_args.lock.fl;
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dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
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block->b_file, fl->fl_pid,
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(long long)fl->fl_start,
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(long long)fl->fl_end, fl->fl_type,
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nlmdbg_cookie2a(&block->b_call->a_args.cookie));
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if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
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kref_get(&block->b_count);
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return block;
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}
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}
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return NULL;
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}
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static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
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{
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if(a->len != b->len)
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return 0;
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if(memcmp(a->data,b->data,a->len))
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return 0;
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return 1;
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}
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/*
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* Find a block with a given NLM cookie.
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*/
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static inline struct nlm_block *
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nlmsvc_find_block(struct nlm_cookie *cookie, struct sockaddr_in *sin)
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{
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struct nlm_block *block;
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for (block = nlm_blocked; block; block = block->b_next) {
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dprintk("cookie: head of blocked queue %p, block %p\n",
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nlm_blocked, block);
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if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie)
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&& nlm_cmp_addr(sin, &block->b_host->h_addr))
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break;
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}
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if (block != NULL)
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kref_get(&block->b_count);
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return block;
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}
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/*
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* Create a block and initialize it.
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*
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* Note: we explicitly set the cookie of the grant reply to that of
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* the blocked lock request. The spec explicitly mentions that the client
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* should _not_ rely on the callback containing the same cookie as the
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* request, but (as I found out later) that's because some implementations
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* do just this. Never mind the standards comittees, they support our
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* logging industries.
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*/
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static inline struct nlm_block *
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nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
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struct nlm_lock *lock, struct nlm_cookie *cookie)
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{
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struct nlm_block *block;
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struct nlm_host *host;
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struct nlm_rqst *call = NULL;
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/* Create host handle for callback */
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host = nlmsvc_lookup_host(rqstp);
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if (host == NULL)
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return NULL;
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call = nlm_alloc_call(host);
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if (call == NULL)
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return NULL;
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/* Allocate memory for block, and initialize arguments */
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block = kzalloc(sizeof(*block), GFP_KERNEL);
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if (block == NULL)
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goto failed;
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kref_init(&block->b_count);
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if (!nlmsvc_setgrantargs(call, lock))
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goto failed_free;
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/* Set notifier function for VFS, and init args */
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call->a_args.lock.fl.fl_flags |= FL_SLEEP;
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call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
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call->a_args.cookie = *cookie; /* see above */
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dprintk("lockd: created block %p...\n", block);
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/* Create and initialize the block */
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block->b_daemon = rqstp->rq_server;
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block->b_host = host;
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block->b_file = file;
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file->f_count++;
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/* Add to file's list of blocks */
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block->b_fnext = file->f_blocks;
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file->f_blocks = block;
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/* Set up RPC arguments for callback */
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block->b_call = call;
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call->a_flags = RPC_TASK_ASYNC;
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call->a_block = block;
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return block;
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failed_free:
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kfree(block);
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failed:
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nlm_release_call(call);
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return NULL;
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}
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/*
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* Delete a block. If the lock was cancelled or the grant callback
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* failed, unlock is set to 1.
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* It is the caller's responsibility to check whether the file
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* can be closed hereafter.
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*/
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static int nlmsvc_unlink_block(struct nlm_block *block)
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{
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int status;
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dprintk("lockd: unlinking block %p...\n", block);
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/* Remove block from list */
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status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
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nlmsvc_remove_block(block);
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return status;
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}
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static void nlmsvc_free_block(struct kref *kref)
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{
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struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
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struct nlm_file *file = block->b_file;
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struct nlm_block **bp;
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dprintk("lockd: freeing block %p...\n", block);
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down(&file->f_sema);
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/* Remove block from file's list of blocks */
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for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
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if (*bp == block) {
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*bp = block->b_fnext;
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break;
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}
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}
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up(&file->f_sema);
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nlmsvc_freegrantargs(block->b_call);
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nlm_release_call(block->b_call);
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nlm_release_file(block->b_file);
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kfree(block);
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}
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static void nlmsvc_release_block(struct nlm_block *block)
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{
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if (block != NULL)
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kref_put(&block->b_count, nlmsvc_free_block);
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}
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static void nlmsvc_act_mark(struct nlm_host *host, struct nlm_file *file)
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{
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struct nlm_block *block;
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down(&file->f_sema);
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for (block = file->f_blocks; block != NULL; block = block->b_fnext)
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block->b_host->h_inuse = 1;
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up(&file->f_sema);
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}
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static void nlmsvc_act_unlock(struct nlm_host *host, struct nlm_file *file)
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{
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struct nlm_block *block;
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restart:
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down(&file->f_sema);
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for (block = file->f_blocks; block != NULL; block = block->b_fnext) {
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if (host != NULL && host != block->b_host)
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continue;
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if (!block->b_queued)
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continue;
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kref_get(&block->b_count);
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up(&file->f_sema);
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nlmsvc_unlink_block(block);
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nlmsvc_release_block(block);
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goto restart;
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}
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up(&file->f_sema);
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}
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/*
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* Loop over all blocks and perform the action specified.
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* (NLM_ACT_CHECK handled by nlmsvc_inspect_file).
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*/
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void
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nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
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{
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if (action == NLM_ACT_MARK)
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nlmsvc_act_mark(host, file);
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else
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nlmsvc_act_unlock(host, file);
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}
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/*
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* Initialize arguments for GRANTED call. The nlm_rqst structure
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* has been cleared already.
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*/
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static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
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{
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locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
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memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
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call->a_args.lock.caller = system_utsname.nodename;
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call->a_args.lock.oh.len = lock->oh.len;
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/* set default data area */
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call->a_args.lock.oh.data = call->a_owner;
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call->a_args.lock.svid = lock->fl.fl_pid;
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if (lock->oh.len > NLMCLNT_OHSIZE) {
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void *data = kmalloc(lock->oh.len, GFP_KERNEL);
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if (!data)
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return 0;
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call->a_args.lock.oh.data = (u8 *) data;
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}
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memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
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return 1;
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}
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static void nlmsvc_freegrantargs(struct nlm_rqst *call)
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{
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if (call->a_args.lock.oh.data != call->a_owner)
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kfree(call->a_args.lock.oh.data);
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}
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/*
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* Attempt to establish a lock, and if it can't be granted, block it
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* if required.
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*/
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u32
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nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
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struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
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{
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struct nlm_block *block, *newblock = NULL;
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int error;
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u32 ret;
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dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
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file->f_file->f_dentry->d_inode->i_sb->s_id,
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file->f_file->f_dentry->d_inode->i_ino,
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lock->fl.fl_type, lock->fl.fl_pid,
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(long long)lock->fl.fl_start,
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(long long)lock->fl.fl_end,
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wait);
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lock->fl.fl_flags &= ~FL_SLEEP;
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again:
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/* Lock file against concurrent access */
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down(&file->f_sema);
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/* Get existing block (in case client is busy-waiting) */
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block = nlmsvc_lookup_block(file, lock);
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if (block == NULL) {
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if (newblock != NULL)
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lock = &newblock->b_call->a_args.lock;
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} else
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lock = &block->b_call->a_args.lock;
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error = posix_lock_file(file->f_file, &lock->fl);
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lock->fl.fl_flags &= ~FL_SLEEP;
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dprintk("lockd: posix_lock_file returned %d\n", error);
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switch(error) {
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case 0:
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ret = nlm_granted;
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goto out;
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case -EAGAIN:
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break;
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case -EDEADLK:
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ret = nlm_deadlock;
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goto out;
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default: /* includes ENOLCK */
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ret = nlm_lck_denied_nolocks;
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goto out;
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}
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ret = nlm_lck_denied;
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if (!wait)
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goto out;
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ret = nlm_lck_blocked;
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if (block != NULL)
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goto out;
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/* If we don't have a block, create and initialize it. Then
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* retry because we may have slept in kmalloc. */
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/* We have to release f_sema as nlmsvc_create_block may try to
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* to claim it while doing host garbage collection */
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if (newblock == NULL) {
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up(&file->f_sema);
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dprintk("lockd: blocking on this lock (allocating).\n");
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if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
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return nlm_lck_denied_nolocks;
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goto again;
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}
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/* Append to list of blocked */
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nlmsvc_insert_block(newblock, NLM_NEVER);
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out:
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up(&file->f_sema);
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nlmsvc_release_block(newblock);
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nlmsvc_release_block(block);
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dprintk("lockd: nlmsvc_lock returned %u\n", ret);
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return ret;
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}
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/*
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* Test for presence of a conflicting lock.
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*/
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u32
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nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
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struct nlm_lock *conflock)
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{
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dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
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file->f_file->f_dentry->d_inode->i_sb->s_id,
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file->f_file->f_dentry->d_inode->i_ino,
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lock->fl.fl_type,
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(long long)lock->fl.fl_start,
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(long long)lock->fl.fl_end);
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|
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if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
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dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
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conflock->fl.fl_type,
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(long long)conflock->fl.fl_start,
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(long long)conflock->fl.fl_end);
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conflock->caller = "somehost"; /* FIXME */
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conflock->oh.len = 0; /* don't return OH info */
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conflock->svid = conflock->fl.fl_pid;
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return nlm_lck_denied;
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}
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return nlm_granted;
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}
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|
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/*
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* Remove a lock.
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* This implies a CANCEL call: We send a GRANT_MSG, the client replies
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* with a GRANT_RES call which gets lost, and calls UNLOCK immediately
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* afterwards. In this case the block will still be there, and hence
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* must be removed.
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*/
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|
u32
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nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
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{
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int error;
|
|
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dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
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file->f_file->f_dentry->d_inode->i_sb->s_id,
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file->f_file->f_dentry->d_inode->i_ino,
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lock->fl.fl_pid,
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(long long)lock->fl.fl_start,
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(long long)lock->fl.fl_end);
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|
|
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/* First, cancel any lock that might be there */
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nlmsvc_cancel_blocked(file, lock);
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lock->fl.fl_type = F_UNLCK;
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error = posix_lock_file(file->f_file, &lock->fl);
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return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
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}
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|
|
/*
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* Cancel a previously blocked request.
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|
*
|
|
* 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;
|
|
int status = 0;
|
|
|
|
dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
|
|
file->f_file->f_dentry->d_inode->i_sb->s_id,
|
|
file->f_file->f_dentry->d_inode->i_ino,
|
|
lock->fl.fl_pid,
|
|
(long long)lock->fl.fl_start,
|
|
(long long)lock->fl.fl_end);
|
|
|
|
down(&file->f_sema);
|
|
block = nlmsvc_lookup_block(file, lock);
|
|
up(&file->f_sema);
|
|
if (block != NULL) {
|
|
status = nlmsvc_unlink_block(block);
|
|
nlmsvc_release_block(block);
|
|
}
|
|
return status ? nlm_lck_denied : 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);
|
|
for (bp = &nlm_blocked; (block = *bp) != 0; 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);
|
|
return;
|
|
}
|
|
}
|
|
|
|
printk(KERN_WARNING "lockd: notification for unknown block!\n");
|
|
}
|
|
|
|
static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
|
|
{
|
|
return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
|
|
}
|
|
|
|
struct lock_manager_operations nlmsvc_lock_operations = {
|
|
.fl_compare_owner = nlmsvc_same_owner,
|
|
.fl_notify = nlmsvc_notify_blocked,
|
|
};
|
|
|
|
/*
|
|
* 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;
|
|
int error;
|
|
|
|
dprintk("lockd: grant blocked lock %p\n", block);
|
|
|
|
/* Unlink block request from list */
|
|
nlmsvc_unlink_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 */
|
|
lock->fl.fl_flags |= FL_SLEEP;
|
|
error = posix_lock_file(file->f_file, &lock->fl);
|
|
lock->fl.fl_flags &= ~FL_SLEEP;
|
|
|
|
switch (error) {
|
|
case 0:
|
|
break;
|
|
case -EAGAIN:
|
|
dprintk("lockd: lock still blocked\n");
|
|
nlmsvc_insert_block(block, NLM_NEVER);
|
|
return;
|
|
default:
|
|
printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
|
|
-error, __FUNCTION__);
|
|
nlmsvc_insert_block(block, 10 * HZ);
|
|
return;
|
|
}
|
|
|
|
callback:
|
|
/* Lock was granted by VFS. */
|
|
dprintk("lockd: GRANTing blocked lock.\n");
|
|
block->b_granted = 1;
|
|
|
|
/* Schedule next grant callback in 30 seconds */
|
|
nlmsvc_insert_block(block, 30 * HZ);
|
|
|
|
/* Call the client */
|
|
kref_get(&block->b_count);
|
|
if (nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
|
|
&nlmsvc_grant_ops) < 0)
|
|
nlmsvc_release_block(block);
|
|
}
|
|
|
|
/*
|
|
* 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, void *data)
|
|
{
|
|
struct nlm_rqst *call = data;
|
|
struct nlm_block *block = call->a_block;
|
|
unsigned long timeout;
|
|
|
|
dprintk("lockd: GRANT_MSG RPC callback\n");
|
|
|
|
/* 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 = 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 = 60 * HZ;
|
|
}
|
|
nlmsvc_insert_block(block, timeout);
|
|
svc_wake_up(block->b_daemon);
|
|
}
|
|
|
|
void nlmsvc_grant_release(void *data)
|
|
{
|
|
struct nlm_rqst *call = data;
|
|
|
|
nlmsvc_release_block(call->a_block);
|
|
}
|
|
|
|
static const struct rpc_call_ops nlmsvc_grant_ops = {
|
|
.rpc_call_done = nlmsvc_grant_callback,
|
|
.rpc_release = nlmsvc_grant_release,
|
|
};
|
|
|
|
/*
|
|
* We received a GRANT_RES callback. Try to find the corresponding
|
|
* block.
|
|
*/
|
|
void
|
|
nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status)
|
|
{
|
|
struct nlm_block *block;
|
|
struct nlm_file *file;
|
|
|
|
dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n",
|
|
*(unsigned int *)(cookie->data),
|
|
ntohl(rqstp->rq_addr.sin_addr.s_addr), status);
|
|
if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr)))
|
|
return;
|
|
file = block->b_file;
|
|
|
|
if (block) {
|
|
if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
|
|
/* Try again in a couple of seconds */
|
|
nlmsvc_insert_block(block, 10 * HZ);
|
|
} else {
|
|
/* Lock is now held by client, or has been rejected.
|
|
* In both cases, the block should be removed. */
|
|
nlmsvc_unlink_block(block);
|
|
}
|
|
}
|
|
nlmsvc_release_block(block);
|
|
}
|
|
|
|
/*
|
|
* 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) != 0) {
|
|
if (block->b_when == NLM_NEVER)
|
|
break;
|
|
if (time_after(block->b_when,jiffies))
|
|
break;
|
|
dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
|
|
block, block->b_when, block->b_done);
|
|
kref_get(&block->b_count);
|
|
if (block->b_done)
|
|
nlmsvc_unlink_block(block);
|
|
else
|
|
nlmsvc_grant_blocked(block);
|
|
nlmsvc_release_block(block);
|
|
}
|
|
|
|
if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
|
|
return (block->b_when - jiffies);
|
|
|
|
return MAX_SCHEDULE_TIMEOUT;
|
|
}
|
|
|