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/*

 * 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/config.h>

#include <linux/types.h>

#include <linux/errno.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/smp_lock.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

#ifdef CONFIG_LOCKD_V4

#define nlm_deadlock    nlm4_deadlock

#else

#define nlm_deadlock    nlm_lck_denied

#endif

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;

/*

 * 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);

        bp = &nlm_blocked;

        if (when != NLM_NEVER) {

                if ((when += jiffies) == NLM_NEVER)

                        when ++;

                while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER)

                        bp = &b->b_next;

        } else

                while ((b = *bp))

                        bp = &b->b_next;

        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,

                                (long long)lock->fl.fl_start,

                                (long long)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("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",

                                block->b_file, fl->fl_pid,

                                (long long)fl->fl_start,

                                (long long)fl->fl_end, fl->fl_type,

                                nlmdbg_cookie2a(&block->b_call.a_args.cookie));

                if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {

                        if (remove) {

                                *head = block->b_next;

                                block->b_queued = 0;

                        }

                        return block;

                }

        }

        return NULL;

}

static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)

{

        if(a->len != b->len)

                return 0;

        if(memcmp(a->data,b->data,a->len))

                return 0;

        return 1;

}

/*

 * Find a block with a given NLM cookie.

 */

static inline struct nlm_block *

nlmsvc_find_block(struct nlm_cookie *cookie,  struct sockaddr_in *sin)

{

        struct nlm_block *block;

        for (block = nlm_blocked; block; block = block->b_next) {

                dprintk("cookie: head of blocked queue %p, block %p\n",

                        nlm_blocked, block);

                if (nlm_cookie_match(&block->b_call.a_args.cookie,cookie)

                                && nlm_cmp_addr(sin, &block->b_host->h_addr))

                        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, struct nlm_cookie *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));

        locks_init_lock(&block->b_call.a_args.lock.fl);

        locks_init_lock(&block->b_call.a_res.lock.fl);

        block->b_host = nlmsvc_lookup_host(rqstp);

        if (block->b_host == NULL) {

                goto failed_free;

        }

        if (!nlmclnt_setgrantargs(&block->b_call, lock))

                goto failed_free;

        /* Set notifier function for VFS, and init args */

        block->b_call.a_args.lock.fl.fl_notify = nlmsvc_notify_blocked;

        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_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_free:

        kfree(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;

                }

        }

        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, struct nlm_cookie *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_dentry->d_inode->i_dev,

                                file->f_file.f_dentry->d_inode->i_ino,

                                lock->fl.fl_type, lock->fl.fl_pid,

                                (long long)lock->fl.fl_start,

                                (long long)lock->fl.fl_end,

                                wait);

        /* Get existing block (in case client is busy-waiting) */

        block = nlmsvc_lookup_block(file, lock, 0);

        lock->fl.fl_flags |= FL_LOCKD;

again:

        /* Lock file against concurrent access */

        down(&file->f_sema);

        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:

                        return nlm_deadlock;

                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 (posix_locks_deadlock(&lock->fl, conflock)) {

                up(&file->f_sema);

                return nlm_deadlock;

        }

        /* If we don't have a block, create and initialize it. Then

         * retry because we may have slept in kmalloc. */

        /* We have to release f_sema as nlmsvc_create_block may try to

         * claim it while doing host garbage collection */

        if (block == NULL) {

                up(&file->f_sema);

                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);

        if (list_empty(&block->b_call.a_args.lock.fl.fl_block)) {

                /* Now add block to block list of the conflicting lock

                   if we haven't done so. */

                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_dentry->d_inode->i_dev,

                                file->f_file.f_dentry->d_inode->i_ino,

                                lock->fl.fl_type,

                                (long long)lock->fl.fl_start,

                                (long long)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, (long long)fl->fl_start,

                                (long long)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_dentry->d_inode->i_dev,

                                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);

        /* 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_dentry->d_inode->i_dev,

                                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);

        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 (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");

}

/*

 * 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_call.a_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, 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, 30 * HZ);

        /* Call the client */

        nlm_get_host(block->b_call.a_host);

        if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,

                                                nlmsvc_grant_callback) < 0)

                nlm_release_host(block->b_call.a_host);

        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;

        struct sockaddr_in      *peer_addr = RPC_PEERADDR(task->tk_client);

        dprintk("lockd: GRANT_MSG RPC callback\n");

        dprintk("callback: looking for cookie %s, host %u.%u.%u.%u\n",

                nlmdbg_cookie2a(&call->a_args.cookie),

                NIPQUAD(peer_addr->sin_addr.s_addr));

        if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) {

                dprintk("lockd: no block for cookie %s, host %u.%u.%u.%u\n",

                                nlmdbg_cookie2a(&call->a_args.cookie),

                                NIPQUAD(peer_addr->sin_addr.s_addr));

                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 = 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);

        block->b_incall = 0;

        nlm_release_host(call->a_host);

}

/*

 * 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;

        file->f_count++;

        down(&file->f_sema);

        if ((block = nlmsvc_find_block(cookie,&rqstp->rq_addr)) != NULL) {

                if (status == NLM_LCK_DENIED_GRACE_PERIOD) {

                        /* Try again in a couple of seconds */

                        nlmsvc_insert_block(block, 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)) {

                if (block->b_when == NLM_NEVER)