r13121: Tag 4.0.0TP1

[Samba.git] / source / ntvfs / common / brlock.c

/* 
   Unix SMB/CIFS implementation.

   generic byte range locking code

   Copyright (C) Andrew Tridgell 1992-2004
   Copyright (C) Jeremy Allison 1992-2000
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/* This module implements a tdb based byte range locking service,
   replacing the fcntl() based byte range locking previously
   used. This allows us to provide the same semantics as NT */

#include "includes.h"
#include "system/filesys.h"
#include "lib/tdb/include/tdb.h"
#include "messaging/messaging.h"
#include "db_wrap.h"
#include "lib/messaging/irpc.h"

/*
  in this module a "DATA_BLOB *file_key" is a blob that uniquely identifies
  a file. For a local posix filesystem this will usually be a combination
  of the device and inode numbers of the file, but it can be anything 
  that uniquely idetifies a file for locking purposes, as long
  as it is applied consistently.
*/

/*
  the lock context contains the elements that define whether one
  lock is the same as another lock
*/
struct lock_context {
        uint32_t server;
        uint16_t smbpid;
        uint16_t tid;
};

/* The data in brlock records is an unsorted linear array of these
   records.  It is unnecessary to store the count as tdb provides the
   size of the record */
struct lock_struct {
        struct lock_context context;
        uint64_t start;
        uint64_t size;
        uint16_t fnum;
        enum brl_type lock_type;
        void *notify_ptr;
};

struct brl_context {
        struct tdb_wrap *w;
        uint32_t server;
        uint16_t tid;
        struct messaging_context *messaging_ctx;
        struct lock_struct last_lock;
};


/*
  Open up the brlock.tdb database. Close it down using
  talloc_free(). We need the messaging_ctx to allow for
  pending lock notifications.
*/
struct brl_context *brl_init(TALLOC_CTX *mem_ctx, uint32_t server, uint16_t tid, 
                             struct messaging_context *messaging_ctx)
{
        char *path;
        struct brl_context *brl;

        brl = talloc(mem_ctx, struct brl_context);
        if (brl == NULL) {
                return NULL;
        }

        path = smbd_tmp_path(brl, "brlock.tdb");
        brl->w = tdb_wrap_open(brl, path, 0,  
                               TDB_DEFAULT, O_RDWR|O_CREAT, 0600);
        talloc_free(path);
        if (brl->w == NULL) {
                talloc_free(brl);
                return NULL;
        }

        brl->server = server;
        brl->tid = tid;
        brl->messaging_ctx = messaging_ctx;
        ZERO_STRUCT(brl->last_lock);

        return brl;
}


/*
  see if two locking contexts are equal
*/
static BOOL brl_same_context(struct lock_context *ctx1, struct lock_context *ctx2)
{
        return (ctx1->server == ctx2->server &&
                ctx1->smbpid == ctx2->smbpid &&
                ctx1->tid == ctx2->tid);
}

/*
  see if lck1 and lck2 overlap
*/
static BOOL brl_overlap(struct lock_struct *lck1, 
                        struct lock_struct *lck2)
{
        /* this extra check is not redundent - it copes with locks
           that go beyond the end of 64 bit file space */
        if (lck1->size != 0 &&
            lck1->start == lck2->start &&
            lck1->size == lck2->size) {
                return True;
        }
            
        if (lck1->start >= (lck2->start+lck2->size) ||
            lck2->start >= (lck1->start+lck1->size)) {
                return False;
        }
        return True;
} 

/*
 See if lock2 can be added when lock1 is in place.
*/
static BOOL brl_conflict(struct lock_struct *lck1, 
                         struct lock_struct *lck2)
{
        /* pending locks don't conflict with anything */
        if (lck1->lock_type >= PENDING_READ_LOCK ||
            lck2->lock_type >= PENDING_READ_LOCK) {
                return False;
        }

        if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) {
                return False;
        }

        if (brl_same_context(&lck1->context, &lck2->context) &&
            lck2->lock_type == READ_LOCK && lck1->fnum == lck2->fnum) {
                return False;
        }

        return brl_overlap(lck1, lck2);
} 


/*
 Check to see if this lock conflicts, but ignore our own locks on the
 same fnum only.
*/
static BOOL brl_conflict_other(struct lock_struct *lck1, struct lock_struct *lck2)
{
        /* pending locks don't conflict with anything */
        if (lck1->lock_type >= PENDING_READ_LOCK ||
            lck2->lock_type >= PENDING_READ_LOCK) {
                return False;
        }

        if (lck1->lock_type == READ_LOCK && lck2->lock_type == READ_LOCK) 
                return False;

        /*
         * note that incoming write calls conflict with existing READ
         * locks even if the context is the same. JRA. See LOCKTEST7
         * in smbtorture.
         */
        if (brl_same_context(&lck1->context, &lck2->context) &&
            lck1->fnum == lck2->fnum &&
            (lck2->lock_type == READ_LOCK || lck1->lock_type == WRITE_LOCK)) {
                return False;
        }

        return brl_overlap(lck1, lck2);
} 


/*
  amazingly enough, w2k3 "remembers" whether the last lock failure
  is the same as this one and changes its error code. I wonder if any
  app depends on this?
*/
static NTSTATUS brl_lock_failed(struct brl_context *brl, struct lock_struct *lock)
{
        if (lock->context.server == brl->last_lock.context.server &&
            lock->context.tid == brl->last_lock.context.tid &&
            lock->fnum == brl->last_lock.fnum &&
            lock->start == brl->last_lock.start &&
            lock->size == brl->last_lock.size) {
                return NT_STATUS_FILE_LOCK_CONFLICT;
        }
        brl->last_lock = *lock;
        if (lock->start >= 0xEF000000 && 
            (lock->start >> 63) == 0) {
                /* amazing the little things you learn with a test
                   suite. Locks beyond this offset (as a 64 bit
                   number!) always generate the conflict error code,
                   unless the top bit is set */
                return NT_STATUS_FILE_LOCK_CONFLICT;
        }
        return NT_STATUS_LOCK_NOT_GRANTED;
}

/*
  Lock a range of bytes.  The lock_type can be a PENDING_*_LOCK, in
  which case a real lock is first tried, and if that fails then a
  pending lock is created. When the pending lock is triggered (by
  someone else closing an overlapping lock range) a messaging
  notification is sent, identified by the notify_ptr
*/
NTSTATUS brl_lock(struct brl_context *brl,
                  DATA_BLOB *file_key, 
                  uint16_t smbpid,
                  uint16_t fnum, 
                  uint64_t start, uint64_t size, 
                  enum brl_type lock_type,
                  void *notify_ptr)
{
        TDB_DATA kbuf, dbuf;
        int count=0, i;
        struct lock_struct lock, *locks=NULL;
        NTSTATUS status;

        kbuf.dptr = (char *)file_key->data;
        kbuf.dsize = file_key->length;

        if (tdb_chainlock(brl->w->tdb, kbuf) != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }

        /* if this is a pending lock, then with the chainlock held we
           try to get the real lock. If we succeed then we don't need
           to make it pending. This prevents a possible race condition
           where the pending lock gets created after the lock that is
           preventing the real lock gets removed */
        if (lock_type >= PENDING_READ_LOCK) {
                enum brl_type rw = (lock_type==PENDING_READ_LOCK? READ_LOCK : WRITE_LOCK);
                status = brl_lock(brl, file_key, smbpid, fnum, start, size, rw, NULL);
                if (NT_STATUS_IS_OK(status)) {
                        tdb_chainunlock(brl->w->tdb, kbuf);
                        return NT_STATUS_OK;
                }
        }

        dbuf = tdb_fetch(brl->w->tdb, kbuf);

        lock.context.smbpid = smbpid;
        lock.context.server = brl->server;
        lock.context.tid = brl->tid;
        lock.start = start;
        lock.size = size;
        lock.fnum = fnum;
        lock.lock_type = lock_type;
        lock.notify_ptr = notify_ptr;

        if (dbuf.dptr) {
                /* there are existing locks - make sure they don't conflict */
                locks = (struct lock_struct *)dbuf.dptr;
                count = dbuf.dsize / sizeof(*locks);
                for (i=0; i<count; i++) {
                        if (brl_conflict(&locks[i], &lock)) {
                                status = brl_lock_failed(brl, &lock);
                                goto fail;
                        }
                }
        }

        /* no conflicts - add it to the list of locks */
        locks = realloc_p(locks, struct lock_struct, count+1);
        if (!locks) {
                status = NT_STATUS_NO_MEMORY;
                goto fail;
        } else {
                dbuf.dptr = (char *)locks;
        }
        locks[count] = lock;
        dbuf.dsize += sizeof(lock);

        if (tdb_store(brl->w->tdb, kbuf, dbuf, TDB_REPLACE) != 0) {
                status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                goto fail;
        }

        free(dbuf.dptr);
        tdb_chainunlock(brl->w->tdb, kbuf);

        /* the caller needs to know if the real lock was granted. If
           we have reached here then it must be a pending lock that
           was granted, so tell them the lock failed */
        if (lock_type >= PENDING_READ_LOCK) {
                return brl_lock_failed(brl, &lock);
        }

        return NT_STATUS_OK;

 fail:

        free(dbuf.dptr);
        tdb_chainunlock(brl->w->tdb, kbuf);
        return status;
}


/*
  we are removing a lock that might be holding up a pending lock. Scan for pending
  locks that cover this range and if we find any then notify the server that it should
  retry the lock
*/
static void brl_notify_unlock(struct brl_context *brl,
                              struct lock_struct *locks, int count, 
                              struct lock_struct *removed_lock)
{
        int i, last_notice;

        /* the last_notice logic is to prevent stampeding on a lock
           range. It prevents us sending hundreds of notifies on the
           same range of bytes. It doesn't prevent all possible
           stampedes, but it does prevent the most common problem */
        last_notice = -1;

        for (i=0;i<count;i++) {
                if (locks[i].lock_type >= PENDING_READ_LOCK &&
                    brl_overlap(&locks[i], removed_lock)) {
                        if (last_notice != -1 && brl_overlap(&locks[i], &locks[last_notice])) {
                                continue;
                        }
                        if (locks[i].lock_type == PENDING_WRITE_LOCK) {
                                last_notice = i;
                        }
                        messaging_send_ptr(brl->messaging_ctx, locks[i].context.server, 
                                           MSG_BRL_RETRY, locks[i].notify_ptr);
                }
        }
}


/*
  send notifications for all pending locks - the file is being closed by this
  user
*/
static void brl_notify_all(struct brl_context *brl,
                           struct lock_struct *locks, int count)
{
        int i;
        for (i=0;i<count;i++) {
                if (locks->lock_type >= PENDING_READ_LOCK) {
                        brl_notify_unlock(brl, locks, count, &locks[i]);
                }
        }
}



/*
 Unlock a range of bytes.
*/
NTSTATUS brl_unlock(struct brl_context *brl,
                    DATA_BLOB *file_key, 
                    uint16_t smbpid,
                    uint16_t fnum,
                    uint64_t start, uint64_t size)
{
        TDB_DATA kbuf, dbuf;
        int count, i;
        struct lock_struct *locks;
        struct lock_context context;
        NTSTATUS status;

        kbuf.dptr = (char *)file_key->data;
        kbuf.dsize = file_key->length;

        if (tdb_chainlock(brl->w->tdb, kbuf) != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }

        dbuf = tdb_fetch(brl->w->tdb, kbuf);
        if (!dbuf.dptr) {
                tdb_chainunlock(brl->w->tdb, kbuf);
                return NT_STATUS_RANGE_NOT_LOCKED;
        }

        context.smbpid = smbpid;
        context.server = brl->server;
        context.tid = brl->tid;

        /* there are existing locks - find a match */
        locks = (struct lock_struct *)dbuf.dptr;
        count = dbuf.dsize / sizeof(*locks);

        for (i=0; i<count; i++) {
                struct lock_struct *lock = &locks[i];
                
                if (brl_same_context(&lock->context, &context) &&
                    lock->fnum == fnum &&
                    lock->start == start &&
                    lock->size == size &&
                    lock->notify_ptr == NULL) {
                        /* found it - delete it */
                        if (count == 1) {
                                if (tdb_delete(brl->w->tdb, kbuf) != 0) {
                                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                                        goto fail;
                                }
                        } else {
                                struct lock_struct removed_lock = *lock;
                                if (i < count-1) {
                                        memmove(&locks[i], &locks[i+1], 
                                                sizeof(*locks)*((count-1) - i));
                                }
                                count--;

                                /* send notifications for any relevant pending locks */
                                brl_notify_unlock(brl, locks, count, &removed_lock);

                                dbuf.dsize = count * sizeof(*locks);

                                if (tdb_store(brl->w->tdb, kbuf, dbuf, TDB_REPLACE) != 0) {
                                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                                        goto fail;
                                }
                        }
                        
                        free(dbuf.dptr);
                        tdb_chainunlock(brl->w->tdb, kbuf);
                        return NT_STATUS_OK;
                }
        }
        
        /* we didn't find it */
        status = NT_STATUS_RANGE_NOT_LOCKED;

 fail:
        free(dbuf.dptr);
        tdb_chainunlock(brl->w->tdb, kbuf);
        return status;
}


/*
  remove a pending lock. This is called when the caller has either
  given up trying to establish a lock or when they have succeeded in
  getting it. In either case they no longer need to be notified.
*/
NTSTATUS brl_remove_pending(struct brl_context *brl,
                            DATA_BLOB *file_key, 
                            void *notify_ptr)
{
        TDB_DATA kbuf, dbuf;
        int count, i;
        struct lock_struct *locks;
        NTSTATUS status;

        kbuf.dptr = (char *)file_key->data;
        kbuf.dsize = file_key->length;

        if (tdb_chainlock(brl->w->tdb, kbuf) != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }

        dbuf = tdb_fetch(brl->w->tdb, kbuf);
        if (!dbuf.dptr) {
                tdb_chainunlock(brl->w->tdb, kbuf);
                return NT_STATUS_RANGE_NOT_LOCKED;
        }

        /* there are existing locks - find a match */
        locks = (struct lock_struct *)dbuf.dptr;
        count = dbuf.dsize / sizeof(*locks);

        for (i=0; i<count; i++) {
                struct lock_struct *lock = &locks[i];
                
                if (lock->notify_ptr == notify_ptr &&
                    lock->context.server == brl->server) {
                        /* found it - delete it */
                        if (count == 1) {
                                if (tdb_delete(brl->w->tdb, kbuf) != 0) {
                                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                                        goto fail;
                                }
                        } else {
                                if (i < count-1) {
                                        memmove(&locks[i], &locks[i+1], 
                                                sizeof(*locks)*((count-1) - i));
                                }
                                count--;
                                dbuf.dsize = count * sizeof(*locks);
                                if (tdb_store(brl->w->tdb, kbuf, dbuf, TDB_REPLACE) != 0) {
                                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                                        goto fail;
                                }
                        }
                        
                        free(dbuf.dptr);
                        tdb_chainunlock(brl->w->tdb, kbuf);
                        return NT_STATUS_OK;
                }
        }
        
        /* we didn't find it */
        status = NT_STATUS_RANGE_NOT_LOCKED;

 fail:
        free(dbuf.dptr);
        tdb_chainunlock(brl->w->tdb, kbuf);
        return status;
}


/*
  Test if we are allowed to perform IO on a region of an open file
*/
NTSTATUS brl_locktest(struct brl_context *brl,
                      DATA_BLOB *file_key, 
                      uint16_t fnum,
                      uint16_t smbpid, 
                      uint64_t start, uint64_t size, 
                      enum brl_type lock_type)
{
        TDB_DATA kbuf, dbuf;
        int count, i;
        struct lock_struct lock, *locks;

        kbuf.dptr = (char *)file_key->data;
        kbuf.dsize = file_key->length;

        dbuf = tdb_fetch(brl->w->tdb, kbuf);
        if (dbuf.dptr == NULL) {
                return NT_STATUS_OK;
        }

        lock.context.smbpid = smbpid;
        lock.context.server = brl->server;
        lock.context.tid = brl->tid;
        lock.start = start;
        lock.size = size;
        lock.fnum = fnum;
        lock.lock_type = lock_type;

        /* there are existing locks - make sure they don't conflict */
        locks = (struct lock_struct *)dbuf.dptr;
        count = dbuf.dsize / sizeof(*locks);

        for (i=0; i<count; i++) {
                if (brl_conflict_other(&locks[i], &lock)) {
                        free(dbuf.dptr);
                        return NT_STATUS_FILE_LOCK_CONFLICT;
                }
        }

        free(dbuf.dptr);
        return NT_STATUS_OK;
}


/*
 Remove any locks associated with a open file.
*/
NTSTATUS brl_close(struct brl_context *brl,
                   DATA_BLOB *file_key, int fnum)
{
        TDB_DATA kbuf, dbuf;
        int count, i, dcount=0;
        struct lock_struct *locks;
        NTSTATUS status;

        kbuf.dptr = (char *)file_key->data;
        kbuf.dsize = file_key->length;

        if (tdb_chainlock(brl->w->tdb, kbuf) != 0) {
                return NT_STATUS_INTERNAL_DB_CORRUPTION;
        }

        dbuf = tdb_fetch(brl->w->tdb, kbuf);
        if (!dbuf.dptr) {
                tdb_chainunlock(brl->w->tdb, kbuf);
                return NT_STATUS_OK;
        }

        /* there are existing locks - remove any for this fnum */
        locks = (struct lock_struct *)dbuf.dptr;
        count = dbuf.dsize / sizeof(*locks);

        for (i=0; i<count; i++) {
                struct lock_struct *lock = &locks[i];

                if (lock->context.tid == brl->tid &&
                    lock->context.server == brl->server &&
                    lock->fnum == fnum) {
                        /* found it - delete it */
                        if (count > 1 && i < count-1) {
                                memmove(&locks[i], &locks[i+1], 
                                        sizeof(*locks)*((count-1) - i));
                        }
                        count--;
                        i--;
                        dcount++;
                }
        }

        status = NT_STATUS_OK;

        if (count == 0) {
                if (tdb_delete(brl->w->tdb, kbuf) != 0) {
                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                }
        } else if (dcount != 0) {
                /* tell all pending lock holders for this file that
                   they have a chance now. This is a bit indiscriminant,
                   but works OK */
                brl_notify_all(brl, locks, count);

                dbuf.dsize = count * sizeof(*locks);

                if (tdb_store(brl->w->tdb, kbuf, dbuf, TDB_REPLACE) != 0) {
                        status = NT_STATUS_INTERNAL_DB_CORRUPTION;
                }
        }

        free(dbuf.dptr);
        tdb_chainunlock(brl->w->tdb, kbuf);

        return status;
}