smbd: some write time fixes
[tprouty/samba.git] / source / smbd / fileio.c
index 1e166275152869a4e2f27d93989c1c153cb1a4b4..095841825a5e34ef2132a15741e320fc7e796c07 100644 (file)
@@ -3,10 +3,11 @@
    Version 1.9.
    read/write to a files_struct
    Copyright (C) Andrew Tridgell 1992-1998
+   Copyright (C) Jeremy Allison 2000-2002. - write cache.
    
    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
+   the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    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.
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "includes.h"
 
-extern int DEBUGLEVEL;
+static bool setup_write_cache(files_struct *, SMB_OFF_T);
 
+/****************************************************************************
+ Read from write cache if we can.
+****************************************************************************/
+
+static bool read_from_write_cache(files_struct *fsp,char *data,SMB_OFF_T pos,size_t n)
+{
+       write_cache *wcp = fsp->wcp;
+
+       if(!wcp) {
+               return False;
+       }
+
+       if( n > wcp->data_size || pos < wcp->offset || pos + n > wcp->offset + wcp->data_size) {
+               return False;
+       }
+
+       memcpy(data, wcp->data + (pos - wcp->offset), n);
+
+       DO_PROFILE_INC(writecache_read_hits);
+
+       return True;
+}
 
 /****************************************************************************
-seek a file. Try to avoid the seek if possible
+ Read from a file.
 ****************************************************************************/
 
-SMB_OFF_T seek_file(files_struct *fsp,SMB_OFF_T pos)
+ssize_t read_file(files_struct *fsp,char *data,SMB_OFF_T pos,size_t n)
 {
-  SMB_OFF_T offset = 0;
-  SMB_OFF_T seek_ret;
+       ssize_t ret=0,readret;
+
+       /* you can't read from print files */
+       if (fsp->print_file) {
+               return -1;
+       }
+
+       /*
+        * Serve from write cache if we can.
+        */
+
+       if(read_from_write_cache(fsp, data, pos, n)) {
+               fsp->fh->pos = pos + n;
+               fsp->fh->position_information = fsp->fh->pos;
+               return n;
+       }
 
-  if (fsp->print_file && lp_postscript(fsp->conn->service))
-    offset = 3;
+       flush_write_cache(fsp, READ_FLUSH);
 
-  seek_ret = fsp->conn->vfs_ops.lseek(fsp->fd_ptr->fd,pos+offset,SEEK_SET);
+       fsp->fh->pos = pos;
 
-  if((seek_ret == -1) || (seek_ret != pos+offset)) {
-    DEBUG(0,("seek_file: sys_lseek failed. Error was %s\n", strerror(errno) ));
-    fsp->pos = -1;
-    return -1;
-  }
+       if (n > 0) {
+#ifdef DMF_FIX
+               int numretries = 3;
+tryagain:
+               readret = SMB_VFS_PREAD(fsp,data,n,pos);
 
-  fsp->pos = seek_ret - offset;
+               if (readret == -1) {
+                       if ((errno == EAGAIN) && numretries) {
+                               DEBUG(3,("read_file EAGAIN retry in 10 seconds\n"));
+                               (void)sleep(10);
+                               --numretries;
+                               goto tryagain;
+                       }
+                       return -1;
+               }
+#else /* NO DMF fix. */
+               readret = SMB_VFS_PREAD(fsp,data,n,pos);
 
-  DEBUG(10,("seek_file: requested pos = %.0f, new pos = %.0f\n",
-        (double)(pos+offset), (double)fsp->pos ));
+               if (readret == -1) {
+                       return -1;
+               }
+#endif
+               if (readret > 0) {
+                       ret += readret;
+               }
+       }
+
+       DEBUG(10,("read_file (%s): pos = %.0f, size = %lu, returned %lu\n",
+               fsp->fsp_name, (double)pos, (unsigned long)n, (long)ret ));
 
-  return(fsp->pos);
+       fsp->fh->pos += ret;
+       fsp->fh->position_information = fsp->fh->pos;
+
+       return(ret);
 }
 
+/* how many write cache buffers have been allocated */
+static unsigned int allocated_write_caches;
+
 /****************************************************************************
-read from a file
+ *Really* write to a file.
 ****************************************************************************/
 
-ssize_t read_file(files_struct *fsp,char *data,SMB_OFF_T pos,size_t n)
+static ssize_t real_write_file(struct smb_request *req,
+                               files_struct *fsp,
+                               const char *data,
+                               SMB_OFF_T pos,
+                               size_t n)
+{
+       ssize_t ret;
+
+        if (pos == -1) {
+                ret = vfs_write_data(req, fsp, data, n);
+        } else {
+               fsp->fh->pos = pos;
+               if (pos && lp_strict_allocate(SNUM(fsp->conn))) {
+                       if (vfs_fill_sparse(fsp, pos) == -1) {
+                               return -1;
+                       }
+               }
+                ret = vfs_pwrite_data(req, fsp, data, n, pos);
+       }
+
+       DEBUG(10,("real_write_file (%s): pos = %.0f, size = %lu, returned %ld\n",
+               fsp->fsp_name, (double)pos, (unsigned long)n, (long)ret ));
+
+       if (ret != -1) {
+               fsp->fh->pos += ret;
+
+/* Yes - this is correct - writes don't update this. JRA. */
+/* Found by Samba4 tests. */
+#if 0
+               fsp->position_information = fsp->pos;
+#endif
+       }
+
+       return ret;
+}
+
+/****************************************************************************
+ File size cache change.
+ Updates size on disk but doesn't flush the cache.
+****************************************************************************/
+
+static int wcp_file_size_change(files_struct *fsp)
+{
+       int ret;
+       write_cache *wcp = fsp->wcp;
+
+       wcp->file_size = wcp->offset + wcp->data_size;
+       ret = SMB_VFS_FTRUNCATE(fsp, wcp->file_size);
+       if (ret == -1) {
+               DEBUG(0,("wcp_file_size_change (%s): ftruncate of size %.0f error %s\n",
+                       fsp->fsp_name, (double)wcp->file_size, strerror(errno) ));
+       }
+       return ret;
+}
+
+static void update_write_time_handler(struct event_context *ctx,
+                                     struct timed_event *te,
+                                     const struct timeval *now,
+                                     void *private_data)
+{
+       files_struct *fsp = (files_struct *)private_data;
+
+       /* Remove the timed event handler. */
+       TALLOC_FREE(fsp->update_write_time_event);
+       DEBUG(5, ("Update write time on %s\n", fsp->fsp_name));
+
+       /* change the write time if not already changed by someone else */
+       update_write_time(fsp);
+}
+
+/*********************************************************
+ Schedule a write time update for WRITE_TIME_UPDATE_USEC_DELAY
+ in the future.
+*********************************************************/
+
+void trigger_write_time_update(struct files_struct *fsp)
+{
+       int delay;
+
+       if (fsp->write_time_forced) {
+               /* No point - "sticky" write times
+                * in effect.
+                */
+               return;
+       }
+
+       if (fsp->update_write_time_triggered) {
+               /*
+                * No point - an event is already scheduled.
+                */
+               return;
+       }
+       fsp->update_write_time_triggered = true;
+
+       delay = lp_parm_int(SNUM(fsp->conn),
+                           "smbd", "writetimeupdatedelay",
+                           WRITE_TIME_UPDATE_USEC_DELAY);
+
+       /* trigger the update 2 seconds later */
+       fsp->update_write_time_on_close = true;
+       fsp->update_write_time_event =
+               event_add_timed(smbd_event_context(), NULL,
+                               timeval_current_ofs(0, delay),
+                               "update_write_time_handler",
+                               update_write_time_handler, fsp);
+}
+
+void trigger_write_time_update_immediate(struct files_struct *fsp)
+{
+        if (fsp->write_time_forced) {
+               /*
+                * No point - "sticky" write times
+                * in effect.
+                */
+                return;
+        }
+
+       TALLOC_FREE(fsp->update_write_time_event);
+       DEBUG(5, ("Update write time immediate on %s\n", fsp->fsp_name));
+
+       fsp->update_write_time_triggered = true;
+
+        fsp->update_write_time_on_close = false;
+       update_write_time(fsp);
+}
+
+/****************************************************************************
+ Write to a file.
+****************************************************************************/
+
+ssize_t write_file(struct smb_request *req,
+                       files_struct *fsp,
+                       const char *data,
+                       SMB_OFF_T pos,
+                       size_t n)
 {
-  ssize_t ret=0,readret;
+       write_cache *wcp = fsp->wcp;
+       ssize_t total_written = 0;
+       int write_path = -1;
+
+       if (fsp->print_file) {
+               fstring sharename;
+               uint32 jobid;
+
+               if (!rap_to_pjobid(fsp->rap_print_jobid, sharename, &jobid)) {
+                       DEBUG(3,("write_file: Unable to map RAP jobid %u to jobid.\n",
+                                               (unsigned int)fsp->rap_print_jobid ));
+                       errno = EBADF;
+                       return -1;
+               }
+
+               return print_job_write(SNUM(fsp->conn), jobid, data, pos, n);
+       }
+
+       if (!fsp->can_write) {
+               errno = EPERM;
+               return -1;
+       }
+
+       if (!fsp->modified) {
+               SMB_STRUCT_STAT st;
+               fsp->modified = True;
+
+               if (SMB_VFS_FSTAT(fsp, &st) == 0) {
+                       int dosmode;
+                       trigger_write_time_update(fsp);
+                       dosmode = dos_mode(fsp->conn,fsp->fsp_name,&st);
+                       if ((lp_store_dos_attributes(SNUM(fsp->conn)) ||
+                                       MAP_ARCHIVE(fsp->conn)) &&
+                                       !IS_DOS_ARCHIVE(dosmode)) {
+                               file_set_dosmode(fsp->conn,fsp->fsp_name,
+                                               dosmode | aARCH,&st,
+                                               NULL,
+                                               false);
+                       }
+
+                       /*
+                        * If this is the first write and we have an exclusive oplock then setup
+                        * the write cache.
+                        */
+
+                       if (EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type) && !wcp) {
+                               setup_write_cache(fsp, st.st_size);
+                               wcp = fsp->wcp;
+                       }
+               }
+       }
+
+#ifdef WITH_PROFILE
+       DO_PROFILE_INC(writecache_total_writes);
+       if (!fsp->oplock_type) {
+               DO_PROFILE_INC(writecache_non_oplock_writes);
+       }
+#endif
+
+       /*
+        * If this file is level II oplocked then we need
+        * to grab the shared memory lock and inform all
+        * other files with a level II lock that they need
+        * to flush their read caches. We keep the lock over
+        * the shared memory area whilst doing this.
+        */
+
+       release_level_2_oplocks_on_change(fsp);
 
-#if USE_READ_PREDICTION
-  if (!fsp->can_write) {
-    ret = read_predict(fsp, fsp->fd_ptr->fd,pos,data,NULL,n);
+#ifdef WITH_PROFILE
+       if (profile_p && profile_p->writecache_total_writes % 500 == 0) {
+               DEBUG(3,("WRITECACHE: initwrites=%u abutted=%u total=%u \
+nonop=%u allocated=%u active=%u direct=%u perfect=%u readhits=%u\n",
+                       profile_p->writecache_init_writes,
+                       profile_p->writecache_abutted_writes,
+                       profile_p->writecache_total_writes,
+                       profile_p->writecache_non_oplock_writes,
+                       profile_p->writecache_allocated_write_caches,
+                       profile_p->writecache_num_write_caches,
+                       profile_p->writecache_direct_writes,
+                       profile_p->writecache_num_perfect_writes,
+                       profile_p->writecache_read_hits ));
 
-    data += ret;
-    n -= ret;
-    pos += ret;
-  }
+               DEBUG(3,("WRITECACHE: Flushes SEEK=%d, READ=%d, WRITE=%d, READRAW=%d, OPLOCK=%d, CLOSE=%d, SYNC=%d\n",
+                       profile_p->writecache_flushed_writes[SEEK_FLUSH],
+                       profile_p->writecache_flushed_writes[READ_FLUSH],
+                       profile_p->writecache_flushed_writes[WRITE_FLUSH],
+                       profile_p->writecache_flushed_writes[READRAW_FLUSH],
+                       profile_p->writecache_flushed_writes[OPLOCK_RELEASE_FLUSH],
+                       profile_p->writecache_flushed_writes[CLOSE_FLUSH],
+                       profile_p->writecache_flushed_writes[SYNC_FLUSH] ));
+       }
 #endif
 
-#if WITH_MMAP
-  if (fsp->mmap_ptr) {
-         SMB_OFF_T num = (fsp->mmap_size > pos) ? (fsp->mmap_size - pos) : 0;
-         num = MIN(n,num);
-         if (num > 0) {
-                 memcpy(data,fsp->mmap_ptr+pos,num);
-                 data += num;
-                 pos += num;
-                 n -= num;
-                 ret += num;
-         }
-  }
+       if (wcp && req->unread_bytes) {
+               /* If we're using receivefile don't
+                * deal with a write cache.
+                */
+               flush_write_cache(fsp, WRITE_FLUSH);
+               delete_write_cache(fsp);
+               wcp = NULL;
+       }
+
+       if(!wcp) {
+               DO_PROFILE_INC(writecache_direct_writes);
+               total_written = real_write_file(req, fsp, data, pos, n);
+               return total_written;
+       }
+
+       DEBUG(9,("write_file (%s)(fd=%d pos=%.0f size=%u) wcp->offset=%.0f wcp->data_size=%u\n",
+               fsp->fsp_name, fsp->fh->fd, (double)pos, (unsigned int)n, (double)wcp->offset, (unsigned int)wcp->data_size));
+
+       fsp->fh->pos = pos + n;
+
+       /*
+        * If we have active cache and it isn't contiguous then we flush.
+        * NOTE: There is a small problem with running out of disk ....
+        */
+
+       if (wcp->data_size) {
+               bool cache_flush_needed = False;
+
+               if ((pos >= wcp->offset) && (pos <= wcp->offset + wcp->data_size)) {
+      
+                       /* ASCII art.... JRA.
+
+      +--------------+-----
+      | Cached data  | Rest of allocated cache buffer....
+      +--------------+-----
+
+            +-------------------+
+            | Data to write     |
+            +-------------------+
+
+                       */
+
+                       /*
+                        * Start of write overlaps or abutts the existing data.
+                        */
+
+                       size_t data_used = MIN((wcp->alloc_size - (pos - wcp->offset)), n);
+
+                       memcpy(wcp->data + (pos - wcp->offset), data, data_used);
+
+                       /*
+                        * Update the current buffer size with the new data.
+                        */
+
+                       if(pos + data_used > wcp->offset + wcp->data_size) {
+                               wcp->data_size = pos + data_used - wcp->offset;
+                       }
+
+                       /*
+                        * Update the file size if changed.
+                        */
+
+                       if (wcp->offset + wcp->data_size > wcp->file_size) {
+                               if (wcp_file_size_change(fsp) == -1) {
+                                       return -1;
+                               }
+                       }
+
+                       /*
+                        * If we used all the data then
+                        * return here.
+                        */
+
+                       if(n == data_used) {
+                               return n;
+                       } else {
+                               cache_flush_needed = True;
+                       }
+                       /*
+                        * Move the start of data forward by the amount used,
+                        * cut down the amount left by the same amount.
+                        */
+
+                       data += data_used;
+                       pos += data_used;
+                       n -= data_used;
+
+                       DO_PROFILE_INC(writecache_abutted_writes);
+                       total_written = data_used;
+
+                       write_path = 1;
+
+               } else if ((pos < wcp->offset) && (pos + n > wcp->offset) && 
+                                       (pos + n <= wcp->offset + wcp->alloc_size)) {
+
+                       /* ASCII art.... JRA.
+
+                        +---------------+
+                        | Cache buffer  |
+                        +---------------+
+
+            +-------------------+
+            | Data to write     |
+            +-------------------+
+
+                       */
+
+                       /*
+                        * End of write overlaps the existing data.
+                        */
+
+                       size_t data_used = pos + n - wcp->offset;
+
+                       memcpy(wcp->data, data + n - data_used, data_used);
+
+                       /*
+                        * Update the current buffer size with the new data.
+                        */
+
+                       if(pos + n > wcp->offset + wcp->data_size) {
+                               wcp->data_size = pos + n - wcp->offset;
+                       }
+
+                       /*
+                        * Update the file size if changed.
+                        */
+
+                       if (wcp->offset + wcp->data_size > wcp->file_size) {
+                               if (wcp_file_size_change(fsp) == -1) {
+                                       return -1;
+                               }
+                       }
+
+                       /*
+                        * We don't need to move the start of data, but we
+                        * cut down the amount left by the amount used.
+                        */
+
+                       n -= data_used;
+
+                       /*
+                        * We cannot have used all the data here.
+                        */
+
+                       cache_flush_needed = True;
+
+                       DO_PROFILE_INC(writecache_abutted_writes);
+                       total_written = data_used;
+
+                       write_path = 2;
+
+               } else if ( (pos >= wcp->file_size) && 
+                                       (wcp->offset + wcp->data_size == wcp->file_size) &&
+                                       (pos > wcp->offset + wcp->data_size) && 
+                                       (pos < wcp->offset + wcp->alloc_size) ) {
+
+                       /* ASCII art.... JRA.
+
+                       End of file ---->|
+
+                        +---------------+---------------+
+                        | Cached data   | Cache buffer  |
+                        +---------------+---------------+
+
+                                              +-------------------+
+                                              | Data to write     |
+                                              +-------------------+
+
+                       */
+
+                       /*
+                        * Non-contiguous write part of which fits within
+                        * the cache buffer and is extending the file
+                        * and the cache contents reflect the current
+                        * data up to the current end of the file.
+                        */
+
+                       size_t data_used;
+
+                       if(pos + n <= wcp->offset + wcp->alloc_size) {
+                               data_used = n;
+                       } else {
+                               data_used = wcp->offset + wcp->alloc_size - pos;
+                       }
+
+                       /*
+                        * Fill in the non-continuous area with zeros.
+                        */
+
+                       memset(wcp->data + wcp->data_size, '\0',
+                               pos - (wcp->offset + wcp->data_size) );
+
+                       memcpy(wcp->data + (pos - wcp->offset), data, data_used);
+
+                       /*
+                        * Update the current buffer size with the new data.
+                        */
+
+                       if(pos + data_used > wcp->offset + wcp->data_size) {
+                               wcp->data_size = pos + data_used - wcp->offset;
+                       }
+
+                       /*
+                        * Update the file size if changed.
+                        */
+
+                       if (wcp->offset + wcp->data_size > wcp->file_size) {
+                               if (wcp_file_size_change(fsp) == -1) {
+                                       return -1;
+                               }
+                       }
+
+                       /*
+                        * If we used all the data then
+                        * return here.
+                        */
+
+                       if(n == data_used) {
+                               return n;
+                       } else {
+                               cache_flush_needed = True;
+                       }
+
+                       /*
+                        * Move the start of data forward by the amount used,
+                        * cut down the amount left by the same amount.
+                        */
+
+                       data += data_used;
+                       pos += data_used;
+                       n -= data_used;
+
+                       DO_PROFILE_INC(writecache_abutted_writes);
+                       total_written = data_used;
+
+                       write_path = 3;
+
+                } else if ( (pos >= wcp->file_size) &&
+                           (n == 1) &&
+                           (wcp->file_size == wcp->offset + wcp->data_size) &&
+                           (pos < wcp->file_size + wcp->alloc_size)) {
+
+                        /*
+
+                End of file ---->|
+
+                 +---------------+---------------+
+                 | Cached data   | Cache buffer  |
+                 +---------------+---------------+
+
+                                 |<------- allocated size ---------------->|
+
+                                                         +--------+
+                                                         | 1 Byte |
+                                                         +--------+
+
+                       MS-Office seems to do this a lot to determine if there's enough
+                       space on the filesystem to write a new file.
+
+                       Change to :
+
+                End of file ---->|
+                                 +-----------------------+--------+
+                                 | Zeroed Cached data    | 1 Byte |
+                                 +-----------------------+--------+
+                        */
+
+                       flush_write_cache(fsp, WRITE_FLUSH);
+                       wcp->offset = wcp->file_size;
+                       wcp->data_size = pos - wcp->file_size + 1;
+                       memset(wcp->data, '\0', wcp->data_size);
+                       memcpy(wcp->data + wcp->data_size-1, data, 1);
+
+                       /*
+                        * Update the file size if changed.
+                        */
+
+                       if (wcp->offset + wcp->data_size > wcp->file_size) {
+                               if (wcp_file_size_change(fsp) == -1) {
+                                       return -1;
+                               }
+                       }
+
+                       return n;
+
+               } else {
+
+                       /* ASCII art..... JRA.
+
+   Case 1).
+
+                        +---------------+---------------+
+                        | Cached data   | Cache buffer  |
+                        +---------------+---------------+
+
+                                                              +-------------------+
+                                                              | Data to write     |
+                                                              +-------------------+
+
+   Case 2).
+
+                           +---------------+---------------+
+                           | Cached data   | Cache buffer  |
+                           +---------------+---------------+
+
+   +-------------------+
+   | Data to write     |
+   +-------------------+
+
+    Case 3).
+
+                           +---------------+---------------+
+                           | Cached data   | Cache buffer  |
+                           +---------------+---------------+
+
+                  +-----------------------------------------------------+
+                  | Data to write                                       |
+                  +-----------------------------------------------------+
+
+                 */
+
+                       /*
+                        * Write is bigger than buffer, or there is no overlap on the
+                        * low or high ends.
+                        */
+
+                       DEBUG(9,("write_file: non cacheable write : fd = %d, pos = %.0f, len = %u, current cache pos = %.0f \
+len = %u\n",fsp->fh->fd, (double)pos, (unsigned int)n, (double)wcp->offset, (unsigned int)wcp->data_size ));
+
+                       /*
+                        * If write would fit in the cache, and is larger than
+                        * the data already in the cache, flush the cache and
+                        * preferentially copy the data new data into it. Otherwise
+                        * just write the data directly.
+                        */
+
+                       if ( n <= wcp->alloc_size && n > wcp->data_size) {
+                               cache_flush_needed = True;
+                       } else {
+                               ssize_t ret = real_write_file(NULL,fsp, data, pos, n);
+
+                               /*
+                                * If the write overlaps the entire cache, then
+                                * discard the current contents of the cache.
+                                * Fix from Rasmus Borup Hansen rbh@math.ku.dk.
+                                */
+
+                               if ((pos <= wcp->offset) &&
+                                               (pos + n >= wcp->offset + wcp->data_size) ) {
+                                       DEBUG(9,("write_file: discarding overwritten write \
+cache: fd = %d, off=%.0f, size=%u\n", fsp->fh->fd, (double)wcp->offset, (unsigned int)wcp->data_size ));
+                                       wcp->data_size = 0;
+                               }
+
+                               DO_PROFILE_INC(writecache_direct_writes);
+                               if (ret == -1) {
+                                       return ret;
+                               }
+
+                               if (pos + ret > wcp->file_size) {
+                                       wcp->file_size = pos + ret;
+                               }
+
+                               return ret;
+                       }
+
+                       write_path = 4;
+
+               }
+
+               if (cache_flush_needed) {
+                       DEBUG(3,("WRITE_FLUSH:%d: due to noncontinuous write: fd = %d, size = %.0f, pos = %.0f, \
+n = %u, wcp->offset=%.0f, wcp->data_size=%u\n",
+                               write_path, fsp->fh->fd, (double)wcp->file_size, (double)pos, (unsigned int)n,
+                               (double)wcp->offset, (unsigned int)wcp->data_size ));
+
+                       flush_write_cache(fsp, WRITE_FLUSH);
+               }
+       }
+
+       /*
+        * If the write request is bigger than the cache
+        * size, write it all out.
+        */
+
+       if (n > wcp->alloc_size ) {
+               ssize_t ret = real_write_file(NULL,fsp, data, pos, n);
+               if (ret == -1) {
+                       return -1;
+               }
+
+               if (pos + ret > wcp->file_size) {
+                       wcp->file_size = pos + n;
+               }
+
+               DO_PROFILE_INC(writecache_direct_writes);
+               return total_written + n;
+       }
+
+       /*
+        * If there's any data left, cache it.
+        */
+
+       if (n) {
+#ifdef WITH_PROFILE
+               if (wcp->data_size) {
+                       DO_PROFILE_INC(writecache_abutted_writes);
+               } else {
+                       DO_PROFILE_INC(writecache_init_writes);
+               }
 #endif
+               memcpy(wcp->data+wcp->data_size, data, n);
+               if (wcp->data_size == 0) {
+                       wcp->offset = pos;
+                       DO_PROFILE_INC(writecache_num_write_caches);
+               }
+               wcp->data_size += n;
 
-  if (seek_file(fsp,pos) == -1) {
-    DEBUG(3,("read_file: Failed to seek to %.0f\n",(double)pos));
-    return(ret);
-  }
+               /*
+                * Update the file size if changed.
+                */
 
-  if (n > 0) {
-    readret = fsp->conn->vfs_ops.read(fsp->fd_ptr->fd,data,n);
-    if (readret > 0) ret += readret;
-  }
+               if (wcp->offset + wcp->data_size > wcp->file_size) {
+                       if (wcp_file_size_change(fsp) == -1) {
+                               return -1;
+                       }
+               }
+               DEBUG(9,("wcp->offset = %.0f wcp->data_size = %u cache return %u\n",
+                       (double)wcp->offset, (unsigned int)wcp->data_size, (unsigned int)n));
 
-  return(ret);
+               total_written += n;
+               return total_written; /* .... that's a write :) */
+       }
+  
+       return total_written;
 }
 
+/****************************************************************************
+ Delete the write cache structure.
+****************************************************************************/
+
+void delete_write_cache(files_struct *fsp)
+{
+       write_cache *wcp;
+
+       if(!fsp) {
+               return;
+       }
+
+       if(!(wcp = fsp->wcp)) {
+               return;
+       }
+
+       DO_PROFILE_DEC(writecache_allocated_write_caches);
+       allocated_write_caches--;
+
+       SMB_ASSERT(wcp->data_size == 0);
+
+       SAFE_FREE(wcp->data);
+       SAFE_FREE(fsp->wcp);
+
+       DEBUG(10,("delete_write_cache: File %s deleted write cache\n", fsp->fsp_name ));
+}
 
 /****************************************************************************
-write to a file
+ Setup the write cache structure.
 ****************************************************************************/
 
-ssize_t write_file(files_struct *fsp,char *data,size_t n)
+static bool setup_write_cache(files_struct *fsp, SMB_OFF_T file_size)
 {
-  if (!fsp->can_write) {
-    errno = EPERM;
-    return(0);
-  }
-
-  if (!fsp->modified) {
-    SMB_STRUCT_STAT st;
-    fsp->modified = True;
-    if (fsp->conn->vfs_ops.fstat(fsp->fd_ptr->fd,&st) == 0) {
-      int dosmode = dos_mode(fsp->conn,fsp->fsp_name,&st);
-      if (MAP_ARCHIVE(fsp->conn) && !IS_DOS_ARCHIVE(dosmode)) {        
-        file_chmod(fsp->conn,fsp->fsp_name,dosmode | aARCH,&st);
-      }
-    }  
-  }
-
-  return(vfs_write_data(fsp,data,n));
+       ssize_t alloc_size = lp_write_cache_size(SNUM(fsp->conn));
+       write_cache *wcp;
+
+       if (allocated_write_caches >= MAX_WRITE_CACHES) {
+               return False;
+       }
+
+       if(alloc_size == 0 || fsp->wcp) {
+               return False;
+       }
+
+       if((wcp = SMB_MALLOC_P(write_cache)) == NULL) {
+               DEBUG(0,("setup_write_cache: malloc fail.\n"));
+               return False;
+       }
+
+       wcp->file_size = file_size;
+       wcp->offset = 0;
+       wcp->alloc_size = alloc_size;
+       wcp->data_size = 0;
+       if((wcp->data = (char *)SMB_MALLOC(wcp->alloc_size)) == NULL) {
+               DEBUG(0,("setup_write_cache: malloc fail for buffer size %u.\n",
+                       (unsigned int)wcp->alloc_size ));
+               SAFE_FREE(wcp);
+               return False;
+       }
+
+       memset(wcp->data, '\0', wcp->alloc_size );
+
+       fsp->wcp = wcp;
+       DO_PROFILE_INC(writecache_allocated_write_caches);
+       allocated_write_caches++;
+
+       DEBUG(10,("setup_write_cache: File %s allocated write cache size %lu\n",
+               fsp->fsp_name, (unsigned long)wcp->alloc_size ));
+
+       return True;
 }
 
+/****************************************************************************
+ Cope with a size change.
+****************************************************************************/
+
+void set_filelen_write_cache(files_struct *fsp, SMB_OFF_T file_size)
+{
+       if(fsp->wcp) {
+               /* The cache *must* have been flushed before we do this. */
+               if (fsp->wcp->data_size != 0) {
+                       char *msg;
+                       asprintf(&msg, "set_filelen_write_cache: size change "
+                                "on file %s with write cache size = %lu\n",
+                                fsp->fsp_name,
+                                (unsigned long)fsp->wcp->data_size);
+                       smb_panic(msg);
+               }
+               fsp->wcp->file_size = file_size;
+       }
+}
 
 /*******************************************************************
-sync a file
+ Flush a write cache struct to disk.
 ********************************************************************/
 
-void sys_sync_file(int fd)
+ssize_t flush_write_cache(files_struct *fsp, enum flush_reason_enum reason)
 {
-#ifdef HAVE_FSYNC
-    fsync(fd);
+       write_cache *wcp = fsp->wcp;
+       size_t data_size;
+       ssize_t ret;
+
+       if(!wcp || !wcp->data_size) {
+               return 0;
+       }
+
+       data_size = wcp->data_size;
+       wcp->data_size = 0;
+
+       DO_PROFILE_DEC_INC(writecache_num_write_caches,writecache_flushed_writes[reason]);
+
+       DEBUG(9,("flushing write cache: fd = %d, off=%.0f, size=%u\n",
+               fsp->fh->fd, (double)wcp->offset, (unsigned int)data_size));
+
+#ifdef WITH_PROFILE
+       if(data_size == wcp->alloc_size) {
+               DO_PROFILE_INC(writecache_num_perfect_writes);
+       }
 #endif
+
+       ret = real_write_file(NULL, fsp, wcp->data, wcp->offset, data_size);
+
+       /*
+        * Ensure file size if kept up to date if write extends file.
+        */
+
+       if ((ret != -1) && (wcp->offset + ret > wcp->file_size)) {
+               wcp->file_size = wcp->offset + ret;
+       }
+
+       return ret;
+}
+
+/*******************************************************************
+sync a file
+********************************************************************/
+
+NTSTATUS sync_file(connection_struct *conn, files_struct *fsp, bool write_through)
+{
+               if (fsp->fh->fd == -1)
+               return NT_STATUS_INVALID_HANDLE;
+
+       if (lp_strict_sync(SNUM(conn)) &&
+           (lp_syncalways(SNUM(conn)) || write_through)) {
+               int ret = flush_write_cache(fsp, SYNC_FLUSH);
+               if (ret == -1) {
+                       return map_nt_error_from_unix(errno);
+               }
+               ret = SMB_VFS_FSYNC(fsp);
+               if (ret == -1) {
+                       return map_nt_error_from_unix(errno);
+               }
+       }
+       return NT_STATUS_OK;
+}
+
+/************************************************************
+ Perform a stat whether a valid fd or not.
+************************************************************/
+
+int fsp_stat(files_struct *fsp, SMB_STRUCT_STAT *pst)
+{
+       if (fsp->fh->fd == -1) {
+               return SMB_VFS_STAT(fsp->conn, fsp->fsp_name, pst);
+       } else {
+               return SMB_VFS_FSTAT(fsp, pst);
+       }
 }