fileio.c

来自「samba-3.0.22.tar.gz 编译smb服务器的源码」· C语言 代码 · 共 861 行 · 第 1/2 页

                       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) &&
			    (pos < wcp->offset + 2*wcp->alloc_size) &&
			    (wcp->file_size == wcp->offset + wcp->data_size)) {

                        /*
                        +---------------+
                        | Cached data   |
                        +---------------+

                                                         +--------+
                                                         | 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.
                        */

			SMB_BIG_UINT new_start = wcp->offset + wcp->data_size;

			flush_write_cache(fsp, WRITE_FLUSH);
			wcp->offset = new_start;
			wcp->data_size = pos - new_start + 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(fsp, data, pos, n);

				/*
				 * If the write overlaps the entire cache, then
				 * discard the current contents of the cache.
				 * Fix from Rasmus Borup Hansen [e-mail].
				 */

				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(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;

		/*
		 * Update the file size if changed.
		 */

		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));

		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 ));
}

/****************************************************************************
 Setup the write cache structure.
****************************************************************************/

static BOOL setup_write_cache(files_struct *fsp, SMB_OFF_T file_size)
{
	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) {
			pstring msg;
			slprintf(msg, sizeof(msg)-1, "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;
	}
}

/*******************************************************************
 Flush a write cache struct to disk.
********************************************************************/

ssize_t flush_write_cache(files_struct *fsp, enum flush_reason_enum reason)
{
	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(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
********************************************************************/

void sync_file(connection_struct *conn, files_struct *fsp, BOOL write_through)
{
       	if (fsp->fh->fd == -1)
		return;

	if (lp_strict_sync(SNUM(conn)) &&
	    (lp_syncalways(SNUM(conn)) || write_through)) {
		flush_write_cache(fsp, SYNC_FLUSH);
		SMB_VFS_FSYNC(fsp,fsp->fh->fd);
	}
}

/************************************************************
 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,fsp->fh->fd, pst);
	}
}