- int res=0; // Return values of different functions we call.
- unsigned long index = pos >> PAGE_CACHE_SHIFT; // Offset in file in pages.
- int from = (pos & (PAGE_CACHE_SIZE - 1)); // Writing offset in first page
- int to = ((pos + write_bytes - 1) & (PAGE_CACHE_SIZE - 1)) + 1;
- /* offset of last modified byte in last
- page */
- struct address_space *mapping = inode->i_mapping; // Pages are mapped here.
- int i; // Simple counter
- int blocks = 0; /* Return value (blocks that should be allocated) */
- struct buffer_head *bh, *head; // Current bufferhead and first bufferhead
- // of a page.
- unsigned block_start, block_end; // Starting and ending offsets of current
- // buffer in the page.
- struct buffer_head *wait[2], **wait_bh=wait; // Buffers for page, if
- // Page appeared to be not up
- // to date. Note how we have
- // at most 2 buffers, this is
- // because we at most may
- // partially overwrite two
- // buffers for one page. One at // the beginning of write area
- // and one at the end.
- // Everything inthe middle gets // overwritten totally.
-
- struct cpu_key key; // cpu key of item that we are going to deal with
- struct item_head *ih = NULL; // pointer to item head that we are going to deal with
- struct buffer_head *itembuf=NULL; // Buffer head that contains items that we are going to deal with
- INITIALIZE_PATH(path); // path to item, that we are going to deal with.
- __u32 * item=NULL; // pointer to item we are going to deal with
- int item_pos=-1; /* Position in indirect item */
-
-
- if ( num_pages < 1 ) {
- reiserfs_warning (inode->i_sb,
- "green-9001: reiserfs_prepare_file_region_for_write "
- "called with zero number of pages to process");
- return -EFAULT;
- }
-
- /* We have 2 loops for pages. In first loop we grab and lock the pages, so
- that nobody would touch these until we release the pages. Then
- we'd start to deal with mapping buffers to blocks. */
- for ( i = 0; i < num_pages; i++) {
- prepared_pages[i] = grab_cache_page(mapping, index + i); // locks the page
- if ( !prepared_pages[i]) {
- res = -ENOMEM;
- goto failed_page_grabbing;
- }
- if (!page_has_buffers(prepared_pages[i]))
- create_empty_buffers(prepared_pages[i], inode->i_sb->s_blocksize, 0);
- }
-
- /* Let's count amount of blocks for a case where all the blocks
- overwritten are new (we will substract already allocated blocks later)*/
- if ( num_pages > 2 )
- /* These are full-overwritten pages so we count all the blocks in
- these pages are counted as needed to be allocated */
- blocks = (num_pages - 2) << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-
- /* count blocks needed for first page (possibly partially written) */
- blocks += ((PAGE_CACHE_SIZE - from) >> inode->i_blkbits) +
- !!(from & (inode->i_sb->s_blocksize-1)); /* roundup */
-
- /* Now we account for last page. If last page == first page (we
- overwrite only one page), we substract all the blocks past the
- last writing position in a page out of already calculated number
- of blocks */
- blocks += ((num_pages > 1) << (PAGE_CACHE_SHIFT-inode->i_blkbits)) -
- ((PAGE_CACHE_SIZE - to) >> inode->i_blkbits);
- /* Note how we do not roundup here since partial blocks still
- should be allocated */
-
- /* Now if all the write area lies past the file end, no point in
- maping blocks, since there is none, so we just zero out remaining
- parts of first and last pages in write area (if needed) */
- if ( (pos & ~((loff_t)PAGE_CACHE_SIZE - 1)) > inode->i_size ) {
- if ( from != 0 ) {/* First page needs to be partially zeroed */
- char *kaddr = kmap_atomic(prepared_pages[0], KM_USER0);
- memset(kaddr, 0, from);
- kunmap_atomic( kaddr, KM_USER0);
- }
- if ( to != PAGE_CACHE_SIZE ) { /* Last page needs to be partially zeroed */
- char *kaddr = kmap_atomic(prepared_pages[num_pages-1], KM_USER0);
- memset(kaddr+to, 0, PAGE_CACHE_SIZE - to);
- kunmap_atomic( kaddr, KM_USER0);
+ int res = 0; // Return values of different functions we call.
+ unsigned long index = pos >> PAGE_CACHE_SHIFT; // Offset in file in pages.
+ int from = (pos & (PAGE_CACHE_SIZE - 1)); // Writing offset in first page
+ int to = ((pos + write_bytes - 1) & (PAGE_CACHE_SIZE - 1)) + 1;
+ /* offset of last modified byte in last
+ page */
+ struct address_space *mapping = inode->i_mapping; // Pages are mapped here.
+ int i; // Simple counter
+ int blocks = 0; /* Return value (blocks that should be allocated) */
+ struct buffer_head *bh, *head; // Current bufferhead and first bufferhead
+ // of a page.
+ unsigned block_start, block_end; // Starting and ending offsets of current
+ // buffer in the page.
+ struct buffer_head *wait[2], **wait_bh = wait; // Buffers for page, if
+ // Page appeared to be not up
+ // to date. Note how we have
+ // at most 2 buffers, this is
+ // because we at most may
+ // partially overwrite two
+ // buffers for one page. One at // the beginning of write area
+ // and one at the end.
+ // Everything inthe middle gets // overwritten totally.
+
+ struct cpu_key key; // cpu key of item that we are going to deal with
+ struct item_head *ih = NULL; // pointer to item head that we are going to deal with
+ struct buffer_head *itembuf = NULL; // Buffer head that contains items that we are going to deal with
+ INITIALIZE_PATH(path); // path to item, that we are going to deal with.
+ __le32 *item = NULL; // pointer to item we are going to deal with
+ int item_pos = -1; /* Position in indirect item */
+
+ if (num_pages < 1) {
+ reiserfs_warning(inode->i_sb,
+ "green-9001: reiserfs_prepare_file_region_for_write "
+ "called with zero number of pages to process");
+ return -EFAULT;