inode.c

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** On success, page_result is set to a locked, pinned page, and bh_result
** is set to an up to date buffer for the last block in the file.  returns 0.
**
** tail conversion is not done, so bh_result might not be valid for writing
** check buffer_mapped(bh_result) and bh_result->b_blocknr != 0 before
** trying to write the block.
**
** on failure, nonzero is returned, page_result and bh_result are untouched.
*/
static int grab_tail_page(struct inode *p_s_inode, 
			  struct page **page_result, 
			  struct buffer_head **bh_result) {

    /* we want the page with the last byte in the file,
    ** not the page that will hold the next byte for appending
    */
    unsigned long index = (p_s_inode->i_size-1) >> PAGE_CACHE_SHIFT ;
    unsigned long pos = 0 ;
    unsigned long start = 0 ;
    unsigned long blocksize = p_s_inode->i_sb->s_blocksize ;
    unsigned long offset = (p_s_inode->i_size) & (PAGE_CACHE_SIZE - 1) ;
    struct buffer_head *bh ;
    struct buffer_head *head ;
    struct page * page ;
    int error ;
    
    /* we know that we are only called with inode->i_size > 0.
    ** we also know that a file tail can never be as big as a block
    ** If i_size % blocksize == 0, our file is currently block aligned
    ** and it won't need converting or zeroing after a truncate.
    */
    if ((offset & (blocksize - 1)) == 0) {
        return -ENOENT ;
    }
    page = grab_cache_page(p_s_inode->i_mapping, index) ;
    error = -ENOMEM ;
    if (!page) {
        goto out ;
    }
    /* start within the page of the last block in the file */
    start = (offset / blocksize) * blocksize ;

    error = block_prepare_write(page, start, offset, 
				reiserfs_get_block_create_0) ;
    if (error)
	goto unlock ;

    kunmap(page) ; /* mapped by block_prepare_write */

    head = page->buffers ;      
    bh = head;
    do {
	if (pos >= start) {
	    break ;
	}
	bh = bh->b_this_page ;
	pos += blocksize ;
    } while(bh != head) ;

    if (!buffer_uptodate(bh)) {
	/* note, this should never happen, prepare_write should
	** be taking care of this for us.  If the buffer isn't up to date,
	** I've screwed up the code to find the buffer, or the code to
	** call prepare_write
	*/
	reiserfs_warning("clm-6000: error reading block %lu on dev %s\n",
	                  bh->b_blocknr, kdevname(bh->b_dev)) ;
	error = -EIO ;
	goto unlock ;
    }
    *bh_result = bh ;
    *page_result = page ;

out:
    return error ;

unlock:
    UnlockPage(page) ;
    page_cache_release(page) ;
    return error ;
}

/*
** vfs version of truncate file.  Must NOT be called with
** a transaction already started.
**
** some code taken from block_truncate_page
*/
void reiserfs_truncate_file(struct inode *p_s_inode, int update_timestamps) {
    struct reiserfs_transaction_handle th ;
    int windex ;

    /* we want the offset for the first byte after the end of the file */
    unsigned long offset = p_s_inode->i_size & (PAGE_CACHE_SIZE - 1) ;
    unsigned blocksize = p_s_inode->i_sb->s_blocksize ;
    unsigned length ;
    struct page *page = NULL ;
    int error ;
    struct buffer_head *bh = NULL ;

    if (p_s_inode->i_size > 0) {
        if ((error = grab_tail_page(p_s_inode, &page, &bh))) {
	    // -ENOENT means we truncated past the end of the file, 
	    // and get_block_create_0 could not find a block to read in,
	    // which is ok.
	    if (error != -ENOENT)
	        reiserfs_warning("clm-6001: grab_tail_page failed %d\n", error);
	    page = NULL ;
	    bh = NULL ;
	}
    }

    /* so, if page != NULL, we have a buffer head for the offset at 
    ** the end of the file. if the bh is mapped, and bh->b_blocknr != 0, 
    ** then we have an unformatted node.  Otherwise, we have a direct item, 
    ** and no zeroing is required on disk.  We zero after the truncate, 
    ** because the truncate might pack the item anyway 
    ** (it will unmap bh if it packs).
    */
    /* it is enough to reserve space in transaction for 2 balancings:
       one for "save" link adding and another for the first
       cut_from_item. 1 is for update_sd */
    journal_begin(&th, p_s_inode->i_sb,  JOURNAL_PER_BALANCE_CNT * 2 + 1 ) ;
    reiserfs_update_inode_transaction(p_s_inode) ;
    windex = push_journal_writer("reiserfs_vfs_truncate_file") ;
    if (update_timestamps)
           /* we are doing real truncate: if the system crashes before the last
              transaction of truncating gets committed - on reboot the file
              either appears truncated properly or not truncated at all */
           add_save_link (&th, p_s_inode, 1);
    reiserfs_do_truncate (&th, p_s_inode, page, update_timestamps) ;
    pop_journal_writer(windex) ;
    journal_end(&th, p_s_inode->i_sb,  JOURNAL_PER_BALANCE_CNT * 2 + 1 ) ;

    if (update_timestamps)
       remove_save_link (p_s_inode, 1/* truncate */);

    if (page) {
        length = offset & (blocksize - 1) ;
	/* if we are not on a block boundary */
	if (length) {
	    length = blocksize - length ;
	    memset((char *)kmap(page) + offset, 0, length) ;   
	    flush_dcache_page(page) ;
	    kunmap(page) ;
	    if (buffer_mapped(bh) && bh->b_blocknr != 0) {
	        mark_buffer_dirty(bh) ;
	    }
	}
	UnlockPage(page) ;
	page_cache_release(page) ;
    }

    return ;
}

static int map_block_for_writepage(struct inode *inode, 
			       struct buffer_head *bh_result, 
                               unsigned long block) {
    struct reiserfs_transaction_handle th ;
    int fs_gen ;
    struct item_head tmp_ih ;
    struct item_head *ih ;
    struct buffer_head *bh ;
    __u32 *item ;
    struct cpu_key key ;
    INITIALIZE_PATH(path) ;
    int pos_in_item ;
    int jbegin_count = JOURNAL_PER_BALANCE_CNT ;
    loff_t byte_offset = (block << inode->i_sb->s_blocksize_bits) + 1 ;
    int retval ;
    int use_get_block = 0 ;
    int bytes_copied = 0 ;
    int copy_size ;

    kmap(bh_result->b_page) ;
start_over:
    lock_kernel() ;
    journal_begin(&th, inode->i_sb, jbegin_count) ;
    reiserfs_update_inode_transaction(inode) ;

    make_cpu_key(&key, inode, byte_offset, TYPE_ANY, 3) ;

research:
    retval = search_for_position_by_key(inode->i_sb, &key, &path) ;
    if (retval != POSITION_FOUND) {
        use_get_block = 1;
	goto out ;
    } 

    bh = get_last_bh(&path) ;
    ih = get_ih(&path) ;
    item = get_item(&path) ;
    pos_in_item = path.pos_in_item ;

    /* we've found an unformatted node */
    if (indirect_item_found(retval, ih)) {
	if (bytes_copied > 0) {
	    reiserfs_warning("clm-6002: bytes_copied %d\n", bytes_copied) ;
	}
        if (!get_block_num(item, pos_in_item)) {
	    /* crap, we are writing to a hole */
	    use_get_block = 1;
	    goto out ;
	}
	set_block_dev_mapped(bh_result, get_block_num(item,pos_in_item),inode);
        mark_buffer_uptodate(bh_result, 1);
    } else if (is_direct_le_ih(ih)) {
        char *p ; 
        p = page_address(bh_result->b_page) ;
        p += (byte_offset -1) & (PAGE_CACHE_SIZE - 1) ;
        copy_size = ih_item_len(ih) - pos_in_item;

	fs_gen = get_generation(inode->i_sb) ;
	copy_item_head(&tmp_ih, ih) ;
	reiserfs_prepare_for_journal(inode->i_sb, bh, 1) ;
	if (fs_changed (fs_gen, inode->i_sb) && item_moved (&tmp_ih, &path)) {
	    reiserfs_restore_prepared_buffer(inode->i_sb, bh) ;
	    goto research;
	}

	memcpy( B_I_PITEM(bh, ih) + pos_in_item, p + bytes_copied, copy_size) ;

	journal_mark_dirty(&th, inode->i_sb, bh) ;
	bytes_copied += copy_size ;
	set_block_dev_mapped(bh_result, 0, inode);
        mark_buffer_uptodate(bh_result, 1);

	/* are there still bytes left? */
        if (bytes_copied < bh_result->b_size && 
	    (byte_offset + bytes_copied) < inode->i_size) {
	    set_cpu_key_k_offset(&key, cpu_key_k_offset(&key) + copy_size) ;
	    goto research ;
	}
    } else {
        reiserfs_warning("clm-6003: bad item inode %lu, device %s\n", inode->i_ino, kdevname(inode->i_sb->s_dev)) ;
        retval = -EIO ;
	goto out ;
    }
    retval = 0 ;
    
out:
    pathrelse(&path) ;
    journal_end(&th, inode->i_sb, jbegin_count) ;
    unlock_kernel() ;

    /* this is where we fill in holes in the file. */
    if (use_get_block) {
	retval = reiserfs_get_block(inode, block, bh_result, 
	                            GET_BLOCK_CREATE | GET_BLOCK_NO_ISEM) ;
	if (!retval) {
	    if (!buffer_mapped(bh_result) || bh_result->b_blocknr == 0) {
	        /* get_block failed to find a mapped unformatted node. */
		use_get_block = 0 ;
		goto start_over ;
	    }
	}
    }
    kunmap(bh_result->b_page) ;
    return retval ;
}

/* helper func to get a buffer head ready for writepage to send to
** ll_rw_block
*/
static inline void submit_bh_for_writepage(struct buffer_head **bhp, int nr) {
    struct buffer_head *bh ;
    int i;
    for(i = 0 ; i < nr ; i++) {
        bh = bhp[i] ;
	lock_buffer(bh) ;
	set_buffer_async_io(bh) ;
	/* submit_bh doesn't care if the buffer is dirty, but nobody
	** later on in the call chain will be cleaning it.  So, we
	** clean the buffer here, it still gets written either way.
	*/
	clear_bit(BH_Dirty, &bh->b_state) ;
	set_bit(BH_Uptodate, &bh->b_state) ;
	submit_bh(WRITE, bh) ;
    }
}

static int reiserfs_write_full_page(struct page *page) {
    struct inode *inode = page->mapping->host ;
    unsigned long end_index = inode->i_size >> PAGE_CACHE_SHIFT ;
    unsigned last_offset = PAGE_CACHE_SIZE;
    int error = 0;
    unsigned long block ;
    unsigned cur_offset = 0 ;
    struct buffer_head *head, *bh ;
    int partial = 0 ;
    struct buffer_head *arr[PAGE_CACHE_SIZE/512] ;
    int nr = 0 ;

    if (!page->buffers) {
        block_prepare_write(page, 0, 0, NULL) ;
	kunmap(page) ;
    }
    /* last page in the file, zero out any contents past the
    ** last byte in the file
    */
    if (page->index >= end_index) {
        last_offset = inode->i_size & (PAGE_CACHE_SIZE - 1) ;
	/* no file contents in this page */
	if (page->index >= end_index + 1 || !last_offset) {
	    error =  -EIO ;
	    goto fail ;
	}
	memset((char *)kmap(page)+last_offset, 0, PAGE_CACHE_SIZE-last_offset) ;
	flush_dcache_page(page) ;
	kunmap(page) ;
    }
    head = page->buffers ;
    bh = head ;
    block = page->index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits) ;
    do {
	/* if this offset in the page is outside the file */
	if (cur_offset >= last_offset) {
	    if (!buffer_uptodate(bh))
	        partial = 1 ;
	} else {
	    /* fast path, buffer mapped to an unformatted node */
	    if (buffer_mapped(bh) && bh->b_blocknr != 0) {
		arr[nr++] = bh ;
	    } else {
		/* buffer not mapped yet, or points to a direct item.
		** search and dirty or log
		*/
		if ((error = map_block_for_writepage(inode, bh, block))) {
		    goto fail ;
		}
		/* map_block_for_writepage either found an unformatted node
		** and mapped it for us, or it found a direct item
		** and logged the changes.  
		*/
		if (buffer_mapped(bh) && bh->b_blocknr != 0) {
		    arr[nr++] = bh ;
		}
	    }
	}
        bh = bh->b_this_page ;
	cur_offset += bh->b_size ;
	block++ ;
    } while(bh != head) ;

    /* if this page only had a direct item, it is very possible for
    ** nr == 0 without there being any kind of error.
    */
    if (nr) {
        submit_bh_for_writepage(arr, nr) ;
    } else {
        UnlockPage(page) ;
    }
    if (!partial)
        SetPageUptodate(page) ;

    return 0 ;

fail:
    if (nr) {
        submit_bh_for_writepage(arr, nr) ;
    } else {
        UnlockPage(page) ;
    }
    ClearPageUptodate(page) ;
    return error ;
}

//
// this is exactly what 2.3.99-pre9's ext2_readpage is
//
static int reiserfs_readpage (struct file *f, struct page * page)
{
    return block_read_full_page (page, reiserfs_get_block);
}


//
// modified from ext2_writepage is
//
static int reiserfs_writepage (struct page * page)
{
    struct inode *inode = page->mapping->host ;
    reiserfs_wait_on_write_block(inode->i_sb) ;
    return reiserfs_write_full_page(page) ;
}


//
// from ext2_prepare_write, but modified
//
int reiserfs_prepare_write(struct file *f, struct page *page, 
			   unsigned from, unsigned to) {
    struct inode *inode = page->mapping->host ;
    reiserfs_wait_on_write_block(inode->i_sb) ;
    fix_tail_page_for_writing(page) ;
    return block_prepare_write(page, from, to, reiserfs_get_block) ;
}


//
// this is exactly what 2.3.99-pre9's ext2_bmap is
//
static int reiserfs_aop_bmap(struct address_space *as, long block) {
  return generic_block_bmap(as, block, reiserfs_bmap) ;
}

static