inode.c

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/*
 * Copyright 2000 by Hans Reiser, licensing governed by reiserfs/README
 */

#include <linux/config.h>
#include <linux/sched.h>
#include <linux/reiserfs_fs.h>
#include <linux/locks.h>
#include <linux/smp_lock.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>

/* args for the create parameter of reiserfs_get_block */
#define GET_BLOCK_NO_CREATE 0 /* don't create new blocks or convert tails */
#define GET_BLOCK_CREATE 1    /* add anything you need to find block */
#define GET_BLOCK_NO_HOLE 2   /* return -ENOENT for file holes */
#define GET_BLOCK_READ_DIRECT 4  /* read the tail if indirect item not found */
#define GET_BLOCK_NO_ISEM     8 /* i_sem is not held, don't preallocate */

static int reiserfs_get_block (struct inode * inode, long block,
			       struct buffer_head * bh_result, int create);
//
// initially this function was derived from minix or ext2's analog and
// evolved as the prototype did
//
void reiserfs_delete_inode (struct inode * inode)
{
    int jbegin_count = JOURNAL_PER_BALANCE_CNT * 2; 
    int windex ;
    struct reiserfs_transaction_handle th ;

  
    lock_kernel() ; 

    /* The = 0 happens when we abort creating a new inode for some reason like lack of space.. */
    if (INODE_PKEY(inode)->k_objectid != 0) { /* also handles bad_inode case */
	down (&inode->i_sem); 

	journal_begin(&th, inode->i_sb, jbegin_count) ;
	reiserfs_update_inode_transaction(inode) ;
	windex = push_journal_writer("delete_inode") ;

	reiserfs_delete_object (&th, inode);
	pop_journal_writer(windex) ;

	journal_end(&th, inode->i_sb, jbegin_count) ;

        up (&inode->i_sem);

        /* all items of file are deleted, so we can remove "save" link */
	remove_save_link (inode, 0/* not truncate */);
    } else {
	/* no object items are in the tree */
	;
    }
    clear_inode (inode); /* note this must go after the journal_end to prevent deadlock */
    inode->i_blocks = 0;
    unlock_kernel() ;
}

static void _make_cpu_key (struct cpu_key * key, int version, __u32 dirid, __u32 objectid, 
	       loff_t offset, int type, int length )
{
    key->version = version;

    key->on_disk_key.k_dir_id = dirid;
    key->on_disk_key.k_objectid = objectid;
    set_cpu_key_k_offset (key, offset);
    set_cpu_key_k_type (key, type);  
    key->key_length = length;
}


/* take base of inode_key (it comes from inode always) (dirid, objectid) and version from an inode, set
   offset and type of key */
void make_cpu_key (struct cpu_key * key, const struct inode * inode, loff_t offset,
	      int type, int length )
{
  _make_cpu_key (key, get_inode_item_key_version (inode), le32_to_cpu (INODE_PKEY (inode)->k_dir_id),
		 le32_to_cpu (INODE_PKEY (inode)->k_objectid), 
		 offset, type, length);
}


//
// when key is 0, do not set version and short key
//
inline void make_le_item_head (struct item_head * ih, const struct cpu_key * key,
			       int version,
			       loff_t offset, int type, int length, 
			       int entry_count/*or ih_free_space*/)
{
    if (key) {
	ih->ih_key.k_dir_id = cpu_to_le32 (key->on_disk_key.k_dir_id);
	ih->ih_key.k_objectid = cpu_to_le32 (key->on_disk_key.k_objectid);
    }
    put_ih_version( ih, version );
    set_le_ih_k_offset (ih, offset);
    set_le_ih_k_type (ih, type);
    put_ih_item_len( ih, length );
    /*    set_ih_free_space (ih, 0);*/
    // for directory items it is entry count, for directs and stat
    // datas - 0xffff, for indirects - 0
    put_ih_entry_count( ih, entry_count );
}

static void add_to_flushlist(struct inode *inode, struct buffer_head *bh) {
    struct inode *jinode = &(SB_JOURNAL(inode->i_sb)->j_dummy_inode) ;

    buffer_insert_inode_queue(bh, jinode) ;
}

//
// FIXME: we might cache recently accessed indirect item (or at least
// first 15 pointers just like ext2 does

// Ugh.  Not too eager for that....
//  I cut the code until such time as I see a convincing argument (benchmark).
// I don't want a bloated inode struct..., and I don't like code complexity....

/* cutting the code is fine, since it really isn't in use yet and is easy
** to add back in.  But, Vladimir has a really good idea here.  Think
** about what happens for reading a file.  For each page,
** The VFS layer calls reiserfs_readpage, who searches the tree to find
** an indirect item.  This indirect item has X number of pointers, where
** X is a big number if we've done the block allocation right.  But,
** we only use one or two of these pointers during each call to readpage,
** needlessly researching again later on.
**
** The size of the cache could be dynamic based on the size of the file.
**
** I'd also like to see us cache the location the stat data item, since
** we are needlessly researching for that frequently.
**
** --chris
*/

/* If this page has a file tail in it, and
** it was read in by get_block_create_0, the page data is valid,
** but tail is still sitting in a direct item, and we can't write to
** it.  So, look through this page, and check all the mapped buffers
** to make sure they have valid block numbers.  Any that don't need
** to be unmapped, so that block_prepare_write will correctly call
** reiserfs_get_block to convert the tail into an unformatted node
*/
static inline void fix_tail_page_for_writing(struct page *page) {
    struct buffer_head *head, *next, *bh ;

    if (page && page->buffers) {
	head = page->buffers ;
	bh = head ;
	do {
	    next = bh->b_this_page ;
	    if (buffer_mapped(bh) && bh->b_blocknr == 0) {
	        reiserfs_unmap_buffer(bh) ;
	    }
	    bh = next ;
	} while (bh != head) ;
    }
}




/* we need to allocate a block for new unformatted node.  Try to figure out
   what point in bitmap reiserfs_new_blocknrs should start from. */
static b_blocknr_t find_tag (struct buffer_head * bh, struct item_head * ih,
			     __u32 * item, int pos_in_item)
{
  __u32 block ;
  if (!is_indirect_le_ih (ih))
	 /* something more complicated could be here */
	 return bh->b_blocknr;

  /* for indirect item: go to left and look for the first non-hole entry in
	  the indirect item */
  if (pos_in_item == I_UNFM_NUM (ih))
	 pos_in_item --;
  while (pos_in_item >= 0) {
	 block = get_block_num(item, pos_in_item) ;
	 if (block)
		return block ;
	 pos_in_item --;
  }
  return bh->b_blocknr;
}


/* reiserfs_get_block does not need to allocate a block only if it has been
   done already or non-hole position has been found in the indirect item */
static inline int allocation_needed (int retval, b_blocknr_t allocated, 
				     struct item_head * ih,
				     __u32 * item, int pos_in_item)
{
  if (allocated)
	 return 0;
  if (retval == POSITION_FOUND && is_indirect_le_ih (ih) && 
      get_block_num(item, pos_in_item))
	 return 0;
  return 1;
}

static inline int indirect_item_found (int retval, struct item_head * ih)
{
  return (retval == POSITION_FOUND) && is_indirect_le_ih (ih);
}


static inline void set_block_dev_mapped (struct buffer_head * bh, 
					 b_blocknr_t block, struct inode * inode)
{
  bh->b_dev = inode->i_dev;
  bh->b_blocknr = block;
  bh->b_state |= (1UL << BH_Mapped);
}


//
// files which were created in the earlier version can not be longer,
// than 2 gb
//
static int file_capable (struct inode * inode, long block)
{
    if (get_inode_item_key_version (inode) != KEY_FORMAT_3_5 || // it is new file.
	block < (1 << (31 - inode->i_sb->s_blocksize_bits))) // old file, but 'block' is inside of 2gb
	return 1;

    return 0;
}

/*static*/ void restart_transaction(struct reiserfs_transaction_handle *th,
				struct inode *inode, struct path *path) {
  struct super_block *s = th->t_super ;
  int len = th->t_blocks_allocated ;

  pathrelse(path) ;
  reiserfs_update_sd(th, inode) ;
  journal_end(th, s, len) ;
  journal_begin(th, s, len) ;
  reiserfs_update_inode_transaction(inode) ;
}

// it is called by get_block when create == 0. Returns block number
// for 'block'-th logical block of file. When it hits direct item it
// returns 0 (being called from bmap) or read direct item into piece
// of page (bh_result)

// Please improve the english/clarity in the comment above, as it is
// hard to understand.

static int _get_block_create_0 (struct inode * inode, long block,
				 struct buffer_head * bh_result,
				 int args)
{
    INITIALIZE_PATH (path);
    struct cpu_key key;
    struct buffer_head * bh;
    struct item_head * ih, tmp_ih;
    int fs_gen ;
    int blocknr;
    char * p = NULL;
    int chars;
    int ret ;
    int done = 0 ;
    unsigned long offset ;

    // prepare the key to look for the 'block'-th block of file
    make_cpu_key (&key, inode,
		  (loff_t)block * inode->i_sb->s_blocksize + 1, TYPE_ANY, 3);

research:
    if (search_for_position_by_key (inode->i_sb, &key, &path) != POSITION_FOUND) {
	pathrelse (&path);
        if (p)
            kunmap(bh_result->b_page) ;
	// We do not return -ENOENT if there is a hole but page is uptodate, because it means
	// That there is some MMAPED data associated with it that is yet to be written to disk.
	if ((args & GET_BLOCK_NO_HOLE) && !Page_Uptodate(bh_result->b_page) ) {
	    return -ENOENT ;
	}
        return 0 ;
    }
    
    //
    bh = get_last_bh (&path);
    ih = get_ih (&path);
    if (is_indirect_le_ih (ih)) {
	__u32 * ind_item = (__u32 *)B_I_PITEM (bh, ih);
	
	/* FIXME: here we could cache indirect item or part of it in
	   the inode to avoid search_by_key in case of subsequent
	   access to file */
	blocknr = get_block_num(ind_item, path.pos_in_item) ;
	ret = 0 ;
	if (blocknr) {
	    bh_result->b_dev = inode->i_dev;
	    bh_result->b_blocknr = blocknr;
	    bh_result->b_state |= (1UL << BH_Mapped);
	} else
	    // We do not return -ENOENT if there is a hole but page is uptodate, because it means
	    // That there is some MMAPED data associated with it that is yet to be written to disk.
	    if ((args & GET_BLOCK_NO_HOLE) && !Page_Uptodate(bh_result->b_page) ) {
		ret = -ENOENT ;
	    }

	pathrelse (&path);
        if (p)
            kunmap(bh_result->b_page) ;
	return ret ;
    }

    // requested data are in direct item(s)
    if (!(args & GET_BLOCK_READ_DIRECT)) {
	// we are called by bmap. FIXME: we can not map block of file
	// when it is stored in direct item(s)
	pathrelse (&path);	
        if (p)
            kunmap(bh_result->b_page) ;
	return -ENOENT;
    }

    /* if we've got a direct item, and the buffer was uptodate,
    ** we don't want to pull data off disk again.  skip to the
    ** end, where we map the buffer and return
    */
    if (buffer_uptodate(bh_result)) {
        goto finished ;
    } else 
	/*
	** grab_tail_page can trigger calls to reiserfs_get_block on up to date
	** pages without any buffers.  If the page is up to date, we don't want
	** read old data off disk.  Set the up to date bit on the buffer instead
	** and jump to the end
	*/
	    if (Page_Uptodate(bh_result->b_page)) {
		mark_buffer_uptodate(bh_result, 1);
		goto finished ;
    }

    // read file tail into part of page
    offset = (cpu_key_k_offset(&key) - 1) & (PAGE_CACHE_SIZE - 1) ;
    fs_gen = get_generation(inode->i_sb) ;
    copy_item_head (&tmp_ih, ih);

    /* we only want to kmap if we are reading the tail into the page.
    ** this is not the common case, so we don't kmap until we are
    ** sure we need to.  But, this means the item might move if
    ** kmap schedules
    */
    if (!p) {
    p = (char *)kmap(bh_result->b_page) ;
    if (fs_changed (fs_gen, inode->i_sb) && item_moved (&tmp_ih, &path)) {
        goto research;
    }
    }
    p += offset ;
    memset (p, 0, inode->i_sb->s_blocksize);
    do {
	if (!is_direct_le_ih (ih)) {
	    BUG ();
        }
	/* make sure we don't read more bytes than actually exist in
	** the file.  This can happen in odd cases where i_size isn't
	** correct, and when direct item padding results in a few 
	** extra bytes at the end of the direct item
	*/
        if ((le_ih_k_offset(ih) + path.pos_in_item) > inode->i_size)
	    break ;
	if ((le_ih_k_offset(ih) - 1 + ih_item_len(ih)) > inode->i_size) {
	    chars = inode->i_size - (le_ih_k_offset(ih) - 1) - path.pos_in_item;
	    done = 1 ;
	} else {
	    chars = ih_item_len(ih) - path.pos_in_item;
	}
	memcpy (p, B_I_PITEM (bh, ih) + path.pos_in_item, chars);

	if (done) 
	    break ;

	p += chars;

	if (PATH_LAST_POSITION (&path) != (B_NR_ITEMS (bh) - 1))
	    // we done, if read direct item is not the last item of
	    // node FIXME: we could try to check right delimiting key
	    // to see whether direct item continues in the right
	    // neighbor or rely on i_size
	    break;

	// update key to look for the next piece
	set_cpu_key_k_offset (&key, cpu_key_k_offset (&key) + chars);
	if (search_for_position_by_key (inode->i_sb, &key, &path) != POSITION_FOUND)
	    // we read something from tail, even if now we got IO_ERROR
	    break;
	bh = get_last_bh (&path);
	ih = get_ih (&path);
    } while (1);

    flush_dcache_page(bh_result->b_page) ;
    kunmap(bh_result->b_page) ;

finished:
    pathrelse (&path);
    bh_result->b_blocknr = 0 ;
    bh_result->b_dev = inode->i_dev;
    mark_buffer_uptodate (bh_result, 1);
    bh_result->b_state |= (1UL << BH_Mapped);
    return 0;
}