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bmap.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/gfs2_ondisk.h>
#include <linux/crc32.h>
#include <linux/lm_interface.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "inode.h"
#include "meta_io.h"
#include "quota.h"
#include "rgrp.h"
#include "trans.h"
#include "dir.h"
#include "util.h"
#include "ops_address.h"

/* This doesn't need to be that large as max 64 bit pointers in a 4k
 * block is 512, so __u16 is fine for that. It saves stack space to
 * keep it small.
 */
struct metapath {
      __u16 mp_list[GFS2_MAX_META_HEIGHT];
};

typedef int (*block_call_t) (struct gfs2_inode *ip, struct buffer_head *dibh,
                       struct buffer_head *bh, __be64 *top,
                       __be64 *bottom, unsigned int height,
                       void *data);

struct strip_mine {
      int sm_first;
      unsigned int sm_height;
};

/**
 * gfs2_unstuffer_page - unstuff a stuffed inode into a block cached by a page
 * @ip: the inode
 * @dibh: the dinode buffer
 * @block: the block number that was allocated
 * @private: any locked page held by the caller process
 *
 * Returns: errno
 */

static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
                         u64 block, struct page *page)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct inode *inode = &ip->i_inode;
      struct buffer_head *bh;
      int release = 0;

      if (!page || page->index) {
            page = grab_cache_page(inode->i_mapping, 0);
            if (!page)
                  return -ENOMEM;
            release = 1;
      }

      if (!PageUptodate(page)) {
            void *kaddr = kmap(page);

            memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode),
                   ip->i_di.di_size);
            memset(kaddr + ip->i_di.di_size, 0,
                   PAGE_CACHE_SIZE - ip->i_di.di_size);
            kunmap(page);

            SetPageUptodate(page);
      }

      if (!page_has_buffers(page))
            create_empty_buffers(page, 1 << inode->i_blkbits,
                             (1 << BH_Uptodate));

      bh = page_buffers(page);

      if (!buffer_mapped(bh))
            map_bh(bh, inode->i_sb, block);

      set_buffer_uptodate(bh);
      if (!gfs2_is_jdata(ip))
            mark_buffer_dirty(bh);
      if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
            gfs2_trans_add_bh(ip->i_gl, bh, 0);

      if (release) {
            unlock_page(page);
            page_cache_release(page);
      }

      return 0;
}

/**
 * gfs2_unstuff_dinode - Unstuff a dinode when the data has grown too big
 * @ip: The GFS2 inode to unstuff
 * @unstuffer: the routine that handles unstuffing a non-zero length file
 * @private: private data for the unstuffer
 *
 * This routine unstuffs a dinode and returns it to a "normal" state such
 * that the height can be grown in the traditional way.
 *
 * Returns: errno
 */

int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page)
{
      struct buffer_head *bh, *dibh;
      struct gfs2_dinode *di;
      u64 block = 0;
      int isdir = gfs2_is_dir(ip);
      int error;

      down_write(&ip->i_rw_mutex);

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            goto out;

      if (ip->i_di.di_size) {
            /* Get a free block, fill it with the stuffed data,
               and write it out to disk */

            if (isdir) {
                  block = gfs2_alloc_meta(ip);

                  error = gfs2_dir_get_new_buffer(ip, block, &bh);
                  if (error)
                        goto out_brelse;
                  gfs2_buffer_copy_tail(bh, sizeof(struct gfs2_meta_header),
                                    dibh, sizeof(struct gfs2_dinode));
                  brelse(bh);
            } else {
                  block = gfs2_alloc_data(ip);

                  error = gfs2_unstuffer_page(ip, dibh, block, page);
                  if (error)
                        goto out_brelse;
            }
      }

      /*  Set up the pointer to the new block  */

      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      di = (struct gfs2_dinode *)dibh->b_data;
      gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));

      if (ip->i_di.di_size) {
            *(__be64 *)(di + 1) = cpu_to_be64(block);
            ip->i_di.di_blocks++;
            gfs2_set_inode_blocks(&ip->i_inode);
            di->di_blocks = cpu_to_be64(ip->i_di.di_blocks);
      }

      ip->i_di.di_height = 1;
      di->di_height = cpu_to_be16(1);

out_brelse:
      brelse(dibh);
out:
      up_write(&ip->i_rw_mutex);
      return error;
}

/**
 * calc_tree_height - Calculate the height of a metadata tree
 * @ip: The GFS2 inode
 * @size: The proposed size of the file
 *
 * Work out how tall a metadata tree needs to be in order to accommodate a
 * file of a particular size. If size is less than the current size of
 * the inode, then the current size of the inode is used instead of the
 * supplied one.
 *
 * Returns: the height the tree should be
 */

static unsigned int calc_tree_height(struct gfs2_inode *ip, u64 size)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      u64 *arr;
      unsigned int max, height;

      if (ip->i_di.di_size > size)
            size = ip->i_di.di_size;

      if (gfs2_is_dir(ip)) {
            arr = sdp->sd_jheightsize;
            max = sdp->sd_max_jheight;
      } else {
            arr = sdp->sd_heightsize;
            max = sdp->sd_max_height;
      }

      for (height = 0; height < max; height++)
            if (arr[height] >= size)
                  break;

      return height;
}

/**
 * build_height - Build a metadata tree of the requested height
 * @ip: The GFS2 inode
 * @height: The height to build to
 *
 *
 * Returns: errno
 */

static int build_height(struct inode *inode, unsigned height)
{
      struct gfs2_inode *ip = GFS2_I(inode);
      unsigned new_height = height - ip->i_di.di_height;
      struct buffer_head *dibh;
      struct buffer_head *blocks[GFS2_MAX_META_HEIGHT];
      struct gfs2_dinode *di;
      int error;
      __be64 *bp;
      u64 bn;
      unsigned n;

      if (height <= ip->i_di.di_height)
            return 0;

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            return error;

      for(n = 0; n < new_height; n++) {
            bn = gfs2_alloc_meta(ip);
            blocks[n] = gfs2_meta_new(ip->i_gl, bn);
            gfs2_trans_add_bh(ip->i_gl, blocks[n], 1);
      }

      n = 0;
      bn = blocks[0]->b_blocknr;
      if (new_height > 1) {
            for(; n < new_height-1; n++) {
                  gfs2_metatype_set(blocks[n], GFS2_METATYPE_IN,
                                GFS2_FORMAT_IN);
                  gfs2_buffer_clear_tail(blocks[n],
                                     sizeof(struct gfs2_meta_header));
                  bp = (__be64 *)(blocks[n]->b_data +
                             sizeof(struct gfs2_meta_header));
                  *bp = cpu_to_be64(blocks[n+1]->b_blocknr);
                  brelse(blocks[n]);
                  blocks[n] = NULL;
            }
      }
      gfs2_metatype_set(blocks[n], GFS2_METATYPE_IN, GFS2_FORMAT_IN);
      gfs2_buffer_copy_tail(blocks[n], sizeof(struct gfs2_meta_header),
                        dibh, sizeof(struct gfs2_dinode));
      brelse(blocks[n]);
      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      di = (struct gfs2_dinode *)dibh->b_data;
      gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
      *(__be64 *)(di + 1) = cpu_to_be64(bn);
      ip->i_di.di_height += new_height;
      ip->i_di.di_blocks += new_height;
      gfs2_set_inode_blocks(&ip->i_inode);
      di->di_height = cpu_to_be16(ip->i_di.di_height);
      di->di_blocks = cpu_to_be64(ip->i_di.di_blocks);
      brelse(dibh);
      return error;
}

/**
 * find_metapath - Find path through the metadata tree
 * @ip: The inode pointer
 * @mp: The metapath to return the result in
 * @block: The disk block to look up
 *
 *   This routine returns a struct metapath structure that defines a path
 *   through the metadata of inode "ip" to get to block "block".
 *
 *   Example:
 *   Given:  "ip" is a height 3 file, "offset" is 101342453, and this is a
 *   filesystem with a blocksize of 4096.
 *
 *   find_metapath() would return a struct metapath structure set to:
 *   mp_offset = 101342453, mp_height = 3, mp_list[0] = 0, mp_list[1] = 48,
 *   and mp_list[2] = 165.
 *
 *   That means that in order to get to the block containing the byte at
 *   offset 101342453, we would load the indirect block pointed to by pointer
 *   0 in the dinode.  We would then load the indirect block pointed to by
 *   pointer 48 in that indirect block.  We would then load the data block
 *   pointed to by pointer 165 in that indirect block.
 *
 *             ----------------------------------------
 *             | Dinode |                             |
 *             |        |                            4|
 *             |        |0 1 2 3 4 5                 9|
 *             |        |                            6|
 *             ----------------------------------------
 *                       |
 *                       |
 *                       V
 *             ----------------------------------------
 *             | Indirect Block                       |
 *             |                                     5|
 *             |            4 4 4 4 4 5 5            1|
 *             |0           5 6 7 8 9 0 1            2|
 *             ----------------------------------------
 *                                |
 *                                |
 *                                V
 *             ----------------------------------------
 *             | Indirect Block                       |
 *             |                         1 1 1 1 1   5|
 *             |                         6 6 6 6 6   1|
 *             |0                        3 4 5 6 7   2|
 *             ----------------------------------------
 *                                           |
 *                                           |
 *                                           V
 *             ----------------------------------------
 *             | Data block containing offset         |
 *             |            101342453                 |
 *             |                                      |
 *             |                                      |
 *             ----------------------------------------
 *
 */

static void find_metapath(struct gfs2_inode *ip, u64 block,
                    struct metapath *mp)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      u64 b = block;
      unsigned int i;

      for (i = ip->i_di.di_height; i--;)
            mp->mp_list[i] = do_div(b, sdp->sd_inptrs);

}

/**
 * metapointer - Return pointer to start of metadata in a buffer
 * @bh: The buffer
 * @height: The metadata height (0 = dinode)
 * @mp: The metapath
 *
 * Return a pointer to the block number of the next height of the metadata
 * tree given a buffer containing the pointer to the current height of the
 * metadata tree.
 */

static inline __be64 *metapointer(struct buffer_head *bh, int *boundary,
                         unsigned int height, const struct metapath *mp)
{
      unsigned int head_size = (height > 0) ?
            sizeof(struct gfs2_meta_header) : sizeof(struct gfs2_dinode);
      __be64 *ptr;
      *boundary = 0;
      ptr = ((__be64 *)(bh->b_data + head_size)) + mp->mp_list[height];
      if (ptr + 1 == (__be64 *)(bh->b_data + bh->b_size))
            *boundary = 1;
      return ptr;
}

/**
 * lookup_block - Get the next metadata block in metadata tree
 * @ip: The GFS2 inode
 * @bh: Buffer containing the pointers to metadata blocks
 * @height: The height of the tree (0 = dinode)
 * @mp: The metapath
 * @create: Non-zero if we may create a new meatdata block
 * @new: Used to indicate if we did create a new metadata block
 * @block: the returned disk block number
 *
 * Given a metatree, complete to a particular height, checks to see if the next
 * height of the tree exists. If not the next height of the tree is created.
 * The block number of the next height of the metadata tree is returned.
 *
 */

static int lookup_block(struct gfs2_inode *ip, struct buffer_head *bh,
                  unsigned int height, struct metapath *mp, int create,
                  int *new, u64 *block)
{
      int boundary;
      __be64 *ptr = metapointer(bh, &boundary, height, mp);

      if (*ptr) {
            *block = be64_to_cpu(*ptr);
            return boundary;
      }

      *block = 0;

      if (!create)
            return 0;

      if (height == ip->i_di.di_height - 1 && !gfs2_is_dir(ip))
            *block = gfs2_alloc_data(ip);
      else
            *block = gfs2_alloc_meta(ip);

      gfs2_trans_add_bh(ip->i_gl, bh, 1);

      *ptr = cpu_to_be64(*block);
      ip->i_di.di_blocks++;
      gfs2_set_inode_blocks(&ip->i_inode);

      *new = 1;
      return 0;
}

static inline void bmap_lock(struct inode *inode, int create)
{
      struct gfs2_inode *ip = GFS2_I(inode);
      if (create)
            down_write(&ip->i_rw_mutex);
      else
            down_read(&ip->i_rw_mutex);
}

static inline void bmap_unlock(struct inode *inode, int create)
{
      struct gfs2_inode *ip = GFS2_I(inode);
      if (create)
            up_write(&ip->i_rw_mutex);
      else
            up_read(&ip->i_rw_mutex);
}

/**
 * gfs2_block_map - Map a block from an inode to a disk block
 * @inode: The inode
 * @lblock: The logical block number
 * @bh_map: The bh to be mapped
 *
 * Find the block number on the current device which corresponds to an
 * inode's block. If the block had to be created, "new" will be set.
 *
 * Returns: errno
 */

int gfs2_block_map(struct inode *inode, u64 lblock, int create,
               struct buffer_head *bh_map)
{
      struct gfs2_inode *ip = GFS2_I(inode);
      struct gfs2_sbd *sdp = GFS2_SB(inode);
      struct buffer_head *bh;
      unsigned int bsize;
      unsigned int height;
      unsigned int end_of_metadata;
      unsigned int x;
      int error = 0;
      int new = 0;
      u64 dblock = 0;
      int boundary;
      unsigned int maxlen = bh_map->b_size >> inode->i_blkbits;
      struct metapath mp;
      u64 size;

      BUG_ON(maxlen == 0);

      if (gfs2_assert_warn(sdp, !gfs2_is_stuffed(ip)))
            return 0;

      bmap_lock(inode, create);
      clear_buffer_mapped(bh_map);
      clear_buffer_new(bh_map);
      clear_buffer_boundary(bh_map);
      bsize = gfs2_is_dir(ip) ? sdp->sd_jbsize : sdp->sd_sb.sb_bsize;
      size = (lblock + 1) * bsize;

      if (size > ip->i_di.di_size) {
            height = calc_tree_height(ip, size);
            if (ip->i_di.di_height < height) {
                  if (!create)
                        goto out_ok;
      
                  error = build_height(inode, height);
                  if (error)
                        goto out_fail;
            }
      }

      find_metapath(ip, lblock, &mp);
      end_of_metadata = ip->i_di.di_height - 1;
      error = gfs2_meta_inode_buffer(ip, &bh);
      if (error)
            goto out_fail;

      for (x = 0; x < end_of_metadata; x++) {
            lookup_block(ip, bh, x, &mp, create, &new, &dblock);
            brelse(bh);
            if (!dblock)
                  goto out_ok;

            error = gfs2_meta_indirect_buffer(ip, x+1, dblock, new, &bh);
            if (error)
                  goto out_fail;
      }

      boundary = lookup_block(ip, bh, end_of_metadata, &mp, create, &new, &dblock);
      if (dblock) {
            map_bh(bh_map, inode->i_sb, dblock);
            if (boundary)
                  set_buffer_boundary(bh_map);
            if (new) {
                  struct buffer_head *dibh;
                  error = gfs2_meta_inode_buffer(ip, &dibh);
                  if (!error) {
                        gfs2_trans_add_bh(ip->i_gl, dibh, 1);
                        gfs2_dinode_out(ip, dibh->b_data);
                        brelse(dibh);
                  }
                  set_buffer_new(bh_map);
                  goto out_brelse;
            }
            while(--maxlen && !buffer_boundary(bh_map)) {
                  u64 eblock;

                  mp.mp_list[end_of_metadata]++;
                  boundary = lookup_block(ip, bh, end_of_metadata, &mp, 0, &new, &eblock);
                  if (eblock != ++dblock)
                        break;
                  bh_map->b_size += (1 << inode->i_blkbits);
                  if (boundary)
                        set_buffer_boundary(bh_map);
            }
      }
out_brelse:
      brelse(bh);
out_ok:
      error = 0;
out_fail:
      bmap_unlock(inode, create);
      return error;
}

int gfs2_extent_map(struct inode *inode, u64 lblock, int *new, u64 *dblock, unsigned *extlen)
{
      struct buffer_head bh = { .b_state = 0, .b_blocknr = 0 };
      int ret;
      int create = *new;

      BUG_ON(!extlen);
      BUG_ON(!dblock);
      BUG_ON(!new);

      bh.b_size = 1 << (inode->i_blkbits + 5);
      ret = gfs2_block_map(inode, lblock, create, &bh);
      *extlen = bh.b_size >> inode->i_blkbits;
      *dblock = bh.b_blocknr;
      if (buffer_new(&bh))
            *new = 1;
      else
            *new = 0;
      return ret;
}

/**
 * recursive_scan - recursively scan through the end of a file
 * @ip: the inode
 * @dibh: the dinode buffer
 * @mp: the path through the metadata to the point to start
 * @height: the height the recursion is at
 * @block: the indirect block to look at
 * @first: 1 if this is the first block
 * @bc: the call to make for each piece of metadata
 * @data: data opaque to this function to pass to @bc
 *
 * When this is first called @height and @block should be zero and
 * @first should be 1.
 *
 * Returns: errno
 */

static int recursive_scan(struct gfs2_inode *ip, struct buffer_head *dibh,
                    struct metapath *mp, unsigned int height,
                    u64 block, int first, block_call_t bc,
                    void *data)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct buffer_head *bh = NULL;
      __be64 *top, *bottom;
      u64 bn;
      int error;
      int mh_size = sizeof(struct gfs2_meta_header);

      if (!height) {
            error = gfs2_meta_inode_buffer(ip, &bh);
            if (error)
                  return error;
            dibh = bh;

            top = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + mp->mp_list[0];
            bottom = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + sdp->sd_diptrs;
      } else {
            error = gfs2_meta_indirect_buffer(ip, height, block, 0, &bh);
            if (error)
                  return error;

            top = (__be64 *)(bh->b_data + mh_size) +
                          (first ? mp->mp_list[height] : 0);

            bottom = (__be64 *)(bh->b_data + mh_size) + sdp->sd_inptrs;
      }

      error = bc(ip, dibh, bh, top, bottom, height, data);
      if (error)
            goto out;

      if (height < ip->i_di.di_height - 1)
            for (; top < bottom; top++, first = 0) {
                  if (!*top)
                        continue;

                  bn = be64_to_cpu(*top);

                  error = recursive_scan(ip, dibh, mp, height + 1, bn,
                                     first, bc, data);
                  if (error)
                        break;
            }

out:
      brelse(bh);
      return error;
}

/**
 * do_strip - Look for a layer a particular layer of the file and strip it off
 * @ip: the inode
 * @dibh: the dinode buffer
 * @bh: A buffer of pointers
 * @top: The first pointer in the buffer
 * @bottom: One more than the last pointer
 * @height: the height this buffer is at
 * @data: a pointer to a struct strip_mine
 *
 * Returns: errno
 */

static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
                struct buffer_head *bh, __be64 *top, __be64 *bottom,
                unsigned int height, void *data)
{
      struct strip_mine *sm = data;
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct gfs2_rgrp_list rlist;
      u64 bn, bstart;
      u32 blen;
      __be64 *p;
      unsigned int rg_blocks = 0;
      int metadata;
      unsigned int revokes = 0;
      int x;
      int error;

      if (!*top)
            sm->sm_first = 0;

      if (height != sm->sm_height)
            return 0;

      if (sm->sm_first) {
            top++;
            sm->sm_first = 0;
      }

      metadata = (height != ip->i_di.di_height - 1);
      if (metadata)
            revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;

      error = gfs2_rindex_hold(sdp, &ip->i_alloc.al_ri_gh);
      if (error)
            return error;

      memset(&rlist, 0, sizeof(struct gfs2_rgrp_list));
      bstart = 0;
      blen = 0;

      for (p = top; p < bottom; p++) {
            if (!*p)
                  continue;

            bn = be64_to_cpu(*p);

            if (bstart + blen == bn)
                  blen++;
            else {
                  if (bstart)
                        gfs2_rlist_add(sdp, &rlist, bstart);

                  bstart = bn;
                  blen = 1;
            }
      }

      if (bstart)
            gfs2_rlist_add(sdp, &rlist, bstart);
      else
            goto out; /* Nothing to do */

      gfs2_rlist_alloc(&rlist, LM_ST_EXCLUSIVE, 0);

      for (x = 0; x < rlist.rl_rgrps; x++) {
            struct gfs2_rgrpd *rgd;
            rgd = rlist.rl_ghs[x].gh_gl->gl_object;
            rg_blocks += rgd->rd_length;
      }

      error = gfs2_glock_nq_m(rlist.rl_rgrps, rlist.rl_ghs);
      if (error)
            goto out_rlist;

      error = gfs2_trans_begin(sdp, rg_blocks + RES_DINODE +
                         RES_INDIRECT + RES_STATFS + RES_QUOTA,
                         revokes);
      if (error)
            goto out_rg_gunlock;

      down_write(&ip->i_rw_mutex);

      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      gfs2_trans_add_bh(ip->i_gl, bh, 1);

      bstart = 0;
      blen = 0;

      for (p = top; p < bottom; p++) {
            if (!*p)
                  continue;

            bn = be64_to_cpu(*p);

            if (bstart + blen == bn)
                  blen++;
            else {
                  if (bstart) {
                        if (metadata)
                              gfs2_free_meta(ip, bstart, blen);
                        else
                              gfs2_free_data(ip, bstart, blen);
                  }

                  bstart = bn;
                  blen = 1;
            }

            *p = 0;
            if (!ip->i_di.di_blocks)
                  gfs2_consist_inode(ip);
            ip->i_di.di_blocks--;
            gfs2_set_inode_blocks(&ip->i_inode);
      }
      if (bstart) {
            if (metadata)
                  gfs2_free_meta(ip, bstart, blen);
            else
                  gfs2_free_data(ip, bstart, blen);
      }

      ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;

      gfs2_dinode_out(ip, dibh->b_data);

      up_write(&ip->i_rw_mutex);

      gfs2_trans_end(sdp);

out_rg_gunlock:
      gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);
out_rlist:
      gfs2_rlist_free(&rlist);
out:
      gfs2_glock_dq_uninit(&ip->i_alloc.al_ri_gh);
      return error;
}

/**
 * do_grow - Make a file look bigger than it is
 * @ip: the inode
 * @size: the size to set the file to
 *
 * Called with an exclusive lock on @ip.
 *
 * Returns: errno
 */

static int do_grow(struct gfs2_inode *ip, u64 size)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct gfs2_alloc *al;
      struct buffer_head *dibh;
      unsigned int h;
      int error;

      al = gfs2_alloc_get(ip);

      error = gfs2_quota_lock(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
      if (error)
            goto out;

      error = gfs2_quota_check(ip, ip->i_inode.i_uid, ip->i_inode.i_gid);
      if (error)
            goto out_gunlock_q;

      al->al_requested = sdp->sd_max_height + RES_DATA;

      error = gfs2_inplace_reserve(ip);
      if (error)
            goto out_gunlock_q;

      error = gfs2_trans_begin(sdp,
                  sdp->sd_max_height + al->al_rgd->rd_length +
                  RES_JDATA + RES_DINODE + RES_STATFS + RES_QUOTA, 0);
      if (error)
            goto out_ipres;

      if (size > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)) {
            if (gfs2_is_stuffed(ip)) {
                  error = gfs2_unstuff_dinode(ip, NULL);
                  if (error)
                        goto out_end_trans;
            }

            h = calc_tree_height(ip, size);
            if (ip->i_di.di_height < h) {
                  down_write(&ip->i_rw_mutex);
                  error = build_height(&ip->i_inode, h);
                  up_write(&ip->i_rw_mutex);
                  if (error)
                        goto out_end_trans;
            }
      }

      ip->i_di.di_size = size;
      ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            goto out_end_trans;

      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      gfs2_dinode_out(ip, dibh->b_data);
      brelse(dibh);

out_end_trans:
      gfs2_trans_end(sdp);
out_ipres:
      gfs2_inplace_release(ip);
out_gunlock_q:
      gfs2_quota_unlock(ip);
out:
      gfs2_alloc_put(ip);
      return error;
}


/**
 * gfs2_block_truncate_page - Deal with zeroing out data for truncate
 *
 * This is partly borrowed from ext3.
 */
static int gfs2_block_truncate_page(struct address_space *mapping)
{
      struct inode *inode = mapping->host;
      struct gfs2_inode *ip = GFS2_I(inode);
      struct gfs2_sbd *sdp = GFS2_SB(inode);
      loff_t from = inode->i_size;
      unsigned long index = from >> PAGE_CACHE_SHIFT;
      unsigned offset = from & (PAGE_CACHE_SIZE-1);
      unsigned blocksize, iblock, length, pos;
      struct buffer_head *bh;
      struct page *page;
      int err;

      page = grab_cache_page(mapping, index);
      if (!page)
            return 0;

      blocksize = inode->i_sb->s_blocksize;
      length = blocksize - (offset & (blocksize - 1));
      iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);

      if (!page_has_buffers(page))
            create_empty_buffers(page, blocksize, 0);

      /* Find the buffer that contains "offset" */
      bh = page_buffers(page);
      pos = blocksize;
      while (offset >= pos) {
            bh = bh->b_this_page;
            iblock++;
            pos += blocksize;
      }

      err = 0;

      if (!buffer_mapped(bh)) {
            gfs2_get_block(inode, iblock, bh, 0);
            /* unmapped? It's a hole - nothing to do */
            if (!buffer_mapped(bh))
                  goto unlock;
      }

      /* Ok, it's mapped. Make sure it's up-to-date */
      if (PageUptodate(page))
            set_buffer_uptodate(bh);

      if (!buffer_uptodate(bh)) {
            err = -EIO;
            ll_rw_block(READ, 1, &bh);
            wait_on_buffer(bh);
            /* Uhhuh. Read error. Complain and punt. */
            if (!buffer_uptodate(bh))
                  goto unlock;
            err = 0;
      }

      if (sdp->sd_args.ar_data == GFS2_DATA_ORDERED || gfs2_is_jdata(ip))
            gfs2_trans_add_bh(ip->i_gl, bh, 0);

      zero_user_page(page, offset, length, KM_USER0);

unlock:
      unlock_page(page);
      page_cache_release(page);
      return err;
}

static int trunc_start(struct gfs2_inode *ip, u64 size)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct buffer_head *dibh;
      int journaled = gfs2_is_jdata(ip);
      int error;

      error = gfs2_trans_begin(sdp,
                         RES_DINODE + (journaled ? RES_JDATA : 0), 0);
      if (error)
            return error;

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            goto out;

      if (gfs2_is_stuffed(ip)) {
            ip->i_di.di_size = size;
            ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
            gfs2_trans_add_bh(ip->i_gl, dibh, 1);
            gfs2_dinode_out(ip, dibh->b_data);
            gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode) + size);
            error = 1;

      } else {
            if (size & (u64)(sdp->sd_sb.sb_bsize - 1))
                  error = gfs2_block_truncate_page(ip->i_inode.i_mapping);

            if (!error) {
                  ip->i_di.di_size = size;
                  ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
                  ip->i_di.di_flags |= GFS2_DIF_TRUNC_IN_PROG;
                  gfs2_trans_add_bh(ip->i_gl, dibh, 1);
                  gfs2_dinode_out(ip, dibh->b_data);
            }
      }

      brelse(dibh);

out:
      gfs2_trans_end(sdp);
      return error;
}

static int trunc_dealloc(struct gfs2_inode *ip, u64 size)
{
      unsigned int height = ip->i_di.di_height;
      u64 lblock;
      struct metapath mp;
      int error;

      if (!size)
            lblock = 0;
      else
            lblock = (size - 1) >> GFS2_SB(&ip->i_inode)->sd_sb.sb_bsize_shift;

      find_metapath(ip, lblock, &mp);
      gfs2_alloc_get(ip);

      error = gfs2_quota_hold(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
      if (error)
            goto out;

      while (height--) {
            struct strip_mine sm;
            sm.sm_first = !!size;
            sm.sm_height = height;

            error = recursive_scan(ip, NULL, &mp, 0, 0, 1, do_strip, &sm);
            if (error)
                  break;
      }

      gfs2_quota_unhold(ip);

out:
      gfs2_alloc_put(ip);
      return error;
}

static int trunc_end(struct gfs2_inode *ip)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct buffer_head *dibh;
      int error;

      error = gfs2_trans_begin(sdp, RES_DINODE, 0);
      if (error)
            return error;

      down_write(&ip->i_rw_mutex);

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            goto out;

      if (!ip->i_di.di_size) {
            ip->i_di.di_height = 0;
            ip->i_di.di_goal_meta =
                  ip->i_di.di_goal_data =
                  ip->i_no_addr;
            gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
      }
      ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
      ip->i_di.di_flags &= ~GFS2_DIF_TRUNC_IN_PROG;

      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      gfs2_dinode_out(ip, dibh->b_data);
      brelse(dibh);

out:
      up_write(&ip->i_rw_mutex);
      gfs2_trans_end(sdp);
      return error;
}

/**
 * do_shrink - make a file smaller
 * @ip: the inode
 * @size: the size to make the file
 * @truncator: function to truncate the last partial block
 *
 * Called with an exclusive lock on @ip.
 *
 * Returns: errno
 */

static int do_shrink(struct gfs2_inode *ip, u64 size)
{
      int error;

      error = trunc_start(ip, size);
      if (error < 0)
            return error;
      if (error > 0)
            return 0;

      error = trunc_dealloc(ip, size);
      if (!error)
            error = trunc_end(ip);

      return error;
}

static int do_touch(struct gfs2_inode *ip, u64 size)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      struct buffer_head *dibh;
      int error;

      error = gfs2_trans_begin(sdp, RES_DINODE, 0);
      if (error)
            return error;

      down_write(&ip->i_rw_mutex);

      error = gfs2_meta_inode_buffer(ip, &dibh);
      if (error)
            goto do_touch_out;

      ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
      gfs2_trans_add_bh(ip->i_gl, dibh, 1);
      gfs2_dinode_out(ip, dibh->b_data);
      brelse(dibh);

do_touch_out:
      up_write(&ip->i_rw_mutex);
      gfs2_trans_end(sdp);
      return error;
}

/**
 * gfs2_truncatei - make a file a given size
 * @ip: the inode
 * @size: the size to make the file
 * @truncator: function to truncate the last partial block
 *
 * The file size can grow, shrink, or stay the same size.
 *
 * Returns: errno
 */

int gfs2_truncatei(struct gfs2_inode *ip, u64 size)
{
      int error;

      if (gfs2_assert_warn(GFS2_SB(&ip->i_inode), S_ISREG(ip->i_inode.i_mode)))
            return -EINVAL;

      if (size > ip->i_di.di_size)
            error = do_grow(ip, size);
      else if (size < ip->i_di.di_size)
            error = do_shrink(ip, size);
      else
            /* update time stamps */
            error = do_touch(ip, size);

      return error;
}

int gfs2_truncatei_resume(struct gfs2_inode *ip)
{
      int error;
      error = trunc_dealloc(ip, ip->i_di.di_size);
      if (!error)
            error = trunc_end(ip);
      return error;
}

int gfs2_file_dealloc(struct gfs2_inode *ip)
{
      return trunc_dealloc(ip, 0);
}

/**
 * gfs2_write_calc_reserv - calculate number of blocks needed to write to a file
 * @ip: the file
 * @len: the number of bytes to be written to the file
 * @data_blocks: returns the number of data blocks required
 * @ind_blocks: returns the number of indirect blocks required
 *
 */

void gfs2_write_calc_reserv(struct gfs2_inode *ip, unsigned int len,
                      unsigned int *data_blocks, unsigned int *ind_blocks)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      unsigned int tmp;

      if (gfs2_is_dir(ip)) {
            *data_blocks = DIV_ROUND_UP(len, sdp->sd_jbsize) + 2;
            *ind_blocks = 3 * (sdp->sd_max_jheight - 1);
      } else {
            *data_blocks = (len >> sdp->sd_sb.sb_bsize_shift) + 3;
            *ind_blocks = 3 * (sdp->sd_max_height - 1);
      }

      for (tmp = *data_blocks; tmp > sdp->sd_diptrs;) {
            tmp = DIV_ROUND_UP(tmp, sdp->sd_inptrs);
            *ind_blocks += tmp;
      }
}

/**
 * gfs2_write_alloc_required - figure out if a write will require an allocation
 * @ip: the file being written to
 * @offset: the offset to write to
 * @len: the number of bytes being written
 * @alloc_required: set to 1 if an alloc is required, 0 otherwise
 *
 * Returns: errno
 */

int gfs2_write_alloc_required(struct gfs2_inode *ip, u64 offset,
                        unsigned int len, int *alloc_required)
{
      struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
      u64 lblock, lblock_stop, dblock;
      u32 extlen;
      int new = 0;
      int error = 0;

      *alloc_required = 0;

      if (!len)
            return 0;

      if (gfs2_is_stuffed(ip)) {
            if (offset + len >
                sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode))
                  *alloc_required = 1;
            return 0;
      }

      if (gfs2_is_dir(ip)) {
            unsigned int bsize = sdp->sd_jbsize;
            lblock = offset;
            do_div(lblock, bsize);
            lblock_stop = offset + len + bsize - 1;
            do_div(lblock_stop, bsize);
      } else {
            unsigned int shift = sdp->sd_sb.sb_bsize_shift;
            lblock = offset >> shift;
            lblock_stop = (offset + len + sdp->sd_sb.sb_bsize - 1) >> shift;
      }

      for (; lblock < lblock_stop; lblock += extlen) {
            error = gfs2_extent_map(&ip->i_inode, lblock, &new, &dblock, &extlen);
            if (error)
                  return error;

            if (!dblock) {
                  *alloc_required = 1;
                  return 0;
            }
      }

      return 0;
}


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