1 files changed, 1482 insertions, 0 deletions

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
new file mode 100644
index 000000000000..b8602cde5b5a
--- /dev/null
+++ b/fs/ext4/indirect.c
@@ -0,0 +1,1482 @@
+/*
+ *  linux/fs/ext4/indirect.c
+ *
+ *  from
+ *
+ *  linux/fs/ext4/inode.c
+ *
+ * Copyright (C) 1992, 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ *  from
+ *
+ *  linux/fs/minix/inode.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  Goal-directed block allocation by Stephen Tweedie
+ *      (sct@redhat.com), 1993, 1998
+ */
+
+#include <linux/module.h>
+#include "ext4_jbd2.h"
+#include "truncate.h"
+
+#include <trace/events/ext4.h>
+
+typedef struct {
+        __le32  *p;
+        __le32  key;
+        struct buffer_head *bh;
+} Indirect;
+
+static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
+{
+        p->key = *(p->p = v);
+        p->bh = bh;
+}
+
+/**
+ *      ext4_block_to_path - parse the block number into array of offsets
+ *      @inode: inode in question (we are only interested in its superblock)
+ *      @i_block: block number to be parsed
+ *      @offsets: array to store the offsets in
+ *      @boundary: set this non-zero if the referred-to block is likely to be
+ *             followed (on disk) by an indirect block.
+ *
+ *      To store the locations of file's data ext4 uses a data structure common
+ *      for UNIX filesystems - tree of pointers anchored in the inode, with
+ *      data blocks at leaves and indirect blocks in intermediate nodes.
+ *      This function translates the block number into path in that tree -
+ *      return value is the path length and @offsets[n] is the offset of
+ *      pointer to (n+1)th node in the nth one. If @block is out of range
+ *      (negative or too large) warning is printed and zero returned.
+ *
+ *      Note: function doesn't find node addresses, so no IO is needed. All
+ *      we need to know is the capacity of indirect blocks (taken from the
+ *      inode->i_sb).
+ */
+
+/*
+ * Portability note: the last comparison (check that we fit into triple
+ * indirect block) is spelled differently, because otherwise on an
+ * architecture with 32-bit longs and 8Kb pages we might get into trouble
+ * if our filesystem had 8Kb blocks. We might use long long, but that would
+ * kill us on x86. Oh, well, at least the sign propagation does not matter -
+ * i_block would have to be negative in the very beginning, so we would not
+ * get there at all.
+ */
+
+static int ext4_block_to_path(struct inode *inode,
+                              ext4_lblk_t i_block,
+                              ext4_lblk_t offsets[4], int *boundary)
+{
+        int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
+        int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
+        const long direct_blocks = EXT4_NDIR_BLOCKS,
+                indirect_blocks = ptrs,
+                double_blocks = (1 << (ptrs_bits * 2));
+        int n = 0;
+        int final = 0;
+
+        if (i_block < direct_blocks) {
+                offsets[n++] = i_block;
+                final = direct_blocks;
+        } else if ((i_block -= direct_blocks) < indirect_blocks) {
+                offsets[n++] = EXT4_IND_BLOCK;
+                offsets[n++] = i_block;
+                final = ptrs;
+        } else if ((i_block -= indirect_blocks) < double_blocks) {
+                offsets[n++] = EXT4_DIND_BLOCK;
+                offsets[n++] = i_block >> ptrs_bits;
+                offsets[n++] = i_block & (ptrs - 1);
+                final = ptrs;
+        } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
+                offsets[n++] = EXT4_TIND_BLOCK;
+                offsets[n++] = i_block >> (ptrs_bits * 2);
+                offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
+                offsets[n++] = i_block & (ptrs - 1);
+                final = ptrs;
+        } else {
+                ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
+                             i_block + direct_blocks +
+                             indirect_blocks + double_blocks, inode->i_ino);
+        }
+        if (boundary)
+                *boundary = final - 1 - (i_block & (ptrs - 1));
+        return n;
+}
+
+/**
+ *      ext4_get_branch - read the chain of indirect blocks leading to data
+ *      @inode: inode in question
+ *      @depth: depth of the chain (1 - direct pointer, etc.)
+ *      @offsets: offsets of pointers in inode/indirect blocks
+ *      @chain: place to store the result
+ *      @err: here we store the error value
+ *
+ *      Function fills the array of triples <key, p, bh> and returns %NULL
+ *      if everything went OK or the pointer to the last filled triple
+ *      (incomplete one) otherwise. Upon the return chain[i].key contains
+ *      the number of (i+1)-th block in the chain (as it is stored in memory,
+ *      i.e. little-endian 32-bit), chain[i].p contains the address of that
+ *      number (it points into struct inode for i==0 and into the bh->b_data
+ *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
+ *      block for i>0 and NULL for i==0. In other words, it holds the block
+ *      numbers of the chain, addresses they were taken from (and where we can
+ *      verify that chain did not change) and buffer_heads hosting these
+ *      numbers.
+ *
+ *      Function stops when it stumbles upon zero pointer (absent block)
+ *              (pointer to last triple returned, *@err == 0)
+ *      or when it gets an IO error reading an indirect block
+ *              (ditto, *@err == -EIO)
+ *      or when it reads all @depth-1 indirect blocks successfully and finds
+ *      the whole chain, all way to the data (returns %NULL, *err == 0).
+ *
+ *      Need to be called with
+ *      down_read(&EXT4_I(inode)->i_data_sem)
+ */
+static Indirect *ext4_get_branch(struct inode *inode, int depth,
+                                 ext4_lblk_t  *offsets,
+                                 Indirect chain[4], int *err)
+{
+        struct super_block *sb = inode->i_sb;
+        Indirect *p = chain;
+        struct buffer_head *bh;
+
+        *err = 0;
+        /* i_data is not going away, no lock needed */
+        add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
+        if (!p->key)
+                goto no_block;
+        while (--depth) {
+                bh = sb_getblk(sb, le32_to_cpu(p->key));
+                if (unlikely(!bh))
+                        goto failure;
+
+                if (!bh_uptodate_or_lock(bh)) {
+                        if (bh_submit_read(bh) < 0) {
+                                put_bh(bh);
+                                goto failure;
+                        }
+                        /* validate block references */
+                        if (ext4_check_indirect_blockref(inode, bh)) {
+                                put_bh(bh);
+                                goto failure;
+                        }
+                }
+
+                add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
+                /* Reader: end */
+                if (!p->key)
+                        goto no_block;
+        }
+        return NULL;
+
+failure:
+        *err = -EIO;
+no_block:
+        return p;
+}
+
+/**
+ *      ext4_find_near - find a place for allocation with sufficient locality
+ *      @inode: owner
+ *      @ind: descriptor of indirect block.
+ *
+ *      This function returns the preferred place for block allocation.
+ *      It is used when heuristic for sequential allocation fails.
+ *      Rules are:
+ *        + if there is a block to the left of our position - allocate near it.
+ *        + if pointer will live in indirect block - allocate near that block.
+ *        + if pointer will live in inode - allocate in the same
+ *          cylinder group.
+ *
+ * In the latter case we colour the starting block by the callers PID to
+ * prevent it from clashing with concurrent allocations for a different inode
+ * in the same block group.   The PID is used here so that functionally related
+ * files will be close-by on-disk.
+ *
+ *      Caller must make sure that @ind is valid and will stay that way.
+ */
+static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
+{
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
+        __le32 *p;
+
+        /* Try to find previous block */
+        for (p = ind->p - 1; p >= start; p--) {
+                if (*p)
+                        return le32_to_cpu(*p);
+        }
+
+        /* No such thing, so let's try location of indirect block */
+        if (ind->bh)
+                return ind->bh->b_blocknr;
+
+        /*
+         * It is going to be referred to from the inode itself? OK, just put it
+         * into the same cylinder group then.
+         */
+        return ext4_inode_to_goal_block(inode);
+}
+
+/**
+ *      ext4_find_goal - find a preferred place for allocation.
+ *      @inode: owner
+ *      @block:  block we want
+ *      @partial: pointer to the last triple within a chain
+ *
+ *      Normally this function find the preferred place for block allocation,
+ *      returns it.
+ *      Because this is only used for non-extent files, we limit the block nr
+ *      to 32 bits.
+ */
+static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
+                                   Indirect *partial)
+{
+        ext4_fsblk_t goal;
+
+        /*
+         * XXX need to get goal block from mballoc's data structures
+         */
+
+        goal = ext4_find_near(inode, partial);
+        goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
+        return goal;
+}
+
+/**
+ *      ext4_blks_to_allocate - Look up the block map and count the number
+ *      of direct blocks need to be allocated for the given branch.
+ *
+ *      @branch: chain of indirect blocks
+ *      @k: number of blocks need for indirect blocks
+ *      @blks: number of data blocks to be mapped.
+ *      @blocks_to_boundary:  the offset in the indirect block
+ *
+ *      return the total number of blocks to be allocate, including the
+ *      direct and indirect blocks.
+ */
+static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
+                                 int blocks_to_boundary)
+{
+        unsigned int count = 0;
+
+        /*
+         * Simple case, [t,d]Indirect block(s) has not allocated yet
+         * then it's clear blocks on that path have not allocated
+         */
+        if (k > 0) {
+                /* right now we don't handle cross boundary allocation */
+                if (blks < blocks_to_boundary + 1)
+                        count += blks;
+                else
+                        count += blocks_to_boundary + 1;
+                return count;
+        }
+
+        count++;
+        while (count < blks && count <= blocks_to_boundary &&
+                le32_to_cpu(*(branch[0].p + count)) == 0) {
+                count++;
+        }
+        return count;
+}
+
+/**
+ *      ext4_alloc_blocks: multiple allocate blocks needed for a branch
+ *      @handle: handle for this transaction
+ *      @inode: inode which needs allocated blocks
+ *      @iblock: the logical block to start allocated at
+ *      @goal: preferred physical block of allocation
+ *      @indirect_blks: the number of blocks need to allocate for indirect
+ *                      blocks
+ *      @blks: number of desired blocks
+ *      @new_blocks: on return it will store the new block numbers for
+ *      the indirect blocks(if needed) and the first direct block,
+ *      @err: on return it will store the error code
+ *
+ *      This function will return the number of blocks allocated as
+ *      requested by the passed-in parameters.
+ */
+static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
+                             ext4_lblk_t iblock, ext4_fsblk_t goal,
+                             int indirect_blks, int blks,
+                             ext4_fsblk_t new_blocks[4], int *err)
+{
+        struct ext4_allocation_request ar;
+        int target, i;
+        unsigned long count = 0, blk_allocated = 0;
+        int index = 0;
+        ext4_fsblk_t current_block = 0;
+        int ret = 0;
+
+        /*
+         * Here we try to allocate the requested multiple blocks at once,
+         * on a best-effort basis.
+         * To build a branch, we should allocate blocks for
+         * the indirect blocks(if not allocated yet), and at least
+         * the first direct block of this branch.  That's the
+         * minimum number of blocks need to allocate(required)
+         */
+        /* first we try to allocate the indirect blocks */
+        target = indirect_blks;
+        while (target > 0) {
+                count = target;
+                /* allocating blocks for indirect blocks and direct blocks */
+                current_block = ext4_new_meta_blocks(handle, inode, goal,
+                                                     0, &count, err);
+                if (*err)
+                        goto failed_out;
+
+                if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
+                        EXT4_ERROR_INODE(inode,
+                                         "current_block %llu + count %lu > %d!",
+                                         current_block, count,
+                                         EXT4_MAX_BLOCK_FILE_PHYS);
+                        *err = -EIO;
+                        goto failed_out;
+                }
+
+                target -= count;
+                /* allocate blocks for indirect blocks */
+                while (index < indirect_blks && count) {
+                        new_blocks[index++] = current_block++;
+                        count--;
+                }
+                if (count > 0) {
+                        /*
+                         * save the new block number
+                         * for the first direct block
+                         */
+                        new_blocks[index] = current_block;
+                        printk(KERN_INFO "%s returned more blocks than "
+                                                "requested\n", __func__);
+                        WARN_ON(1);
+                        break;
+                }
+        }
+
+        target = blks - count ;
+        blk_allocated = count;
+        if (!target)
+                goto allocated;
+        /* Now allocate data blocks */
+        memset(&ar, 0, sizeof(ar));
+        ar.inode = inode;
+        ar.goal = goal;
+        ar.len = target;
+        ar.logical = iblock;
+        if (S_ISREG(inode->i_mode))
+                /* enable in-core preallocation only for regular files */
+                ar.flags = EXT4_MB_HINT_DATA;
+
+        current_block = ext4_mb_new_blocks(handle, &ar, err);
+        if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
+                EXT4_ERROR_INODE(inode,
+                                 "current_block %llu + ar.len %d > %d!",
+                                 current_block, ar.len,
+                                 EXT4_MAX_BLOCK_FILE_PHYS);
+                *err = -EIO;
+                goto failed_out;
+        }
+
+        if (*err && (target == blks)) {
+                /*
+                 * if the allocation failed and we didn't allocate
+                 * any blocks before
+                 */
+                goto failed_out;
+        }
+        if (!*err) {
+                if (target == blks) {
+                        /*
+                         * save the new block number
+                         * for the first direct block
+                         */
+                        new_blocks[index] = current_block;
+                }
+                blk_allocated += ar.len;
+        }
+allocated:
+        /* total number of blocks allocated for direct blocks */
+        ret = blk_allocated;
+        *err = 0;
+        return ret;
+failed_out:
+        for (i = 0; i < index; i++)
+                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
+        return ret;
+}
+
+/**
+ *      ext4_alloc_branch - allocate and set up a chain of blocks.
+ *      @handle: handle for this transaction
+ *      @inode: owner
+ *      @indirect_blks: number of allocated indirect blocks
+ *      @blks: number of allocated direct blocks
+ *      @goal: preferred place for allocation
+ *      @offsets: offsets (in the blocks) to store the pointers to next.
+ *      @branch: place to store the chain in.
+ *
+ *      This function allocates blocks, zeroes out all but the last one,
+ *      links them into chain and (if we are synchronous) writes them to disk.
+ *      In other words, it prepares a branch that can be spliced onto the
+ *      inode. It stores the information about that chain in the branch[], in
+ *      the same format as ext4_get_branch() would do. We are calling it after
+ *      we had read the existing part of chain and partial points to the last
+ *      triple of that (one with zero ->key). Upon the exit we have the same
+ *      picture as after the successful ext4_get_block(), except that in one
+ *      place chain is disconnected - *branch->p is still zero (we did not
+ *      set the last link), but branch->key contains the number that should
+ *      be placed into *branch->p to fill that gap.
+ *
+ *      If allocation fails we free all blocks we've allocated (and forget
+ *      their buffer_heads) and return the error value the from failed
+ *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
+ *      as described above and return 0.
+ */
+static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
+                             ext4_lblk_t iblock, int indirect_blks,
+                             int *blks, ext4_fsblk_t goal,
+                             ext4_lblk_t *offsets, Indirect *branch)
+{
+        int blocksize = inode->i_sb->s_blocksize;
+        int i, n = 0;
+        int err = 0;
+        struct buffer_head *bh;
+        int num;
+        ext4_fsblk_t new_blocks[4];
+        ext4_fsblk_t current_block;
+
+        num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
+                                *blks, new_blocks, &err);
+        if (err)
+                return err;
+
+        branch[0].key = cpu_to_le32(new_blocks[0]);
+        /*
+         * metadata blocks and data blocks are allocated.
+         */
+        for (n = 1; n <= indirect_blks;  n++) {
+                /*
+                 * Get buffer_head for parent block, zero it out
+                 * and set the pointer to new one, then send
+                 * parent to disk.
+                 */
+                bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
+                if (unlikely(!bh)) {
+                        err = -EIO;
+                        goto failed;
+                }
+
+                branch[n].bh = bh;
+                lock_buffer(bh);
+                BUFFER_TRACE(bh, "call get_create_access");
+                err = ext4_journal_get_create_access(handle, bh);
+                if (err) {
+                        /* Don't brelse(bh) here; it's done in
+                         * ext4_journal_forget() below */
+                        unlock_buffer(bh);
+                        goto failed;
+                }
+
+                memset(bh->b_data, 0, blocksize);
+                branch[n].p = (__le32 *) bh->b_data + offsets[n];
+                branch[n].key = cpu_to_le32(new_blocks[n]);
+                *branch[n].p = branch[n].key;
+                if (n == indirect_blks) {
+                        current_block = new_blocks[n];
+                        /*
+                         * End of chain, update the last new metablock of
+                         * the chain to point to the new allocated
+                         * data blocks numbers
+                         */
+                        for (i = 1; i < num; i++)
+                                *(branch[n].p + i) = cpu_to_le32(++current_block);
+                }
+                BUFFER_TRACE(bh, "marking uptodate");
+                set_buffer_uptodate(bh);
+                unlock_buffer(bh);
+
+                BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
+                err = ext4_handle_dirty_metadata(handle, inode, bh);
+                if (err)
+                        goto failed;
+        }
+        *blks = num;
+        return err;
+failed:
+        /* Allocation failed, free what we already allocated */
+        ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
+        for (i = 1; i <= n ; i++) {
+                /*
+                 * branch[i].bh is newly allocated, so there is no
+                 * need to revoke the block, which is why we don't
+                 * need to set EXT4_FREE_BLOCKS_METADATA.
+                 */
+                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
+                                 EXT4_FREE_BLOCKS_FORGET);
+        }
+        for (i = n+1; i < indirect_blks; i++)
+                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
+
+        ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
+
+        return err;
+}
+
+/**
+ * ext4_splice_branch - splice the allocated branch onto inode.
+ * @handle: handle for this transaction
+ * @inode: owner
+ * @block: (logical) number of block we are adding
+ * @chain: chain of indirect blocks (with a missing link - see
+ *      ext4_alloc_branch)
+ * @where: location of missing link
+ * @num:   number of indirect blocks we are adding
+ * @blks:  number of direct blocks we are adding
+ *
+ * This function fills the missing link and does all housekeeping needed in
+ * inode (->i_blocks, etc.). In case of success we end up with the full
+ * chain to new block and return 0.
+ */
+static int ext4_splice_branch(handle_t *handle, struct inode *inode,
+                              ext4_lblk_t block, Indirect *where, int num,
+                              int blks)
+{
+        int i;
+        int err = 0;
+        ext4_fsblk_t current_block;
+
+        /*
+         * If we're splicing into a [td]indirect block (as opposed to the
+         * inode) then we need to get write access to the [td]indirect block
+         * before the splice.
+         */
+        if (where->bh) {
+                BUFFER_TRACE(where->bh, "get_write_access");
+                err = ext4_journal_get_write_access(handle, where->bh);
+                if (err)
+                        goto err_out;
+        }
+        /* That's it */
+
+        *where->p = where->key;
+
+        /*
+         * Update the host buffer_head or inode to point to more just allocated
+         * direct blocks blocks
+         */
+        if (num == 0 && blks > 1) {
+                current_block = le32_to_cpu(where->key) + 1;
+                for (i = 1; i < blks; i++)
+                        *(where->p + i) = cpu_to_le32(current_block++);
+        }
+
+        /* We are done with atomic stuff, now do the rest of housekeeping */
+        /* had we spliced it onto indirect block? */
+        if (where->bh) {
+                /*
+                 * If we spliced it onto an indirect block, we haven't
+                 * altered the inode.  Note however that if it is being spliced
+                 * onto an indirect block at the very end of the file (the
+                 * file is growing) then we *will* alter the inode to reflect
+                 * the new i_size.  But that is not done here - it is done in
+                 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
+                 */
+                jbd_debug(5, "splicing indirect only\n");
+                BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
+                err = ext4_handle_dirty_metadata(handle, inode, where->bh);
+                if (err)
+                        goto err_out;
+        } else {
+                /*
+                 * OK, we spliced it into the inode itself on a direct block.
+                 */
+                ext4_mark_inode_dirty(handle, inode);
+                jbd_debug(5, "splicing direct\n");
+        }
+        return err;
+
+err_out:
+        for (i = 1; i <= num; i++) {
+                /*
+                 * branch[i].bh is newly allocated, so there is no
+                 * need to revoke the block, which is why we don't
+                 * need to set EXT4_FREE_BLOCKS_METADATA.
+                 */
+                ext4_free_blocks(handle, inode, where[i].bh, 0, 1,
+                                 EXT4_FREE_BLOCKS_FORGET);
+        }
+        ext4_free_blocks(handle, inode, NULL, le32_to_cpu(where[num].key),
+                         blks, 0);
+
+        return err;
+}
+
+/*
+ * The ext4_ind_map_blocks() function handles non-extents inodes
+ * (i.e., using the traditional indirect/double-indirect i_blocks
+ * scheme) for ext4_map_blocks().
+ *
+ * Allocation strategy is simple: if we have to allocate something, we will
+ * have to go the whole way to leaf. So let's do it before attaching anything
+ * to tree, set linkage between the newborn blocks, write them if sync is
+ * required, recheck the path, free and repeat if check fails, otherwise
+ * set the last missing link (that will protect us from any truncate-generated
+ * removals - all blocks on the path are immune now) and possibly force the
+ * write on the parent block.
+ * That has a nice additional property: no special recovery from the failed
+ * allocations is needed - we simply release blocks and do not touch anything
+ * reachable from inode.
+ *
+ * `handle' can be NULL if create == 0.
+ *
+ * return > 0, # of blocks mapped or allocated.
+ * return = 0, if plain lookup failed.
+ * return < 0, error case.
+ *
+ * The ext4_ind_get_blocks() function should be called with
+ * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
+ * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
+ * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
+ * blocks.
+ */
+int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
+                        struct ext4_map_blocks *map,
+                        int flags)
+{
+        int err = -EIO;
+        ext4_lblk_t offsets[4];
+        Indirect chain[4];
+        Indirect *partial;
+        ext4_fsblk_t goal;
+        int indirect_blks;
+        int blocks_to_boundary = 0;
+        int depth;
+        int count = 0;
+        ext4_fsblk_t first_block = 0;
+
+        trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
+        J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
+        J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
+        depth = ext4_block_to_path(inode, map->m_lblk, offsets,
+                                   &blocks_to_boundary);
+
+        if (depth == 0)
+                goto out;
+
+        partial = ext4_get_branch(inode, depth, offsets, chain, &err);
+
+        /* Simplest case - block found, no allocation needed */
+        if (!partial) {
+                first_block = le32_to_cpu(chain[depth - 1].key);
+                count++;
+                /*map more blocks*/
+                while (count < map->m_len && count <= blocks_to_boundary) {
+                        ext4_fsblk_t blk;
+
+                        blk = le32_to_cpu(*(chain[depth-1].p + count));
+
+                        if (blk == first_block + count)
+                                count++;
+                        else
+                                break;
+                }
+                goto got_it;
+        }
+
+        /* Next simple case - plain lookup or failed read of indirect block */
+        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
+                goto cleanup;
+
+        /*
+         * Okay, we need to do block allocation.
+        */
+        goal = ext4_find_goal(inode, map->m_lblk, partial);
+
+        /* the number of blocks need to allocate for [d,t]indirect blocks */
+        indirect_blks = (chain + depth) - partial - 1;
+
+        /*
+         * Next look up the indirect map to count the totoal number of
+         * direct blocks to allocate for this branch.
+         */
+        count = ext4_blks_to_allocate(partial, indirect_blks,
+                                      map->m_len, blocks_to_boundary);
+        /*
+         * Block out ext4_truncate while we alter the tree
+         */
+        err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
+                                &count, goal,
+                                offsets + (partial - chain), partial);
+
+        /*
+         * The ext4_splice_branch call will free and forget any buffers
+         * on the new chain if there is a failure, but that risks using
+         * up transaction credits, especially for bitmaps where the
+         * credits cannot be returned.  Can we handle this somehow?  We
+         * may need to return -EAGAIN upwards in the worst case.  --sct
+         */
+        if (!err)
+                err = ext4_splice_branch(handle, inode, map->m_lblk,
+                                         partial, indirect_blks, count);
+        if (err)
+                goto cleanup;
+
+        map->m_flags |= EXT4_MAP_NEW;
+
+        ext4_update_inode_fsync_trans(handle, inode, 1);
+got_it:
+        map->m_flags |= EXT4_MAP_MAPPED;
+        map->m_pblk = le32_to_cpu(chain[depth-1].key);
+        map->m_len = count;
+        if (count > blocks_to_boundary)
+                map->m_flags |= EXT4_MAP_BOUNDARY;
+        err = count;
+        /* Clean up and exit */
+        partial = chain + depth - 1;    /* the whole chain */
+cleanup:
+        while (partial > chain) {
+                BUFFER_TRACE(partial->bh, "call brelse");
+                brelse(partial->bh);
+                partial--;
+        }
+out:
+        trace_ext4_ind_map_blocks_exit(inode, map->m_lblk,
+                                map->m_pblk, map->m_len, err);
+        return err;
+}
+
+/*
+ * O_DIRECT for ext3 (or indirect map) based files
+ *
+ * If the O_DIRECT write will extend the file then add this inode to the
+ * orphan list.  So recovery will truncate it back to the original size
+ * if the machine crashes during the write.
+ *
+ * If the O_DIRECT write is intantiating holes inside i_size and the machine
+ * crashes then stale disk data _may_ be exposed inside the file. But current
+ * VFS code falls back into buffered path in that case so we are safe.
+ */
+ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
+                           const struct iovec *iov, loff_t offset,
+                           unsigned long nr_segs)
+{
+        struct file *file = iocb->ki_filp;
+        struct inode *inode = file->f_mapping->host;
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        handle_t *handle;
+        ssize_t ret;
+        int orphan = 0;
+        size_t count = iov_length(iov, nr_segs);
+        int retries = 0;
+
+        if (rw == WRITE) {
+                loff_t final_size = offset + count;
+
+                if (final_size > inode->i_size) {
+                        /* Credits for sb + inode write */
+                        handle = ext4_journal_start(inode, 2);
+                        if (IS_ERR(handle)) {
+                                ret = PTR_ERR(handle);
+                                goto out;
+                        }
+                        ret = ext4_orphan_add(handle, inode);
+                        if (ret) {
+                                ext4_journal_stop(handle);
+                                goto out;
+                        }
+                        orphan = 1;
+                        ei->i_disksize = inode->i_size;
+                        ext4_journal_stop(handle);
+                }
+        }
+
+retry:
+        if (rw == READ && ext4_should_dioread_nolock(inode))
+                ret = __blockdev_direct_IO(rw, iocb, inode,
+                                 inode->i_sb->s_bdev, iov,
+                                 offset, nr_segs,
+                                 ext4_get_block, NULL, NULL, 0);
+        else {
+                ret = blockdev_direct_IO(rw, iocb, inode, iov,
+                                 offset, nr_segs, ext4_get_block);
+
+                if (unlikely((rw & WRITE) && ret < 0)) {
+                        loff_t isize = i_size_read(inode);
+                        loff_t end = offset + iov_length(iov, nr_segs);
+
+                        if (end > isize)
+                                ext4_truncate_failed_write(inode);
+                }
+        }
+        if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
+                goto retry;
+
+        if (orphan) {
+                int err;
+
+                /* Credits for sb + inode write */
+                handle = ext4_journal_start(inode, 2);
+                if (IS_ERR(handle)) {
+                        /* This is really bad luck. We've written the data
+                         * but cannot extend i_size. Bail out and pretend
+                         * the write failed... */
+                        ret = PTR_ERR(handle);
+                        if (inode->i_nlink)
+                                ext4_orphan_del(NULL, inode);
+
+                        goto out;
+                }
+                if (inode->i_nlink)
+                        ext4_orphan_del(handle, inode);
+                if (ret > 0) {
+                        loff_t end = offset + ret;
+                        if (end > inode->i_size) {
+                                ei->i_disksize = end;
+                                i_size_write(inode, end);
+                                /*
+                                 * We're going to return a positive `ret'
+                                 * here due to non-zero-length I/O, so there's
+                                 * no way of reporting error returns from
+                                 * ext4_mark_inode_dirty() to userspace.  So
+                                 * ignore it.
+                                 */
+                                ext4_mark_inode_dirty(handle, inode);
+                        }
+                }
+                err = ext4_journal_stop(handle);
+                if (ret == 0)
+                        ret = err;
+        }
+out:
+        return ret;
+}
+
+/*
+ * Calculate the number of metadata blocks need to reserve
+ * to allocate a new block at @lblocks for non extent file based file
+ */
+int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
+{
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
+        int blk_bits;
+
+        if (lblock < EXT4_NDIR_BLOCKS)
+                return 0;
+
+        lblock -= EXT4_NDIR_BLOCKS;
+
+        if (ei->i_da_metadata_calc_len &&
+            (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
+                ei->i_da_metadata_calc_len++;
+                return 0;
+        }
+        ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
+        ei->i_da_metadata_calc_len = 1;
+        blk_bits = order_base_2(lblock);
+        return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
+}
+
+int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk)
+{
+        int indirects;
+
+        /* if nrblocks are contiguous */
+        if (chunk) {
+                /*
+                 * With N contiguous data blocks, we need at most
+                 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
+                 * 2 dindirect blocks, and 1 tindirect block
+                 */
+                return DIV_ROUND_UP(nrblocks,
+                                    EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
+        }
+        /*
+         * if nrblocks are not contiguous, worse case, each block touch
+         * a indirect block, and each indirect block touch a double indirect
+         * block, plus a triple indirect block
+         */
+        indirects = nrblocks * 2 + 1;
+        return indirects;
+}
+
+/*
+ * Truncate transactions can be complex and absolutely huge.  So we need to
+ * be able to restart the transaction at a conventient checkpoint to make
+ * sure we don't overflow the journal.
+ *
+ * start_transaction gets us a new handle for a truncate transaction,
+ * and extend_transaction tries to extend the existing one a bit.  If
+ * extend fails, we need to propagate the failure up and restart the
+ * transaction in the top-level truncate loop. --sct
+ */
+static handle_t *start_transaction(struct inode *inode)
+{
+        handle_t *result;
+
+        result = ext4_journal_start(inode, ext4_blocks_for_truncate(inode));
+        if (!IS_ERR(result))
+                return result;
+
+        ext4_std_error(inode->i_sb, PTR_ERR(result));
+        return result;
+}
+
+/*
+ * Try to extend this transaction for the purposes of truncation.
+ *
+ * Returns 0 if we managed to create more room.  If we can't create more
+ * room, and the transaction must be restarted we return 1.
+ */
+static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
+{
+        if (!ext4_handle_valid(handle))
+                return 0;
+        if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
+                return 0;
+        if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
+                return 0;
+        return 1;
+}
+
+/*
+ * Probably it should be a library function... search for first non-zero word
+ * or memcmp with zero_page, whatever is better for particular architecture.
+ * Linus?
+ */
+static inline int all_zeroes(__le32 *p, __le32 *q)
+{
+        while (p < q)
+                if (*p++)
+                        return 0;
+        return 1;
+}
+
+/**
+ *      ext4_find_shared - find the indirect blocks for partial truncation.
+ *      @inode:   inode in question
+ *      @depth:   depth of the affected branch
+ *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
+ *      @chain:   place to store the pointers to partial indirect blocks
+ *      @top:     place to the (detached) top of branch
+ *
+ *      This is a helper function used by ext4_truncate().
+ *
+ *      When we do truncate() we may have to clean the ends of several
+ *      indirect blocks but leave the blocks themselves alive. Block is
+ *      partially truncated if some data below the new i_size is referred
+ *      from it (and it is on the path to the first completely truncated
+ *      data block, indeed).  We have to free the top of that path along
+ *      with everything to the right of the path. Since no allocation
+ *      past the truncation point is possible until ext4_truncate()
+ *      finishes, we may safely do the latter, but top of branch may
+ *      require special attention - pageout below the truncation point
+ *      might try to populate it.
+ *
+ *      We atomically detach the top of branch from the tree, store the
+ *      block number of its root in *@top, pointers to buffer_heads of
+ *      partially truncated blocks - in @chain[].bh and pointers to
+ *      their last elements that should not be removed - in
+ *      @chain[].p. Return value is the pointer to last filled element
+ *      of @chain.
+ *
+ *      The work left to caller to do the actual freeing of subtrees:
+ *              a) free the subtree starting from *@top
+ *              b) free the subtrees whose roots are stored in
+ *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
+ *              c) free the subtrees growing from the inode past the @chain[0].
+ *                      (no partially truncated stuff there).  */
+
+static Indirect *ext4_find_shared(struct inode *inode, int depth,
+                                  ext4_lblk_t offsets[4], Indirect chain[4],
+                                  __le32 *top)
+{
+        Indirect *partial, *p;
+        int k, err;
+
+        *top = 0;
+        /* Make k index the deepest non-null offset + 1 */
+        for (k = depth; k > 1 && !offsets[k-1]; k--)
+                ;
+        partial = ext4_get_branch(inode, k, offsets, chain, &err);
+        /* Writer: pointers */
+        if (!partial)
+                partial = chain + k-1;
+        /*
+         * If the branch acquired continuation since we've looked at it -
+         * fine, it should all survive and (new) top doesn't belong to us.
+         */
+        if (!partial->key && *partial->p)
+                /* Writer: end */
+                goto no_top;
+        for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
+                ;
+        /*
+         * OK, we've found the last block that must survive. The rest of our
+         * branch should be detached before unlocking. However, if that rest
+         * of branch is all ours and does not grow immediately from the inode
+         * it's easier to cheat and just decrement partial->p.
+         */
+        if (p == chain + k - 1 && p > chain) {
+                p->p--;
+        } else {
+                *top = *p->p;
+                /* Nope, don't do this in ext4.  Must leave the tree intact */
+#if 0
+                *p->p = 0;
+#endif
+        }
+        /* Writer: end */
+
+        while (partial > p) {
+                brelse(partial->bh);
+                partial--;
+        }
+no_top:
+        return partial;
+}
+
+/*
+ * Zero a number of block pointers in either an inode or an indirect block.
+ * If we restart the transaction we must again get write access to the
+ * indirect block for further modification.
+ *
+ * We release `count' blocks on disk, but (last - first) may be greater
+ * than `count' because there can be holes in there.
+ *
+ * Return 0 on success, 1 on invalid block range
+ * and < 0 on fatal error.
+ */
+static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
+                             struct buffer_head *bh,
+                             ext4_fsblk_t block_to_free,
+                             unsigned long count, __le32 *first,
+                             __le32 *last)
+{
+        __le32 *p;
+        int     flags = EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_VALIDATED;
+        int     err;
+
+        if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
+                flags |= EXT4_FREE_BLOCKS_METADATA;
+
+        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
+                                   count)) {
+                EXT4_ERROR_INODE(inode, "attempt to clear invalid "
+                                 "blocks %llu len %lu",
+                                 (unsigned long long) block_to_free, count);
+                return 1;
+        }
+
+        if (try_to_extend_transaction(handle, inode)) {
+                if (bh) {
+                        BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
+                        err = ext4_handle_dirty_metadata(handle, inode, bh);
+                        if (unlikely(err))
+                                goto out_err;
+                }
+                err = ext4_mark_inode_dirty(handle, inode);
+                if (unlikely(err))
+                        goto out_err;
+                err = ext4_truncate_restart_trans(handle, inode,
+                                        ext4_blocks_for_truncate(inode));
+                if (unlikely(err))
+                        goto out_err;
+                if (bh) {
+                        BUFFER_TRACE(bh, "retaking write access");
+                        err = ext4_journal_get_write_access(handle, bh);
+                        if (unlikely(err))
+                                goto out_err;
+                }
+        }
+
+        for (p = first; p < last; p++)
+                *p = 0;
+
+        ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
+        return 0;
+out_err:
+        ext4_std_error(inode->i_sb, err);
+        return err;
+}
+
+/**
+ * ext4_free_data - free a list of data blocks
+ * @handle:     handle for this transaction
+ * @inode:      inode we are dealing with
+ * @this_bh:    indirect buffer_head which contains *@first and *@last
+ * @first:      array of block numbers
+ * @last:       points immediately past the end of array
+ *
+ * We are freeing all blocks referred from that array (numbers are stored as
+ * little-endian 32-bit) and updating @inode->i_blocks appropriately.
+ *
+ * We accumulate contiguous runs of blocks to free.  Conveniently, if these
+ * blocks are contiguous then releasing them at one time will only affect one
+ * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
+ * actually use a lot of journal space.
+ *
+ * @this_bh will be %NULL if @first and @last point into the inode's direct
+ * block pointers.
+ */
+static void ext4_free_data(handle_t *handle, struct inode *inode,
+                           struct buffer_head *this_bh,
+                           __le32 *first, __le32 *last)
+{
+        ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
+        unsigned long count = 0;            /* Number of blocks in the run */
+        __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
+                                               corresponding to
+                                               block_to_free */
+        ext4_fsblk_t nr;                    /* Current block # */
+        __le32 *p;                          /* Pointer into inode/ind
+                                               for current block */
+        int err = 0;
+
+        if (this_bh) {                          /* For indirect block */
+                BUFFER_TRACE(this_bh, "get_write_access");
+                err = ext4_journal_get_write_access(handle, this_bh);
+                /* Important: if we can't update the indirect pointers
+                 * to the blocks, we can't free them. */
+                if (err)
+                        return;
+        }
+
+        for (p = first; p < last; p++) {
+                nr = le32_to_cpu(*p);
+                if (nr) {
+                        /* accumulate blocks to free if they're contiguous */
+                        if (count == 0) {
+                                block_to_free = nr;
+                                block_to_free_p = p;
+                                count = 1;
+                        } else if (nr == block_to_free + count) {
+                                count++;
+                        } else {
+                                err = ext4_clear_blocks(handle, inode, this_bh,
+                                                        block_to_free, count,
+                                                        block_to_free_p, p);
+                                if (err)
+                                        break;
+                                block_to_free = nr;
+                                block_to_free_p = p;
+                                count = 1;
+                        }
+                }
+        }
+
+        if (!err && count > 0)
+                err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
+                                        count, block_to_free_p, p);
+        if (err < 0)
+                /* fatal error */
+                return;
+
+        if (this_bh) {
+                BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
+
+                /*
+                 * The buffer head should have an attached journal head at this
+                 * point. However, if the data is corrupted and an indirect
+                 * block pointed to itself, it would have been detached when
+                 * the block was cleared. Check for this instead of OOPSing.
+                 */
+                if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
+                        ext4_handle_dirty_metadata(handle, inode, this_bh);
+                else
+                        EXT4_ERROR_INODE(inode,
+                                         "circular indirect block detected at "
+                                         "block %llu",
+                                (unsigned long long) this_bh->b_blocknr);
+        }
+}
+
+/**
+ *      ext4_free_branches - free an array of branches
+ *      @handle: JBD handle for this transaction
+ *      @inode: inode we are dealing with
+ *      @parent_bh: the buffer_head which contains *@first and *@last
+ *      @first: array of block numbers
+ *      @last:  pointer immediately past the end of array
+ *      @depth: depth of the branches to free
+ *
+ *      We are freeing all blocks referred from these branches (numbers are
+ *      stored as little-endian 32-bit) and updating @inode->i_blocks
+ *      appropriately.
+ */
+static void ext4_free_branches(handle_t *handle, struct inode *inode,
+                               struct buffer_head *parent_bh,
+                               __le32 *first, __le32 *last, int depth)
+{
+        ext4_fsblk_t nr;
+        __le32 *p;
+
+        if (ext4_handle_is_aborted(handle))
+                return;
+
+        if (depth--) {
+                struct buffer_head *bh;
+                int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
+                p = last;
+                while (--p >= first) {
+                        nr = le32_to_cpu(*p);
+                        if (!nr)
+                                continue;               /* A hole */
+
+                        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
+                                                   nr, 1)) {
+                                EXT4_ERROR_INODE(inode,
+                                                 "invalid indirect mapped "
+                                                 "block %lu (level %d)",
+                                                 (unsigned long) nr, depth);
+                                break;
+                        }
+
+                        /* Go read the buffer for the next level down */
+                        bh = sb_bread(inode->i_sb, nr);
+
+                        /*
+                         * A read failure? Report error and clear slot
+                         * (should be rare).
+                         */
+                        if (!bh) {
+                                EXT4_ERROR_INODE_BLOCK(inode, nr,
+                                                       "Read failure");
+                                continue;
+                        }
+
+                        /* This zaps the entire block.  Bottom up. */
+                        BUFFER_TRACE(bh, "free child branches");
+                        ext4_free_branches(handle, inode, bh,
+                                        (__le32 *) bh->b_data,
+                                        (__le32 *) bh->b_data + addr_per_block,
+                                        depth);
+                        brelse(bh);
+
+                        /*
+                         * Everything below this this pointer has been
+                         * released.  Now let this top-of-subtree go.
+                         *
+                         * We want the freeing of this indirect block to be
+                         * atomic in the journal with the updating of the
+                         * bitmap block which owns it.  So make some room in
+                         * the journal.
+                         *
+                         * We zero the parent pointer *after* freeing its
+                         * pointee in the bitmaps, so if extend_transaction()
+                         * for some reason fails to put the bitmap changes and
+                         * the release into the same transaction, recovery
+                         * will merely complain about releasing a free block,
+                         * rather than leaking blocks.
+                         */
+                        if (ext4_handle_is_aborted(handle))
+                                return;
+                        if (try_to_extend_transaction(handle, inode)) {
+                                ext4_mark_inode_dirty(handle, inode);
+                                ext4_truncate_restart_trans(handle, inode,
+                                            ext4_blocks_for_truncate(inode));
+                        }
+
+                        /*
+                         * The forget flag here is critical because if
+                         * we are journaling (and not doing data
+                         * journaling), we have to make sure a revoke
+                         * record is written to prevent the journal
+                         * replay from overwriting the (former)
+                         * indirect block if it gets reallocated as a
+                         * data block.  This must happen in the same
+                         * transaction where the data blocks are
+                         * actually freed.
+                         */
+                        ext4_free_blocks(handle, inode, NULL, nr, 1,
+                                         EXT4_FREE_BLOCKS_METADATA|
+                                         EXT4_FREE_BLOCKS_FORGET);
+
+                        if (parent_bh) {
+                                /*
+                                 * The block which we have just freed is
+                                 * pointed to by an indirect block: journal it
+                                 */
+                                BUFFER_TRACE(parent_bh, "get_write_access");
+                                if (!ext4_journal_get_write_access(handle,
+                                                                   parent_bh)){
+                                        *p = 0;
+                                        BUFFER_TRACE(parent_bh,
+                                        "call ext4_handle_dirty_metadata");
+                                        ext4_handle_dirty_metadata(handle,
+                                                                   inode,
+                                                                   parent_bh);
+                                }
+                        }
+                }
+        } else {
+                /* We have reached the bottom of the tree. */
+                BUFFER_TRACE(parent_bh, "free data blocks");
+                ext4_free_data(handle, inode, parent_bh, first, last);
+        }
+}
+
+void ext4_ind_truncate(struct inode *inode)
+{
+        handle_t *handle;
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        __le32 *i_data = ei->i_data;
+        int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
+        struct address_space *mapping = inode->i_mapping;
+        ext4_lblk_t offsets[4];
+        Indirect chain[4];
+        Indirect *partial;
+        __le32 nr = 0;
+        int n = 0;
+        ext4_lblk_t last_block, max_block;
+        unsigned blocksize = inode->i_sb->s_blocksize;
+
+        handle = start_transaction(inode);
+        if (IS_ERR(handle))
+                return;         /* AKPM: return what? */
+
+        last_block = (inode->i_size + blocksize-1)
+                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
+        max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
+                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
+
+        if (inode->i_size & (blocksize - 1))
+                if (ext4_block_truncate_page(handle, mapping, inode->i_size))
+                        goto out_stop;
+
+        if (last_block != max_block) {
+                n = ext4_block_to_path(inode, last_block, offsets, NULL);
+                if (n == 0)
+                        goto out_stop;  /* error */
+        }
+
+        /*
+         * OK.  This truncate is going to happen.  We add the inode to the
+         * orphan list, so that if this truncate spans multiple transactions,
+         * and we crash, we will resume the truncate when the filesystem
+         * recovers.  It also marks the inode dirty, to catch the new size.
+         *
+         * Implication: the file must always be in a sane, consistent
+         * truncatable state while each transaction commits.
+         */
+        if (ext4_orphan_add(handle, inode))
+                goto out_stop;
+
+        /*
+         * From here we block out all ext4_get_block() callers who want to
+         * modify the block allocation tree.
+         */
+        down_write(&ei->i_data_sem);
+
+        ext4_discard_preallocations(inode);
+
+        /*
+         * The orphan list entry will now protect us from any crash which
+         * occurs before the truncate completes, so it is now safe to propagate
+         * the new, shorter inode size (held for now in i_size) into the
+         * on-disk inode. We do this via i_disksize, which is the value which
+         * ext4 *really* writes onto the disk inode.
+         */
+        ei->i_disksize = inode->i_size;
+
+        if (last_block == max_block) {
+                /*
+                 * It is unnecessary to free any data blocks if last_block is
+                 * equal to the indirect block limit.
+                 */
+                goto out_unlock;
+        } else if (n == 1) {            /* direct blocks */
+                ext4_free_data(handle, inode, NULL, i_data+offsets[0],
+                               i_data + EXT4_NDIR_BLOCKS);
+                goto do_indirects;
+        }
+
+        partial = ext4_find_shared(inode, n, offsets, chain, &nr);
+        /* Kill the top of shared branch (not detached) */
+        if (nr) {
+                if (partial == chain) {
+                        /* Shared branch grows from the inode */
+                        ext4_free_branches(handle, inode, NULL,
+                                           &nr, &nr+1, (chain+n-1) - partial);
+                        *partial->p = 0;
+                        /*
+                         * We mark the inode dirty prior to restart,
+                         * and prior to stop.  No need for it here.
+                         */
+                } else {
+                        /* Shared branch grows from an indirect block */
+                        BUFFER_TRACE(partial->bh, "get_write_access");
+                        ext4_free_branches(handle, inode, partial->bh,
+                                        partial->p,
+                                        partial->p+1, (chain+n-1) - partial);
+                }
+        }
+        /* Clear the ends of indirect blocks on the shared branch */
+        while (partial > chain) {
+                ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
+                                   (__le32*)partial->bh->b_data+addr_per_block,
+                                   (chain+n-1) - partial);
+                BUFFER_TRACE(partial->bh, "call brelse");
+                brelse(partial->bh);
+                partial--;
+        }
+do_indirects:
+        /* Kill the remaining (whole) subtrees */
+        switch (offsets[0]) {
+        default:
+                nr = i_data[EXT4_IND_BLOCK];
+                if (nr) {
+                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
+                        i_data[EXT4_IND_BLOCK] = 0;
+                }
+        case EXT4_IND_BLOCK:
+                nr = i_data[EXT4_DIND_BLOCK];
+                if (nr) {
+                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
+                        i_data[EXT4_DIND_BLOCK] = 0;
+                }
+        case EXT4_DIND_BLOCK:
+                nr = i_data[EXT4_TIND_BLOCK];
+                if (nr) {
+                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
+                        i_data[EXT4_TIND_BLOCK] = 0;
+                }
+        case EXT4_TIND_BLOCK:
+                ;
+        }
+
+out_unlock:
+        up_write(&ei->i_data_sem);
+        inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
+        ext4_mark_inode_dirty(handle, inode);
+
+        /*
+         * In a multi-transaction truncate, we only make the final transaction
+         * synchronous
+         */
+        if (IS_SYNC(inode))
+                ext4_handle_sync(handle);
+out_stop:
+        /*
+         * If this was a simple ftruncate(), and the file will remain alive
+         * then we need to clear up the orphan record which we created above.
+         * However, if this was a real unlink then we were called by
+         * ext4_delete_inode(), and we allow that function to clean up the
+         * orphan info for us.
+         */
+        if (inode->i_nlink)
+                ext4_orphan_del(handle, inode);
+
+        ext4_journal_stop(handle);
+        trace_ext4_truncate_exit(inode);
+}
+