inode.c

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/*
 *  linux/fs/ext2/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * 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
 *  ([email protected]), 1993, 1998
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *  ([email protected])
 *
 *  Assorted race fixes, rewrite of ext2_get_block() by Al Viro, 2000
 */

#include <linux/time.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/fiemap.h>
#include <linux/namei.h>
#include "ext2.h"
#include "acl.h"
#include "xip.h"

static int __ext2_write_inode(struct inode *inode, int do_sync);

/*
 * Test whether an inode is a fast symlink.
 */
static inline int ext2_inode_is_fast_symlink(struct inode *inode)
{
    int ea_blocks = EXT2_I(inode)->i_file_acl ?
        (inode->i_sb->s_blocksize >> 9) : 0;

    return (S_ISLNK(inode->i_mode) &&
        inode->i_blocks - ea_blocks == 0);
}

static void ext2_truncate_blocks(struct inode *inode, loff_t offset);

static void ext2_write_failed(struct address_space *mapping, loff_t to)
{
    struct inode *inode = mapping->host;

    if (to > inode->i_size) {
        truncate_pagecache(inode, to, inode->i_size);
        ext2_truncate_blocks(inode, inode->i_size);
    }
}

/*
 * Called at the last iput() if i_nlink is zero.
 */
void ext2_evict_inode(struct inode * inode)
{
    struct ext2_block_alloc_info *rsv;
    int want_delete = 0;

    if (!inode->i_nlink && !is_bad_inode(inode)) {
        want_delete = 1;
        dquot_initialize(inode);
    } else {
        dquot_drop(inode);
    }

    truncate_inode_pages(&inode->i_data, 0);

    if (want_delete) {
        sb_start_intwrite(inode->i_sb);
        /* set dtime */
        EXT2_I(inode)->i_dtime  = get_seconds();
        mark_inode_dirty(inode);
        __ext2_write_inode(inode, inode_needs_sync(inode));
        /* truncate to 0 */
        inode->i_size = 0;
        if (inode->i_blocks)
            ext2_truncate_blocks(inode, 0);
    }

    invalidate_inode_buffers(inode);
    clear_inode(inode);

    ext2_discard_reservation(inode);
    rsv = EXT2_I(inode)->i_block_alloc_info;
    EXT2_I(inode)->i_block_alloc_info = NULL;
    if (unlikely(rsv))
        kfree(rsv);

    if (want_delete) {
        ext2_free_inode(inode);
        sb_end_intwrite(inode->i_sb);
    }
}

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;
}

static inline int verify_chain(Indirect *from, Indirect *to)
{
    while (from <= to && from->key == *from->p)
        from++;
    return (from > to);
}

/*
 * 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 ext2_block_to_path(struct inode *inode,
            long i_block, int offsets[4], int *boundary)
{
    int ptrs = EXT2_ADDR_PER_BLOCK(inode->i_sb);
    int ptrs_bits = EXT2_ADDR_PER_BLOCK_BITS(inode->i_sb);
    const long direct_blocks = EXT2_NDIR_BLOCKS,
        indirect_blocks = ptrs,
        double_blocks = (1 << (ptrs_bits * 2));
    int n = 0;
    int final = 0;

    if (i_block < 0) {
        ext2_msg(inode->i_sb, KERN_WARNING,
            "warning: %s: block < 0", __func__);
    } else if (i_block < direct_blocks) {
        offsets[n++] = i_block;
        final = direct_blocks;
    } else if ( (i_block -= direct_blocks) < indirect_blocks) {
        offsets[n++] = EXT2_IND_BLOCK;
        offsets[n++] = i_block;
        final = ptrs;
    } else if ((i_block -= indirect_blocks) < double_blocks) {
        offsets[n++] = EXT2_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++] = EXT2_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 {
        ext2_msg(inode->i_sb, KERN_WARNING,
            "warning: %s: block is too big", __func__);
    }
    if (boundary)
        *boundary = final - 1 - (i_block & (ptrs - 1));

    return n;
}

static Indirect *ext2_get_branch(struct inode *inode,
                 int depth,
                 int *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, EXT2_I(inode)->i_data + *offsets);
    if (!p->key)
        goto no_block;
    while (--depth) {
        bh = sb_bread(sb, le32_to_cpu(p->key));
        if (!bh)
            goto failure;
        read_lock(&EXT2_I(inode)->i_meta_lock);
        if (!verify_chain(chain, p))
            goto changed;
        add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
        read_unlock(&EXT2_I(inode)->i_meta_lock);
        if (!p->key)
            goto no_block;
    }
    return NULL;

changed:
    read_unlock(&EXT2_I(inode)->i_meta_lock);
    brelse(bh);
    *err = -EAGAIN;
    goto no_block;
failure:
    *err = -EIO;
no_block:
    return p;
}

static ext2_fsblk_t ext2_find_near(struct inode *inode, Indirect *ind)
{
    struct ext2_inode_info *ei = EXT2_I(inode);
    __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
    __le32 *p;
    ext2_fsblk_t bg_start;
    ext2_fsblk_t colour;

    /* 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 from inode itself? OK, just put it into
     * the same cylinder group then.
     */
    bg_start = ext2_group_first_block_no(inode->i_sb, ei->i_block_group);
    colour = (current->pid % 16) *
            (EXT2_BLOCKS_PER_GROUP(inode->i_sb) / 16);
    return bg_start + colour;
}

static inline ext2_fsblk_t ext2_find_goal(struct inode *inode, long block,
                      Indirect *partial)
{
    struct ext2_block_alloc_info *block_i;

    block_i = EXT2_I(inode)->i_block_alloc_info;

    /*
     * try the heuristic for sequential allocation,
     * failing that at least try to get decent locality.
     */
    if (block_i && (block == block_i->last_alloc_logical_block + 1)
        && (block_i->last_alloc_physical_block != 0)) {
        return block_i->last_alloc_physical_block + 1;
    }

    return ext2_find_near(inode, partial);
}

static int
ext2_blks_to_allocate(Indirect * branch, int k, unsigned long blks,
        int blocks_to_boundary)
{
    unsigned long 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 don't hanel 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;
}

static int ext2_alloc_blocks(struct inode *inode,
            ext2_fsblk_t goal, int indirect_blks, int blks,
            ext2_fsblk_t new_blocks[4], int *err)
{
    int target, i;
    unsigned long count = 0;
    int index = 0;
    ext2_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)
     */
    target = blks + indirect_blks;

    while (1) {
        count = target;
        /* allocating blocks for indirect blocks and direct blocks */
        current_block = ext2_new_blocks(inode,goal,&count,err);
        if (*err)
            goto failed_out;

        target -= count;
        /* allocate blocks for indirect blocks */
        while (index < indirect_blks && count) {
            new_blocks[index++] = current_block++;
            count--;
        }

        if (count > 0)
            break;
    }

    /* save the new block number for the first direct block */
    new_blocks[index] = current_block;

    /* total number of blocks allocated for direct blocks */
    ret = count;
    *err = 0;
    return ret;
failed_out:
    for (i = 0; i <index; i++)
        ext2_free_blocks(inode, new_blocks[i], 1);
    if (index)
        mark_inode_dirty(inode);
    return ret;
}

static int ext2_alloc_branch(struct inode *inode,
            int indirect_blks, int *blks, ext2_fsblk_t goal,
            int *offsets, Indirect *branch)
{
    int blocksize = inode->i_sb->s_blocksize;
    int i, n = 0;
    int err = 0;
    struct buffer_head *bh;
    int num;
    ext2_fsblk_t new_blocks[4];
    ext2_fsblk_t current_block;

    num = ext2_alloc_blocks(inode, 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]);
        branch[n].bh = bh;
        lock_buffer(bh);
        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);
        }
        set_buffer_uptodate(bh);
        unlock_buffer(bh);
        mark_buffer_dirty_inode(bh, inode);
        /* We used to sync bh here if IS_SYNC(inode).
         * But we now rely upon generic_write_sync()
         * and b_inode_buffers.  But not for directories.
         */
        if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
            sync_dirty_buffer(bh);
    }
    *blks = num;
    return err;
}

static void ext2_splice_branch(struct inode *inode,
            long block, Indirect *where, int num, int blks)
{
    int i;
    struct ext2_block_alloc_info *block_i;
    ext2_fsblk_t current_block;

    block_i = EXT2_I(inode)->i_block_alloc_info;

    /* XXX LOCKING probably should have i_meta_lock ?*/
    /* 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++);
    }

    /*
     * update the most recently allocated logical & physical block
     * in i_block_alloc_info, to assist find the proper goal block for next
     * allocation
     */
    if (block_i) {
        block_i->last_alloc_logical_block = block + blks - 1;
        block_i->last_alloc_physical_block =
                le32_to_cpu(where[num].key) + blks - 1;
    }

    /* We are done with atomic stuff, now do the rest of housekeeping */

    /* had we spliced it onto indirect block? */
    if (where->bh)
        mark_buffer_dirty_inode(where->bh, inode);

    inode->i_ctime = CURRENT_TIME_SEC;
    mark_inode_dirty(inode);
}

/*
 * 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.
 */
static int ext2_get_blocks(struct inode *inode,
               sector_t iblock, unsigned long maxblocks,
               struct buffer_head *bh_result,
               int create)
{
    int err = -EIO;
    int offsets[4];
    Indirect chain[4];
    Indirect *partial;
    ext2_fsblk_t goal;
    int indirect_blks;
    int blocks_to_boundary = 0;
    int depth;
    struct ext2_inode_info *ei = EXT2_I(inode);
    int count = 0;
    ext2_fsblk_t first_block = 0;

    depth = ext2_block_to_path(inode,iblock,offsets,&blocks_to_boundary);

    if (depth == 0)
        return (err);

    partial = ext2_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);
        clear_buffer_new(bh_result); /* What's this do? */
        count++;
        /*map more blocks*/
        while (count < maxblocks && count <= blocks_to_boundary) {
            ext2_fsblk_t blk;

            if (!verify_chain(chain, chain + depth - 1)) {
                /*
                 * Indirect block might be removed by
                 * truncate while we were reading it.
                 * Handling of that case: forget what we've
                 * got now, go to reread.
                 */
                err = -EAGAIN;
                count = 0;
                break;
            }
            blk = le32_to_cpu(*(chain[depth-1].p + count));
            if (blk == first_block + count)
                count++;
            else
                break;
        }
        if (err != -EAGAIN)
            goto got_it;
    }

    /* Next simple case - plain lookup or failed read of indirect block */
    if (!create || err == -EIO)
        goto cleanup;

    mutex_lock(&ei->truncate_mutex);
    /*
     * If the indirect block is missing while we are reading
     * the chain(ext2_get_branch() returns -EAGAIN err), or
     * if the chain has been changed after we grab the semaphore,
     * (either because another process truncated this branch, or
     * another get_block allocated this branch) re-grab the chain to see if
     * the request block has been allocated or not.
     *
     * Since we already block the truncate/other get_block
     * at this point, we will have the current copy of the chain when we
     * splice the branch into the tree.
     */
    if (err == -EAGAIN || !verify_chain(chain, partial)) {
        while (partial > chain) {
            brelse(partial->bh);
            partial--;
        }
        partial = ext2_get_branch(inode, depth, offsets, chain, &err);
        if (!partial) {
            count++;
            mutex_unlock(&ei->truncate_mutex);
            if (err)
                goto cleanup;
            clear_buffer_new(bh_result);
            goto got_it;
        }
    }

    /*
     * Okay, we need to do block allocation.  Lazily initialize the block
     * allocation info here if necessary
    */
    if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
        ext2_init_block_alloc_info(inode);

    goal = ext2_find_goal(inode, iblock, 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 = ext2_blks_to_allocate(partial, indirect_blks,
                    maxblocks, blocks_to_boundary);
    /*
     * XXX ???? Block out ext2_truncate while we alter the tree
     */
    err = ext2_alloc_branch(inode, indirect_blks, &count, goal,
                offsets + (partial - chain), partial);

    if (err) {
        mutex_unlock(&ei->truncate_mutex);
        goto cleanup;
    }

    if (ext2_use_xip(inode->i_sb)) {
        /*
         * we need to clear the block
         */
        err = ext2_clear_xip_target (inode,
            le32_to_cpu(chain[depth-1].key));
        if (err) {
            mutex_unlock(&ei->truncate_mutex);
            goto cleanup;
        }
    }

    ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
    mutex_unlock(&ei->truncate_mutex);
    set_buffer_new(bh_result);
got_it:
    map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
    if (count > blocks_to_boundary)
        set_buffer_boundary(bh_result);
    err = count;
    /* Clean up and exit */
    partial = chain + depth - 1;    /* the whole chain */
cleanup:
    while (partial > chain) {
        brelse(partial->bh);
        partial--;
    }
    return err;
}

int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
{
    unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
    int ret = ext2_get_blocks(inode, iblock, max_blocks,
                  bh_result, create);
    if (ret > 0) {
        bh_result->b_size = (ret << inode->i_blkbits);
        ret = 0;
    }
    return ret;

}

int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
        u64 start, u64 len)
{
    return generic_block_fiemap(inode, fieinfo, start, len,
                    ext2_get_block);
}

static int ext2_writepage(struct page *page, struct writeback_control *wbc)
{
    return block_write_full_page(page, ext2_get_block, wbc);
}

static int ext2_readpage(struct file *file, struct page *page)
{
    return mpage_readpage(page, ext2_get_block);
}

static int
ext2_readpages(struct file *file, struct address_space *mapping,
        struct list_head *pages, unsigned nr_pages)
{
    return mpage_readpages(mapping, pages, nr_pages, ext2_get_block);
}

static int
ext2_write_begin(struct file *file, struct address_space *mapping,
        loff_t pos, unsigned len, unsigned flags,
        struct page **pagep, void **fsdata)
{
    int ret;

    ret = block_write_begin(mapping, pos, len, flags, pagep,
                ext2_get_block);
    if (ret < 0)
        ext2_write_failed(mapping, pos + len);
    return ret;
}

static int ext2_write_end(struct file *file, struct address_space *mapping,
            loff_t pos, unsigned len, unsigned copied,
            struct page *page, void *fsdata)
{
    int ret;

    ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
    if (ret < len)
        ext2_write_failed(mapping, pos + len);
    return ret;
}

static int
ext2_nobh_write_begin(struct file *file, struct address_space *mapping,
        loff_t pos, unsigned len, unsigned flags,
        struct page **pagep, void **fsdata)
{
    int ret;

    ret = nobh_write_begin(mapping, pos, len, flags, pagep, fsdata,
                   ext2_get_block);
    if (ret < 0)
        ext2_write_failed(mapping, pos + len);
    return ret;
}

static int ext2_nobh_writepage(struct page *page,
            struct writeback_control *wbc)
{
    return nobh_writepage(page, ext2_get_block, wbc);
}

static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping,block,ext2_get_block);
}

static ssize_t
ext2_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 address_space *mapping = file->f_mapping;
    struct inode *inode = mapping->host;
    ssize_t ret;

    ret = blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
                 ext2_get_block);
    if (ret < 0 && (rw & WRITE))
        ext2_write_failed(mapping, offset + iov_length(iov, nr_segs));
    return ret;
}

static int
ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
    return mpage_writepages(mapping, wbc, ext2_get_block);
}

const struct address_space_operations ext2_aops = {
    .readpage       = ext2_readpage,
    .readpages      = ext2_readpages,
    .writepage      = ext2_writepage,
    .write_begin        = ext2_write_begin,
    .write_end      = ext2_write_end,
    .bmap           = ext2_bmap,
    .direct_IO      = ext2_direct_IO,
    .writepages     = ext2_writepages,
    .migratepage        = buffer_migrate_page,
    .is_partially_uptodate  = block_is_partially_uptodate,
    .error_remove_page  = generic_error_remove_page,
};

const struct address_space_operations ext2_aops_xip = {
    .bmap           = ext2_bmap,
    .get_xip_mem        = ext2_get_xip_mem,
};

const struct address_space_operations ext2_nobh_aops = {
    .readpage       = ext2_readpage,
    .readpages      = ext2_readpages,
    .writepage      = ext2_nobh_writepage,
    .write_begin        = ext2_nobh_write_begin,
    .write_end      = nobh_write_end,
    .bmap           = ext2_bmap,
    .direct_IO      = ext2_direct_IO,
    .writepages     = ext2_writepages,
    .migratepage        = buffer_migrate_page,
    .error_remove_page  = generic_error_remove_page,
};

/*
 * 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;
}

static Indirect *ext2_find_shared(struct inode *inode,
                int depth,
                int offsets[4],
                Indirect chain[4],
                __le32 *top)
{
    Indirect *partial, *p;
    int k, err;

    *top = 0;
    for (k = depth; k > 1 && !offsets[k-1]; k--)
        ;
    partial = ext2_get_branch(inode, k, offsets, chain, &err);
    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.
     */
    write_lock(&EXT2_I(inode)->i_meta_lock);
    if (!partial->key && *partial->p) {
        write_unlock(&EXT2_I(inode)->i_meta_lock);
        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;
        *p->p = 0;
    }
    write_unlock(&EXT2_I(inode)->i_meta_lock);

    while(partial > p)
    {
        brelse(partial->bh);
        partial--;
    }
no_top:
    return partial;
}

static inline void ext2_free_data(struct inode *inode, __le32 *p, __le32 *q)
{
    unsigned long block_to_free = 0, count = 0;
    unsigned long nr;

    for ( ; p < q ; p++) {
        nr = le32_to_cpu(*p);
        if (nr) {
            *p = 0;
            /* accumulate blocks to free if they're contiguous */
            if (count == 0)
                goto free_this;
            else if (block_to_free == nr - count)
                count++;
            else {
                ext2_free_blocks (inode, block_to_free, count);
                mark_inode_dirty(inode);
            free_this:
                block_to_free = nr;
                count = 1;
            }
        }
    }
    if (count > 0) {
        ext2_free_blocks (inode, block_to_free, count);
        mark_inode_dirty(inode);
    }
}

static void ext2_free_branches(struct inode *inode, __le32 *p, __le32 *q, int depth)
{
    struct buffer_head * bh;
    unsigned long nr;

    if (depth--) {
        int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
        for ( ; p < q ; p++) {
            nr = le32_to_cpu(*p);
            if (!nr)
                continue;
            *p = 0;
            bh = sb_bread(inode->i_sb, nr);
            /*
             * A read failure? Report error and clear slot
             * (should be rare).
             */ 
            if (!bh) {
                ext2_error(inode->i_sb, "ext2_free_branches",
                    "Read failure, inode=%ld, block=%ld",
                    inode->i_ino, nr);
                continue;
            }
            ext2_free_branches(inode,
                       (__le32*)bh->b_data,
                       (__le32*)bh->b_data + addr_per_block,
                       depth);
            bforget(bh);
            ext2_free_blocks(inode, nr, 1);
            mark_inode_dirty(inode);
        }
    } else
        ext2_free_data(inode, p, q);
}

static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
{
    __le32 *i_data = EXT2_I(inode)->i_data;
    struct ext2_inode_info *ei = EXT2_I(inode);
    int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
    int offsets[4];
    Indirect chain[4];
    Indirect *partial;
    __le32 nr = 0;
    int n;
    long iblock;
    unsigned blocksize;
    blocksize = inode->i_sb->s_blocksize;
    iblock = (offset + blocksize-1) >> EXT2_BLOCK_SIZE_BITS(inode->i_sb);

    n = ext2_block_to_path(inode, iblock, offsets, NULL);
    if (n == 0)
        return;

    /*
     * From here we block out all ext2_get_block() callers who want to
     * modify the block allocation tree.
     */
    mutex_lock(&ei->truncate_mutex);

    if (n == 1) {
        ext2_free_data(inode, i_data+offsets[0],
                    i_data + EXT2_NDIR_BLOCKS);
        goto do_indirects;
    }

    partial = ext2_find_shared(inode, n, offsets, chain, &nr);
    /* Kill the top of shared branch (already detached) */
    if (nr) {
        if (partial == chain)
            mark_inode_dirty(inode);
        else
            mark_buffer_dirty_inode(partial->bh, inode);
        ext2_free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
    }
    /* Clear the ends of indirect blocks on the shared branch */
    while (partial > chain) {
        ext2_free_branches(inode,
                   partial->p + 1,
                   (__le32*)partial->bh->b_data+addr_per_block,
                   (chain+n-1) - partial);
        mark_buffer_dirty_inode(partial->bh, inode);
        brelse (partial->bh);
        partial--;
    }
do_indirects:
    /* Kill the remaining (whole) subtrees */
    switch (offsets[0]) {
        default:
            nr = i_data[EXT2_IND_BLOCK];
            if (nr) {
                i_data[EXT2_IND_BLOCK] = 0;
                mark_inode_dirty(inode);
                ext2_free_branches(inode, &nr, &nr+1, 1);
            }
        case EXT2_IND_BLOCK:
            nr = i_data[EXT2_DIND_BLOCK];
            if (nr) {
                i_data[EXT2_DIND_BLOCK] = 0;
                mark_inode_dirty(inode);
                ext2_free_branches(inode, &nr, &nr+1, 2);
            }
        case EXT2_DIND_BLOCK:
            nr = i_data[EXT2_TIND_BLOCK];
            if (nr) {
                i_data[EXT2_TIND_BLOCK] = 0;
                mark_inode_dirty(inode);
                ext2_free_branches(inode, &nr, &nr+1, 3);
            }
        case EXT2_TIND_BLOCK:
            ;
    }

    ext2_discard_reservation(inode);

    mutex_unlock(&ei->truncate_mutex);
}

static void ext2_truncate_blocks(struct inode *inode, loff_t offset)
{
    /*
     * XXX: it seems like a bug here that we don't allow
     * IS_APPEND inode to have blocks-past-i_size trimmed off.
     * review and fix this.
     *
     * Also would be nice to be able to handle IO errors and such,
     * but that's probably too much to ask.
     */
    if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
        S_ISLNK(inode->i_mode)))
        return;
    if (ext2_inode_is_fast_symlink(inode))
        return;
    if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
        return;
    __ext2_truncate_blocks(inode, offset);
}

static int ext2_setsize(struct inode *inode, loff_t newsize)
{
    int error;

    if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
        S_ISLNK(inode->i_mode)))
        return -EINVAL;
    if (ext2_inode_is_fast_symlink(inode))
        return -EINVAL;
    if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
        return -EPERM;

    inode_dio_wait(inode);

    if (mapping_is_xip(inode->i_mapping))
        error = xip_truncate_page(inode->i_mapping, newsize);
    else if (test_opt(inode->i_sb, NOBH))
        error = nobh_truncate_page(inode->i_mapping,
                newsize, ext2_get_block);
    else
        error = block_truncate_page(inode->i_mapping,
                newsize, ext2_get_block);
    if (error)
        return error;

    truncate_setsize(inode, newsize);
    __ext2_truncate_blocks(inode, newsize);

    inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
    if (inode_needs_sync(inode)) {
        sync_mapping_buffers(inode->i_mapping);
        sync_inode_metadata(inode, 1);
    } else {
        mark_inode_dirty(inode);
    }

    return 0;
}

static struct ext2_inode *ext2_get_inode(struct super_block *sb, ino_t ino,
                    struct buffer_head **p)
{
    struct buffer_head * bh;
    unsigned long block_group;
    unsigned long block;
    unsigned long offset;
    struct ext2_group_desc * gdp;

    *p = NULL;
    if ((ino != EXT2_ROOT_INO && ino < EXT2_FIRST_INO(sb)) ||
        ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
        goto Einval;

    block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
    gdp = ext2_get_group_desc(sb, block_group, NULL);
    if (!gdp)
        goto Egdp;
    /*
     * Figure out the offset within the block group inode table
     */
    offset = ((ino - 1) % EXT2_INODES_PER_GROUP(sb)) * EXT2_INODE_SIZE(sb);
    block = le32_to_cpu(gdp->bg_inode_table) +
        (offset >> EXT2_BLOCK_SIZE_BITS(sb));
    if (!(bh = sb_bread(sb, block)))
        goto Eio;

    *p = bh;
    offset &= (EXT2_BLOCK_SIZE(sb) - 1);
    return (struct ext2_inode *) (bh->b_data + offset);

Einval:
    ext2_error(sb, "ext2_get_inode", "bad inode number: %lu",
           (unsigned long) ino);
    return ERR_PTR(-EINVAL);
Eio:
    ext2_error(sb, "ext2_get_inode",
           "unable to read inode block - inode=%lu, block=%lu",
           (unsigned long) ino, block);
Egdp:
    return ERR_PTR(-EIO);
}

void ext2_set_inode_flags(struct inode *inode)
{
    unsigned int flags = EXT2_I(inode)->i_flags;

    inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
    if (flags & EXT2_SYNC_FL)
        inode->i_flags |= S_SYNC;
    if (flags & EXT2_APPEND_FL)
        inode->i_flags |= S_APPEND;
    if (flags & EXT2_IMMUTABLE_FL)
        inode->i_flags |= S_IMMUTABLE;
    if (flags & EXT2_NOATIME_FL)
        inode->i_flags |= S_NOATIME;
    if (flags & EXT2_DIRSYNC_FL)
        inode->i_flags |= S_DIRSYNC;
}

/* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
void ext2_get_inode_flags(struct ext2_inode_info *ei)
{
    unsigned int flags = ei->vfs_inode.i_flags;

    ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
            EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
    if (flags & S_SYNC)
        ei->i_flags |= EXT2_SYNC_FL;
    if (flags & S_APPEND)
        ei->i_flags |= EXT2_APPEND_FL;
    if (flags & S_IMMUTABLE)
        ei->i_flags |= EXT2_IMMUTABLE_FL;
    if (flags & S_NOATIME)
        ei->i_flags |= EXT2_NOATIME_FL;
    if (flags & S_DIRSYNC)
        ei->i_flags |= EXT2_DIRSYNC_FL;
}

struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
{
    struct ext2_inode_info *ei;
    struct buffer_head * bh;
    struct ext2_inode *raw_inode;
    struct inode *inode;
    long ret = -EIO;
    int n;
    uid_t i_uid;
    gid_t i_gid;

    inode = iget_locked(sb, ino);
    if (!inode)
        return ERR_PTR(-ENOMEM);
    if (!(inode->i_state & I_NEW))
        return inode;

    ei = EXT2_I(inode);
    ei->i_block_alloc_info = NULL;

    raw_inode = ext2_get_inode(inode->i_sb, ino, &bh);
    if (IS_ERR(raw_inode)) {
        ret = PTR_ERR(raw_inode);
        goto bad_inode;
    }

    inode->i_mode = le16_to_cpu(raw_inode->i_mode);
    i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
    i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
    if (!(test_opt (inode->i_sb, NO_UID32))) {
        i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
        i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
    }
    i_uid_write(inode, i_uid);
    i_gid_write(inode, i_gid);
    set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
    inode->i_size = le32_to_cpu(raw_inode->i_size);
    inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime);
    inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime);
    inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime);
    inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
    ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
    /* We now have enough fields to check if the inode was active or not.
     * This is needed because nfsd might try to access dead inodes
     * the test is that same one that e2fsck uses
     * NeilBrown 1999oct15
     */
    if (inode->i_nlink == 0 && (inode->i_mode == 0 || ei->i_dtime)) {
        /* this inode is deleted */
        brelse (bh);
        ret = -ESTALE;
        goto bad_inode;
    }
    inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
    ei->i_flags = le32_to_cpu(raw_inode->i_flags);
    ei->i_faddr = le32_to_cpu(raw_inode->i_faddr);
    ei->i_frag_no = raw_inode->i_frag;
    ei->i_frag_size = raw_inode->i_fsize;
    ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
    ei->i_dir_acl = 0;
    if (S_ISREG(inode->i_mode))
        inode->i_size |= ((__u64)le32_to_cpu(raw_inode->i_size_high)) << 32;
    else
        ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
    ei->i_dtime = 0;
    inode->i_generation = le32_to_cpu(raw_inode->i_generation);
    ei->i_state = 0;
    ei->i_block_group = (ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
    ei->i_dir_start_lookup = 0;

    /*
     * NOTE! The in-memory inode i_data array is in little-endian order
     * even on big-endian machines: we do NOT byteswap the block numbers!
     */
    for (n = 0; n < EXT2_N_BLOCKS; n++)
        ei->i_data[n] = raw_inode->i_block[n];

    if (S_ISREG(inode->i_mode)) {
        inode->i_op = &ext2_file_inode_operations;
        if (ext2_use_xip(inode->i_sb)) {
            inode->i_mapping->a_ops = &ext2_aops_xip;
            inode->i_fop = &ext2_xip_file_operations;
        } else if (test_opt(inode->i_sb, NOBH)) {
            inode->i_mapping->a_ops = &ext2_nobh_aops;
            inode->i_fop = &ext2_file_operations;
        } else {
            inode->i_mapping->a_ops = &ext2_aops;
            inode->i_fop = &ext2_file_operations;
        }
    } else if (S_ISDIR(inode->i_mode)) {
        inode->i_op = &ext2_dir_inode_operations;
        inode->i_fop = &ext2_dir_operations;
        if (test_opt(inode->i_sb, NOBH))
            inode->i_mapping->a_ops = &ext2_nobh_aops;
        else
            inode->i_mapping->a_ops = &ext2_aops;
    } else if (S_ISLNK(inode->i_mode)) {
        if (ext2_inode_is_fast_symlink(inode)) {
            inode->i_op = &ext2_fast_symlink_inode_operations;
            nd_terminate_link(ei->i_data, inode->i_size,
                sizeof(ei->i_data) - 1);
        } else {
            inode->i_op = &ext2_symlink_inode_operations;
            if (test_opt(inode->i_sb, NOBH))
                inode->i_mapping->a_ops = &ext2_nobh_aops;
            else
                inode->i_mapping->a_ops = &ext2_aops;
        }
    } else {
        inode->i_op = &ext2_special_inode_operations;
        if (raw_inode->i_block[0])
            init_special_inode(inode, inode->i_mode,
               old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
        else 
            init_special_inode(inode, inode->i_mode,
               new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
    }
    brelse (bh);
    ext2_set_inode_flags(inode);
    unlock_new_inode(inode);
    return inode;
    
bad_inode:
    iget_failed(inode);
    return ERR_PTR(ret);
}

static int __ext2_write_inode(struct inode *inode, int do_sync)
{
    struct ext2_inode_info *ei = EXT2_I(inode);
    struct super_block *sb = inode->i_sb;
    ino_t ino = inode->i_ino;
    uid_t uid = i_uid_read(inode);
    gid_t gid = i_gid_read(inode);
    struct buffer_head * bh;
    struct ext2_inode * raw_inode = ext2_get_inode(sb, ino, &bh);
    int n;
    int err = 0;

    if (IS_ERR(raw_inode))
        return -EIO;

    /* For fields not not tracking in the in-memory inode,
     * initialise them to zero for new inodes. */
    if (ei->i_state & EXT2_STATE_NEW)
        memset(raw_inode, 0, EXT2_SB(sb)->s_inode_size);

    ext2_get_inode_flags(ei);
    raw_inode->i_mode = cpu_to_le16(inode->i_mode);
    if (!(test_opt(sb, NO_UID32))) {
        raw_inode->i_uid_low = cpu_to_le16(low_16_bits(uid));
        raw_inode->i_gid_low = cpu_to_le16(low_16_bits(gid));
/*
 * Fix up interoperability with old kernels. Otherwise, old inodes get
 * re-used with the upper 16 bits of the uid/gid intact
 */
        if (!ei->i_dtime) {
            raw_inode->i_uid_high = cpu_to_le16(high_16_bits(uid));
            raw_inode->i_gid_high = cpu_to_le16(high_16_bits(gid));
        } else {
            raw_inode->i_uid_high = 0;
            raw_inode->i_gid_high = 0;
        }
    } else {
        raw_inode->i_uid_low = cpu_to_le16(fs_high2lowuid(uid));
        raw_inode->i_gid_low = cpu_to_le16(fs_high2lowgid(gid));
        raw_inode->i_uid_high = 0;
        raw_inode->i_gid_high = 0;
    }
    raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
    raw_inode->i_size = cpu_to_le32(inode->i_size);
    raw_inode->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
    raw_inode->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
    raw_inode->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);

    raw_inode->i_blocks = cpu_to_le32(inode->i_blocks);
    raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
    raw_inode->i_flags = cpu_to_le32(ei->i_flags);
    raw_inode->i_faddr = cpu_to_le32(ei->i_faddr);
    raw_inode->i_frag = ei->i_frag_no;
    raw_inode->i_fsize = ei->i_frag_size;
    raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
    if (!S_ISREG(inode->i_mode))
        raw_inode->i_dir_acl = cpu_to_le32(ei->i_dir_acl);
    else {
        raw_inode->i_size_high = cpu_to_le32(inode->i_size >> 32);
        if (inode->i_size > 0x7fffffffULL) {
            if (!EXT2_HAS_RO_COMPAT_FEATURE(sb,
                    EXT2_FEATURE_RO_COMPAT_LARGE_FILE) ||
                EXT2_SB(sb)->s_es->s_rev_level ==
                    cpu_to_le32(EXT2_GOOD_OLD_REV)) {
                   /* If this is the first large file
                * created, add a flag to the superblock.
                */
                spin_lock(&EXT2_SB(sb)->s_lock);
                ext2_update_dynamic_rev(sb);
                EXT2_SET_RO_COMPAT_FEATURE(sb,
                    EXT2_FEATURE_RO_COMPAT_LARGE_FILE);
                spin_unlock(&EXT2_SB(sb)->s_lock);
                ext2_write_super(sb);
            }
        }
    }
    
    raw_inode->i_generation = cpu_to_le32(inode->i_generation);
    if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
        if (old_valid_dev(inode->i_rdev)) {
            raw_inode->i_block[0] =
                cpu_to_le32(old_encode_dev(inode->i_rdev));
            raw_inode->i_block[1] = 0;
        } else {
            raw_inode->i_block[0] = 0;
            raw_inode->i_block[1] =
                cpu_to_le32(new_encode_dev(inode->i_rdev));
            raw_inode->i_block[2] = 0;
        }
    } else for (n = 0; n < EXT2_N_BLOCKS; n++)
        raw_inode->i_block[n] = ei->i_data[n];
    mark_buffer_dirty(bh);
    if (do_sync) {
        sync_dirty_buffer(bh);
        if (buffer_req(bh) && !buffer_uptodate(bh)) {
            printk ("IO error syncing ext2 inode [%s:%08lx]\n",
                sb->s_id, (unsigned long) ino);
            err = -EIO;
        }
    }
    ei->i_state &= ~EXT2_STATE_NEW;
    brelse (bh);
    return err;
}

int ext2_write_inode(struct inode *inode, struct writeback_control *wbc)
{
    return __ext2_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
}

int ext2_setattr(struct dentry *dentry, struct iattr *iattr)
{
    struct inode *inode = dentry->d_inode;
    int error;

    error = inode_change_ok(inode, iattr);
    if (error)
        return error;

    if (is_quota_modification(inode, iattr))
        dquot_initialize(inode);
    if ((iattr->ia_valid & ATTR_UID && !uid_eq(iattr->ia_uid, inode->i_uid)) ||
        (iattr->ia_valid & ATTR_GID && !gid_eq(iattr->ia_gid, inode->i_gid))) {
        error = dquot_transfer(inode, iattr);
        if (error)
            return error;
    }
    if (iattr->ia_valid & ATTR_SIZE && iattr->ia_size != inode->i_size) {
        error = ext2_setsize(inode, iattr->ia_size);
        if (error)
            return error;
    }
    setattr_copy(inode, iattr);
    if (iattr->ia_valid & ATTR_MODE)
        error = ext2_acl_chmod(inode);
    mark_inode_dirty(inode);

    return error;
}