file.c

Go to the documentation of this file.

/*
 * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2011 Anton Altaparmakov and Tuxera Inc.
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/buffer_head.h>
#include <linux/gfp.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/uio.h>
#include <linux/writeback.h>

#include <asm/page.h>
#include <asm/uaccess.h>

#include "attrib.h"
#include "bitmap.h"
#include "inode.h"
#include "debug.h"
#include "lcnalloc.h"
#include "malloc.h"
#include "mft.h"
#include "ntfs.h"

static int ntfs_file_open(struct inode *vi, struct file *filp)
{
    if (sizeof(unsigned long) < 8) {
        if (i_size_read(vi) > MAX_LFS_FILESIZE)
            return -EOVERFLOW;
    }
    return generic_file_open(vi, filp);
}

#ifdef NTFS_RW

static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)
{
    s64 old_init_size;
    loff_t old_i_size;
    pgoff_t index, end_index;
    unsigned long flags;
    struct inode *vi = VFS_I(ni);
    ntfs_inode *base_ni;
    MFT_RECORD *m = NULL;
    ATTR_RECORD *a;
    ntfs_attr_search_ctx *ctx = NULL;
    struct address_space *mapping;
    struct page *page = NULL;
    u8 *kattr;
    int err;
    u32 attr_len;

    read_lock_irqsave(&ni->size_lock, flags);
    old_init_size = ni->initialized_size;
    old_i_size = i_size_read(vi);
    BUG_ON(new_init_size > ni->allocated_size);
    read_unlock_irqrestore(&ni->size_lock, flags);
    ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
            "old_initialized_size 0x%llx, "
            "new_initialized_size 0x%llx, i_size 0x%llx.",
            vi->i_ino, (unsigned)le32_to_cpu(ni->type),
            (unsigned long long)old_init_size,
            (unsigned long long)new_init_size, old_i_size);
    if (!NInoAttr(ni))
        base_ni = ni;
    else
        base_ni = ni->ext.base_ntfs_ino;
    /* Use goto to reduce indentation and we need the label below anyway. */
    if (NInoNonResident(ni))
        goto do_non_resident_extend;
    BUG_ON(old_init_size != old_i_size);
    m = map_mft_record(base_ni);
    if (IS_ERR(m)) {
        err = PTR_ERR(m);
        m = NULL;
        goto err_out;
    }
    ctx = ntfs_attr_get_search_ctx(base_ni, m);
    if (unlikely(!ctx)) {
        err = -ENOMEM;
        goto err_out;
    }
    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
            CASE_SENSITIVE, 0, NULL, 0, ctx);
    if (unlikely(err)) {
        if (err == -ENOENT)
            err = -EIO;
        goto err_out;
    }
    m = ctx->mrec;
    a = ctx->attr;
    BUG_ON(a->non_resident);
    /* The total length of the attribute value. */
    attr_len = le32_to_cpu(a->data.resident.value_length);
    BUG_ON(old_i_size != (loff_t)attr_len);
    /*
     * Do the zeroing in the mft record and update the attribute size in
     * the mft record.
     */
    kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
    memset(kattr + attr_len, 0, new_init_size - attr_len);
    a->data.resident.value_length = cpu_to_le32((u32)new_init_size);
    /* Finally, update the sizes in the vfs and ntfs inodes. */
    write_lock_irqsave(&ni->size_lock, flags);
    i_size_write(vi, new_init_size);
    ni->initialized_size = new_init_size;
    write_unlock_irqrestore(&ni->size_lock, flags);
    goto done;
do_non_resident_extend:
    /*
     * If the new initialized size @new_init_size exceeds the current file
     * size (vfs inode->i_size), we need to extend the file size to the
     * new initialized size.
     */
    if (new_init_size > old_i_size) {
        m = map_mft_record(base_ni);
        if (IS_ERR(m)) {
            err = PTR_ERR(m);
            m = NULL;
            goto err_out;
        }
        ctx = ntfs_attr_get_search_ctx(base_ni, m);
        if (unlikely(!ctx)) {
            err = -ENOMEM;
            goto err_out;
        }
        err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                CASE_SENSITIVE, 0, NULL, 0, ctx);
        if (unlikely(err)) {
            if (err == -ENOENT)
                err = -EIO;
            goto err_out;
        }
        m = ctx->mrec;
        a = ctx->attr;
        BUG_ON(!a->non_resident);
        BUG_ON(old_i_size != (loff_t)
                sle64_to_cpu(a->data.non_resident.data_size));
        a->data.non_resident.data_size = cpu_to_sle64(new_init_size);
        flush_dcache_mft_record_page(ctx->ntfs_ino);
        mark_mft_record_dirty(ctx->ntfs_ino);
        /* Update the file size in the vfs inode. */
        i_size_write(vi, new_init_size);
        ntfs_attr_put_search_ctx(ctx);
        ctx = NULL;
        unmap_mft_record(base_ni);
        m = NULL;
    }
    mapping = vi->i_mapping;
    index = old_init_size >> PAGE_CACHE_SHIFT;
    end_index = (new_init_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
    do {
        /*
         * Read the page.  If the page is not present, this will zero
         * the uninitialized regions for us.
         */
        page = read_mapping_page(mapping, index, NULL);
        if (IS_ERR(page)) {
            err = PTR_ERR(page);
            goto init_err_out;
        }
        if (unlikely(PageError(page))) {
            page_cache_release(page);
            err = -EIO;
            goto init_err_out;
        }
        /*
         * Update the initialized size in the ntfs inode.  This is
         * enough to make ntfs_writepage() work.
         */
        write_lock_irqsave(&ni->size_lock, flags);
        ni->initialized_size = (s64)(index + 1) << PAGE_CACHE_SHIFT;
        if (ni->initialized_size > new_init_size)
            ni->initialized_size = new_init_size;
        write_unlock_irqrestore(&ni->size_lock, flags);
        /* Set the page dirty so it gets written out. */
        set_page_dirty(page);
        page_cache_release(page);
        /*
         * Play nice with the vm and the rest of the system.  This is
         * very much needed as we can potentially be modifying the
         * initialised size from a very small value to a really huge
         * value, e.g.
         *  f = open(somefile, O_TRUNC);
         *  truncate(f, 10GiB);
         *  seek(f, 10GiB);
         *  write(f, 1);
         * And this would mean we would be marking dirty hundreds of
         * thousands of pages or as in the above example more than
         * two and a half million pages!
         *
         * TODO: For sparse pages could optimize this workload by using
         * the FsMisc / MiscFs page bit as a "PageIsSparse" bit.  This
         * would be set in readpage for sparse pages and here we would
         * not need to mark dirty any pages which have this bit set.
         * The only caveat is that we have to clear the bit everywhere
         * where we allocate any clusters that lie in the page or that
         * contain the page.
         *
         * TODO: An even greater optimization would be for us to only
         * call readpage() on pages which are not in sparse regions as
         * determined from the runlist.  This would greatly reduce the
         * number of pages we read and make dirty in the case of sparse
         * files.
         */
        balance_dirty_pages_ratelimited(mapping);
        cond_resched();
    } while (++index < end_index);
    read_lock_irqsave(&ni->size_lock, flags);
    BUG_ON(ni->initialized_size != new_init_size);
    read_unlock_irqrestore(&ni->size_lock, flags);
    /* Now bring in sync the initialized_size in the mft record. */
    m = map_mft_record(base_ni);
    if (IS_ERR(m)) {
        err = PTR_ERR(m);
        m = NULL;
        goto init_err_out;
    }
    ctx = ntfs_attr_get_search_ctx(base_ni, m);
    if (unlikely(!ctx)) {
        err = -ENOMEM;
        goto init_err_out;
    }
    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
            CASE_SENSITIVE, 0, NULL, 0, ctx);
    if (unlikely(err)) {
        if (err == -ENOENT)
            err = -EIO;
        goto init_err_out;
    }
    m = ctx->mrec;
    a = ctx->attr;
    BUG_ON(!a->non_resident);
    a->data.non_resident.initialized_size = cpu_to_sle64(new_init_size);
done:
    flush_dcache_mft_record_page(ctx->ntfs_ino);
    mark_mft_record_dirty(ctx->ntfs_ino);
    if (ctx)
        ntfs_attr_put_search_ctx(ctx);
    if (m)
        unmap_mft_record(base_ni);
    ntfs_debug("Done, initialized_size 0x%llx, i_size 0x%llx.",
            (unsigned long long)new_init_size, i_size_read(vi));
    return 0;
init_err_out:
    write_lock_irqsave(&ni->size_lock, flags);
    ni->initialized_size = old_init_size;
    write_unlock_irqrestore(&ni->size_lock, flags);
err_out:
    if (ctx)
        ntfs_attr_put_search_ctx(ctx);
    if (m)
        unmap_mft_record(base_ni);
    ntfs_debug("Failed.  Returning error code %i.", err);
    return err;
}

static inline void ntfs_fault_in_pages_readable(const char __user *uaddr,
        int bytes)
{
    const char __user *end;
    volatile char c;

    /* Set @end to the first byte outside the last page we care about. */
    end = (const char __user*)PAGE_ALIGN((unsigned long)uaddr + bytes);

    while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
        ;
}

static inline void ntfs_fault_in_pages_readable_iovec(const struct iovec *iov,
        size_t iov_ofs, int bytes)
{
    do {
        const char __user *buf;
        unsigned len;

        buf = iov->iov_base + iov_ofs;
        len = iov->iov_len - iov_ofs;
        if (len > bytes)
            len = bytes;
        ntfs_fault_in_pages_readable(buf, len);
        bytes -= len;
        iov++;
        iov_ofs = 0;
    } while (bytes);
}

static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
        pgoff_t index, const unsigned nr_pages, struct page **pages,
        struct page **cached_page)
{
    int err, nr;

    BUG_ON(!nr_pages);
    err = nr = 0;
    do {
        pages[nr] = find_lock_page(mapping, index);
        if (!pages[nr]) {
            if (!*cached_page) {
                *cached_page = page_cache_alloc(mapping);
                if (unlikely(!*cached_page)) {
                    err = -ENOMEM;
                    goto err_out;
                }
            }
            err = add_to_page_cache_lru(*cached_page, mapping, index,
                    GFP_KERNEL);
            if (unlikely(err)) {
                if (err == -EEXIST)
                    continue;
                goto err_out;
            }
            pages[nr] = *cached_page;
            *cached_page = NULL;
        }
        index++;
        nr++;
    } while (nr < nr_pages);
out:
    return err;
err_out:
    while (nr > 0) {
        unlock_page(pages[--nr]);
        page_cache_release(pages[nr]);
    }
    goto out;
}

static inline int ntfs_submit_bh_for_read(struct buffer_head *bh)
{
    lock_buffer(bh);
    get_bh(bh);
    bh->b_end_io = end_buffer_read_sync;
    return submit_bh(READ, bh);
}

static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
        unsigned nr_pages, s64 pos, size_t bytes)
{
    VCN vcn, highest_vcn = 0, cpos, cend, bh_cpos, bh_cend;
    LCN lcn;
    s64 bh_pos, vcn_len, end, initialized_size;
    sector_t lcn_block;
    struct page *page;
    struct inode *vi;
    ntfs_inode *ni, *base_ni = NULL;
    ntfs_volume *vol;
    runlist_element *rl, *rl2;
    struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
    ntfs_attr_search_ctx *ctx = NULL;
    MFT_RECORD *m = NULL;
    ATTR_RECORD *a = NULL;
    unsigned long flags;
    u32 attr_rec_len = 0;
    unsigned blocksize, u;
    int err, mp_size;
    bool rl_write_locked, was_hole, is_retry;
    unsigned char blocksize_bits;
    struct {
        u8 runlist_merged:1;
        u8 mft_attr_mapped:1;
        u8 mp_rebuilt:1;
        u8 attr_switched:1;
    } status = { 0, 0, 0, 0 };

    BUG_ON(!nr_pages);
    BUG_ON(!pages);
    BUG_ON(!*pages);
    vi = pages[0]->mapping->host;
    ni = NTFS_I(vi);
    vol = ni->vol;
    ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
            "index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
            vi->i_ino, ni->type, pages[0]->index, nr_pages,
            (long long)pos, bytes);
    blocksize = vol->sb->s_blocksize;
    blocksize_bits = vol->sb->s_blocksize_bits;
    u = 0;
    do {
        page = pages[u];
        BUG_ON(!page);
        /*
         * create_empty_buffers() will create uptodate/dirty buffers if
         * the page is uptodate/dirty.
         */
        if (!page_has_buffers(page)) {
            create_empty_buffers(page, blocksize, 0);
            if (unlikely(!page_has_buffers(page)))
                return -ENOMEM;
        }
    } while (++u < nr_pages);
    rl_write_locked = false;
    rl = NULL;
    err = 0;
    vcn = lcn = -1;
    vcn_len = 0;
    lcn_block = -1;
    was_hole = false;
    cpos = pos >> vol->cluster_size_bits;
    end = pos + bytes;
    cend = (end + vol->cluster_size - 1) >> vol->cluster_size_bits;
    /*
     * Loop over each page and for each page over each buffer.  Use goto to
     * reduce indentation.
     */
    u = 0;
do_next_page:
    page = pages[u];
    bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
    bh = head = page_buffers(page);
    do {
        VCN cdelta;
        s64 bh_end;
        unsigned bh_cofs;

        /* Clear buffer_new on all buffers to reinitialise state. */
        if (buffer_new(bh))
            clear_buffer_new(bh);
        bh_end = bh_pos + blocksize;
        bh_cpos = bh_pos >> vol->cluster_size_bits;
        bh_cofs = bh_pos & vol->cluster_size_mask;
        if (buffer_mapped(bh)) {
            /*
             * The buffer is already mapped.  If it is uptodate,
             * ignore it.
             */
            if (buffer_uptodate(bh))
                continue;
            /*
             * The buffer is not uptodate.  If the page is uptodate
             * set the buffer uptodate and otherwise ignore it.
             */
            if (PageUptodate(page)) {
                set_buffer_uptodate(bh);
                continue;
            }
            /*
             * Neither the page nor the buffer are uptodate.  If
             * the buffer is only partially being written to, we
             * need to read it in before the write, i.e. now.
             */
            if ((bh_pos < pos && bh_end > pos) ||
                    (bh_pos < end && bh_end > end)) {
                /*
                 * If the buffer is fully or partially within
                 * the initialized size, do an actual read.
                 * Otherwise, simply zero the buffer.
                 */
                read_lock_irqsave(&ni->size_lock, flags);
                initialized_size = ni->initialized_size;
                read_unlock_irqrestore(&ni->size_lock, flags);
                if (bh_pos < initialized_size) {
                    ntfs_submit_bh_for_read(bh);
                    *wait_bh++ = bh;
                } else {
                    zero_user(page, bh_offset(bh),
                            blocksize);
                    set_buffer_uptodate(bh);
                }
            }
            continue;
        }
        /* Unmapped buffer.  Need to map it. */
        bh->b_bdev = vol->sb->s_bdev;
        /*
         * If the current buffer is in the same clusters as the map
         * cache, there is no need to check the runlist again.  The
         * map cache is made up of @vcn, which is the first cached file
         * cluster, @vcn_len which is the number of cached file
         * clusters, @lcn is the device cluster corresponding to @vcn,
         * and @lcn_block is the block number corresponding to @lcn.
         */
        cdelta = bh_cpos - vcn;
        if (likely(!cdelta || (cdelta > 0 && cdelta < vcn_len))) {
map_buffer_cached:
            BUG_ON(lcn < 0);
            bh->b_blocknr = lcn_block +
                    (cdelta << (vol->cluster_size_bits -
                    blocksize_bits)) +
                    (bh_cofs >> blocksize_bits);
            set_buffer_mapped(bh);
            /*
             * If the page is uptodate so is the buffer.  If the
             * buffer is fully outside the write, we ignore it if
             * it was already allocated and we mark it dirty so it
             * gets written out if we allocated it.  On the other
             * hand, if we allocated the buffer but we are not
             * marking it dirty we set buffer_new so we can do
             * error recovery.
             */
            if (PageUptodate(page)) {
                if (!buffer_uptodate(bh))
                    set_buffer_uptodate(bh);
                if (unlikely(was_hole)) {
                    /* We allocated the buffer. */
                    unmap_underlying_metadata(bh->b_bdev,
                            bh->b_blocknr);
                    if (bh_end <= pos || bh_pos >= end)
                        mark_buffer_dirty(bh);
                    else
                        set_buffer_new(bh);
                }
                continue;
            }
            /* Page is _not_ uptodate. */
            if (likely(!was_hole)) {
                /*
                 * Buffer was already allocated.  If it is not
                 * uptodate and is only partially being written
                 * to, we need to read it in before the write,
                 * i.e. now.
                 */
                if (!buffer_uptodate(bh) && bh_pos < end &&
                        bh_end > pos &&
                        (bh_pos < pos ||
                        bh_end > end)) {
                    /*
                     * If the buffer is fully or partially
                     * within the initialized size, do an
                     * actual read.  Otherwise, simply zero
                     * the buffer.
                     */
                    read_lock_irqsave(&ni->size_lock,
                            flags);
                    initialized_size = ni->initialized_size;
                    read_unlock_irqrestore(&ni->size_lock,
                            flags);
                    if (bh_pos < initialized_size) {
                        ntfs_submit_bh_for_read(bh);
                        *wait_bh++ = bh;
                    } else {
                        zero_user(page, bh_offset(bh),
                                blocksize);
                        set_buffer_uptodate(bh);
                    }
                }
                continue;
            }
            /* We allocated the buffer. */
            unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
            /*
             * If the buffer is fully outside the write, zero it,
             * set it uptodate, and mark it dirty so it gets
             * written out.  If it is partially being written to,
             * zero region surrounding the write but leave it to
             * commit write to do anything else.  Finally, if the
             * buffer is fully being overwritten, do nothing.
             */
            if (bh_end <= pos || bh_pos >= end) {
                if (!buffer_uptodate(bh)) {
                    zero_user(page, bh_offset(bh),
                            blocksize);
                    set_buffer_uptodate(bh);
                }
                mark_buffer_dirty(bh);
                continue;
            }
            set_buffer_new(bh);
            if (!buffer_uptodate(bh) &&
                    (bh_pos < pos || bh_end > end)) {
                u8 *kaddr;
                unsigned pofs;
                    
                kaddr = kmap_atomic(page);
                if (bh_pos < pos) {
                    pofs = bh_pos & ~PAGE_CACHE_MASK;
                    memset(kaddr + pofs, 0, pos - bh_pos);
                }
                if (bh_end > end) {
                    pofs = end & ~PAGE_CACHE_MASK;
                    memset(kaddr + pofs, 0, bh_end - end);
                }
                kunmap_atomic(kaddr);
                flush_dcache_page(page);
            }
            continue;
        }
        /*
         * Slow path: this is the first buffer in the cluster.  If it
         * is outside allocated size and is not uptodate, zero it and
         * set it uptodate.
         */
        read_lock_irqsave(&ni->size_lock, flags);
        initialized_size = ni->allocated_size;
        read_unlock_irqrestore(&ni->size_lock, flags);
        if (bh_pos > initialized_size) {
            if (PageUptodate(page)) {
                if (!buffer_uptodate(bh))
                    set_buffer_uptodate(bh);
            } else if (!buffer_uptodate(bh)) {
                zero_user(page, bh_offset(bh), blocksize);
                set_buffer_uptodate(bh);
            }
            continue;
        }
        is_retry = false;
        if (!rl) {
            down_read(&ni->runlist.lock);
retry_remap:
            rl = ni->runlist.rl;
        }
        if (likely(rl != NULL)) {
            /* Seek to element containing target cluster. */
            while (rl->length && rl[1].vcn <= bh_cpos)
                rl++;
            lcn = ntfs_rl_vcn_to_lcn(rl, bh_cpos);
            if (likely(lcn >= 0)) {
                /*
                 * Successful remap, setup the map cache and
                 * use that to deal with the buffer.
                 */
                was_hole = false;
                vcn = bh_cpos;
                vcn_len = rl[1].vcn - vcn;
                lcn_block = lcn << (vol->cluster_size_bits -
                        blocksize_bits);
                cdelta = 0;
                /*
                 * If the number of remaining clusters touched
                 * by the write is smaller or equal to the
                 * number of cached clusters, unlock the
                 * runlist as the map cache will be used from
                 * now on.
                 */
                if (likely(vcn + vcn_len >= cend)) {
                    if (rl_write_locked) {
                        up_write(&ni->runlist.lock);
                        rl_write_locked = false;
                    } else
                        up_read(&ni->runlist.lock);
                    rl = NULL;
                }
                goto map_buffer_cached;
            }
        } else
            lcn = LCN_RL_NOT_MAPPED;
        /*
         * If it is not a hole and not out of bounds, the runlist is
         * probably unmapped so try to map it now.
         */
        if (unlikely(lcn != LCN_HOLE && lcn != LCN_ENOENT)) {
            if (likely(!is_retry && lcn == LCN_RL_NOT_MAPPED)) {
                /* Attempt to map runlist. */
                if (!rl_write_locked) {
                    /*
                     * We need the runlist locked for
                     * writing, so if it is locked for
                     * reading relock it now and retry in
                     * case it changed whilst we dropped
                     * the lock.
                     */
                    up_read(&ni->runlist.lock);
                    down_write(&ni->runlist.lock);
                    rl_write_locked = true;
                    goto retry_remap;
                }
                err = ntfs_map_runlist_nolock(ni, bh_cpos,
                        NULL);
                if (likely(!err)) {
                    is_retry = true;
                    goto retry_remap;
                }
                /*
                 * If @vcn is out of bounds, pretend @lcn is
                 * LCN_ENOENT.  As long as the buffer is out
                 * of bounds this will work fine.
                 */
                if (err == -ENOENT) {
                    lcn = LCN_ENOENT;
                    err = 0;
                    goto rl_not_mapped_enoent;
                }
            } else
                err = -EIO;
            /* Failed to map the buffer, even after retrying. */
            bh->b_blocknr = -1;
            ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
                    "attribute type 0x%x, vcn 0x%llx, "
                    "vcn offset 0x%x, because its "
                    "location on disk could not be "
                    "determined%s (error code %i).",
                    ni->mft_no, ni->type,
                    (unsigned long long)bh_cpos,
                    (unsigned)bh_pos &
                    vol->cluster_size_mask,
                    is_retry ? " even after retrying" : "",
                    err);
            break;
        }
rl_not_mapped_enoent:
        /*
         * The buffer is in a hole or out of bounds.  We need to fill
         * the hole, unless the buffer is in a cluster which is not
         * touched by the write, in which case we just leave the buffer
         * unmapped.  This can only happen when the cluster size is
         * less than the page cache size.
         */
        if (unlikely(vol->cluster_size < PAGE_CACHE_SIZE)) {
            bh_cend = (bh_end + vol->cluster_size - 1) >>
                    vol->cluster_size_bits;
            if ((bh_cend <= cpos || bh_cpos >= cend)) {
                bh->b_blocknr = -1;
                /*
                 * If the buffer is uptodate we skip it.  If it
                 * is not but the page is uptodate, we can set
                 * the buffer uptodate.  If the page is not
                 * uptodate, we can clear the buffer and set it
                 * uptodate.  Whether this is worthwhile is
                 * debatable and this could be removed.
                 */
                if (PageUptodate(page)) {
                    if (!buffer_uptodate(bh))
                        set_buffer_uptodate(bh);
                } else if (!buffer_uptodate(bh)) {
                    zero_user(page, bh_offset(bh),
                        blocksize);
                    set_buffer_uptodate(bh);
                }
                continue;
            }
        }
        /*
         * Out of bounds buffer is invalid if it was not really out of
         * bounds.
         */
        BUG_ON(lcn != LCN_HOLE);
        /*
         * We need the runlist locked for writing, so if it is locked
         * for reading relock it now and retry in case it changed
         * whilst we dropped the lock.
         */
        BUG_ON(!rl);
        if (!rl_write_locked) {
            up_read(&ni->runlist.lock);
            down_write(&ni->runlist.lock);
            rl_write_locked = true;
            goto retry_remap;
        }
        /* Find the previous last allocated cluster. */
        BUG_ON(rl->lcn != LCN_HOLE);
        lcn = -1;
        rl2 = rl;
        while (--rl2 >= ni->runlist.rl) {
            if (rl2->lcn >= 0) {
                lcn = rl2->lcn + rl2->length;
                break;
            }
        }
        rl2 = ntfs_cluster_alloc(vol, bh_cpos, 1, lcn, DATA_ZONE,
                false);
        if (IS_ERR(rl2)) {
            err = PTR_ERR(rl2);
            ntfs_debug("Failed to allocate cluster, error code %i.",
                    err);
            break;
        }
        lcn = rl2->lcn;
        rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
        if (IS_ERR(rl)) {
            err = PTR_ERR(rl);
            if (err != -ENOMEM)
                err = -EIO;
            if (ntfs_cluster_free_from_rl(vol, rl2)) {
                ntfs_error(vol->sb, "Failed to release "
                        "allocated cluster in error "
                        "code path.  Run chkdsk to "
                        "recover the lost cluster.");
                NVolSetErrors(vol);
            }
            ntfs_free(rl2);
            break;
        }
        ni->runlist.rl = rl;
        status.runlist_merged = 1;
        ntfs_debug("Allocated cluster, lcn 0x%llx.",
                (unsigned long long)lcn);
        /* Map and lock the mft record and get the attribute record. */
        if (!NInoAttr(ni))
            base_ni = ni;
        else
            base_ni = ni->ext.base_ntfs_ino;
        m = map_mft_record(base_ni);
        if (IS_ERR(m)) {
            err = PTR_ERR(m);
            break;
        }
        ctx = ntfs_attr_get_search_ctx(base_ni, m);
        if (unlikely(!ctx)) {
            err = -ENOMEM;
            unmap_mft_record(base_ni);
            break;
        }
        status.mft_attr_mapped = 1;
        err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                CASE_SENSITIVE, bh_cpos, NULL, 0, ctx);
        if (unlikely(err)) {
            if (err == -ENOENT)
                err = -EIO;
            break;
        }
        m = ctx->mrec;
        a = ctx->attr;
        /*
         * Find the runlist element with which the attribute extent
         * starts.  Note, we cannot use the _attr_ version because we
         * have mapped the mft record.  That is ok because we know the
         * runlist fragment must be mapped already to have ever gotten
         * here, so we can just use the _rl_ version.
         */
        vcn = sle64_to_cpu(a->data.non_resident.lowest_vcn);
        rl2 = ntfs_rl_find_vcn_nolock(rl, vcn);
        BUG_ON(!rl2);
        BUG_ON(!rl2->length);
        BUG_ON(rl2->lcn < LCN_HOLE);
        highest_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
        /*
         * If @highest_vcn is zero, calculate the real highest_vcn
         * (which can really be zero).
         */
        if (!highest_vcn)
            highest_vcn = (sle64_to_cpu(
                    a->data.non_resident.allocated_size) >>
                    vol->cluster_size_bits) - 1;
        /*
         * Determine the size of the mapping pairs array for the new
         * extent, i.e. the old extent with the hole filled.
         */
        mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, vcn,
                highest_vcn);
        if (unlikely(mp_size <= 0)) {
            if (!(err = mp_size))
                err = -EIO;
            ntfs_debug("Failed to get size for mapping pairs "
                    "array, error code %i.", err);
            break;
        }
        /*
         * Resize the attribute record to fit the new mapping pairs
         * array.
         */
        attr_rec_len = le32_to_cpu(a->length);
        err = ntfs_attr_record_resize(m, a, mp_size + le16_to_cpu(
                a->data.non_resident.mapping_pairs_offset));
        if (unlikely(err)) {
            BUG_ON(err != -ENOSPC);
            // TODO: Deal with this by using the current attribute
            // and fill it with as much of the mapping pairs
            // array as possible.  Then loop over each attribute
            // extent rewriting the mapping pairs arrays as we go
            // along and if when we reach the end we have not
            // enough space, try to resize the last attribute
            // extent and if even that fails, add a new attribute
            // extent.
            // We could also try to resize at each step in the hope
            // that we will not need to rewrite every single extent.
            // Note, we may need to decompress some extents to fill
            // the runlist as we are walking the extents...
            ntfs_error(vol->sb, "Not enough space in the mft "
                    "record for the extended attribute "
                    "record.  This case is not "
                    "implemented yet.");
            err = -EOPNOTSUPP;
            break ;
        }
        status.mp_rebuilt = 1;
        /*
         * Generate the mapping pairs array directly into the attribute
         * record.
         */
        err = ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
                a->data.non_resident.mapping_pairs_offset),
                mp_size, rl2, vcn, highest_vcn, NULL);
        if (unlikely(err)) {
            ntfs_error(vol->sb, "Cannot fill hole in inode 0x%lx, "
                    "attribute type 0x%x, because building "
                    "the mapping pairs failed with error "
                    "code %i.", vi->i_ino,
                    (unsigned)le32_to_cpu(ni->type), err);
            err = -EIO;
            break;
        }
        /* Update the highest_vcn but only if it was not set. */
        if (unlikely(!a->data.non_resident.highest_vcn))
            a->data.non_resident.highest_vcn =
                    cpu_to_sle64(highest_vcn);
        /*
         * If the attribute is sparse/compressed, update the compressed
         * size in the ntfs_inode structure and the attribute record.
         */
        if (likely(NInoSparse(ni) || NInoCompressed(ni))) {
            /*
             * If we are not in the first attribute extent, switch
             * to it, but first ensure the changes will make it to
             * disk later.
             */
            if (a->data.non_resident.lowest_vcn) {
                flush_dcache_mft_record_page(ctx->ntfs_ino);
                mark_mft_record_dirty(ctx->ntfs_ino);
                ntfs_attr_reinit_search_ctx(ctx);
                err = ntfs_attr_lookup(ni->type, ni->name,
                        ni->name_len, CASE_SENSITIVE,
                        0, NULL, 0, ctx);
                if (unlikely(err)) {
                    status.attr_switched = 1;
                    break;
                }
                /* @m is not used any more so do not set it. */
                a = ctx->attr;
            }
            write_lock_irqsave(&ni->size_lock, flags);
            ni->itype.compressed.size += vol->cluster_size;
            a->data.non_resident.compressed_size =
                    cpu_to_sle64(ni->itype.compressed.size);
            write_unlock_irqrestore(&ni->size_lock, flags);
        }
        /* Ensure the changes make it to disk. */
        flush_dcache_mft_record_page(ctx->ntfs_ino);
        mark_mft_record_dirty(ctx->ntfs_ino);
        ntfs_attr_put_search_ctx(ctx);
        unmap_mft_record(base_ni);
        /* Successfully filled the hole. */
        status.runlist_merged = 0;
        status.mft_attr_mapped = 0;
        status.mp_rebuilt = 0;
        /* Setup the map cache and use that to deal with the buffer. */
        was_hole = true;
        vcn = bh_cpos;
        vcn_len = 1;
        lcn_block = lcn << (vol->cluster_size_bits - blocksize_bits);
        cdelta = 0;
        /*
         * If the number of remaining clusters in the @pages is smaller
         * or equal to the number of cached clusters, unlock the
         * runlist as the map cache will be used from now on.
         */
        if (likely(vcn + vcn_len >= cend)) {
            up_write(&ni->runlist.lock);
            rl_write_locked = false;
            rl = NULL;
        }
        goto map_buffer_cached;
    } while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
    /* If there are no errors, do the next page. */
    if (likely(!err && ++u < nr_pages))
        goto do_next_page;
    /* If there are no errors, release the runlist lock if we took it. */
    if (likely(!err)) {
        if (unlikely(rl_write_locked)) {
            up_write(&ni->runlist.lock);
            rl_write_locked = false;
        } else if (unlikely(rl))
            up_read(&ni->runlist.lock);
        rl = NULL;
    }
    /* If we issued read requests, let them complete. */
    read_lock_irqsave(&ni->size_lock, flags);
    initialized_size = ni->initialized_size;
    read_unlock_irqrestore(&ni->size_lock, flags);
    while (wait_bh > wait) {
        bh = *--wait_bh;
        wait_on_buffer(bh);
        if (likely(buffer_uptodate(bh))) {
            page = bh->b_page;
            bh_pos = ((s64)page->index << PAGE_CACHE_SHIFT) +
                    bh_offset(bh);
            /*
             * If the buffer overflows the initialized size, need
             * to zero the overflowing region.
             */
            if (unlikely(bh_pos + blocksize > initialized_size)) {
                int ofs = 0;

                if (likely(bh_pos < initialized_size))
                    ofs = initialized_size - bh_pos;
                zero_user_segment(page, bh_offset(bh) + ofs,
                        blocksize);
            }
        } else /* if (unlikely(!buffer_uptodate(bh))) */
            err = -EIO;
    }
    if (likely(!err)) {
        /* Clear buffer_new on all buffers. */
        u = 0;
        do {
            bh = head = page_buffers(pages[u]);
            do {
                if (buffer_new(bh))
                    clear_buffer_new(bh);
            } while ((bh = bh->b_this_page) != head);
        } while (++u < nr_pages);
        ntfs_debug("Done.");
        return err;
    }
    if (status.attr_switched) {
        /* Get back to the attribute extent we modified. */
        ntfs_attr_reinit_search_ctx(ctx);
        if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
                CASE_SENSITIVE, bh_cpos, NULL, 0, ctx)) {
            ntfs_error(vol->sb, "Failed to find required "
                    "attribute extent of attribute in "
                    "error code path.  Run chkdsk to "
                    "recover.");
            write_lock_irqsave(&ni->size_lock, flags);
            ni->itype.compressed.size += vol->cluster_size;
            write_unlock_irqrestore(&ni->size_lock, flags);
            flush_dcache_mft_record_page(ctx->ntfs_ino);
            mark_mft_record_dirty(ctx->ntfs_ino);
            /*
             * The only thing that is now wrong is the compressed
             * size of the base attribute extent which chkdsk
             * should be able to fix.
             */
            NVolSetErrors(vol);
        } else {
            m = ctx->mrec;
            a = ctx->attr;
            status.attr_switched = 0;
        }
    }
    /*
     * If the runlist has been modified, need to restore it by punching a
     * hole into it and we then need to deallocate the on-disk cluster as
     * well.  Note, we only modify the runlist if we are able to generate a
     * new mapping pairs array, i.e. only when the mapped attribute extent
     * is not switched.
     */
    if (status.runlist_merged && !status.attr_switched) {
        BUG_ON(!rl_write_locked);
        /* Make the file cluster we allocated sparse in the runlist. */
        if (ntfs_rl_punch_nolock(vol, &ni->runlist, bh_cpos, 1)) {
            ntfs_error(vol->sb, "Failed to punch hole into "
                    "attribute runlist in error code "
                    "path.  Run chkdsk to recover the "
                    "lost cluster.");
            NVolSetErrors(vol);
        } else /* if (success) */ {
            status.runlist_merged = 0;
            /*
             * Deallocate the on-disk cluster we allocated but only
             * if we succeeded in punching its vcn out of the
             * runlist.
             */
            down_write(&vol->lcnbmp_lock);
            if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
                ntfs_error(vol->sb, "Failed to release "
                        "allocated cluster in error "
                        "code path.  Run chkdsk to "
                        "recover the lost cluster.");
                NVolSetErrors(vol);
            }
            up_write(&vol->lcnbmp_lock);
        }
    }
    /*
     * Resize the attribute record to its old size and rebuild the mapping
     * pairs array.  Note, we only can do this if the runlist has been
     * restored to its old state which also implies that the mapped
     * attribute extent is not switched.
     */
    if (status.mp_rebuilt && !status.runlist_merged) {
        if (ntfs_attr_record_resize(m, a, attr_rec_len)) {
            ntfs_error(vol->sb, "Failed to restore attribute "
                    "record in error code path.  Run "
                    "chkdsk to recover.");
            NVolSetErrors(vol);
        } else /* if (success) */ {
            if (ntfs_mapping_pairs_build(vol, (u8*)a +
                    le16_to_cpu(a->data.non_resident.
                    mapping_pairs_offset), attr_rec_len -
                    le16_to_cpu(a->data.non_resident.
                    mapping_pairs_offset), ni->runlist.rl,
                    vcn, highest_vcn, NULL)) {
                ntfs_error(vol->sb, "Failed to restore "
                        "mapping pairs array in error "
                        "code path.  Run chkdsk to "
                        "recover.");
                NVolSetErrors(vol);
            }
            flush_dcache_mft_record_page(ctx->ntfs_ino);
            mark_mft_record_dirty(ctx->ntfs_ino);
        }
    }
    /* Release the mft record and the attribute. */
    if (status.mft_attr_mapped) {
        ntfs_attr_put_search_ctx(ctx);
        unmap_mft_record(base_ni);
    }
    /* Release the runlist lock. */
    if (rl_write_locked)
        up_write(&ni->runlist.lock);
    else if (rl)
        up_read(&ni->runlist.lock);
    /*
     * Zero out any newly allocated blocks to avoid exposing stale data.
     * If BH_New is set, we know that the block was newly allocated above
     * and that it has not been fully zeroed and marked dirty yet.
     */
    nr_pages = u;
    u = 0;
    end = bh_cpos << vol->cluster_size_bits;
    do {
        page = pages[u];
        bh = head = page_buffers(page);
        do {
            if (u == nr_pages &&
                    ((s64)page->index << PAGE_CACHE_SHIFT) +
                    bh_offset(bh) >= end)
                break;
            if (!buffer_new(bh))
                continue;
            clear_buffer_new(bh);
            if (!buffer_uptodate(bh)) {
                if (PageUptodate(page))
                    set_buffer_uptodate(bh);
                else {
                    zero_user(page, bh_offset(bh),
                            blocksize);
                    set_buffer_uptodate(bh);
                }
            }
            mark_buffer_dirty(bh);
        } while ((bh = bh->b_this_page) != head);
    } while (++u <= nr_pages);
    ntfs_error(vol->sb, "Failed.  Returning error code %i.", err);
    return err;
}

/*
 * Copy as much as we can into the pages and return the number of bytes which
 * were successfully copied.  If a fault is encountered then clear the pages
 * out to (ofs + bytes) and return the number of bytes which were copied.
 */
static inline size_t ntfs_copy_from_user(struct page **pages,
        unsigned nr_pages, unsigned ofs, const char __user *buf,
        size_t bytes)
{
    struct page **last_page = pages + nr_pages;
    char *addr;
    size_t total = 0;
    unsigned len;
    int left;

    do {
        len = PAGE_CACHE_SIZE - ofs;
        if (len > bytes)
            len = bytes;
        addr = kmap_atomic(*pages);
        left = __copy_from_user_inatomic(addr + ofs, buf, len);
        kunmap_atomic(addr);
        if (unlikely(left)) {
            /* Do it the slow way. */
            addr = kmap(*pages);
            left = __copy_from_user(addr + ofs, buf, len);
            kunmap(*pages);
            if (unlikely(left))
                goto err_out;
        }
        total += len;
        bytes -= len;
        if (!bytes)
            break;
        buf += len;
        ofs = 0;
    } while (++pages < last_page);
out:
    return total;
err_out:
    total += len - left;
    /* Zero the rest of the target like __copy_from_user(). */
    while (++pages < last_page) {
        bytes -= len;
        if (!bytes)
            break;
        len = PAGE_CACHE_SIZE;
        if (len > bytes)
            len = bytes;
        zero_user(*pages, 0, len);
    }
    goto out;
}

static size_t __ntfs_copy_from_user_iovec_inatomic(char *vaddr,
        const struct iovec *iov, size_t iov_ofs, size_t bytes)
{
    size_t total = 0;

    while (1) {
        const char __user *buf = iov->iov_base + iov_ofs;
        unsigned len;
        size_t left;

        len = iov->iov_len - iov_ofs;
        if (len > bytes)
            len = bytes;
        left = __copy_from_user_inatomic(vaddr, buf, len);
        total += len;
        bytes -= len;
        vaddr += len;
        if (unlikely(left)) {
            total -= left;
            break;
        }
        if (!bytes)
            break;
        iov++;
        iov_ofs = 0;
    }
    return total;
}

static inline void ntfs_set_next_iovec(const struct iovec **iovp,
        size_t *iov_ofsp, size_t bytes)
{
    const struct iovec *iov = *iovp;
    size_t iov_ofs = *iov_ofsp;

    while (bytes) {
        unsigned len;

        len = iov->iov_len - iov_ofs;
        if (len > bytes)
            len = bytes;
        bytes -= len;
        iov_ofs += len;
        if (iov->iov_len == iov_ofs) {
            iov++;
            iov_ofs = 0;
        }
    }
    *iovp = iov;
    *iov_ofsp = iov_ofs;
}

/*
 * This has the same side-effects and return value as ntfs_copy_from_user().
 * The difference is that on a fault we need to memset the remainder of the
 * pages (out to offset + bytes), to emulate ntfs_copy_from_user()'s
 * single-segment behaviour.
 *
 * We call the same helper (__ntfs_copy_from_user_iovec_inatomic()) both when
 * atomic and when not atomic.  This is ok because it calls
 * __copy_from_user_inatomic() and it is ok to call this when non-atomic.  In
 * fact, the only difference between __copy_from_user_inatomic() and
 * __copy_from_user() is that the latter calls might_sleep() and the former
 * should not zero the tail of the buffer on error.  And on many architectures
 * __copy_from_user_inatomic() is just defined to __copy_from_user() so it
 * makes no difference at all on those architectures.
 */
static inline size_t ntfs_copy_from_user_iovec(struct page **pages,
        unsigned nr_pages, unsigned ofs, const struct iovec **iov,
        size_t *iov_ofs, size_t bytes)
{
    struct page **last_page = pages + nr_pages;
    char *addr;
    size_t copied, len, total = 0;

    do {
        len = PAGE_CACHE_SIZE - ofs;
        if (len > bytes)
            len = bytes;
        addr = kmap_atomic(*pages);
        copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,
                *iov, *iov_ofs, len);
        kunmap_atomic(addr);
        if (unlikely(copied != len)) {
            /* Do it the slow way. */
            addr = kmap(*pages);
            copied = __ntfs_copy_from_user_iovec_inatomic(addr +
                    ofs, *iov, *iov_ofs, len);
            if (unlikely(copied != len))
                goto err_out;
            kunmap(*pages);
        }
        total += len;
        ntfs_set_next_iovec(iov, iov_ofs, len);
        bytes -= len;
        if (!bytes)
            break;
        ofs = 0;
    } while (++pages < last_page);
out:
    return total;
err_out:
    BUG_ON(copied > len);
    /* Zero the rest of the target like __copy_from_user(). */
    memset(addr + ofs + copied, 0, len - copied);
    kunmap(*pages);
    total += copied;
    ntfs_set_next_iovec(iov, iov_ofs, copied);
    while (++pages < last_page) {
        bytes -= len;
        if (!bytes)
            break;
        len = PAGE_CACHE_SIZE;
        if (len > bytes)
            len = bytes;
        zero_user(*pages, 0, len);
    }
    goto out;
}

static inline void ntfs_flush_dcache_pages(struct page **pages,
        unsigned nr_pages)
{
    BUG_ON(!nr_pages);
    /*
     * Warning: Do not do the decrement at the same time as the call to
     * flush_dcache_page() because it is a NULL macro on i386 and hence the
     * decrement never happens so the loop never terminates.
     */
    do {
        --nr_pages;
        flush_dcache_page(pages[nr_pages]);
    } while (nr_pages > 0);
}

static inline int ntfs_commit_pages_after_non_resident_write(
        struct page **pages, const unsigned nr_pages,
        s64 pos, size_t bytes)
{
    s64 end, initialized_size;
    struct inode *vi;
    ntfs_inode *ni, *base_ni;
    struct buffer_head *bh, *head;
    ntfs_attr_search_ctx *ctx;
    MFT_RECORD *m;
    ATTR_RECORD *a;
    unsigned long flags;
    unsigned blocksize, u;
    int err;

    vi = pages[0]->mapping->host;
    ni = NTFS_I(vi);
    blocksize = vi->i_sb->s_blocksize;
    end = pos + bytes;
    u = 0;
    do {
        s64 bh_pos;
        struct page *page;
        bool partial;

        page = pages[u];
        bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
        bh = head = page_buffers(page);
        partial = false;
        do {
            s64 bh_end;

            bh_end = bh_pos + blocksize;
            if (bh_end <= pos || bh_pos >= end) {
                if (!buffer_uptodate(bh))
                    partial = true;
            } else {
                set_buffer_uptodate(bh);
                mark_buffer_dirty(bh);
            }
        } while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
        /*
         * If all buffers are now uptodate but the page is not, set the
         * page uptodate.
         */
        if (!partial && !PageUptodate(page))
            SetPageUptodate(page);
    } while (++u < nr_pages);
    /*
     * Finally, if we do not need to update initialized_size or i_size we
     * are finished.
     */
    read_lock_irqsave(&ni->size_lock, flags);
    initialized_size = ni->initialized_size;
    read_unlock_irqrestore(&ni->size_lock, flags);
    if (end <= initialized_size) {
        ntfs_debug("Done.");
        return 0;
    }
    /*
     * Update initialized_size/i_size as appropriate, both in the inode and
     * the mft record.
     */
    if (!NInoAttr(ni))
        base_ni = ni;
    else
        base_ni = ni->ext.base_ntfs_ino;
    /* Map, pin, and lock the mft record. */
    m = map_mft_record(base_ni);
    if (IS_ERR(m)) {
        err = PTR_ERR(m);
        m = NULL;
        ctx = NULL;
        goto err_out;
    }
    BUG_ON(!NInoNonResident(ni));
    ctx = ntfs_attr_get_search_ctx(base_ni, m);
    if (unlikely(!ctx)) {
        err = -ENOMEM;
        goto err_out;
    }
    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
            CASE_SENSITIVE, 0, NULL, 0, ctx);
    if (unlikely(err)) {
        if (err == -ENOENT)
            err = -EIO;
        goto err_out;
    }
    a = ctx->attr;
    BUG_ON(!a->non_resident);
    write_lock_irqsave(&ni->size_lock, flags);
    BUG_ON(end > ni->allocated_size);
    ni->initialized_size = end;
    a->data.non_resident.initialized_size = cpu_to_sle64(end);
    if (end > i_size_read(vi)) {
        i_size_write(vi, end);
        a->data.non_resident.data_size =
                a->data.non_resident.initialized_size;
    }
    write_unlock_irqrestore(&ni->size_lock, flags);
    /* Mark the mft record dirty, so it gets written back. */
    flush_dcache_mft_record_page(ctx->ntfs_ino);
    mark_mft_record_dirty(ctx->ntfs_ino);
    ntfs_attr_put_search_ctx(ctx);
    unmap_mft_record(base_ni);
    ntfs_debug("Done.");
    return 0;
err_out:
    if (ctx)
        ntfs_attr_put_search_ctx(ctx);
    if (m)
        unmap_mft_record(base_ni);
    ntfs_error(vi->i_sb, "Failed to update initialized_size/i_size (error "
            "code %i).", err);
    if (err != -ENOMEM)
        NVolSetErrors(ni->vol);
    return err;
}

static int ntfs_commit_pages_after_write(struct page **pages,
        const unsigned nr_pages, s64 pos, size_t bytes)
{
    s64 end, initialized_size;
    loff_t i_size;
    struct inode *vi;
    ntfs_inode *ni, *base_ni;
    struct page *page;
    ntfs_attr_search_ctx *ctx;
    MFT_RECORD *m;
    ATTR_RECORD *a;
    char *kattr, *kaddr;
    unsigned long flags;
    u32 attr_len;
    int err;

    BUG_ON(!nr_pages);
    BUG_ON(!pages);
    page = pages[0];
    BUG_ON(!page);
    vi = page->mapping->host;
    ni = NTFS_I(vi);
    ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
            "index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
            vi->i_ino, ni->type, page->index, nr_pages,
            (long long)pos, bytes);
    if (NInoNonResident(ni))
        return ntfs_commit_pages_after_non_resident_write(pages,
                nr_pages, pos, bytes);
    BUG_ON(nr_pages > 1);
    /*
     * Attribute is resident, implying it is not compressed, encrypted, or
     * sparse.
     */
    if (!NInoAttr(ni))
        base_ni = ni;
    else
        base_ni = ni->ext.base_ntfs_ino;
    BUG_ON(NInoNonResident(ni));
    /* Map, pin, and lock the mft record. */
    m = map_mft_record(base_ni);
    if (IS_ERR(m)) {
        err = PTR_ERR(m);
        m = NULL;
        ctx = NULL;
        goto err_out;
    }
    ctx = ntfs_attr_get_search_ctx(base_ni, m);
    if (unlikely(!ctx)) {
        err = -ENOMEM;
        goto err_out;
    }
    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
            CASE_SENSITIVE, 0, NULL, 0, ctx);
    if (unlikely(err)) {
        if (err == -ENOENT)
            err = -EIO;
        goto err_out;
    }
    a = ctx->attr;
    BUG_ON(a->non_resident);
    /* The total length of the attribute value. */
    attr_len = le32_to_cpu(a->data.resident.value_length);
    i_size = i_size_read(vi);
    BUG_ON(attr_len != i_size);
    BUG_ON(pos > attr_len);
    end = pos + bytes;
    BUG_ON(end > le32_to_cpu(a->length) -
            le16_to_cpu(a->data.resident.value_offset));
    kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
    kaddr = kmap_atomic(page);
    /* Copy the received data from the page to the mft record. */
    memcpy(kattr + pos, kaddr + pos, bytes);
    /* Update the attribute length if necessary. */
    if (end > attr_len) {
        attr_len = end;
        a->data.resident.value_length = cpu_to_le32(attr_len);
    }
    /*
     * If the page is not uptodate, bring the out of bounds area(s)
     * uptodate by copying data from the mft record to the page.
     */
    if (!PageUptodate(page)) {
        if (pos > 0)
            memcpy(kaddr, kattr, pos);
        if (end < attr_len)
            memcpy(kaddr + end, kattr + end, attr_len - end);
        /* Zero the region outside the end of the attribute value. */
        memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
        flush_dcache_page(page);
        SetPageUptodate(page);
    }
    kunmap_atomic(kaddr);
    /* Update initialized_size/i_size if necessary. */
    read_lock_irqsave(&ni->size_lock, flags);
    initialized_size = ni->initialized_size;
    BUG_ON(end > ni->allocated_size);
    read_unlock_irqrestore(&ni->size_lock, flags);
    BUG_ON(initialized_size != i_size);
    if (end > initialized_size) {
        write_lock_irqsave(&ni->size_lock, flags);
        ni->initialized_size = end;
        i_size_write(vi, end);
        write_unlock_irqrestore(&ni->size_lock, flags);
    }
    /* Mark the mft record dirty, so it gets written back. */
    flush_dcache_mft_record_page(ctx->ntfs_ino);
    mark_mft_record_dirty(ctx->ntfs_ino);
    ntfs_attr_put_search_ctx(ctx);
    unmap_mft_record(base_ni);
    ntfs_debug("Done.");
    return 0;
err_out:
    if (err == -ENOMEM) {
        ntfs_warning(vi->i_sb, "Error allocating memory required to "
                "commit the write.");
        if (PageUptodate(page)) {
            ntfs_warning(vi->i_sb, "Page is uptodate, setting "
                    "dirty so the write will be retried "
                    "later on by the VM.");
            /*
             * Put the page on mapping->dirty_pages, but leave its
             * buffers' dirty state as-is.
             */
            __set_page_dirty_nobuffers(page);
            err = 0;
        } else
            ntfs_error(vi->i_sb, "Page is not uptodate.  Written "
                    "data has been lost.");
    } else {
        ntfs_error(vi->i_sb, "Resident attribute commit write failed "
                "with error %i.", err);
        NVolSetErrors(ni->vol);
    }
    if (ctx)
        ntfs_attr_put_search_ctx(ctx);
    if (m)
        unmap_mft_record(base_ni);
    return err;
}

static ssize_t ntfs_file_buffered_write(struct kiocb *iocb,
        const struct iovec *iov, unsigned long nr_segs,
        loff_t pos, loff_t *ppos, size_t count)
{
    struct file *file = iocb->ki_filp;
    struct address_space *mapping = file->f_mapping;
    struct inode *vi = mapping->host;
    ntfs_inode *ni = NTFS_I(vi);
    ntfs_volume *vol = ni->vol;
    struct page *pages[NTFS_MAX_PAGES_PER_CLUSTER];
    struct page *cached_page = NULL;
    char __user *buf = NULL;
    s64 end, ll;
    VCN last_vcn;
    LCN lcn;
    unsigned long flags;
    size_t bytes, iov_ofs = 0;  /* Offset in the current iovec. */
    ssize_t status, written;
    unsigned nr_pages;
    int err;

    ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
            "pos 0x%llx, count 0x%lx.",
            vi->i_ino, (unsigned)le32_to_cpu(ni->type),
            (unsigned long long)pos, (unsigned long)count);
    if (unlikely(!count))
        return 0;
    BUG_ON(NInoMstProtected(ni));
    /*
     * If the attribute is not an index root and it is encrypted or
     * compressed, we cannot write to it yet.  Note we need to check for
     * AT_INDEX_ALLOCATION since this is the type of both directory and
     * index inodes.
     */
    if (ni->type != AT_INDEX_ALLOCATION) {
        /* If file is encrypted, deny access, just like NT4. */
        if (NInoEncrypted(ni)) {
            /*
             * Reminder for later: Encrypted files are _always_
             * non-resident so that the content can always be
             * encrypted.
             */
            ntfs_debug("Denying write access to encrypted file.");
            return -EACCES;
        }
        if (NInoCompressed(ni)) {
            /* Only unnamed $DATA attribute can be compressed. */
            BUG_ON(ni->type != AT_DATA);
            BUG_ON(ni->name_len);
            /*
             * Reminder for later: If resident, the data is not
             * actually compressed.  Only on the switch to non-
             * resident does compression kick in.  This is in
             * contrast to encrypted files (see above).
             */
            ntfs_error(vi->i_sb, "Writing to compressed files is "
                    "not implemented yet.  Sorry.");
            return -EOPNOTSUPP;
        }
    }
    /*
     * If a previous ntfs_truncate() failed, repeat it and abort if it
     * fails again.
     */
    if (unlikely(NInoTruncateFailed(ni))) {
        inode_dio_wait(vi);
        err = ntfs_truncate(vi);
        if (err || NInoTruncateFailed(ni)) {
            if (!err)
                err = -EIO;
            ntfs_error(vol->sb, "Cannot perform write to inode "
                    "0x%lx, attribute type 0x%x, because "
                    "ntfs_truncate() failed (error code "
                    "%i).", vi->i_ino,
                    (unsigned)le32_to_cpu(ni->type), err);
            return err;
        }
    }
    /* The first byte after the write. */
    end = pos + count;
    /*
     * If the write goes beyond the allocated size, extend the allocation
     * to cover the whole of the write, rounded up to the nearest cluster.
     */
    read_lock_irqsave(&ni->size_lock, flags);
    ll = ni->allocated_size;
    read_unlock_irqrestore(&ni->size_lock, flags);
    if (end > ll) {
        /* Extend the allocation without changing the data size. */
        ll = ntfs_attr_extend_allocation(ni, end, -1, pos);
        if (likely(ll >= 0)) {
            BUG_ON(pos >= ll);
            /* If the extension was partial truncate the write. */
            if (end > ll) {
                ntfs_debug("Truncating write to inode 0x%lx, "
                        "attribute type 0x%x, because "
                        "the allocation was only "
                        "partially extended.",
                        vi->i_ino, (unsigned)
                        le32_to_cpu(ni->type));
                end = ll;
                count = ll - pos;
            }
        } else {
            err = ll;
            read_lock_irqsave(&ni->size_lock, flags);
            ll = ni->allocated_size;
            read_unlock_irqrestore(&ni->size_lock, flags);
            /* Perform a partial write if possible or fail. */
            if (pos < ll) {
                ntfs_debug("Truncating write to inode 0x%lx, "
                        "attribute type 0x%x, because "
                        "extending the allocation "
                        "failed (error code %i).",
                        vi->i_ino, (unsigned)
                        le32_to_cpu(ni->type), err);
                end = ll;
                count = ll - pos;
            } else {
                ntfs_error(vol->sb, "Cannot perform write to "
                        "inode 0x%lx, attribute type "
                        "0x%x, because extending the "
                        "allocation failed (error "
                        "code %i).", vi->i_ino,
                        (unsigned)
                        le32_to_cpu(ni->type), err);
                return err;
            }
        }
    }
    written = 0;
    /*
     * If the write starts beyond the initialized size, extend it up to the
     * beginning of the write and initialize all non-sparse space between
     * the old initialized size and the new one.  This automatically also
     * increments the vfs inode->i_size to keep it above or equal to the
     * initialized_size.
     */
    read_lock_irqsave(&ni->size_lock, flags);
    ll = ni->initialized_size;
    read_unlock_irqrestore(&ni->size_lock, flags);
    if (pos > ll) {
        err = ntfs_attr_extend_initialized(ni, pos);
        if (err < 0) {
            ntfs_error(vol->sb, "Cannot perform write to inode "
                    "0x%lx, attribute type 0x%x, because "
                    "extending the initialized size "
                    "failed (error code %i).", vi->i_ino,
                    (unsigned)le32_to_cpu(ni->type), err);
            status = err;
            goto err_out;
        }
    }
    /*
     * Determine the number of pages per cluster for non-resident
     * attributes.
     */
    nr_pages = 1;
    if (vol->cluster_size > PAGE_CACHE_SIZE && NInoNonResident(ni))
        nr_pages = vol->cluster_size >> PAGE_CACHE_SHIFT;
    /* Finally, perform the actual write. */
    last_vcn = -1;
    if (likely(nr_segs == 1))
        buf = iov->iov_base;
    do {
        VCN vcn;
        pgoff_t idx, start_idx;
        unsigned ofs, do_pages, u;
        size_t copied;

        start_idx = idx = pos >> PAGE_CACHE_SHIFT;
        ofs = pos & ~PAGE_CACHE_MASK;
        bytes = PAGE_CACHE_SIZE - ofs;
        do_pages = 1;
        if (nr_pages > 1) {
            vcn = pos >> vol->cluster_size_bits;
            if (vcn != last_vcn) {
                last_vcn = vcn;
                /*
                 * Get the lcn of the vcn the write is in.  If
                 * it is a hole, need to lock down all pages in
                 * the cluster.
                 */
                down_read(&ni->runlist.lock);
                lcn = ntfs_attr_vcn_to_lcn_nolock(ni, pos >>
                        vol->cluster_size_bits, false);
                up_read(&ni->runlist.lock);
                if (unlikely(lcn < LCN_HOLE)) {
                    status = -EIO;
                    if (lcn == LCN_ENOMEM)
                        status = -ENOMEM;
                    else
                        ntfs_error(vol->sb, "Cannot "
                            "perform write to "
                            "inode 0x%lx, "
                            "attribute type 0x%x, "
                            "because the attribute "
                            "is corrupt.",
                            vi->i_ino, (unsigned)
                            le32_to_cpu(ni->type));
                    break;
                }
                if (lcn == LCN_HOLE) {
                    start_idx = (pos & ~(s64)
                            vol->cluster_size_mask)
                            >> PAGE_CACHE_SHIFT;
                    bytes = vol->cluster_size - (pos &
                            vol->cluster_size_mask);
                    do_pages = nr_pages;
                }
            }
        }
        if (bytes > count)
            bytes = count;
        /*
         * Bring in the user page(s) that we will copy from _first_.
         * Otherwise there is a nasty deadlock on copying from the same
         * page(s) as we are writing to, without it/them being marked
         * up-to-date.  Note, at present there is nothing to stop the
         * pages being swapped out between us bringing them into memory
         * and doing the actual copying.
         */
        if (likely(nr_segs == 1))
            ntfs_fault_in_pages_readable(buf, bytes);
        else
            ntfs_fault_in_pages_readable_iovec(iov, iov_ofs, bytes);
        /* Get and lock @do_pages starting at index @start_idx. */
        status = __ntfs_grab_cache_pages(mapping, start_idx, do_pages,
                pages, &cached_page);
        if (unlikely(status))
            break;
        /*
         * For non-resident attributes, we need to fill any holes with
         * actual clusters and ensure all bufferes are mapped.  We also
         * need to bring uptodate any buffers that are only partially
         * being written to.
         */
        if (NInoNonResident(ni)) {
            status = ntfs_prepare_pages_for_non_resident_write(
                    pages, do_pages, pos, bytes);
            if (unlikely(status)) {
                loff_t i_size;

                do {
                    unlock_page(pages[--do_pages]);
                    page_cache_release(pages[do_pages]);
                } while (do_pages);
                /*
                 * The write preparation may have instantiated
                 * allocated space outside i_size.  Trim this
                 * off again.  We can ignore any errors in this
                 * case as we will just be waisting a bit of
                 * allocated space, which is not a disaster.
                 */
                i_size = i_size_read(vi);
                if (pos + bytes > i_size)
                    vmtruncate(vi, i_size);
                break;
            }
        }
        u = (pos >> PAGE_CACHE_SHIFT) - pages[0]->index;
        if (likely(nr_segs == 1)) {
            copied = ntfs_copy_from_user(pages + u, do_pages - u,
                    ofs, buf, bytes);
            buf += copied;
        } else
            copied = ntfs_copy_from_user_iovec(pages + u,
                    do_pages - u, ofs, &iov, &iov_ofs,
                    bytes);
        ntfs_flush_dcache_pages(pages + u, do_pages - u);
        status = ntfs_commit_pages_after_write(pages, do_pages, pos,
                bytes);
        if (likely(!status)) {
            written += copied;
            count -= copied;
            pos += copied;
            if (unlikely(copied != bytes))
                status = -EFAULT;
        }
        do {
            unlock_page(pages[--do_pages]);
            mark_page_accessed(pages[do_pages]);
            page_cache_release(pages[do_pages]);
        } while (do_pages);
        if (unlikely(status))
            break;
        balance_dirty_pages_ratelimited(mapping);
        cond_resched();
    } while (count);
err_out:
    *ppos = pos;
    if (cached_page)
        page_cache_release(cached_page);
    ntfs_debug("Done.  Returning %s (written 0x%lx, status %li).",
            written ? "written" : "status", (unsigned long)written,
            (long)status);
    return written ? written : status;
}

static ssize_t ntfs_file_aio_write_nolock(struct kiocb *iocb,
        const struct iovec *iov, unsigned long nr_segs, loff_t *ppos)
{
    struct file *file = iocb->ki_filp;
    struct address_space *mapping = file->f_mapping;
    struct inode *inode = mapping->host;
    loff_t pos;
    size_t count;       /* after file limit checks */
    ssize_t written, err;

    count = 0;
    err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
    if (err)
        return err;
    pos = *ppos;
    /* We can write back this queue in page reclaim. */
    current->backing_dev_info = mapping->backing_dev_info;
    written = 0;
    err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
    if (err)
        goto out;
    if (!count)
        goto out;
    err = file_remove_suid(file);
    if (err)
        goto out;
    err = file_update_time(file);
    if (err)
        goto out;
    written = ntfs_file_buffered_write(iocb, iov, nr_segs, pos, ppos,
            count);
out:
    current->backing_dev_info = NULL;
    return written ? written : err;
}

static ssize_t ntfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
        unsigned long nr_segs, loff_t pos)
{
    struct file *file = iocb->ki_filp;
    struct address_space *mapping = file->f_mapping;
    struct inode *inode = mapping->host;
    ssize_t ret;

    BUG_ON(iocb->ki_pos != pos);

    sb_start_write(inode->i_sb);
    mutex_lock(&inode->i_mutex);
    ret = ntfs_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos);
    mutex_unlock(&inode->i_mutex);
    if (ret > 0) {
        int err = generic_write_sync(file, pos, ret);
        if (err < 0)
            ret = err;
    }
    sb_end_write(inode->i_sb);
    return ret;
}

static int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
               int datasync)
{
    struct inode *vi = filp->f_mapping->host;
    int err, ret = 0;

    ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);

    err = filemap_write_and_wait_range(vi->i_mapping, start, end);
    if (err)
        return err;
    mutex_lock(&vi->i_mutex);

    BUG_ON(S_ISDIR(vi->i_mode));
    if (!datasync || !NInoNonResident(NTFS_I(vi)))
        ret = __ntfs_write_inode(vi, 1);
    write_inode_now(vi, !datasync);
    /*
     * NOTE: If we were to use mapping->private_list (see ext2 and
     * fs/buffer.c) for dirty blocks then we could optimize the below to be
     * sync_mapping_buffers(vi->i_mapping).
     */
    err = sync_blockdev(vi->i_sb->s_bdev);
    if (unlikely(err && !ret))
        ret = err;
    if (likely(!ret))
        ntfs_debug("Done.");
    else
        ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
                "%u.", datasync ? "data" : "", vi->i_ino, -ret);
    mutex_unlock(&vi->i_mutex);
    return ret;
}

#endif /* NTFS_RW */

const struct file_operations ntfs_file_ops = {
    .llseek     = generic_file_llseek,   /* Seek inside file. */
    .read       = do_sync_read,      /* Read from file. */
    .aio_read   = generic_file_aio_read, /* Async read from file. */
#ifdef NTFS_RW
    .write      = do_sync_write,     /* Write to file. */
    .aio_write  = ntfs_file_aio_write,   /* Async write to file. */
    /*.release  = ,*/            /* Last file is closed.  See
                            fs/ext2/file.c::
                            ext2_release_file() for
                            how to use this to discard
                            preallocated space for
                            write opened files. */
    .fsync      = ntfs_file_fsync,   /* Sync a file to disk. */
    /*.aio_fsync    = ,*/            /* Sync all outstanding async
                            i/o operations on a
                            kiocb. */
#endif /* NTFS_RW */
    /*.ioctl    = ,*/            /* Perform function on the
                            mounted filesystem. */
    .mmap       = generic_file_mmap,     /* Mmap file. */
    .open       = ntfs_file_open,    /* Open file. */
    .splice_read    = generic_file_splice_read /* Zero-copy data send with
                            the data source being on
                            the ntfs partition.  We do
                            not need to care about the
                            data destination. */
    /*.sendpage = ,*/            /* Zero-copy data send with
                            the data destination being
                            on the ntfs partition.  We
                            do not need to care about
                            the data source. */
};

const struct inode_operations ntfs_file_inode_ops = {
#ifdef NTFS_RW
    .truncate   = ntfs_truncate_vfs,
    .setattr    = ntfs_setattr,
#endif /* NTFS_RW */
};

const struct file_operations ntfs_empty_file_ops = {};

const struct inode_operations ntfs_empty_inode_ops = {};