Root/fs/ntfs/aops.c

1/**
2 * aops.c - NTFS kernel address space operations and page cache handling.
3 * Part of the Linux-NTFS project.
4 *
5 * Copyright (c) 2001-2007 Anton Altaparmakov
6 * Copyright (c) 2002 Richard Russon
7 *
8 * This program/include file is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as published
10 * by the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program/include file is distributed in the hope that it will be
14 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
15 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program (in the main directory of the Linux-NTFS
20 * distribution in the file COPYING); if not, write to the Free Software
21 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 */
23
24#include <linux/errno.h>
25#include <linux/fs.h>
26#include <linux/gfp.h>
27#include <linux/mm.h>
28#include <linux/pagemap.h>
29#include <linux/swap.h>
30#include <linux/buffer_head.h>
31#include <linux/writeback.h>
32#include <linux/bit_spinlock.h>
33
34#include "aops.h"
35#include "attrib.h"
36#include "debug.h"
37#include "inode.h"
38#include "mft.h"
39#include "runlist.h"
40#include "types.h"
41#include "ntfs.h"
42
43/**
44 * ntfs_end_buffer_async_read - async io completion for reading attributes
45 * @bh: buffer head on which io is completed
46 * @uptodate: whether @bh is now uptodate or not
47 *
48 * Asynchronous I/O completion handler for reading pages belonging to the
49 * attribute address space of an inode. The inodes can either be files or
50 * directories or they can be fake inodes describing some attribute.
51 *
52 * If NInoMstProtected(), perform the post read mst fixups when all IO on the
53 * page has been completed and mark the page uptodate or set the error bit on
54 * the page. To determine the size of the records that need fixing up, we
55 * cheat a little bit by setting the index_block_size in ntfs_inode to the ntfs
56 * record size, and index_block_size_bits, to the log(base 2) of the ntfs
57 * record size.
58 */
59static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
60{
61    unsigned long flags;
62    struct buffer_head *first, *tmp;
63    struct page *page;
64    struct inode *vi;
65    ntfs_inode *ni;
66    int page_uptodate = 1;
67
68    page = bh->b_page;
69    vi = page->mapping->host;
70    ni = NTFS_I(vi);
71
72    if (likely(uptodate)) {
73        loff_t i_size;
74        s64 file_ofs, init_size;
75
76        set_buffer_uptodate(bh);
77
78        file_ofs = ((s64)page->index << PAGE_CACHE_SHIFT) +
79                bh_offset(bh);
80        read_lock_irqsave(&ni->size_lock, flags);
81        init_size = ni->initialized_size;
82        i_size = i_size_read(vi);
83        read_unlock_irqrestore(&ni->size_lock, flags);
84        if (unlikely(init_size > i_size)) {
85            /* Race with shrinking truncate. */
86            init_size = i_size;
87        }
88        /* Check for the current buffer head overflowing. */
89        if (unlikely(file_ofs + bh->b_size > init_size)) {
90            int ofs;
91            void *kaddr;
92
93            ofs = 0;
94            if (file_ofs < init_size)
95                ofs = init_size - file_ofs;
96            local_irq_save(flags);
97            kaddr = kmap_atomic(page, KM_BIO_SRC_IRQ);
98            memset(kaddr + bh_offset(bh) + ofs, 0,
99                    bh->b_size - ofs);
100            flush_dcache_page(page);
101            kunmap_atomic(kaddr, KM_BIO_SRC_IRQ);
102            local_irq_restore(flags);
103        }
104    } else {
105        clear_buffer_uptodate(bh);
106        SetPageError(page);
107        ntfs_error(ni->vol->sb, "Buffer I/O error, logical block "
108                "0x%llx.", (unsigned long long)bh->b_blocknr);
109    }
110    first = page_buffers(page);
111    local_irq_save(flags);
112    bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
113    clear_buffer_async_read(bh);
114    unlock_buffer(bh);
115    tmp = bh;
116    do {
117        if (!buffer_uptodate(tmp))
118            page_uptodate = 0;
119        if (buffer_async_read(tmp)) {
120            if (likely(buffer_locked(tmp)))
121                goto still_busy;
122            /* Async buffers must be locked. */
123            BUG();
124        }
125        tmp = tmp->b_this_page;
126    } while (tmp != bh);
127    bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
128    local_irq_restore(flags);
129    /*
130     * If none of the buffers had errors then we can set the page uptodate,
131     * but we first have to perform the post read mst fixups, if the
132     * attribute is mst protected, i.e. if NInoMstProteced(ni) is true.
133     * Note we ignore fixup errors as those are detected when
134     * map_mft_record() is called which gives us per record granularity
135     * rather than per page granularity.
136     */
137    if (!NInoMstProtected(ni)) {
138        if (likely(page_uptodate && !PageError(page)))
139            SetPageUptodate(page);
140    } else {
141        u8 *kaddr;
142        unsigned int i, recs;
143        u32 rec_size;
144
145        rec_size = ni->itype.index.block_size;
146        recs = PAGE_CACHE_SIZE / rec_size;
147        /* Should have been verified before we got here... */
148        BUG_ON(!recs);
149        local_irq_save(flags);
150        kaddr = kmap_atomic(page, KM_BIO_SRC_IRQ);
151        for (i = 0; i < recs; i++)
152            post_read_mst_fixup((NTFS_RECORD*)(kaddr +
153                    i * rec_size), rec_size);
154        kunmap_atomic(kaddr, KM_BIO_SRC_IRQ);
155        local_irq_restore(flags);
156        flush_dcache_page(page);
157        if (likely(page_uptodate && !PageError(page)))
158            SetPageUptodate(page);
159    }
160    unlock_page(page);
161    return;
162still_busy:
163    bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
164    local_irq_restore(flags);
165    return;
166}
167
168/**
169 * ntfs_read_block - fill a @page of an address space with data
170 * @page: page cache page to fill with data
171 *
172 * Fill the page @page of the address space belonging to the @page->host inode.
173 * We read each buffer asynchronously and when all buffers are read in, our io
174 * completion handler ntfs_end_buffer_read_async(), if required, automatically
175 * applies the mst fixups to the page before finally marking it uptodate and
176 * unlocking it.
177 *
178 * We only enforce allocated_size limit because i_size is checked for in
179 * generic_file_read().
180 *
181 * Return 0 on success and -errno on error.
182 *
183 * Contains an adapted version of fs/buffer.c::block_read_full_page().
184 */
185static int ntfs_read_block(struct page *page)
186{
187    loff_t i_size;
188    VCN vcn;
189    LCN lcn;
190    s64 init_size;
191    struct inode *vi;
192    ntfs_inode *ni;
193    ntfs_volume *vol;
194    runlist_element *rl;
195    struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
196    sector_t iblock, lblock, zblock;
197    unsigned long flags;
198    unsigned int blocksize, vcn_ofs;
199    int i, nr;
200    unsigned char blocksize_bits;
201
202    vi = page->mapping->host;
203    ni = NTFS_I(vi);
204    vol = ni->vol;
205
206    /* $MFT/$DATA must have its complete runlist in memory at all times. */
207    BUG_ON(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni));
208
209    blocksize = vol->sb->s_blocksize;
210    blocksize_bits = vol->sb->s_blocksize_bits;
211
212    if (!page_has_buffers(page)) {
213        create_empty_buffers(page, blocksize, 0);
214        if (unlikely(!page_has_buffers(page))) {
215            unlock_page(page);
216            return -ENOMEM;
217        }
218    }
219    bh = head = page_buffers(page);
220    BUG_ON(!bh);
221
222    /*
223     * We may be racing with truncate. To avoid some of the problems we
224     * now take a snapshot of the various sizes and use those for the whole
225     * of the function. In case of an extending truncate it just means we
226     * may leave some buffers unmapped which are now allocated. This is
227     * not a problem since these buffers will just get mapped when a write
228     * occurs. In case of a shrinking truncate, we will detect this later
229     * on due to the runlist being incomplete and if the page is being
230     * fully truncated, truncate will throw it away as soon as we unlock
231     * it so no need to worry what we do with it.
232     */
233    iblock = (s64)page->index << (PAGE_CACHE_SHIFT - blocksize_bits);
234    read_lock_irqsave(&ni->size_lock, flags);
235    lblock = (ni->allocated_size + blocksize - 1) >> blocksize_bits;
236    init_size = ni->initialized_size;
237    i_size = i_size_read(vi);
238    read_unlock_irqrestore(&ni->size_lock, flags);
239    if (unlikely(init_size > i_size)) {
240        /* Race with shrinking truncate. */
241        init_size = i_size;
242    }
243    zblock = (init_size + blocksize - 1) >> blocksize_bits;
244
245    /* Loop through all the buffers in the page. */
246    rl = NULL;
247    nr = i = 0;
248    do {
249        int err = 0;
250
251        if (unlikely(buffer_uptodate(bh)))
252            continue;
253        if (unlikely(buffer_mapped(bh))) {
254            arr[nr++] = bh;
255            continue;
256        }
257        bh->b_bdev = vol->sb->s_bdev;
258        /* Is the block within the allowed limits? */
259        if (iblock < lblock) {
260            bool is_retry = false;
261
262            /* Convert iblock into corresponding vcn and offset. */
263            vcn = (VCN)iblock << blocksize_bits >>
264                    vol->cluster_size_bits;
265            vcn_ofs = ((VCN)iblock << blocksize_bits) &
266                    vol->cluster_size_mask;
267            if (!rl) {
268lock_retry_remap:
269                down_read(&ni->runlist.lock);
270                rl = ni->runlist.rl;
271            }
272            if (likely(rl != NULL)) {
273                /* Seek to element containing target vcn. */
274                while (rl->length && rl[1].vcn <= vcn)
275                    rl++;
276                lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
277            } else
278                lcn = LCN_RL_NOT_MAPPED;
279            /* Successful remap. */
280            if (lcn >= 0) {
281                /* Setup buffer head to correct block. */
282                bh->b_blocknr = ((lcn << vol->cluster_size_bits)
283                        + vcn_ofs) >> blocksize_bits;
284                set_buffer_mapped(bh);
285                /* Only read initialized data blocks. */
286                if (iblock < zblock) {
287                    arr[nr++] = bh;
288                    continue;
289                }
290                /* Fully non-initialized data block, zero it. */
291                goto handle_zblock;
292            }
293            /* It is a hole, need to zero it. */
294            if (lcn == LCN_HOLE)
295                goto handle_hole;
296            /* If first try and runlist unmapped, map and retry. */
297            if (!is_retry && lcn == LCN_RL_NOT_MAPPED) {
298                is_retry = true;
299                /*
300                 * Attempt to map runlist, dropping lock for
301                 * the duration.
302                 */
303                up_read(&ni->runlist.lock);
304                err = ntfs_map_runlist(ni, vcn);
305                if (likely(!err))
306                    goto lock_retry_remap;
307                rl = NULL;
308            } else if (!rl)
309                up_read(&ni->runlist.lock);
310            /*
311             * If buffer is outside the runlist, treat it as a
312             * hole. This can happen due to concurrent truncate
313             * for example.
314             */
315            if (err == -ENOENT || lcn == LCN_ENOENT) {
316                err = 0;
317                goto handle_hole;
318            }
319            /* Hard error, zero out region. */
320            if (!err)
321                err = -EIO;
322            bh->b_blocknr = -1;
323            SetPageError(page);
324            ntfs_error(vol->sb, "Failed to read from inode 0x%lx, "
325                    "attribute type 0x%x, vcn 0x%llx, "
326                    "offset 0x%x because its location on "
327                    "disk could not be determined%s "
328                    "(error code %i).", ni->mft_no,
329                    ni->type, (unsigned long long)vcn,
330                    vcn_ofs, is_retry ? " even after "
331                    "retrying" : "", err);
332        }
333        /*
334         * Either iblock was outside lblock limits or
335         * ntfs_rl_vcn_to_lcn() returned error. Just zero that portion
336         * of the page and set the buffer uptodate.
337         */
338handle_hole:
339        bh->b_blocknr = -1UL;
340        clear_buffer_mapped(bh);
341handle_zblock:
342        zero_user(page, i * blocksize, blocksize);
343        if (likely(!err))
344            set_buffer_uptodate(bh);
345    } while (i++, iblock++, (bh = bh->b_this_page) != head);
346
347    /* Release the lock if we took it. */
348    if (rl)
349        up_read(&ni->runlist.lock);
350
351    /* Check we have at least one buffer ready for i/o. */
352    if (nr) {
353        struct buffer_head *tbh;
354
355        /* Lock the buffers. */
356        for (i = 0; i < nr; i++) {
357            tbh = arr[i];
358            lock_buffer(tbh);
359            tbh->b_end_io = ntfs_end_buffer_async_read;
360            set_buffer_async_read(tbh);
361        }
362        /* Finally, start i/o on the buffers. */
363        for (i = 0; i < nr; i++) {
364            tbh = arr[i];
365            if (likely(!buffer_uptodate(tbh)))
366                submit_bh(READ, tbh);
367            else
368                ntfs_end_buffer_async_read(tbh, 1);
369        }
370        return 0;
371    }
372    /* No i/o was scheduled on any of the buffers. */
373    if (likely(!PageError(page)))
374        SetPageUptodate(page);
375    else /* Signal synchronous i/o error. */
376        nr = -EIO;
377    unlock_page(page);
378    return nr;
379}
380
381/**
382 * ntfs_readpage - fill a @page of a @file with data from the device
383 * @file: open file to which the page @page belongs or NULL
384 * @page: page cache page to fill with data
385 *
386 * For non-resident attributes, ntfs_readpage() fills the @page of the open
387 * file @file by calling the ntfs version of the generic block_read_full_page()
388 * function, ntfs_read_block(), which in turn creates and reads in the buffers
389 * associated with the page asynchronously.
390 *
391 * For resident attributes, OTOH, ntfs_readpage() fills @page by copying the
392 * data from the mft record (which at this stage is most likely in memory) and
393 * fills the remainder with zeroes. Thus, in this case, I/O is synchronous, as
394 * even if the mft record is not cached at this point in time, we need to wait
395 * for it to be read in before we can do the copy.
396 *
397 * Return 0 on success and -errno on error.
398 */
399static int ntfs_readpage(struct file *file, struct page *page)
400{
401    loff_t i_size;
402    struct inode *vi;
403    ntfs_inode *ni, *base_ni;
404    u8 *addr;
405    ntfs_attr_search_ctx *ctx;
406    MFT_RECORD *mrec;
407    unsigned long flags;
408    u32 attr_len;
409    int err = 0;
410
411retry_readpage:
412    BUG_ON(!PageLocked(page));
413    vi = page->mapping->host;
414    i_size = i_size_read(vi);
415    /* Is the page fully outside i_size? (truncate in progress) */
416    if (unlikely(page->index >= (i_size + PAGE_CACHE_SIZE - 1) >>
417            PAGE_CACHE_SHIFT)) {
418        zero_user(page, 0, PAGE_CACHE_SIZE);
419        ntfs_debug("Read outside i_size - truncated?");
420        goto done;
421    }
422    /*
423     * This can potentially happen because we clear PageUptodate() during
424     * ntfs_writepage() of MstProtected() attributes.
425     */
426    if (PageUptodate(page)) {
427        unlock_page(page);
428        return 0;
429    }
430    ni = NTFS_I(vi);
431    /*
432     * Only $DATA attributes can be encrypted and only unnamed $DATA
433     * attributes can be compressed. Index root can have the flags set but
434     * this means to create compressed/encrypted files, not that the
435     * attribute is compressed/encrypted. Note we need to check for
436     * AT_INDEX_ALLOCATION since this is the type of both directory and
437     * index inodes.
438     */
439    if (ni->type != AT_INDEX_ALLOCATION) {
440        /* If attribute is encrypted, deny access, just like NT4. */
441        if (NInoEncrypted(ni)) {
442            BUG_ON(ni->type != AT_DATA);
443            err = -EACCES;
444            goto err_out;
445        }
446        /* Compressed data streams are handled in compress.c. */
447        if (NInoNonResident(ni) && NInoCompressed(ni)) {
448            BUG_ON(ni->type != AT_DATA);
449            BUG_ON(ni->name_len);
450            return ntfs_read_compressed_block(page);
451        }
452    }
453    /* NInoNonResident() == NInoIndexAllocPresent() */
454    if (NInoNonResident(ni)) {
455        /* Normal, non-resident data stream. */
456        return ntfs_read_block(page);
457    }
458    /*
459     * Attribute is resident, implying it is not compressed or encrypted.
460     * This also means the attribute is smaller than an mft record and
461     * hence smaller than a page, so can simply zero out any pages with
462     * index above 0. Note the attribute can actually be marked compressed
463     * but if it is resident the actual data is not compressed so we are
464     * ok to ignore the compressed flag here.
465     */
466    if (unlikely(page->index > 0)) {
467        zero_user(page, 0, PAGE_CACHE_SIZE);
468        goto done;
469    }
470    if (!NInoAttr(ni))
471        base_ni = ni;
472    else
473        base_ni = ni->ext.base_ntfs_ino;
474    /* Map, pin, and lock the mft record. */
475    mrec = map_mft_record(base_ni);
476    if (IS_ERR(mrec)) {
477        err = PTR_ERR(mrec);
478        goto err_out;
479    }
480    /*
481     * If a parallel write made the attribute non-resident, drop the mft
482     * record and retry the readpage.
483     */
484    if (unlikely(NInoNonResident(ni))) {
485        unmap_mft_record(base_ni);
486        goto retry_readpage;
487    }
488    ctx = ntfs_attr_get_search_ctx(base_ni, mrec);
489    if (unlikely(!ctx)) {
490        err = -ENOMEM;
491        goto unm_err_out;
492    }
493    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
494            CASE_SENSITIVE, 0, NULL, 0, ctx);
495    if (unlikely(err))
496        goto put_unm_err_out;
497    attr_len = le32_to_cpu(ctx->attr->data.resident.value_length);
498    read_lock_irqsave(&ni->size_lock, flags);
499    if (unlikely(attr_len > ni->initialized_size))
500        attr_len = ni->initialized_size;
501    i_size = i_size_read(vi);
502    read_unlock_irqrestore(&ni->size_lock, flags);
503    if (unlikely(attr_len > i_size)) {
504        /* Race with shrinking truncate. */
505        attr_len = i_size;
506    }
507    addr = kmap_atomic(page, KM_USER0);
508    /* Copy the data to the page. */
509    memcpy(addr, (u8*)ctx->attr +
510            le16_to_cpu(ctx->attr->data.resident.value_offset),
511            attr_len);
512    /* Zero the remainder of the page. */
513    memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
514    flush_dcache_page(page);
515    kunmap_atomic(addr, KM_USER0);
516put_unm_err_out:
517    ntfs_attr_put_search_ctx(ctx);
518unm_err_out:
519    unmap_mft_record(base_ni);
520done:
521    SetPageUptodate(page);
522err_out:
523    unlock_page(page);
524    return err;
525}
526
527#ifdef NTFS_RW
528
529/**
530 * ntfs_write_block - write a @page to the backing store
531 * @page: page cache page to write out
532 * @wbc: writeback control structure
533 *
534 * This function is for writing pages belonging to non-resident, non-mst
535 * protected attributes to their backing store.
536 *
537 * For a page with buffers, map and write the dirty buffers asynchronously
538 * under page writeback. For a page without buffers, create buffers for the
539 * page, then proceed as above.
540 *
541 * If a page doesn't have buffers the page dirty state is definitive. If a page
542 * does have buffers, the page dirty state is just a hint, and the buffer dirty
543 * state is definitive. (A hint which has rules: dirty buffers against a clean
544 * page is illegal. Other combinations are legal and need to be handled. In
545 * particular a dirty page containing clean buffers for example.)
546 *
547 * Return 0 on success and -errno on error.
548 *
549 * Based on ntfs_read_block() and __block_write_full_page().
550 */
551static int ntfs_write_block(struct page *page, struct writeback_control *wbc)
552{
553    VCN vcn;
554    LCN lcn;
555    s64 initialized_size;
556    loff_t i_size;
557    sector_t block, dblock, iblock;
558    struct inode *vi;
559    ntfs_inode *ni;
560    ntfs_volume *vol;
561    runlist_element *rl;
562    struct buffer_head *bh, *head;
563    unsigned long flags;
564    unsigned int blocksize, vcn_ofs;
565    int err;
566    bool need_end_writeback;
567    unsigned char blocksize_bits;
568
569    vi = page->mapping->host;
570    ni = NTFS_I(vi);
571    vol = ni->vol;
572
573    ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, page index "
574            "0x%lx.", ni->mft_no, ni->type, page->index);
575
576    BUG_ON(!NInoNonResident(ni));
577    BUG_ON(NInoMstProtected(ni));
578    blocksize = vol->sb->s_blocksize;
579    blocksize_bits = vol->sb->s_blocksize_bits;
580    if (!page_has_buffers(page)) {
581        BUG_ON(!PageUptodate(page));
582        create_empty_buffers(page, blocksize,
583                (1 << BH_Uptodate) | (1 << BH_Dirty));
584        if (unlikely(!page_has_buffers(page))) {
585            ntfs_warning(vol->sb, "Error allocating page "
586                    "buffers. Redirtying page so we try "
587                    "again later.");
588            /*
589             * Put the page back on mapping->dirty_pages, but leave
590             * its buffers' dirty state as-is.
591             */
592            redirty_page_for_writepage(wbc, page);
593            unlock_page(page);
594            return 0;
595        }
596    }
597    bh = head = page_buffers(page);
598    BUG_ON(!bh);
599
600    /* NOTE: Different naming scheme to ntfs_read_block()! */
601
602    /* The first block in the page. */
603    block = (s64)page->index << (PAGE_CACHE_SHIFT - blocksize_bits);
604
605    read_lock_irqsave(&ni->size_lock, flags);
606    i_size = i_size_read(vi);
607    initialized_size = ni->initialized_size;
608    read_unlock_irqrestore(&ni->size_lock, flags);
609
610    /* The first out of bounds block for the data size. */
611    dblock = (i_size + blocksize - 1) >> blocksize_bits;
612
613    /* The last (fully or partially) initialized block. */
614    iblock = initialized_size >> blocksize_bits;
615
616    /*
617     * Be very careful. We have no exclusion from __set_page_dirty_buffers
618     * here, and the (potentially unmapped) buffers may become dirty at
619     * any time. If a buffer becomes dirty here after we've inspected it
620     * then we just miss that fact, and the page stays dirty.
621     *
622     * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
623     * handle that here by just cleaning them.
624     */
625
626    /*
627     * Loop through all the buffers in the page, mapping all the dirty
628     * buffers to disk addresses and handling any aliases from the
629     * underlying block device's mapping.
630     */
631    rl = NULL;
632    err = 0;
633    do {
634        bool is_retry = false;
635
636        if (unlikely(block >= dblock)) {
637            /*
638             * Mapped buffers outside i_size will occur, because
639             * this page can be outside i_size when there is a
640             * truncate in progress. The contents of such buffers
641             * were zeroed by ntfs_writepage().
642             *
643             * FIXME: What about the small race window where
644             * ntfs_writepage() has not done any clearing because
645             * the page was within i_size but before we get here,
646             * vmtruncate() modifies i_size?
647             */
648            clear_buffer_dirty(bh);
649            set_buffer_uptodate(bh);
650            continue;
651        }
652
653        /* Clean buffers are not written out, so no need to map them. */
654        if (!buffer_dirty(bh))
655            continue;
656
657        /* Make sure we have enough initialized size. */
658        if (unlikely((block >= iblock) &&
659                (initialized_size < i_size))) {
660            /*
661             * If this page is fully outside initialized size, zero
662             * out all pages between the current initialized size
663             * and the current page. Just use ntfs_readpage() to do
664             * the zeroing transparently.
665             */
666            if (block > iblock) {
667                // TODO:
668                // For each page do:
669                // - read_cache_page()
670                // Again for each page do:
671                // - wait_on_page_locked()
672                // - Check (PageUptodate(page) &&
673                // !PageError(page))
674                // Update initialized size in the attribute and
675                // in the inode.
676                // Again, for each page do:
677                // __set_page_dirty_buffers();
678                // page_cache_release()
679                // We don't need to wait on the writes.
680                // Update iblock.
681            }
682            /*
683             * The current page straddles initialized size. Zero
684             * all non-uptodate buffers and set them uptodate (and
685             * dirty?). Note, there aren't any non-uptodate buffers
686             * if the page is uptodate.
687             * FIXME: For an uptodate page, the buffers may need to
688             * be written out because they were not initialized on
689             * disk before.
690             */
691            if (!PageUptodate(page)) {
692                // TODO:
693                // Zero any non-uptodate buffers up to i_size.
694                // Set them uptodate and dirty.
695            }
696            // TODO:
697            // Update initialized size in the attribute and in the
698            // inode (up to i_size).
699            // Update iblock.
700            // FIXME: This is inefficient. Try to batch the two
701            // size changes to happen in one go.
702            ntfs_error(vol->sb, "Writing beyond initialized size "
703                    "is not supported yet. Sorry.");
704            err = -EOPNOTSUPP;
705            break;
706            // Do NOT set_buffer_new() BUT DO clear buffer range
707            // outside write request range.
708            // set_buffer_uptodate() on complete buffers as well as
709            // set_buffer_dirty().
710        }
711
712        /* No need to map buffers that are already mapped. */
713        if (buffer_mapped(bh))
714            continue;
715
716        /* Unmapped, dirty buffer. Need to map it. */
717        bh->b_bdev = vol->sb->s_bdev;
718
719        /* Convert block into corresponding vcn and offset. */
720        vcn = (VCN)block << blocksize_bits;
721        vcn_ofs = vcn & vol->cluster_size_mask;
722        vcn >>= vol->cluster_size_bits;
723        if (!rl) {
724lock_retry_remap:
725            down_read(&ni->runlist.lock);
726            rl = ni->runlist.rl;
727        }
728        if (likely(rl != NULL)) {
729            /* Seek to element containing target vcn. */
730            while (rl->length && rl[1].vcn <= vcn)
731                rl++;
732            lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
733        } else
734            lcn = LCN_RL_NOT_MAPPED;
735        /* Successful remap. */
736        if (lcn >= 0) {
737            /* Setup buffer head to point to correct block. */
738            bh->b_blocknr = ((lcn << vol->cluster_size_bits) +
739                    vcn_ofs) >> blocksize_bits;
740            set_buffer_mapped(bh);
741            continue;
742        }
743        /* It is a hole, need to instantiate it. */
744        if (lcn == LCN_HOLE) {
745            u8 *kaddr;
746            unsigned long *bpos, *bend;
747
748            /* Check if the buffer is zero. */
749            kaddr = kmap_atomic(page, KM_USER0);
750            bpos = (unsigned long *)(kaddr + bh_offset(bh));
751            bend = (unsigned long *)((u8*)bpos + blocksize);
752            do {
753                if (unlikely(*bpos))
754                    break;
755            } while (likely(++bpos < bend));
756            kunmap_atomic(kaddr, KM_USER0);
757            if (bpos == bend) {
758                /*
759                 * Buffer is zero and sparse, no need to write
760                 * it.
761                 */
762                bh->b_blocknr = -1;
763                clear_buffer_dirty(bh);
764                continue;
765            }
766            // TODO: Instantiate the hole.
767            // clear_buffer_new(bh);
768            // unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
769            ntfs_error(vol->sb, "Writing into sparse regions is "
770                    "not supported yet. Sorry.");
771            err = -EOPNOTSUPP;
772            break;
773        }
774        /* If first try and runlist unmapped, map and retry. */
775        if (!is_retry && lcn == LCN_RL_NOT_MAPPED) {
776            is_retry = true;
777            /*
778             * Attempt to map runlist, dropping lock for
779             * the duration.
780             */
781            up_read(&ni->runlist.lock);
782            err = ntfs_map_runlist(ni, vcn);
783            if (likely(!err))
784                goto lock_retry_remap;
785            rl = NULL;
786        } else if (!rl)
787            up_read(&ni->runlist.lock);
788        /*
789         * If buffer is outside the runlist, truncate has cut it out
790         * of the runlist. Just clean and clear the buffer and set it
791         * uptodate so it can get discarded by the VM.
792         */
793        if (err == -ENOENT || lcn == LCN_ENOENT) {
794            bh->b_blocknr = -1;
795            clear_buffer_dirty(bh);
796            zero_user(page, bh_offset(bh), blocksize);
797            set_buffer_uptodate(bh);
798            err = 0;
799            continue;
800        }
801        /* Failed to map the buffer, even after retrying. */
802        if (!err)
803            err = -EIO;
804        bh->b_blocknr = -1;
805        ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
806                "attribute type 0x%x, vcn 0x%llx, offset 0x%x "
807                "because its location on disk could not be "
808                "determined%s (error code %i).", ni->mft_no,
809                ni->type, (unsigned long long)vcn,
810                vcn_ofs, is_retry ? " even after "
811                "retrying" : "", err);
812        break;
813    } while (block++, (bh = bh->b_this_page) != head);
814
815    /* Release the lock if we took it. */
816    if (rl)
817        up_read(&ni->runlist.lock);
818
819    /* For the error case, need to reset bh to the beginning. */
820    bh = head;
821
822    /* Just an optimization, so ->readpage() is not called later. */
823    if (unlikely(!PageUptodate(page))) {
824        int uptodate = 1;
825        do {
826            if (!buffer_uptodate(bh)) {
827                uptodate = 0;
828                bh = head;
829                break;
830            }
831        } while ((bh = bh->b_this_page) != head);
832        if (uptodate)
833            SetPageUptodate(page);
834    }
835
836    /* Setup all mapped, dirty buffers for async write i/o. */
837    do {
838        if (buffer_mapped(bh) && buffer_dirty(bh)) {
839            lock_buffer(bh);
840            if (test_clear_buffer_dirty(bh)) {
841                BUG_ON(!buffer_uptodate(bh));
842                mark_buffer_async_write(bh);
843            } else
844                unlock_buffer(bh);
845        } else if (unlikely(err)) {
846            /*
847             * For the error case. The buffer may have been set
848             * dirty during attachment to a dirty page.
849             */
850            if (err != -ENOMEM)
851                clear_buffer_dirty(bh);
852        }
853    } while ((bh = bh->b_this_page) != head);
854
855    if (unlikely(err)) {
856        // TODO: Remove the -EOPNOTSUPP check later on...
857        if (unlikely(err == -EOPNOTSUPP))
858            err = 0;
859        else if (err == -ENOMEM) {
860            ntfs_warning(vol->sb, "Error allocating memory. "
861                    "Redirtying page so we try again "
862                    "later.");
863            /*
864             * Put the page back on mapping->dirty_pages, but
865             * leave its buffer's dirty state as-is.
866             */
867            redirty_page_for_writepage(wbc, page);
868            err = 0;
869        } else
870            SetPageError(page);
871    }
872
873    BUG_ON(PageWriteback(page));
874    set_page_writeback(page); /* Keeps try_to_free_buffers() away. */
875
876    /* Submit the prepared buffers for i/o. */
877    need_end_writeback = true;
878    do {
879        struct buffer_head *next = bh->b_this_page;
880        if (buffer_async_write(bh)) {
881            submit_bh(WRITE, bh);
882            need_end_writeback = false;
883        }
884        bh = next;
885    } while (bh != head);
886    unlock_page(page);
887
888    /* If no i/o was started, need to end_page_writeback(). */
889    if (unlikely(need_end_writeback))
890        end_page_writeback(page);
891
892    ntfs_debug("Done.");
893    return err;
894}
895
896/**
897 * ntfs_write_mst_block - write a @page to the backing store
898 * @page: page cache page to write out
899 * @wbc: writeback control structure
900 *
901 * This function is for writing pages belonging to non-resident, mst protected
902 * attributes to their backing store. The only supported attributes are index
903 * allocation and $MFT/$DATA. Both directory inodes and index inodes are
904 * supported for the index allocation case.
905 *
906 * The page must remain locked for the duration of the write because we apply
907 * the mst fixups, write, and then undo the fixups, so if we were to unlock the
908 * page before undoing the fixups, any other user of the page will see the
909 * page contents as corrupt.
910 *
911 * We clear the page uptodate flag for the duration of the function to ensure
912 * exclusion for the $MFT/$DATA case against someone mapping an mft record we
913 * are about to apply the mst fixups to.
914 *
915 * Return 0 on success and -errno on error.
916 *
917 * Based on ntfs_write_block(), ntfs_mft_writepage(), and
918 * write_mft_record_nolock().
919 */
920static int ntfs_write_mst_block(struct page *page,
921        struct writeback_control *wbc)
922{
923    sector_t block, dblock, rec_block;
924    struct inode *vi = page->mapping->host;
925    ntfs_inode *ni = NTFS_I(vi);
926    ntfs_volume *vol = ni->vol;
927    u8 *kaddr;
928    unsigned int rec_size = ni->itype.index.block_size;
929    ntfs_inode *locked_nis[PAGE_CACHE_SIZE / rec_size];
930    struct buffer_head *bh, *head, *tbh, *rec_start_bh;
931    struct buffer_head *bhs[MAX_BUF_PER_PAGE];
932    runlist_element *rl;
933    int i, nr_locked_nis, nr_recs, nr_bhs, max_bhs, bhs_per_rec, err, err2;
934    unsigned bh_size, rec_size_bits;
935    bool sync, is_mft, page_is_dirty, rec_is_dirty;
936    unsigned char bh_size_bits;
937
938    ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, page index "
939            "0x%lx.", vi->i_ino, ni->type, page->index);
940    BUG_ON(!NInoNonResident(ni));
941    BUG_ON(!NInoMstProtected(ni));
942    is_mft = (S_ISREG(vi->i_mode) && !vi->i_ino);
943    /*
944     * NOTE: ntfs_write_mst_block() would be called for $MFTMirr if a page
945     * in its page cache were to be marked dirty. However this should
946     * never happen with the current driver and considering we do not
947     * handle this case here we do want to BUG(), at least for now.
948     */
949    BUG_ON(!(is_mft || S_ISDIR(vi->i_mode) ||
950            (NInoAttr(ni) && ni->type == AT_INDEX_ALLOCATION)));
951    bh_size = vol->sb->s_blocksize;
952    bh_size_bits = vol->sb->s_blocksize_bits;
953    max_bhs = PAGE_CACHE_SIZE / bh_size;
954    BUG_ON(!max_bhs);
955    BUG_ON(max_bhs > MAX_BUF_PER_PAGE);
956
957    /* Were we called for sync purposes? */
958    sync = (wbc->sync_mode == WB_SYNC_ALL);
959
960    /* Make sure we have mapped buffers. */
961    bh = head = page_buffers(page);
962    BUG_ON(!bh);
963
964    rec_size_bits = ni->itype.index.block_size_bits;
965    BUG_ON(!(PAGE_CACHE_SIZE >> rec_size_bits));
966    bhs_per_rec = rec_size >> bh_size_bits;
967    BUG_ON(!bhs_per_rec);
968
969    /* The first block in the page. */
970    rec_block = block = (sector_t)page->index <<
971            (PAGE_CACHE_SHIFT - bh_size_bits);
972
973    /* The first out of bounds block for the data size. */
974    dblock = (i_size_read(vi) + bh_size - 1) >> bh_size_bits;
975
976    rl = NULL;
977    err = err2 = nr_bhs = nr_recs = nr_locked_nis = 0;
978    page_is_dirty = rec_is_dirty = false;
979    rec_start_bh = NULL;
980    do {
981        bool is_retry = false;
982
983        if (likely(block < rec_block)) {
984            if (unlikely(block >= dblock)) {
985                clear_buffer_dirty(bh);
986                set_buffer_uptodate(bh);
987                continue;
988            }
989            /*
990             * This block is not the first one in the record. We
991             * ignore the buffer's dirty state because we could
992             * have raced with a parallel mark_ntfs_record_dirty().
993             */
994            if (!rec_is_dirty)
995                continue;
996            if (unlikely(err2)) {
997                if (err2 != -ENOMEM)
998                    clear_buffer_dirty(bh);
999                continue;
1000            }
1001        } else /* if (block == rec_block) */ {
1002            BUG_ON(block > rec_block);
1003            /* This block is the first one in the record. */
1004            rec_block += bhs_per_rec;
1005            err2 = 0;
1006            if (unlikely(block >= dblock)) {
1007                clear_buffer_dirty(bh);
1008                continue;
1009            }
1010            if (!buffer_dirty(bh)) {
1011                /* Clean records are not written out. */
1012                rec_is_dirty = false;
1013                continue;
1014            }
1015            rec_is_dirty = true;
1016            rec_start_bh = bh;
1017        }
1018        /* Need to map the buffer if it is not mapped already. */
1019        if (unlikely(!buffer_mapped(bh))) {
1020            VCN vcn;
1021            LCN lcn;
1022            unsigned int vcn_ofs;
1023
1024            bh->b_bdev = vol->sb->s_bdev;
1025            /* Obtain the vcn and offset of the current block. */
1026            vcn = (VCN)block << bh_size_bits;
1027            vcn_ofs = vcn & vol->cluster_size_mask;
1028            vcn >>= vol->cluster_size_bits;
1029            if (!rl) {
1030lock_retry_remap:
1031                down_read(&ni->runlist.lock);
1032                rl = ni->runlist.rl;
1033            }
1034            if (likely(rl != NULL)) {
1035                /* Seek to element containing target vcn. */
1036                while (rl->length && rl[1].vcn <= vcn)
1037                    rl++;
1038                lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
1039            } else
1040                lcn = LCN_RL_NOT_MAPPED;
1041            /* Successful remap. */
1042            if (likely(lcn >= 0)) {
1043                /* Setup buffer head to correct block. */
1044                bh->b_blocknr = ((lcn <<
1045                        vol->cluster_size_bits) +
1046                        vcn_ofs) >> bh_size_bits;
1047                set_buffer_mapped(bh);
1048            } else {
1049                /*
1050                 * Remap failed. Retry to map the runlist once
1051                 * unless we are working on $MFT which always
1052                 * has the whole of its runlist in memory.
1053                 */
1054                if (!is_mft && !is_retry &&
1055                        lcn == LCN_RL_NOT_MAPPED) {
1056                    is_retry = true;
1057                    /*
1058                     * Attempt to map runlist, dropping
1059                     * lock for the duration.
1060                     */
1061                    up_read(&ni->runlist.lock);
1062                    err2 = ntfs_map_runlist(ni, vcn);
1063                    if (likely(!err2))
1064                        goto lock_retry_remap;
1065                    if (err2 == -ENOMEM)
1066                        page_is_dirty = true;
1067                    lcn = err2;
1068                } else {
1069                    err2 = -EIO;
1070                    if (!rl)
1071                        up_read(&ni->runlist.lock);
1072                }
1073                /* Hard error. Abort writing this record. */
1074                if (!err || err == -ENOMEM)
1075                    err = err2;
1076                bh->b_blocknr = -1;
1077                ntfs_error(vol->sb, "Cannot write ntfs record "
1078                        "0x%llx (inode 0x%lx, "
1079                        "attribute type 0x%x) because "
1080                        "its location on disk could "
1081                        "not be determined (error "
1082                        "code %lli).",
1083                        (long long)block <<
1084                        bh_size_bits >>
1085                        vol->mft_record_size_bits,
1086                        ni->mft_no, ni->type,
1087                        (long long)lcn);
1088                /*
1089                 * If this is not the first buffer, remove the
1090                 * buffers in this record from the list of
1091                 * buffers to write and clear their dirty bit
1092                 * if not error -ENOMEM.
1093                 */
1094                if (rec_start_bh != bh) {
1095                    while (bhs[--nr_bhs] != rec_start_bh)
1096                        ;
1097                    if (err2 != -ENOMEM) {
1098                        do {
1099                            clear_buffer_dirty(
1100                                rec_start_bh);
1101                        } while ((rec_start_bh =
1102                                rec_start_bh->
1103                                b_this_page) !=
1104                                bh);
1105                    }
1106                }
1107                continue;
1108            }
1109        }
1110        BUG_ON(!buffer_uptodate(bh));
1111        BUG_ON(nr_bhs >= max_bhs);
1112        bhs[nr_bhs++] = bh;
1113    } while (block++, (bh = bh->b_this_page) != head);
1114    if (unlikely(rl))
1115        up_read(&ni->runlist.lock);
1116    /* If there were no dirty buffers, we are done. */
1117    if (!nr_bhs)
1118        goto done;
1119    /* Map the page so we can access its contents. */
1120    kaddr = kmap(page);
1121    /* Clear the page uptodate flag whilst the mst fixups are applied. */
1122    BUG_ON(!PageUptodate(page));
1123    ClearPageUptodate(page);
1124    for (i = 0; i < nr_bhs; i++) {
1125        unsigned int ofs;
1126
1127        /* Skip buffers which are not at the beginning of records. */
1128        if (i % bhs_per_rec)
1129            continue;
1130        tbh = bhs[i];
1131        ofs = bh_offset(tbh);
1132        if (is_mft) {
1133            ntfs_inode *tni;
1134            unsigned long mft_no;
1135
1136            /* Get the mft record number. */
1137            mft_no = (((s64)page->index << PAGE_CACHE_SHIFT) + ofs)
1138                    >> rec_size_bits;
1139            /* Check whether to write this mft record. */
1140            tni = NULL;
1141            if (!ntfs_may_write_mft_record(vol, mft_no,
1142                    (MFT_RECORD*)(kaddr + ofs), &tni)) {
1143                /*
1144                 * The record should not be written. This
1145                 * means we need to redirty the page before
1146                 * returning.
1147                 */
1148                page_is_dirty = true;
1149                /*
1150                 * Remove the buffers in this mft record from
1151                 * the list of buffers to write.
1152                 */
1153                do {
1154                    bhs[i] = NULL;
1155                } while (++i % bhs_per_rec);
1156                continue;
1157            }
1158            /*
1159             * The record should be written. If a locked ntfs
1160             * inode was returned, add it to the array of locked
1161             * ntfs inodes.
1162             */
1163            if (tni)
1164                locked_nis[nr_locked_nis++] = tni;
1165        }
1166        /* Apply the mst protection fixups. */
1167        err2 = pre_write_mst_fixup((NTFS_RECORD*)(kaddr + ofs),
1168                rec_size);
1169        if (unlikely(err2)) {
1170            if (!err || err == -ENOMEM)
1171                err = -EIO;
1172            ntfs_error(vol->sb, "Failed to apply mst fixups "
1173                    "(inode 0x%lx, attribute type 0x%x, "
1174                    "page index 0x%lx, page offset 0x%x)!"
1175                    " Unmount and run chkdsk.", vi->i_ino,
1176                    ni->type, page->index, ofs);
1177            /*
1178             * Mark all the buffers in this record clean as we do
1179             * not want to write corrupt data to disk.
1180             */
1181            do {
1182                clear_buffer_dirty(bhs[i]);
1183                bhs[i] = NULL;
1184            } while (++i % bhs_per_rec);
1185            continue;
1186        }
1187        nr_recs++;
1188    }
1189    /* If no records are to be written out, we are done. */
1190    if (!nr_recs)
1191        goto unm_done;
1192    flush_dcache_page(page);
1193    /* Lock buffers and start synchronous write i/o on them. */
1194    for (i = 0; i < nr_bhs; i++) {
1195        tbh = bhs[i];
1196        if (!tbh)
1197            continue;
1198        if (!trylock_buffer(tbh))
1199            BUG();
1200        /* The buffer dirty state is now irrelevant, just clean it. */
1201        clear_buffer_dirty(tbh);
1202        BUG_ON(!buffer_uptodate(tbh));
1203        BUG_ON(!buffer_mapped(tbh));
1204        get_bh(tbh);
1205        tbh->b_end_io = end_buffer_write_sync;
1206        submit_bh(WRITE, tbh);
1207    }
1208    /* Synchronize the mft mirror now if not @sync. */
1209    if (is_mft && !sync)
1210        goto do_mirror;
1211do_wait:
1212    /* Wait on i/o completion of buffers. */
1213    for (i = 0; i < nr_bhs; i++) {
1214        tbh = bhs[i];
1215        if (!tbh)
1216            continue;
1217        wait_on_buffer(tbh);
1218        if (unlikely(!buffer_uptodate(tbh))) {
1219            ntfs_error(vol->sb, "I/O error while writing ntfs "
1220                    "record buffer (inode 0x%lx, "
1221                    "attribute type 0x%x, page index "
1222                    "0x%lx, page offset 0x%lx)! Unmount "
1223                    "and run chkdsk.", vi->i_ino, ni->type,
1224                    page->index, bh_offset(tbh));
1225            if (!err || err == -ENOMEM)
1226                err = -EIO;
1227            /*
1228             * Set the buffer uptodate so the page and buffer
1229             * states do not become out of sync.
1230             */
1231            set_buffer_uptodate(tbh);
1232        }
1233    }
1234    /* If @sync, now synchronize the mft mirror. */
1235    if (is_mft && sync) {
1236do_mirror:
1237        for (i = 0; i < nr_bhs; i++) {
1238            unsigned long mft_no;
1239            unsigned int ofs;
1240
1241            /*
1242             * Skip buffers which are not at the beginning of
1243             * records.
1244             */
1245            if (i % bhs_per_rec)
1246                continue;
1247            tbh = bhs[i];
1248            /* Skip removed buffers (and hence records). */
1249            if (!tbh)
1250                continue;
1251            ofs = bh_offset(tbh);
1252            /* Get the mft record number. */
1253            mft_no = (((s64)page->index << PAGE_CACHE_SHIFT) + ofs)
1254                    >> rec_size_bits;
1255            if (mft_no < vol->mftmirr_size)
1256                ntfs_sync_mft_mirror(vol, mft_no,
1257                        (MFT_RECORD*)(kaddr + ofs),
1258                        sync);
1259        }
1260        if (!sync)
1261            goto do_wait;
1262    }
1263    /* Remove the mst protection fixups again. */
1264    for (i = 0; i < nr_bhs; i++) {
1265        if (!(i % bhs_per_rec)) {
1266            tbh = bhs[i];
1267            if (!tbh)
1268                continue;
1269            post_write_mst_fixup((NTFS_RECORD*)(kaddr +
1270                    bh_offset(tbh)));
1271        }
1272    }
1273    flush_dcache_page(page);
1274unm_done:
1275    /* Unlock any locked inodes. */
1276    while (nr_locked_nis-- > 0) {
1277        ntfs_inode *tni, *base_tni;
1278        
1279        tni = locked_nis[nr_locked_nis];
1280        /* Get the base inode. */
1281        mutex_lock(&tni->extent_lock);
1282        if (tni->nr_extents >= 0)
1283            base_tni = tni;
1284        else {
1285            base_tni = tni->ext.base_ntfs_ino;
1286            BUG_ON(!base_tni);
1287        }
1288        mutex_unlock(&tni->extent_lock);
1289        ntfs_debug("Unlocking %s inode 0x%lx.",
1290                tni == base_tni ? "base" : "extent",
1291                tni->mft_no);
1292        mutex_unlock(&tni->mrec_lock);
1293        atomic_dec(&tni->count);
1294        iput(VFS_I(base_tni));
1295    }
1296    SetPageUptodate(page);
1297    kunmap(page);
1298done:
1299    if (unlikely(err && err != -ENOMEM)) {
1300        /*
1301         * Set page error if there is only one ntfs record in the page.
1302         * Otherwise we would loose per-record granularity.
1303         */
1304        if (ni->itype.index.block_size == PAGE_CACHE_SIZE)
1305            SetPageError(page);
1306        NVolSetErrors(vol);
1307    }
1308    if (page_is_dirty) {
1309        ntfs_debug("Page still contains one or more dirty ntfs "
1310                "records. Redirtying the page starting at "
1311                "record 0x%lx.", page->index <<
1312                (PAGE_CACHE_SHIFT - rec_size_bits));
1313        redirty_page_for_writepage(wbc, page);
1314        unlock_page(page);
1315    } else {
1316        /*
1317         * Keep the VM happy. This must be done otherwise the
1318         * radix-tree tag PAGECACHE_TAG_DIRTY remains set even though
1319         * the page is clean.
1320         */
1321        BUG_ON(PageWriteback(page));
1322        set_page_writeback(page);
1323        unlock_page(page);
1324        end_page_writeback(page);
1325    }
1326    if (likely(!err))
1327        ntfs_debug("Done.");
1328    return err;
1329}
1330
1331/**
1332 * ntfs_writepage - write a @page to the backing store
1333 * @page: page cache page to write out
1334 * @wbc: writeback control structure
1335 *
1336 * This is called from the VM when it wants to have a dirty ntfs page cache
1337 * page cleaned. The VM has already locked the page and marked it clean.
1338 *
1339 * For non-resident attributes, ntfs_writepage() writes the @page by calling
1340 * the ntfs version of the generic block_write_full_page() function,
1341 * ntfs_write_block(), which in turn if necessary creates and writes the
1342 * buffers associated with the page asynchronously.
1343 *
1344 * For resident attributes, OTOH, ntfs_writepage() writes the @page by copying
1345 * the data to the mft record (which at this stage is most likely in memory).
1346 * The mft record is then marked dirty and written out asynchronously via the
1347 * vfs inode dirty code path for the inode the mft record belongs to or via the
1348 * vm page dirty code path for the page the mft record is in.
1349 *
1350 * Based on ntfs_readpage() and fs/buffer.c::block_write_full_page().
1351 *
1352 * Return 0 on success and -errno on error.
1353 */
1354static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
1355{
1356    loff_t i_size;
1357    struct inode *vi = page->mapping->host;
1358    ntfs_inode *base_ni = NULL, *ni = NTFS_I(vi);
1359    char *addr;
1360    ntfs_attr_search_ctx *ctx = NULL;
1361    MFT_RECORD *m = NULL;
1362    u32 attr_len;
1363    int err;
1364
1365retry_writepage:
1366    BUG_ON(!PageLocked(page));
1367    i_size = i_size_read(vi);
1368    /* Is the page fully outside i_size? (truncate in progress) */
1369    if (unlikely(page->index >= (i_size + PAGE_CACHE_SIZE - 1) >>
1370            PAGE_CACHE_SHIFT)) {
1371        /*
1372         * The page may have dirty, unmapped buffers. Make them
1373         * freeable here, so the page does not leak.
1374         */
1375        block_invalidatepage(page, 0);
1376        unlock_page(page);
1377        ntfs_debug("Write outside i_size - truncated?");
1378        return 0;
1379    }
1380    /*
1381     * Only $DATA attributes can be encrypted and only unnamed $DATA
1382     * attributes can be compressed. Index root can have the flags set but
1383     * this means to create compressed/encrypted files, not that the
1384     * attribute is compressed/encrypted. Note we need to check for
1385     * AT_INDEX_ALLOCATION since this is the type of both directory and
1386     * index inodes.
1387     */
1388    if (ni->type != AT_INDEX_ALLOCATION) {
1389        /* If file is encrypted, deny access, just like NT4. */
1390        if (NInoEncrypted(ni)) {
1391            unlock_page(page);
1392            BUG_ON(ni->type != AT_DATA);
1393            ntfs_debug("Denying write access to encrypted file.");
1394            return -EACCES;
1395        }
1396        /* Compressed data streams are handled in compress.c. */
1397        if (NInoNonResident(ni) && NInoCompressed(ni)) {
1398            BUG_ON(ni->type != AT_DATA);
1399            BUG_ON(ni->name_len);
1400            // TODO: Implement and replace this with
1401            // return ntfs_write_compressed_block(page);
1402            unlock_page(page);
1403            ntfs_error(vi->i_sb, "Writing to compressed files is "
1404                    "not supported yet. Sorry.");
1405            return -EOPNOTSUPP;
1406        }
1407        // TODO: Implement and remove this check.
1408        if (NInoNonResident(ni) && NInoSparse(ni)) {
1409            unlock_page(page);
1410            ntfs_error(vi->i_sb, "Writing to sparse files is not "
1411                    "supported yet. Sorry.");
1412            return -EOPNOTSUPP;
1413        }
1414    }
1415    /* NInoNonResident() == NInoIndexAllocPresent() */
1416    if (NInoNonResident(ni)) {
1417        /* We have to zero every time due to mmap-at-end-of-file. */
1418        if (page->index >= (i_size >> PAGE_CACHE_SHIFT)) {
1419            /* The page straddles i_size. */
1420            unsigned int ofs = i_size & ~PAGE_CACHE_MASK;
1421            zero_user_segment(page, ofs, PAGE_CACHE_SIZE);
1422        }
1423        /* Handle mst protected attributes. */
1424        if (NInoMstProtected(ni))
1425            return ntfs_write_mst_block(page, wbc);
1426        /* Normal, non-resident data stream. */
1427        return ntfs_write_block(page, wbc);
1428    }
1429    /*
1430     * Attribute is resident, implying it is not compressed, encrypted, or
1431     * mst protected. This also means the attribute is smaller than an mft
1432     * record and hence smaller than a page, so can simply return error on
1433     * any pages with index above 0. Note the attribute can actually be
1434     * marked compressed but if it is resident the actual data is not
1435     * compressed so we are ok to ignore the compressed flag here.
1436     */
1437    BUG_ON(page_has_buffers(page));
1438    BUG_ON(!PageUptodate(page));
1439    if (unlikely(page->index > 0)) {
1440        ntfs_error(vi->i_sb, "BUG()! page->index (0x%lx) > 0. "
1441                "Aborting write.", page->index);
1442        BUG_ON(PageWriteback(page));
1443        set_page_writeback(page);
1444        unlock_page(page);
1445        end_page_writeback(page);
1446        return -EIO;
1447    }
1448    if (!NInoAttr(ni))
1449        base_ni = ni;
1450    else
1451        base_ni = ni->ext.base_ntfs_ino;
1452    /* Map, pin, and lock the mft record. */
1453    m = map_mft_record(base_ni);
1454    if (IS_ERR(m)) {
1455        err = PTR_ERR(m);
1456        m = NULL;
1457        ctx = NULL;
1458        goto err_out;
1459    }
1460    /*
1461     * If a parallel write made the attribute non-resident, drop the mft
1462     * record and retry the writepage.
1463     */
1464    if (unlikely(NInoNonResident(ni))) {
1465        unmap_mft_record(base_ni);
1466        goto retry_writepage;
1467    }
1468    ctx = ntfs_attr_get_search_ctx(base_ni, m);
1469    if (unlikely(!ctx)) {
1470        err = -ENOMEM;
1471        goto err_out;
1472    }
1473    err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
1474            CASE_SENSITIVE, 0, NULL, 0, ctx);
1475    if (unlikely(err))
1476        goto err_out;
1477    /*
1478     * Keep the VM happy. This must be done otherwise the radix-tree tag
1479     * PAGECACHE_TAG_DIRTY remains set even though the page is clean.
1480     */
1481    BUG_ON(PageWriteback(page));
1482    set_page_writeback(page);
1483    unlock_page(page);
1484    attr_len = le32_to_cpu(ctx->attr->data.resident.value_length);
1485    i_size = i_size_read(vi);
1486    if (unlikely(attr_len > i_size)) {
1487        /* Race with shrinking truncate or a failed truncate. */
1488        attr_len = i_size;
1489        /*
1490         * If the truncate failed, fix it up now. If a concurrent
1491         * truncate, we do its job, so it does not have to do anything.
1492         */
1493        err = ntfs_resident_attr_value_resize(ctx->mrec, ctx->attr,
1494                attr_len);
1495        /* Shrinking cannot fail. */
1496        BUG_ON(err);
1497    }
1498    addr = kmap_atomic(page, KM_USER0);
1499    /* Copy the data from the page to the mft record. */
1500    memcpy((u8*)ctx->attr +
1501            le16_to_cpu(ctx->attr->data.resident.value_offset),
1502            addr, attr_len);
1503    /* Zero out of bounds area in the page cache page. */
1504    memset(addr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
1505    kunmap_atomic(addr, KM_USER0);
1506    flush_dcache_page(page);
1507    flush_dcache_mft_record_page(ctx->ntfs_ino);
1508    /* We are done with the page. */
1509    end_page_writeback(page);
1510    /* Finally, mark the mft record dirty, so it gets written back. */
1511    mark_mft_record_dirty(ctx->ntfs_ino);
1512    ntfs_attr_put_search_ctx(ctx);
1513    unmap_mft_record(base_ni);
1514    return 0;
1515err_out:
1516    if (err == -ENOMEM) {
1517        ntfs_warning(vi->i_sb, "Error allocating memory. Redirtying "
1518                "page so we try again later.");
1519        /*
1520         * Put the page back on mapping->dirty_pages, but leave its
1521         * buffers' dirty state as-is.
1522         */
1523        redirty_page_for_writepage(wbc, page);
1524        err = 0;
1525    } else {
1526        ntfs_error(vi->i_sb, "Resident attribute write failed with "
1527                "error %i.", err);
1528        SetPageError(page);
1529        NVolSetErrors(ni->vol);
1530    }
1531    unlock_page(page);
1532    if (ctx)
1533        ntfs_attr_put_search_ctx(ctx);
1534    if (m)
1535        unmap_mft_record(base_ni);
1536    return err;
1537}
1538
1539#endif /* NTFS_RW */
1540
1541/**
1542 * ntfs_aops - general address space operations for inodes and attributes
1543 */
1544const struct address_space_operations ntfs_aops = {
1545    .readpage = ntfs_readpage, /* Fill page with data. */
1546#ifdef NTFS_RW
1547    .writepage = ntfs_writepage, /* Write dirty page to disk. */
1548#endif /* NTFS_RW */
1549    .migratepage = buffer_migrate_page, /* Move a page cache page from
1550                           one physical page to an
1551                           other. */
1552    .error_remove_page = generic_error_remove_page,
1553};
1554
1555/**
1556 * ntfs_mst_aops - general address space operations for mst protecteed inodes
1557 * and attributes
1558 */
1559const struct address_space_operations ntfs_mst_aops = {
1560    .readpage = ntfs_readpage, /* Fill page with data. */
1561#ifdef NTFS_RW
1562    .writepage = ntfs_writepage, /* Write dirty page to disk. */
1563    .set_page_dirty = __set_page_dirty_nobuffers, /* Set the page dirty
1564                           without touching the buffers
1565                           belonging to the page. */
1566#endif /* NTFS_RW */
1567    .migratepage = buffer_migrate_page, /* Move a page cache page from
1568                           one physical page to an
1569                           other. */
1570    .error_remove_page = generic_error_remove_page,
1571};
1572
1573#ifdef NTFS_RW
1574
1575/**
1576 * mark_ntfs_record_dirty - mark an ntfs record dirty
1577 * @page: page containing the ntfs record to mark dirty
1578 * @ofs: byte offset within @page at which the ntfs record begins
1579 *
1580 * Set the buffers and the page in which the ntfs record is located dirty.
1581 *
1582 * The latter also marks the vfs inode the ntfs record belongs to dirty
1583 * (I_DIRTY_PAGES only).
1584 *
1585 * If the page does not have buffers, we create them and set them uptodate.
1586 * The page may not be locked which is why we need to handle the buffers under
1587 * the mapping->private_lock. Once the buffers are marked dirty we no longer
1588 * need the lock since try_to_free_buffers() does not free dirty buffers.
1589 */
1590void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs) {
1591    struct address_space *mapping = page->mapping;
1592    ntfs_inode *ni = NTFS_I(mapping->host);
1593    struct buffer_head *bh, *head, *buffers_to_free = NULL;
1594    unsigned int end, bh_size, bh_ofs;
1595
1596    BUG_ON(!PageUptodate(page));
1597    end = ofs + ni->itype.index.block_size;
1598    bh_size = VFS_I(ni)->i_sb->s_blocksize;
1599    spin_lock(&mapping->private_lock);
1600    if (unlikely(!page_has_buffers(page))) {
1601        spin_unlock(&mapping->private_lock);
1602        bh = head = alloc_page_buffers(page, bh_size, 1);
1603        spin_lock(&mapping->private_lock);
1604        if (likely(!page_has_buffers(page))) {
1605            struct buffer_head *tail;
1606
1607            do {
1608                set_buffer_uptodate(bh);
1609                tail = bh;
1610                bh = bh->b_this_page;
1611            } while (bh);
1612            tail->b_this_page = head;
1613            attach_page_buffers(page, head);
1614        } else
1615            buffers_to_free = bh;
1616    }
1617    bh = head = page_buffers(page);
1618    BUG_ON(!bh);
1619    do {
1620        bh_ofs = bh_offset(bh);
1621        if (bh_ofs + bh_size <= ofs)
1622            continue;
1623        if (unlikely(bh_ofs >= end))
1624            break;
1625        set_buffer_dirty(bh);
1626    } while ((bh = bh->b_this_page) != head);
1627    spin_unlock(&mapping->private_lock);
1628    __set_page_dirty_nobuffers(page);
1629    if (unlikely(buffers_to_free)) {
1630        do {
1631            bh = buffers_to_free->b_this_page;
1632            free_buffer_head(buffers_to_free);
1633            buffers_to_free = bh;
1634        } while (buffers_to_free);
1635    }
1636}
1637
1638#endif /* NTFS_RW */
1639

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