The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/aops.c

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    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  */
   59 static 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);
   98                         memset(kaddr + bh_offset(bh) + ofs, 0,
   99                                         bh->b_size - ofs);
  100                         flush_dcache_page(page);
  101                         kunmap_atomic(kaddr);
  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);
  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);
  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;
  162 still_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  */
  185 static 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) {
  268 lock_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                  */
  338 handle_hole:
  339                 bh->b_blocknr = -1UL;
  340                 clear_buffer_mapped(bh);
  341 handle_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  */
  399 static 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 
  411 retry_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);
  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);
  516 put_unm_err_out:
  517         ntfs_attr_put_search_ctx(ctx);
  518 unm_err_out:
  519         unmap_mft_record(base_ni);
  520 done:
  521         SetPageUptodate(page);
  522 err_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  */
  551 static 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) {
  724 lock_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);
  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);
  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  */
  920 static 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) {
 1030 lock_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;
 1211 do_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) {
 1236 do_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);
 1274 unm_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);
 1298 done:
 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  */
 1354 static 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 
 1365 retry_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);
 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);
 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;
 1515 err_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  */
 1544 const 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  */
 1559 const 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  */
 1590 void 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 */

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