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[reactos.git] / reactos / drivers / fs / ntfs / linux-ntfs / mft.c

/**
 * mft.c - NTFS kernel mft record operations. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2001-2003 Anton Altaparmakov
 * Copyright (c) 2002 Richard Russon
 *
 * This program/include file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program/include file is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/swap.h>

#include "ntfs.h"

/**
 * __format_mft_record - initialize an empty mft record
 * @m:          mapped, pinned and locked for writing mft record
 * @size:       size of the mft record
 * @rec_no:     mft record number / inode number
 *
 * Private function to initialize an empty mft record. Use one of the two
 * provided format_mft_record() functions instead.
 */
static void __format_mft_record(MFT_RECORD *m, const int size,
                const unsigned long rec_no)
{
        ATTR_RECORD *a;

        memset(m, 0, size);
        m->magic = magic_FILE;
        /* Aligned to 2-byte boundary. */
        m->usa_ofs = cpu_to_le16((sizeof(MFT_RECORD) + 1) & ~1);
        m->usa_count = cpu_to_le16(size / NTFS_BLOCK_SIZE + 1);
        /* Set the update sequence number to 1. */
        *(u16*)((char*)m + ((sizeof(MFT_RECORD) + 1) & ~1)) = cpu_to_le16(1);
        m->lsn = cpu_to_le64(0LL);
        m->sequence_number = cpu_to_le16(1);
        m->link_count = cpu_to_le16(0);
        /* Aligned to 8-byte boundary. */
        m->attrs_offset = cpu_to_le16((le16_to_cpu(m->usa_ofs) +
                        (le16_to_cpu(m->usa_count) << 1) + 7) & ~7);
        m->flags = cpu_to_le16(0);
        /*
         * Using attrs_offset plus eight bytes (for the termination attribute),
         * aligned to 8-byte boundary.
         */
        m->bytes_in_use = cpu_to_le32((le16_to_cpu(m->attrs_offset) + 8 + 7) &
                        ~7);
        m->bytes_allocated = cpu_to_le32(size);
        m->base_mft_record = cpu_to_le64((MFT_REF)0);
        m->next_attr_instance = cpu_to_le16(0);
        a = (ATTR_RECORD*)((char*)m + le16_to_cpu(m->attrs_offset));
        a->type = AT_END;
        a->length = cpu_to_le32(0);
}

/**
 * format_mft_record - initialize an empty mft record
 * @ni:         ntfs inode of mft record
 * @mft_rec:    mapped, pinned and locked mft record (optional)
 *
 * Initialize an empty mft record. This is used when extending the MFT.
 *
 * If @mft_rec is NULL, we call map_mft_record() to obtain the
 * record and we unmap it again when finished.
 *
 * We return 0 on success or -errno on error.
 */
int format_mft_record(ntfs_inode *ni, MFT_RECORD *mft_rec)
{
        MFT_RECORD *m;

        if (mft_rec)
                m = mft_rec;
        else {
                m = map_mft_record(ni);
                if (IS_ERR(m))
                        return PTR_ERR(m);
        }
        __format_mft_record(m, ni->vol->mft_record_size, ni->mft_no);
        if (!mft_rec) {
                // FIXME: Need to set the mft record dirty!
                unmap_mft_record(ni);
        }
        return 0;
}

/**
 * ntfs_readpage - external declaration, function is in fs/ntfs/aops.c
 */
extern int ntfs_readpage(struct file *, struct page *);

/**
 * ntfs_mft_aops - address space operations for access to $MFT
 *
 * Address space operations for access to $MFT. This allows us to simply use
 * ntfs_map_page() in map_mft_record_page().
 */
struct address_space_operations ntfs_mft_aops = {
        .readpage       = ntfs_readpage,        /* Fill page with data. */
        .sync_page      = block_sync_page,      /* Currently, just unplugs the
                                                   disk request queue. */
};

/**
 * map_mft_record_page - map the page in which a specific mft record resides
 * @ni:         ntfs inode whose mft record page to map
 *
 * This maps the page in which the mft record of the ntfs inode @ni is situated
 * and returns a pointer to the mft record within the mapped page.
 *
 * Return value needs to be checked with IS_ERR() and if that is true PTR_ERR()
 * contains the negative error code returned.
 */
static inline MFT_RECORD *map_mft_record_page(ntfs_inode *ni)
{
        ntfs_volume *vol = ni->vol;
        struct inode *mft_vi = vol->mft_ino;
        struct page *page;
        unsigned long index, ofs, end_index;

        BUG_ON(ni->page);
        /*
         * The index into the page cache and the offset within the page cache
         * page of the wanted mft record. FIXME: We need to check for
         * overflowing the unsigned long, but I don't think we would ever get
         * here if the volume was that big...
         */
        index = ni->mft_no << vol->mft_record_size_bits >> PAGE_CACHE_SHIFT;
        ofs = (ni->mft_no << vol->mft_record_size_bits) & ~PAGE_CACHE_MASK;

        /* The maximum valid index into the page cache for $MFT's data. */
        end_index = mft_vi->i_size >> PAGE_CACHE_SHIFT;

        /* If the wanted index is out of bounds the mft record doesn't exist. */
        if (unlikely(index >= end_index)) {
                if (index > end_index || (mft_vi->i_size & ~PAGE_CACHE_MASK) <
                                ofs + vol->mft_record_size) {
                        page = ERR_PTR(-ENOENT);
                        goto err_out;
                }
        }
        /* Read, map, and pin the page. */
        page = ntfs_map_page(mft_vi->i_mapping, index);
        if (likely(!IS_ERR(page))) {
                ni->page = page;
                ni->page_ofs = ofs;
                return page_address(page) + ofs;
        }
err_out:
        ni->page = NULL;
        ni->page_ofs = 0;
        ntfs_error(vol->sb, "Failed with error code %lu.", -PTR_ERR(page));
        return (void*)page;
}

/**
 * map_mft_record - map, pin and lock an mft record
 * @ni:         ntfs inode whose MFT record to map
 *
 * First, take the mrec_lock semaphore. We might now be sleeping, while waiting
 * for the semaphore if it was already locked by someone else.
 *
 * The page of the record is mapped using map_mft_record_page() before being
 * returned to the caller.
 *
 * This in turn uses ntfs_map_page() to get the page containing the wanted mft
 * record (it in turn calls read_cache_page() which reads it in from disk if
 * necessary, increments the use count on the page so that it cannot disappear
 * under us and returns a reference to the page cache page).
 *
 * If read_cache_page() invokes ntfs_readpage() to load the page from disk, it
 * sets PG_locked and clears PG_uptodate on the page. Once I/O has completed
 * and the post-read mst fixups on each mft record in the page have been
 * performed, the page gets PG_uptodate set and PG_locked cleared (this is done
 * in our asynchronous I/O completion handler end_buffer_read_mft_async()).
 * ntfs_map_page() waits for PG_locked to become clear and checks if
 * PG_uptodate is set and returns an error code if not. This provides
 * sufficient protection against races when reading/using the page.
 *
 * However there is the write mapping to think about. Doing the above described
 * checking here will be fine, because when initiating the write we will set
 * PG_locked and clear PG_uptodate making sure nobody is touching the page
 * contents. Doing the locking this way means that the commit to disk code in
 * the page cache code paths is automatically sufficiently locked with us as
 * we will not touch a page that has been locked or is not uptodate. The only
 * locking problem then is them locking the page while we are accessing it.
 *
 * So that code will end up having to own the mrec_lock of all mft
 * records/inodes present in the page before I/O can proceed. In that case we
 * wouldn't need to bother with PG_locked and PG_uptodate as nobody will be
 * accessing anything without owning the mrec_lock semaphore. But we do need
 * to use them because of the read_cache_page() invocation and the code becomes
 * so much simpler this way that it is well worth it.
 *
 * The mft record is now ours and we return a pointer to it. You need to check
 * the returned pointer with IS_ERR() and if that is true, PTR_ERR() will return
 * the error code.
 *
 * NOTE: Caller is responsible for setting the mft record dirty before calling
 * unmap_mft_record(). This is obviously only necessary if the caller really
 * modified the mft record...
 * Q: Do we want to recycle one of the VFS inode state bits instead?
 * A: No, the inode ones mean we want to change the mft record, not we want to
 * write it out.
 */
MFT_RECORD *map_mft_record(ntfs_inode *ni)
{
        MFT_RECORD *m;

        ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

        /* Make sure the ntfs inode doesn't go away. */
        atomic_inc(&ni->count);

        /* Serialize access to this mft record. */
        down(&ni->mrec_lock);

        m = map_mft_record_page(ni);
        if (likely(!IS_ERR(m)))
                return m;

        up(&ni->mrec_lock);
        atomic_dec(&ni->count);
        ntfs_error(ni->vol->sb, "Failed with error code %lu.", -PTR_ERR(m));
        return m;
}

/**
 * unmap_mft_record_page - unmap the page in which a specific mft record resides
 * @ni:         ntfs inode whose mft record page to unmap
 *
 * This unmaps the page in which the mft record of the ntfs inode @ni is
 * situated and returns. This is a NOOP if highmem is not configured.
 *
 * The unmap happens via ntfs_unmap_page() which in turn decrements the use
 * count on the page thus releasing it from the pinned state.
 *
 * We do not actually unmap the page from memory of course, as that will be
 * done by the page cache code itself when memory pressure increases or
 * whatever.
 */
static inline void unmap_mft_record_page(ntfs_inode *ni)
{
        BUG_ON(!ni->page);

        // TODO: If dirty, blah...
        ntfs_unmap_page(ni->page);
        ni->page = NULL;
        ni->page_ofs = 0;
        return;
}

/**
 * unmap_mft_record - release a mapped mft record
 * @ni:         ntfs inode whose MFT record to unmap
 *
 * We release the page mapping and the mrec_lock mutex which unmaps the mft
 * record and releases it for others to get hold of. We also release the ntfs
 * inode by decrementing the ntfs inode reference count.
 *
 * NOTE: If caller has modified the mft record, it is imperative to set the mft
 * record dirty BEFORE calling unmap_mft_record().
 */
void unmap_mft_record(ntfs_inode *ni)
{
        struct page *page = ni->page;

        BUG_ON(!page);

        ntfs_debug("Entering for mft_no 0x%lx.", ni->mft_no);

        unmap_mft_record_page(ni);
        up(&ni->mrec_lock);
        atomic_dec(&ni->count);
        /*
         * If pure ntfs_inode, i.e. no vfs inode attached, we leave it to
         * ntfs_clear_extent_inode() in the extent inode case, and to the
         * caller in the non-extent, yet pure ntfs inode case, to do the actual
         * tear down of all structures and freeing of all allocated memory.
         */
        return;
}

/**
 * map_extent_mft_record - load an extent inode and attach it to its base
 * @base_ni:    base ntfs inode
 * @mref:       mft reference of the extent inode to load (in little endian)
 * @ntfs_ino:   on successful return, pointer to the ntfs_inode structure
 *
 * Load the extent mft record @mref and attach it to its base inode @base_ni.
 * Return the mapped extent mft record if IS_ERR(result) is false. Otherwise
 * PTR_ERR(result) gives the negative error code.
 *
 * On successful return, @ntfs_ino contains a pointer to the ntfs_inode
 * structure of the mapped extent inode.
 */
MFT_RECORD *map_extent_mft_record(ntfs_inode *base_ni, MFT_REF mref,
                ntfs_inode **ntfs_ino)
{
        MFT_RECORD *m;
        ntfs_inode *ni = NULL;
        ntfs_inode **extent_nis = NULL;
        int i;
        unsigned long mft_no = MREF_LE(mref);
        u16 seq_no = MSEQNO_LE(mref);
        BOOL destroy_ni = FALSE;

        ntfs_debug("Mapping extent mft record 0x%lx (base mft record 0x%lx).",
                        mft_no, base_ni->mft_no);
        /* Make sure the base ntfs inode doesn't go away. */
        atomic_inc(&base_ni->count);
        /*
         * Check if this extent inode has already been added to the base inode,
         * in which case just return it. If not found, add it to the base
         * inode before returning it.
         */
        down(&base_ni->extent_lock);
        if (base_ni->nr_extents > 0) {
                extent_nis = base_ni->ext.extent_ntfs_inos;
                for (i = 0; i < base_ni->nr_extents; i++) {
                        if (mft_no != extent_nis[i]->mft_no)
                                continue;
                        ni = extent_nis[i];
                        /* Make sure the ntfs inode doesn't go away. */
                        atomic_inc(&ni->count);
                        break;
                }
        }
        if (likely(ni != NULL)) {
                up(&base_ni->extent_lock);
                atomic_dec(&base_ni->count);
                /* We found the record; just have to map and return it. */
                m = map_mft_record(ni);
                /* map_mft_record() has incremented this on success. */
                atomic_dec(&ni->count);
                if (likely(!IS_ERR(m))) {
                        /* Verify the sequence number. */
                        if (likely(le16_to_cpu(m->sequence_number) == seq_no)) {
                                ntfs_debug("Done 1.");
                                *ntfs_ino = ni;
                                return m;
                        }
                        unmap_mft_record(ni);
                        ntfs_error(base_ni->vol->sb, "Found stale extent mft "
                                        "reference! Corrupt file system. "
                                        "Run chkdsk.");
                        return ERR_PTR(-EIO);
                }
map_err_out:
                ntfs_error(base_ni->vol->sb, "Failed to map extent "
                                "mft record, error code %ld.", -PTR_ERR(m));
                return m;
        }
        /* Record wasn't there. Get a new ntfs inode and initialize it. */
        ni = ntfs_new_extent_inode(base_ni->vol->sb, mft_no);
        if (unlikely(!ni)) {
                up(&base_ni->extent_lock);
                atomic_dec(&base_ni->count);
                return ERR_PTR(-ENOMEM);
        }
        ni->vol = base_ni->vol;
        ni->seq_no = seq_no;
        ni->nr_extents = -1;
        ni->ext.base_ntfs_ino = base_ni;
        /* Now map the record. */
        m = map_mft_record(ni);
        if (unlikely(IS_ERR(m))) {
                up(&base_ni->extent_lock);
                atomic_dec(&base_ni->count);
                ntfs_clear_extent_inode(ni);
                goto map_err_out;
        }
        /* Verify the sequence number. */
        if (unlikely(le16_to_cpu(m->sequence_number) != seq_no)) {
                ntfs_error(base_ni->vol->sb, "Found stale extent mft "
                                "reference! Corrupt file system. Run chkdsk.");
                destroy_ni = TRUE;
                m = ERR_PTR(-EIO);
                goto unm_err_out;
        }
        /* Attach extent inode to base inode, reallocating memory if needed. */
        if (!(base_ni->nr_extents & 3)) {
                ntfs_inode **tmp;
                int new_size = (base_ni->nr_extents + 4) * sizeof(ntfs_inode *);

                tmp = (ntfs_inode **)kmalloc(new_size, GFP_NOFS);
                if (unlikely(!tmp)) {
                        ntfs_error(base_ni->vol->sb, "Failed to allocate "
                                        "internal buffer.");
                        destroy_ni = TRUE;
                        m = ERR_PTR(-ENOMEM);
                        goto unm_err_out;
                }
                if (base_ni->ext.extent_ntfs_inos) {
                        memcpy(tmp, base_ni->ext.extent_ntfs_inos, new_size -
                                        4 * sizeof(ntfs_inode *));
                        kfree(base_ni->ext.extent_ntfs_inos);
                }
                base_ni->ext.extent_ntfs_inos = tmp;
        }
        base_ni->ext.extent_ntfs_inos[base_ni->nr_extents++] = ni;
        up(&base_ni->extent_lock);
        atomic_dec(&base_ni->count);
        ntfs_debug("Done 2.");
        *ntfs_ino = ni;
        return m;
unm_err_out:
        unmap_mft_record(ni);
        up(&base_ni->extent_lock);
        atomic_dec(&base_ni->count);
        /*
         * If the extent inode was not attached to the base inode we need to
         * release it or we will leak memory.
         */
        if (destroy_ni)
                ntfs_clear_extent_inode(ni);
        return m;
}