lcnalloc.c

linux 内核源代码

/*
 * lcnalloc.c - Cluster (de)allocation code.  Part of the Linux-NTFS project.
 *
 * Copyright (c) 2004-2005 Anton Altaparmakov
 *
 * 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
 */

#ifdef NTFS_RW

#include <linux/pagemap.h>

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

/**
 * ntfs_cluster_free_from_rl_nolock - free clusters from runlist
 * @vol:	mounted ntfs volume on which to free the clusters
 * @rl:		runlist describing the clusters to free
 *
 * Free all the clusters described by the runlist @rl on the volume @vol.  In
 * the case of an error being returned, at least some of the clusters were not
 * freed.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - The volume lcn bitmap must be locked for writing on entry and is
 *	      left locked on return.
 */
int ntfs_cluster_free_from_rl_nolock(ntfs_volume *vol,
		const runlist_element *rl)
{
	struct inode *lcnbmp_vi = vol->lcnbmp_ino;
	int ret = 0;

	ntfs_debug("Entering.");
	if (!rl)
		return 0;
	for (; rl->length; rl++) {
		int err;

		if (rl->lcn < 0)
			continue;
		err = ntfs_bitmap_clear_run(lcnbmp_vi, rl->lcn, rl->length);
		if (unlikely(err && (!ret || ret == -ENOMEM) && ret != err))
			ret = err;
	}
	ntfs_debug("Done.");
	return ret;
}

/**
 * ntfs_cluster_alloc - allocate clusters on an ntfs volume
 * @vol:	mounted ntfs volume on which to allocate the clusters
 * @start_vcn:	vcn to use for the first allocated cluster
 * @count:	number of clusters to allocate
 * @start_lcn:	starting lcn at which to allocate the clusters (or -1 if none)
 * @zone:	zone from which to allocate the clusters
 * @is_extension:	if 'true', this is an attribute extension
 *
 * Allocate @count clusters preferably starting at cluster @start_lcn or at the
 * current allocator position if @start_lcn is -1, on the mounted ntfs volume
 * @vol. @zone is either DATA_ZONE for allocation of normal clusters or
 * MFT_ZONE for allocation of clusters for the master file table, i.e. the
 * $MFT/$DATA attribute.
 *
 * @start_vcn specifies the vcn of the first allocated cluster.  This makes
 * merging the resulting runlist with the old runlist easier.
 *
 * If @is_extension is 'true', the caller is allocating clusters to extend an
 * attribute and if it is 'false', the caller is allocating clusters to fill a
 * hole in an attribute.  Practically the difference is that if @is_extension
 * is 'true' the returned runlist will be terminated with LCN_ENOENT and if
 * @is_extension is 'false' the runlist will be terminated with
 * LCN_RL_NOT_MAPPED.
 *
 * You need to check the return value with IS_ERR().  If this is false, the
 * function was successful and the return value is a runlist describing the
 * allocated cluster(s).  If IS_ERR() is true, the function failed and
 * PTR_ERR() gives you the error code.
 *
 * Notes on the allocation algorithm
 * =================================
 *
 * There are two data zones.  First is the area between the end of the mft zone
 * and the end of the volume, and second is the area between the start of the
 * volume and the start of the mft zone.  On unmodified/standard NTFS 1.x
 * volumes, the second data zone does not exist due to the mft zone being
 * expanded to cover the start of the volume in order to reserve space for the
 * mft bitmap attribute.
 *
 * This is not the prettiest function but the complexity stems from the need of
 * implementing the mft vs data zoned approach and from the fact that we have
 * access to the lcn bitmap in portions of up to 8192 bytes at a time, so we
 * need to cope with crossing over boundaries of two buffers.  Further, the
 * fact that the allocator allows for caller supplied hints as to the location
 * of where allocation should begin and the fact that the allocator keeps track
 * of where in the data zones the next natural allocation should occur,
 * contribute to the complexity of the function.  But it should all be
 * worthwhile, because this allocator should: 1) be a full implementation of
 * the MFT zone approach used by Windows NT, 2) cause reduction in
 * fragmentation, and 3) be speedy in allocations (the code is not optimized
 * for speed, but the algorithm is, so further speed improvements are probably
 * possible).
 *
 * FIXME: We should be monitoring cluster allocation and increment the MFT zone
 * size dynamically but this is something for the future.  We will just cause
 * heavier fragmentation by not doing it and I am not even sure Windows would
 * grow the MFT zone dynamically, so it might even be correct not to do this.
 * The overhead in doing dynamic MFT zone expansion would be very large and
 * unlikely worth the effort. (AIA)
 *
 * TODO: I have added in double the required zone position pointer wrap around
 * logic which can be optimized to having only one of the two logic sets.
 * However, having the double logic will work fine, but if we have only one of
 * the sets and we get it wrong somewhere, then we get into trouble, so
 * removing the duplicate logic requires _very_ careful consideration of _all_
 * possible code paths.  So at least for now, I am leaving the double logic -
 * better safe than sorry... (AIA)
 *
 * Locking: - The volume lcn bitmap must be unlocked on entry and is unlocked
 *	      on return.
 *	    - This function takes the volume lcn bitmap lock for writing and
 *	      modifies the bitmap contents.
 */
runlist_element *ntfs_cluster_alloc(ntfs_volume *vol, const VCN start_vcn,
		const s64 count, const LCN start_lcn,
		const NTFS_CLUSTER_ALLOCATION_ZONES zone,
		const bool is_extension)
{
	LCN zone_start, zone_end, bmp_pos, bmp_initial_pos, last_read_pos, lcn;
	LCN prev_lcn = 0, prev_run_len = 0, mft_zone_size;
	s64 clusters;
	loff_t i_size;
	struct inode *lcnbmp_vi;
	runlist_element *rl = NULL;
	struct address_space *mapping;
	struct page *page = NULL;
	u8 *buf, *byte;
	int err = 0, rlpos, rlsize, buf_size;
	u8 pass, done_zones, search_zone, need_writeback = 0, bit;

	ntfs_debug("Entering for start_vcn 0x%llx, count 0x%llx, start_lcn "
			"0x%llx, zone %s_ZONE.", (unsigned long long)start_vcn,
			(unsigned long long)count,
			(unsigned long long)start_lcn,
			zone == MFT_ZONE ? "MFT" : "DATA");
	BUG_ON(!vol);
	lcnbmp_vi = vol->lcnbmp_ino;
	BUG_ON(!lcnbmp_vi);
	BUG_ON(start_vcn < 0);
	BUG_ON(count < 0);
	BUG_ON(start_lcn < -1);
	BUG_ON(zone < FIRST_ZONE);
	BUG_ON(zone > LAST_ZONE);

	/* Return NULL if @count is zero. */
	if (!count)
		return NULL;
	/* Take the lcnbmp lock for writing. */
	down_write(&vol->lcnbmp_lock);
	/*
	 * If no specific @start_lcn was requested, use the current data zone
	 * position, otherwise use the requested @start_lcn but make sure it
	 * lies outside the mft zone.  Also set done_zones to 0 (no zones done)
	 * and pass depending on whether we are starting inside a zone (1) or
	 * at the beginning of a zone (2).  If requesting from the MFT_ZONE,
	 * we either start at the current position within the mft zone or at
	 * the specified position.  If the latter is out of bounds then we start
	 * at the beginning of the MFT_ZONE.
	 */
	done_zones = 0;
	pass = 1;
	/*
	 * zone_start and zone_end are the current search range.  search_zone
	 * is 1 for mft zone, 2 for data zone 1 (end of mft zone till end of
	 * volume) and 4 for data zone 2 (start of volume till start of mft
	 * zone).
	 */
	zone_start = start_lcn;
	if (zone_start < 0) {
		if (zone == DATA_ZONE)
			zone_start = vol->data1_zone_pos;
		else
			zone_start = vol->mft_zone_pos;
		if (!zone_start) {
			/*
			 * Zone starts at beginning of volume which means a
			 * single pass is sufficient.
			 */
			pass = 2;
		}
	} else if (zone == DATA_ZONE && zone_start >= vol->mft_zone_start &&
			zone_start < vol->mft_zone_end) {
		zone_start = vol->mft_zone_end;
		/*
		 * Starting at beginning of data1_zone which means a single
		 * pass in this zone is sufficient.
		 */
		pass = 2;
	} else if (zone == MFT_ZONE && (zone_start < vol->mft_zone_start ||
			zone_start >= vol->mft_zone_end)) {
		zone_start = vol->mft_lcn;
		if (!vol->mft_zone_end)
			zone_start = 0;
		/*
		 * Starting at beginning of volume which means a single pass
		 * is sufficient.
		 */
		pass = 2;
	}
	if (zone == MFT_ZONE) {
		zone_end = vol->mft_zone_end;
		search_zone = 1;
	} else /* if (zone == DATA_ZONE) */ {
		/* Skip searching the mft zone. */
		done_zones |= 1;
		if (zone_start >= vol->mft_zone_end) {
			zone_end = vol->nr_clusters;
			search_zone = 2;
		} else {
			zone_end = vol->mft_zone_start;
			search_zone = 4;
		}
	}
	/*
	 * bmp_pos is the current bit position inside the bitmap.  We use
	 * bmp_initial_pos to determine whether or not to do a zone switch.
	 */
	bmp_pos = bmp_initial_pos = zone_start;

	/* Loop until all clusters are allocated, i.e. clusters == 0. */
	clusters = count;
	rlpos = rlsize = 0;
	mapping = lcnbmp_vi->i_mapping;
	i_size = i_size_read(lcnbmp_vi);
	while (1) {
		ntfs_debug("Start of outer while loop: done_zones 0x%x, "
				"search_zone %i, pass %i, zone_start 0x%llx, "
				"zone_end 0x%llx, bmp_initial_pos 0x%llx, "
				"bmp_pos 0x%llx, rlpos %i, rlsize %i.",
				done_zones, search_zone, pass,
				(unsigned long long)zone_start,
				(unsigned long long)zone_end,
				(unsigned long long)bmp_initial_pos,
				(unsigned long long)bmp_pos, rlpos, rlsize);
		/* Loop until we run out of free clusters. */
		last_read_pos = bmp_pos >> 3;
		ntfs_debug("last_read_pos 0x%llx.",
				(unsigned long long)last_read_pos);
		if (last_read_pos > i_size) {
			ntfs_debug("End of attribute reached.  "
					"Skipping to zone_pass_done.");
			goto zone_pass_done;
		}
		if (likely(page)) {
			if (need_writeback) {
				ntfs_debug("Marking page dirty.");
				flush_dcache_page(page);
				set_page_dirty(page);
				need_writeback = 0;
			}
			ntfs_unmap_page(page);
		}
		page = ntfs_map_page(mapping, last_read_pos >>
				PAGE_CACHE_SHIFT);
		if (IS_ERR(page)) {
			err = PTR_ERR(page);
			ntfs_error(vol->sb, "Failed to map page.");
			goto out;
		}
		buf_size = last_read_pos & ~PAGE_CACHE_MASK;
		buf = page_address(page) + buf_size;
		buf_size = PAGE_CACHE_SIZE - buf_size;
		if (unlikely(last_read_pos + buf_size > i_size))
			buf_size = i_size - last_read_pos;
		buf_size <<= 3;
		lcn = bmp_pos & 7;
		bmp_pos &= ~(LCN)7;
		ntfs_debug("Before inner while loop: buf_size %i, lcn 0x%llx, "
				"bmp_pos 0x%llx, need_writeback %i.", buf_size,
				(unsigned long long)lcn,
				(unsigned long long)bmp_pos, need_writeback);
		while (lcn < buf_size && lcn + bmp_pos < zone_end) {
			byte = buf + (lcn >> 3);
			ntfs_debug("In inner while loop: buf_size %i, "
					"lcn 0x%llx, bmp_pos 0x%llx, "
					"need_writeback %i, byte ofs 0x%x, "
					"*byte 0x%x.", buf_size,
					(unsigned long long)lcn,
					(unsigned long long)bmp_pos,
					need_writeback,
					(unsigned int)(lcn >> 3),
					(unsigned int)*byte);
			/* Skip full bytes. */
			if (*byte == 0xff) {
				lcn = (lcn + 8) & ~(LCN)7;
				ntfs_debug("Continuing while loop 1.");
				continue;
			}
			bit = 1 << (lcn & 7);
			ntfs_debug("bit 0x%x.", bit);
			/* If the bit is already set, go onto the next one. */
			if (*byte & bit) {
				lcn++;
				ntfs_debug("Continuing while loop 2.");
				continue;
			}
			/*
			 * Allocate more memory if needed, including space for
			 * the terminator element.
			 * ntfs_malloc_nofs() operates on whole pages only.
			 */
			if ((rlpos + 2) * sizeof(*rl) > rlsize) {
				runlist_element *rl2;

				ntfs_debug("Reallocating memory.");
				if (!rl)
					ntfs_debug("First free bit is at LCN "