path: root/fs/xfs/xfs_buf_item.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_buf_item.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_quota.h"
#include "xfs_dquot_item.h"
#include "xfs_dquot.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"


struct kmem_cache	*xfs_buf_item_cache;

static inline struct xfs_buf_log_item *BUF_ITEM(struct xfs_log_item *lip)
{
	return container_of(lip, struct xfs_buf_log_item, bli_item);
}

/* Is this log iovec plausibly large enough to contain the buffer log format? */
bool
xfs_buf_log_check_iovec(
	struct xfs_log_iovec		*iovec)
{
	struct xfs_buf_log_format	*blfp = iovec->i_addr;
	char				*bmp_end;
	char				*item_end;

	if (offsetof(struct xfs_buf_log_format, blf_data_map) > iovec->i_len)
		return false;

	item_end = (char *)iovec->i_addr + iovec->i_len;
	bmp_end = (char *)&blfp->blf_data_map[blfp->blf_map_size];
	return bmp_end <= item_end;
}

static inline int
xfs_buf_log_format_size(
	struct xfs_buf_log_format *blfp)
{
	return offsetof(struct xfs_buf_log_format, blf_data_map) +
			(blfp->blf_map_size * sizeof(blfp->blf_data_map[0]));
}

static inline bool
xfs_buf_item_straddle(
	struct xfs_buf		*bp,
	uint			offset,
	int			first_bit,
	int			nbits)
{
	void			*first, *last;

	first = xfs_buf_offset(bp, offset + (first_bit << XFS_BLF_SHIFT));
	last = xfs_buf_offset(bp,
			offset + ((first_bit + nbits) << XFS_BLF_SHIFT));

	if (last - first != nbits * XFS_BLF_CHUNK)
		return true;
	return false;
}

/*
 * Return the number of log iovecs and space needed to log the given buf log
 * item segment.
 *
 * It calculates this as 1 iovec for the buf log format structure and 1 for each
 * stretch of non-contiguous chunks to be logged.  Contiguous chunks are logged
 * in a single iovec.
 */
STATIC void
xfs_buf_item_size_segment(
	struct xfs_buf_log_item		*bip,
	struct xfs_buf_log_format	*blfp,
	uint				offset,
	int				*nvecs,
	int				*nbytes)
{
	struct xfs_buf			*bp = bip->bli_buf;
	int				first_bit;
	int				nbits;
	int				next_bit;
	int				last_bit;

	first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size, 0);
	if (first_bit == -1)
		return;

	(*nvecs)++;
	*nbytes += xfs_buf_log_format_size(blfp);

	do {
		nbits = xfs_contig_bits(blfp->blf_data_map,
					blfp->blf_map_size, first_bit);
		ASSERT(nbits > 0);

		/*
		 * Straddling a page is rare because we don't log contiguous
		 * chunks of unmapped buffers anywhere.
		 */
		if (nbits > 1 &&
		    xfs_buf_item_straddle(bp, offset, first_bit, nbits))
			goto slow_scan;

		(*nvecs)++;
		*nbytes += nbits * XFS_BLF_CHUNK;

		/*
		 * This takes the bit number to start looking from and
		 * returns the next set bit from there.  It returns -1
		 * if there are no more bits set or the start bit is
		 * beyond the end of the bitmap.
		 */
		first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size,
					(uint)first_bit + nbits + 1);
	} while (first_bit != -1);

	return;

slow_scan:
	/* Count the first bit we jumped out of the above loop from */
	(*nvecs)++;
	*nbytes += XFS_BLF_CHUNK;
	last_bit = first_bit;
	while (last_bit != -1) {
		/*
		 * This takes the bit number to start looking from and
		 * returns the next set bit from there.  It returns -1
		 * if there are no more bits set or the start bit is
		 * beyond the end of the bitmap.
		 */
		next_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size,
					last_bit + 1);
		/*
		 * If we run out of bits, leave the loop,
		 * else if we find a new set of bits bump the number of vecs,
		 * else keep scanning the current set of bits.
		 */
		if (next_bit == -1) {
			break;
		} else if (next_bit != last_bit + 1 ||
		           xfs_buf_item_straddle(bp, offset, first_bit, nbits)) {
			last_bit = next_bit;
			first_bit = next_bit;
			(*nvecs)++;
			nbits = 1;
		} else {
			last_bit++;
			nbits++;
		}
		*nbytes += XFS_BLF_CHUNK;
	}
}

/*
 * Return the number of log iovecs and space needed to log the given buf log
 * item.
 *
 * Discontiguous buffers need a format structure per region that is being
 * logged. This makes the changes in the buffer appear to log recovery as though
 * they came from separate buffers, just like would occur if multiple buffers
 * were used instead of a single discontiguous buffer. This enables
 * discontiguous buffers to be in-memory constructs, completely transparent to
 * what ends up on disk.
 *
 * If the XFS_BLI_STALE flag has been set, then log nothing but the buf log
 * format structures. If the item has previously been logged and has dirty
 * regions, we do not relog them in stale buffers. This has the effect of
 * reducing the size of the relogged item by the amount of dirty data tracked
 * by the log item. This can result in the committing transaction reducing the
 * amount of space being consumed by the CIL.
 */
STATIC void
xfs_buf_item_size(
	struct xfs_log_item