C++ page_has_buffers函数代码示例

static int __gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc)
{
	struct inode *inode = page->mapping->host;
	struct gfs2_inode *ip = GFS2_I(inode);
	struct gfs2_sbd *sdp = GFS2_SB(inode);

	if (PageChecked(page)) {
		ClearPageChecked(page);
		if (!page_has_buffers(page)) {
			create_empty_buffers(page, inode->i_sb->s_blocksize,
					     (1 << BH_Dirty)|(1 << BH_Uptodate));
		}
		gfs2_page_add_databufs(ip, page, 0, sdp->sd_vfs->s_blocksize-1);
	}
	return block_write_full_page(page, gfs2_get_block_noalloc, wbc);
}

int nilfs_copy_dirty_pages(struct address_space *dmap,
			   struct address_space *smap)
{
	struct pagevec pvec;
	unsigned int i;
	pgoff_t index = 0;
	int err = 0;

	pagevec_init(&pvec, 0);
repeat:
	if (!pagevec_lookup_tag(&pvec, smap, &index, PAGECACHE_TAG_DIRTY,
				PAGEVEC_SIZE))
		return 0;

	for (i = 0; i < pagevec_count(&pvec); i++) {
		struct page *page = pvec.pages[i], *dpage;

		lock_page(page);
		if (unlikely(!PageDirty(page)))
			NILFS_PAGE_BUG(page, "inconsistent dirty state");

		dpage = grab_cache_page(dmap, page->index);
		if (unlikely(!dpage)) {
			/* No empty page is added to the page cache */
			err = -ENOMEM;
			unlock_page(page);
			break;
		}
		if (unlikely(!page_has_buffers(page)))
			NILFS_PAGE_BUG(page,
				       "found empty page in dat page cache");

		nilfs_copy_page(dpage, page, 1);
		__set_page_dirty_nobuffers(dpage);

		unlock_page(dpage);
		page_cache_release(dpage);
		unlock_page(page);
	}
	pagevec_release(&pvec);
	cond_resched();

	if (likely(!err))
		goto repeat;
	return err;
}

static int gfs2_ordered_writepage(struct page *page,
				  struct writeback_control *wbc)
{
	struct inode *inode = page->mapping->host;
	struct gfs2_inode *ip = GFS2_I(inode);
	int ret;

	ret = gfs2_writepage_common(page, wbc);
	if (ret <= 0)
		return ret;

	if (!page_has_buffers(page)) {
		create_empty_buffers(page, inode->i_sb->s_blocksize,
				     (1 << BH_Dirty)|(1 << BH_Uptodate));
	}
	gfs2_page_add_databufs(ip, page, 0, inode->i_sb->s_blocksize-1);
	return block_write_full_page(page, gfs2_get_block_noalloc, wbc);
}

static struct buffer_head *
__nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
		       int blkbits, unsigned long b_state)

{
	unsigned long first_block;
	struct buffer_head *bh;

	if (!page_has_buffers(page))
		create_empty_buffers(page, 1 << blkbits, b_state);

	first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
	bh = nilfs_page_get_nth_block(page, block - first_block);

	touch_buffer(bh);
	wait_on_buffer(bh);
	return bh;
}

struct buffer_head *gfs2_getbuf(struct gfs2_glock *gl, u64 blkno, int create)
{
	struct address_space *mapping = gl->gl_aspace->i_mapping;
	struct gfs2_sbd *sdp = gl->gl_sbd;
	struct page *page;
	struct buffer_head *bh;
	unsigned int shift;
	unsigned long index;
	unsigned int bufnum;

	shift = PAGE_CACHE_SHIFT - sdp->sd_sb.sb_bsize_shift;
	index = blkno >> shift;             /* convert block to page */
	bufnum = blkno - (index << shift);  /* block buf index within page */

	if (create) {
		for (;;) {
			page = grab_cache_page(mapping, index);
			if (page)
				break;
			yield();
		}
	} else {
		page = find_lock_page(mapping, index);
		if (!page)
			return NULL;
	}

	if (!page_has_buffers(page))
		create_empty_buffers(page, sdp->sd_sb.sb_bsize, 0);

	/* Locate header for our buffer within our page */
	for (bh = page_buffers(page); bufnum--; bh = bh->b_this_page)
		/* Do nothing */;
	get_bh(bh);

	if (!buffer_mapped(bh))
		map_bh(bh, sdp->sd_vfs, blkno);

	unlock_page(page);
	mark_page_accessed(page);
	page_cache_release(page);

	return bh;
}

/**
 * nilfs_copy_page -- copy the page with buffers
 * @dst: destination page
 * @src: source page
 * @copy_dirty: flag whether to copy dirty states on the page's buffer heads.
 *
 * This function is for both data pages and btnode pages.  The dirty flag
 * should be treated by caller.  The page must not be under i/o.
 * Both src and dst page must be locked
 */
static void nilfs_copy_page(struct page *dst, struct page *src, int copy_dirty)
{
	struct buffer_head *dbh, *dbufs, *sbh, *sbufs;
	unsigned long mask = NILFS_BUFFER_INHERENT_BITS;

	BUG_ON(PageWriteback(dst));

	sbh = sbufs = page_buffers(src);
	if (!page_has_buffers(dst))
		create_empty_buffers(dst, sbh->b_size, 0);

	if (copy_dirty)
		mask |= BIT(BH_Dirty);

	dbh = dbufs = page_buffers(dst);
	do {
		lock_buffer(sbh);
		lock_buffer(dbh);
		dbh->b_state = sbh->b_state & mask;
		dbh->b_blocknr = sbh->b_blocknr;
		dbh->b_bdev = sbh->b_bdev;
		sbh = sbh->b_this_page;
		dbh = dbh->b_this_page;
	} while (dbh != dbufs);

	copy_highpage(dst, src);

	if (PageUptodate(src) && !PageUptodate(dst))
		SetPageUptodate(dst);
	else if (!PageUptodate(src) && PageUptodate(dst))
		ClearPageUptodate(dst);
	if (PageMappedToDisk(src) && !PageMappedToDisk(dst))
		SetPageMappedToDisk(dst);
	else if (!PageMappedToDisk(src) && PageMappedToDisk(dst))
		ClearPageMappedToDisk(dst);

	do {
		unlock_buffer(sbh);
		unlock_buffer(dbh);
		sbh = sbh->b_this_page;
		dbh = dbh->b_this_page;
	} while (dbh != dbufs);
}

void
xfs_page_trace(
	int		tag,
	struct inode	*inode,
	struct page	*page,
	int		mask)
{
	xfs_inode_t	*ip;
	bhv_desc_t	*bdp;
	vnode_t		*vp = LINVFS_GET_VP(inode);
	loff_t		isize = i_size_read(inode);
	loff_t		offset = page->index << PAGE_CACHE_SHIFT;
	int		delalloc = -1, unmapped = -1, unwritten = -1;

	if (page_has_buffers(page))
		xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);

	bdp = vn_bhv_lookup(VN_BHV_HEAD(vp), &xfs_vnodeops);
	ip = XFS_BHVTOI(bdp);
	if (!ip->i_rwtrace)
		return;

	ktrace_enter(ip->i_rwtrace,
		(void *)((unsigned long)tag),
		(void *)ip,
		(void *)inode,
		(void *)page,
		(void *)((unsigned long)mask),
		(void *)((unsigned long)((ip->i_d.di_size >> 32) & 0xffffffff)),
		(void *)((unsigned long)(ip->i_d.di_size & 0xffffffff)),
		(void *)((unsigned long)((isize >> 32) & 0xffffffff)),
		(void *)((unsigned long)(isize & 0xffffffff)),
		(void *)((unsigned long)((offset >> 32) & 0xffffffff)),
		(void *)((unsigned long)(offset & 0xffffffff)),
		(void *)((unsigned long)delalloc),
		(void *)((unsigned long)unmapped),
		(void *)((unsigned long)unwritten),
		(void *)NULL,
		(void *)NULL);
}

/**
 * nilfs_clear_dirty_page - discard dirty page
 * @page: dirty page that will be discarded
 * @silent: suppress [true] or print [false] warning messages
 */
void nilfs_clear_dirty_page(struct page *page, bool silent)
{
	struct inode *inode = page->mapping->host;
	struct super_block *sb = inode->i_sb;

	BUG_ON(!PageLocked(page));

	if (!silent) {
		nilfs_warning(sb, __func__,
				"discard page: offset %lld, ino %lu",
				page_offset(page), inode->i_ino);
	}

	ClearPageUptodate(page);
	ClearPageMappedToDisk(page);

	if (page_has_buffers(page)) {
		struct buffer_head *bh, *head;

		bh = head = page_buffers(page);
		do {
			lock_buffer(bh);
			if (!silent) {
				nilfs_warning(sb, __func__,
					"discard block %llu, size %zu",
					(u64)bh->b_blocknr, bh->b_size);
			}
			clear_buffer_async_write(bh);
			clear_buffer_dirty(bh);
			clear_buffer_nilfs_volatile(bh);
			clear_buffer_nilfs_checked(bh);
			clear_buffer_nilfs_redirected(bh);
			clear_buffer_uptodate(bh);
			clear_buffer_mapped(bh);
			unlock_buffer(bh);
		} while (bh = bh->b_this_page, bh != head);
	}

	__nilfs_clear_page_dirty(page);
}

static inline void print_buffers(struct page *page, sector_t block)
{
	struct buffer_head *bh, *head;

	if(!page_has_buffers(page)) {
		printk("Warning: page doesn't have buffers, not sure how that happened, allocating buffer !!!\n");
		create_empty_buffers(page, LFS_BSIZE, 0);
		bh = head = page_buffers(page);
		do {
			map_bh(bh, page->mapping->host->i_sb, block++); 
			bh = bh->b_this_page;
		} while(bh != head);
	}

	bh = head = page_buffers(page);
	do {
		if(!buffer_mapped(bh))
			dprintk("The buffer seems to be not mapped ??");
		//dprintk("mapped to blocknr = %Lu\n", bh->b_blocknr);
		bh = bh->b_this_page;
	} while(bh != head);
}

static int tux3_set_page_dirty_assert(struct page *page)
{
	struct buffer_head *head, *buffer;

	/* See comment of tux3_set_page_dirty() */
	ClearPageReclaim(page);

	/* Is there any cases to be called for old page of forked page? */
	WARN_ON(PageForked(page));

	/* This page should be dirty already, otherwise we will lost data. */
	assert(PageDirty(page));
	/* All buffers should be dirty already, otherwise we will lost data. */
	assert(page_has_buffers(page));
	head = buffer = page_buffers(page);
	do {
		assert(buffer_dirty(buffer));
		buffer = buffer->b_this_page;
	} while (buffer != head);

	return 0;
}

/**
 * nilfs_clear_dirty_page - discard dirty page
 * @page: dirty page that will be discarded
 * @silent: suppress [true] or print [false] warning messages
 */
void nilfs_clear_dirty_page(struct page *page, bool silent)
{
	struct inode *inode = page->mapping->host;
	struct super_block *sb = inode->i_sb;

	BUG_ON(!PageLocked(page));

	if (!silent) {
		nilfs_warning(sb, __func__,
				"discard page: offset %lld, ino %lu",
				page_offset(page), inode->i_ino);
	}

	ClearPageUptodate(page);
	ClearPageMappedToDisk(page);

	if (page_has_buffers(page)) {
		struct buffer_head *bh, *head;
		const unsigned long clear_bits =
			(1 << BH_Uptodate | 1 << BH_Dirty | 1 << BH_Mapped |
			 1 << BH_Async_Write | 1 << BH_NILFS_Volatile |
			 1 << BH_NILFS_Checked | 1 << BH_NILFS_Redirected);

		bh = head = page_buffers(page);
		do {
			lock_buffer(bh);
			if (!silent) {
				nilfs_warning(sb, __func__,
					"discard block %llu, size %zu",
					(u64)bh->b_blocknr, bh->b_size);
			}
			set_mask_bits(&bh->b_state, clear_bits, 0);
			unlock_buffer(bh);
		} while (bh = bh->b_this_page, bh != head);
	}

	__nilfs_clear_page_dirty(page);
}

static void gfs2_invalidatepage(struct page *page, unsigned long offset)
{
	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
	struct buffer_head *bh, *head;
	unsigned long pos = 0;

	BUG_ON(!PageLocked(page));
	if (offset == 0)
		ClearPageChecked(page);
	if (!page_has_buffers(page))
		goto out;

	bh = head = page_buffers(page);
	do {
		if (offset <= pos)
			gfs2_discard(sdp, bh);
		pos += bh->b_size;
		bh = bh->b_this_page;
	} while (bh != head);
out:
	if (offset == 0)
		try_to_release_page(page, 0);
}

/**
 * nilfs_clear_dirty_page - discard dirty page
 * @page: dirty page that will be discarded
 * @silent: suppress [true] or print [false] warning messages
 */
void nilfs_clear_dirty_page(struct page *page, bool silent)
{
	struct inode *inode = page->mapping->host;
	struct super_block *sb = inode->i_sb;

	BUG_ON(!PageLocked(page));

	if (!silent)
		nilfs_msg(sb, KERN_WARNING,
			  "discard dirty page: offset=%lld, ino=%lu",
			  page_offset(page), inode->i_ino);

	ClearPageUptodate(page);
	ClearPageMappedToDisk(page);

	if (page_has_buffers(page)) {
		struct buffer_head *bh, *head;
		const unsigned long clear_bits =
			(BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
			 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
			 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));

		bh = head = page_buffers(page);
		do {
			lock_buffer(bh);
			if (!silent)
				nilfs_msg(sb, KERN_WARNING,
					  "discard dirty block: blocknr=%llu, size=%zu",
					  (u64)bh->b_blocknr, bh->b_size);

			set_mask_bits(&bh->b_state, clear_bits, 0);
			unlock_buffer(bh);
		} while (bh = bh->b_this_page, bh != head);
	}

	__nilfs_clear_page_dirty(page);
}

/*
 * We have our BIO, so we can now mark the buffers clean.  Make
 * sure to only clean buffers which we know we'll be writing.
 */
static void clean_buffers(struct page *page, unsigned first_unmapped)
{
	unsigned buffer_counter = 0;
	struct buffer_head *bh, *head;
	if (!page_has_buffers(page))
		return;
	head = page_buffers(page);
	bh = head;

	do {
		if (buffer_counter++ == first_unmapped)
			break;
		clear_buffer_dirty(bh);
		bh = bh->b_this_page;
	} while (bh != head);

	/*
	 * we cannot drop the bh if the page is not uptodate or a concurrent
	 * readpage would fail to serialize with the bh and it would read from
	 * disk before we reach the platter.
	 */
	if (buffer_heads_over_limit && PageUptodate(page))
		try_to_free_buffers(page);
}

/**
 * sync_mft_mirror - synchronize an mft record to the mft mirror
 * @ni:		ntfs inode whose mft record to synchronize
 * @m:		mapped, mst protected (extent) mft record to synchronize
 * @sync:	if true, wait for i/o completion
 *
 * Write the mapped, mst protected (extent) mft record @m described by the
 * (regular or extent) ntfs inode @ni to the mft mirror ($MFTMirr).
 *
 * On success return 0.  On error return -errno and set the volume errors flag
 * in the ntfs_volume to which @ni belongs.
 *
 * NOTE:  We always perform synchronous i/o and ignore the @sync parameter.
 *
 * TODO:  If @sync is false, want to do truly asynchronous i/o, i.e. just
 * schedule i/o via ->writepage or do it via kntfsd or whatever.
 */
static int sync_mft_mirror(ntfs_inode *ni, MFT_RECORD *m, int sync)
{
	ntfs_volume *vol = ni->vol;
	struct page *page;
	unsigned int blocksize = vol->sb->s_blocksize;
	int max_bhs = vol->mft_record_size / blocksize;
	struct buffer_head *bhs[max_bhs];
	struct buffer_head *bh, *head;
	u8 *kmirr;
	unsigned int block_start, block_end, m_start, m_end;
	int i_bhs, nr_bhs, err = 0;

	ntfs_debug("Entering for inode 0x%lx.", ni->mft_no);
	BUG_ON(!max_bhs);
	if (unlikely(!vol->mftmirr_ino)) {
		/* This could happen during umount... */
		err = sync_mft_mirror_umount(ni, m);
		if (likely(!err))
			return err;
		goto err_out;
	}
	/* Get the page containing the mirror copy of the mft record @m. */
	page = ntfs_map_page(vol->mftmirr_ino->i_mapping, ni->mft_no >>
			(PAGE_CACHE_SHIFT - vol->mft_record_size_bits));
	if (unlikely(IS_ERR(page))) {
		ntfs_error(vol->sb, "Failed to map mft mirror page.");
		err = PTR_ERR(page);
		goto err_out;
	}
	/*
	 * Exclusion against other writers.   This should never be a problem
	 * since the page in which the mft record @m resides is also locked and
	 * hence any other writers would be held up there but it is better to
	 * make sure no one is writing from elsewhere.
	 */
	lock_page(page);
	/* The address in the page of the mirror copy of the mft record @m. */
	kmirr = page_address(page) + ((ni->mft_no << vol->mft_record_size_bits)
			& ~PAGE_CACHE_MASK);
	/* Copy the mst protected mft record to the mirror. */
	memcpy(kmirr, m, vol->mft_record_size);
	/* Make sure we have mapped buffers. */
	if (!page_has_buffers(page)) {
no_buffers_err_out:
		ntfs_error(vol->sb, "Writing mft mirror records without "
				"existing buffers is not implemented yet.  %s",
				ntfs_please_email);
		err = -EOPNOTSUPP;
		goto unlock_err_out;
	}
	bh = head = page_buffers(page);
	if (!bh)
		goto no_buffers_err_out;
	nr_bhs = 0;
	block_start = 0;
	m_start = kmirr - (u8*)page_address(page);
	m_end = m_start + vol->mft_record_size;
	do {
		block_end = block_start + blocksize;
		/*
		 * If the buffer is outside the mft record, just skip it,
		 * clearing it if it is dirty to make sure it is not written
		 * out.  It should never be marked dirty but better be safe.
		 */
		if ((block_end <= m_start) || (block_start >= m_end)) {
			if (buffer_dirty(bh)) {
				ntfs_warning(vol->sb, "Clearing dirty mft "
						"record page buffer.  %s",
						ntfs_please_email);
				clear_buffer_dirty(bh);
			}
			continue;
		}
		if (!buffer_mapped(bh)) {
			ntfs_error(vol->sb, "Writing mft mirror records "
					"without existing mapped buffers is "
					"not implemented yet.  %s",
					ntfs_please_email);
			err = -EOPNOTSUPP;
			continue;
		}
		if (!buffer_uptodate(bh)) {
			ntfs_error(vol->sb, "Writing mft mirror records "
//.........这里部分代码省略.........