nilfs2: buffer and page operations

/*

 * page.c - buffer/page management specific to NILFS

 *

 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.

 *

 * This program 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 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; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 *

 * Written by Ryusuke Konishi <ryusuke@osrg.net>,

 *            Seiji Kihara <kihara@osrg.net>.

 */

#include <linux/pagemap.h>

#include <linux/writeback.h>

#include <linux/swap.h>

#include <linux/bitops.h>

#include <linux/page-flags.h>

#include <linux/list.h>

#include <linux/highmem.h>

#include <linux/pagevec.h>

#include "nilfs.h"

#include "page.h"

#include "mdt.h"

#define NILFS_BUFFER_INHERENT_BITS  \

	((1UL << BH_Uptodate) | (1UL << BH_Mapped) | (1UL << BH_NILFS_Node) | \

	 (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated))

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_CACHE_SHIFT - blkbits);

	bh = nilfs_page_get_nth_block(page, block - first_block);

	touch_buffer(bh);

	wait_on_buffer(bh);

	return bh;

}

/*

 * Since the page cache of B-tree node pages or data page cache of pseudo

 * inodes does not have a valid mapping->host pointer, calling

 * mark_buffer_dirty() for their buffers causes a NULL pointer dereference;

 * it calls __mark_inode_dirty(NULL) through __set_page_dirty().

 * To avoid this problem, the old style mark_buffer_dirty() is used instead.

 */

void nilfs_mark_buffer_dirty(struct buffer_head *bh)

{

	if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))

		__set_page_dirty_nobuffers(bh->b_page);

}

struct buffer_head *nilfs_grab_buffer(struct inode *inode,

				      struct address_space *mapping,

				      unsigned long blkoff,

				      unsigned long b_state)

{

	int blkbits = inode->i_blkbits;

	pgoff_t index = blkoff >> (PAGE_CACHE_SHIFT - blkbits);

	struct page *page, *opage;

	struct buffer_head *bh, *obh;

	page = grab_cache_page(mapping, index);

	if (unlikely(!page))

		return NULL;

	bh = __nilfs_get_page_block(page, blkoff, index, blkbits, b_state);

	if (unlikely(!bh)) {

		unlock_page(page);

		page_cache_release(page);

		return NULL;

	}

	if (!buffer_uptodate(bh) && mapping->assoc_mapping != NULL) {

		/*

		 * Shadow page cache uses assoc_mapping to point its original

		 * page cache.  The following code tries the original cache

		 * if the given cache is a shadow and it didn't hit.

		 */

		opage = find_lock_page(mapping->assoc_mapping, index);

		if (!opage)

			return bh;

		obh = __nilfs_get_page_block(opage, blkoff, index, blkbits,

					     b_state);

		if (buffer_uptodate(obh)) {

			nilfs_copy_buffer(bh, obh);

			if (buffer_dirty(obh)) {

				nilfs_mark_buffer_dirty(bh);

				if (!buffer_nilfs_node(bh) && NILFS_MDT(inode))

					nilfs_mdt_mark_dirty(inode);

			}

		}

		brelse(obh);

		unlock_page(opage);

		page_cache_release(opage);

	}

	return bh;

}

/**

 * nilfs_forget_buffer - discard dirty state

 * @inode: owner inode of the buffer

 * @bh: buffer head of the buffer to be discarded

 */

void nilfs_forget_buffer(struct buffer_head *bh)

{

	struct page *page = bh->b_page;

	lock_buffer(bh);

	clear_buffer_nilfs_volatile(bh);

	if (test_clear_buffer_dirty(bh) && nilfs_page_buffers_clean(page))

		__nilfs_clear_page_dirty(page);

	clear_buffer_uptodate(bh);

	clear_buffer_mapped(bh);

	bh->b_blocknr = -1;

	ClearPageUptodate(page);

	ClearPageMappedToDisk(page);

	unlock_buffer(bh);

	brelse(bh);

}

/**

 * nilfs_copy_buffer -- copy buffer data and flags

 * @dbh: destination buffer

 * @sbh: source buffer

 */

void nilfs_copy_buffer(struct buffer_head *dbh, struct buffer_head *sbh)

{

	void *kaddr0, *kaddr1;

	unsigned long bits;

	struct page *spage = sbh->b_page, *dpage = dbh->b_page;

	struct buffer_head *bh;

	kaddr0 = kmap_atomic(spage, KM_USER0);

	kaddr1 = kmap_atomic(dpage, KM_USER1);

	memcpy(kaddr1 + bh_offset(dbh), kaddr0 + bh_offset(sbh), sbh->b_size);

	kunmap_atomic(kaddr1, KM_USER1);

	kunmap_atomic(kaddr0, KM_USER0);

	dbh->b_state = sbh->b_state & NILFS_BUFFER_INHERENT_BITS;

	dbh->b_blocknr = sbh->b_blocknr;

	dbh->b_bdev = sbh->b_bdev;

	bh = dbh;

	bits = sbh->b_state & ((1UL << BH_Uptodate) | (1UL << BH_Mapped));

	while ((bh = bh->b_this_page) != dbh) {

		lock_buffer(bh);

		bits &= bh->b_state;

		unlock_buffer(bh);

	}

	if (bits & (1UL << BH_Uptodate))

		SetPageUptodate(dpage);

	else

		ClearPageUptodate(dpage);

	if (bits & (1UL << BH_Mapped))

		SetPageMappedToDisk(dpage);

	else

		ClearPageMappedToDisk(dpage);

}

/**

 * nilfs_page_buffers_clean - check if a page has dirty buffers or not.

 * @page: page to be checked

 *

 * nilfs_page_buffers_clean() returns zero if the page has dirty buffers.

 * Otherwise, it returns non-zero value.

 */

int nilfs_page_buffers_clean(struct page *page)

{

	struct buffer_head *bh, *head;

	bh = head = page_buffers(page);

	do {

		if (buffer_dirty(bh))

			return 0;

		bh = bh->b_this_page;

	} while (bh != head);

	return 1;

}

void nilfs_page_bug(struct page *page)

{

	struct address_space *m;

	unsigned long ino = 0;

	if (unlikely(!page)) {

		printk(KERN_CRIT "NILFS_PAGE_BUG(NULL)\n");

		return;

	}

	m = page->mapping;

	if (m) {

		struct inode *inode = NILFS_AS_I(m);

		if (inode != NULL)

			ino = inode->i_ino;

	}

	printk(KERN_CRIT "NILFS_PAGE_BUG(%p): cnt=%d index#=%llu flags=0x%lx "

	       "mapping=%p ino=%lu\n",

	       page, atomic_read(&page->_count),

	       (unsigned long long)page->index, page->flags, m, ino);

	if (page_has_buffers(page)) {

		struct buffer_head *bh, *head;

		int i = 0;

		bh = head = page_buffers(page);

		do {

			printk(KERN_CRIT

			       " BH[%d] %p: cnt=%d block#=%llu state=0x%lx\n",

			       i++, bh, atomic_read(&bh->b_count),

			       (unsigned long long)bh->b_blocknr, bh->b_state);

			bh = bh->b_this_page;

		} while (bh != head);

	}

}

/**

 * nilfs_alloc_private_page - allocate a private page with buffer heads

 *

 * Return Value: On success, a pointer to the allocated page is returned.

 * On error, NULL is returned.

 */

struct page *nilfs_alloc_private_page(struct block_device *bdev, int size,

				      unsigned long state)

{

	struct buffer_head *bh, *head, *tail;

	struct page *page;

	page = alloc_page(GFP_NOFS); /* page_count of the returned page is 1 */

	if (unlikely(!page))

		return NULL;

	lock_page(page);

	head = alloc_page_buffers(page, size, 0);

	if (unlikely(!head)) {

		unlock_page(page);

		__free_page(page);

		return NULL;

	}

	bh = head;

	do {

		bh->b_state = (1UL << BH_NILFS_Allocated) | state;

		tail = bh;

		bh->b_bdev = bdev;

		bh = bh->b_this_page;

	} while (bh);

	tail->b_this_page = head;

	attach_page_buffers(page, head);

	return page;

}

void nilfs_free_private_page(struct page *page)

{

	BUG_ON(!PageLocked(page));

	BUG_ON(page->mapping);

	if (page_has_buffers(page) && !try_to_free_buffers(page))

		NILFS_PAGE_BUG(page, "failed to free page");

	unlock_page(page);

	__free_page(page);

}

/**

 * 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 fuction 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 |= (1UL << 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);

}

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;

}

/**

 * nilfs_copy_back_pages -- copy back pages to orignal cache from shadow cache

 * @dmap: destination page cache

 * @smap: source page cache

 *

 * No pages must no be added to the cache during this process.

 * This must be ensured by the caller.

 */

void nilfs_copy_back_pages(struct address_space *dmap,

			   struct address_space *smap)

{

	struct pagevec pvec;

	unsigned int i, n;

	pgoff_t index = 0;

	int err;

	pagevec_init(&pvec, 0);

repeat:

	n = pagevec_lookup(&pvec, smap, index, PAGEVEC_SIZE);

	if (!n)

		return;

	index = pvec.pages[n - 1]->index + 1;

	for (i = 0; i < pagevec_count(&pvec); i++) {

		struct page *page = pvec.pages[i], *dpage;

		pgoff_t offset = page->index;

		lock_page(page);

		dpage = find_lock_page(dmap, offset);

		if (dpage) {

			/* override existing page on the destination cache */

			BUG_ON(PageDirty(dpage));

			nilfs_copy_page(dpage, page, 0);

			unlock_page(dpage);

			page_cache_release(dpage);

		} else {

			struct page *page2;

			/* move the page to the destination cache */

			spin_lock_irq(&smap->tree_lock);

			page2 = radix_tree_delete(&smap->page_tree, offset);

			if (unlikely(page2 != page))

				NILFS_PAGE_BUG(page, "page removal failed "

					       "(offset=%lu, page2=%p)",

					       offset, page2);

			smap->nrpages--;

			spin_unlock_irq(&smap->tree_lock);

			spin_lock_irq(&dmap->tree_lock);

			err = radix_tree_insert(&dmap->page_tree, offset, page);

			if (unlikely(err < 0)) {

				BUG_ON(err == -EEXIST);

				page->mapping = NULL;

				page_cache_release(page); /* for cache */

			} else {

				page->mapping = dmap;

				dmap->nrpages++;

				if (PageDirty(page))

					radix_tree_tag_set(&dmap->page_tree,

							   offset,

							   PAGECACHE_TAG_DIRTY);

			}

			spin_unlock_irq(&dmap->tree_lock);

		}

		unlock_page(page);

	}

	pagevec_release(&pvec);

	cond_resched();

	goto repeat;

}

void nilfs_clear_dirty_pages(struct address_space *mapping)

{

	struct pagevec pvec;

	unsigned int i;

	pgoff_t index = 0;

	pagevec_init(&pvec, 0);

	while (pagevec_lookup_tag(&pvec, mapping, &index, PAGECACHE_TAG_DIRTY,

				  PAGEVEC_SIZE)) {

		for (i = 0; i < pagevec_count(&pvec); i++) {

			struct page *page = pvec.pages[i];

			struct buffer_head *bh, *head;

			lock_page(page);

			ClearPageUptodate(page);

			ClearPageMappedToDisk(page);

			bh = head = page_buffers(page);

			do {

				lock_buffer(bh);

				clear_buffer_dirty(bh);

				clear_buffer_nilfs_volatile(bh);

				clear_buffer_uptodate(bh);

				clear_buffer_mapped(bh);

				unlock_buffer(bh);

				bh = bh->b_this_page;

			} while (bh != head);

			__nilfs_clear_page_dirty(page);

			unlock_page(page);

		}

		pagevec_release(&pvec);

		cond_resched();

	}

}

unsigned nilfs_page_count_clean_buffers(struct page *page,

					unsigned from, unsigned to)

{

	unsigned block_start, block_end;

	struct buffer_head *bh, *head;

	unsigned nc = 0;

	for (bh = head = page_buffers(page), block_start = 0;

	     bh != head || !block_start;

	     block_start = block_end, bh = bh->b_this_page) {

		block_end = block_start + bh->b_size;

		if (block_end > from && block_start < to && !buffer_dirty(bh))

			nc++;

	}

	return nc;

}

/*

 * NILFS2 needs clear_page_dirty() in the following two cases:

 *

 * 1) For B-tree node pages and data pages of the dat/gcdat, NILFS2 clears

 *    page dirty flags when it copies back pages from the shadow cache

 *    (gcdat->{i_mapping,i_btnode_cache}) to its original cache

 *    (dat->{i_mapping,i_btnode_cache}).

 *

 * 2) Some B-tree operations like insertion or deletion may dispose buffers

 *    in dirty state, and this needs to cancel the dirty state of their pages.

 */

int __nilfs_clear_page_dirty(struct page *page)

{

	struct address_space *mapping = page->mapping;

	if (mapping) {

		spin_lock_irq(&mapping->tree_lock);

		if (test_bit(PG_dirty, &page->flags)) {

			radix_tree_tag_clear(&mapping->page_tree,

					     page_index(page),

					     PAGECACHE_TAG_DIRTY);

			spin_unlock_irq(&mapping->tree_lock);

			return clear_page_dirty_for_io(page);

		}

		spin_unlock_irq(&mapping->tree_lock);

		return 0;

	}

	return TestClearPageDirty(page);

}

/*

 * page.h - buffer/page management specific to NILFS

 *

 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.

 *

 * This program 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 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; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 *

 * Written by Ryusuke Konishi <ryusuke@osrg.net>,

 *            Seiji Kihara <kihara@osrg.net>.

 */

#ifndef _NILFS_PAGE_H

#define _NILFS_PAGE_H

#include <linux/buffer_head.h>

#include "nilfs.h"

/*

 * Extended buffer state bits

 */

enum {

	BH_NILFS_Allocated = BH_PrivateStart,

	BH_NILFS_Node,

	BH_NILFS_Volatile,

};

BUFFER_FNS(NILFS_Allocated, nilfs_allocated)	/* nilfs private buffers */

BUFFER_FNS(NILFS_Node, nilfs_node)		/* nilfs node buffers */

BUFFER_FNS(NILFS_Volatile, nilfs_volatile)

void nilfs_mark_buffer_dirty(struct buffer_head *bh);

int __nilfs_clear_page_dirty(struct page *);

struct buffer_head *nilfs_grab_buffer(struct inode *, struct address_space *,

				      unsigned long, unsigned long);

void nilfs_forget_buffer(struct buffer_head *);

void nilfs_copy_buffer(struct buffer_head *, struct buffer_head *);

int nilfs_page_buffers_clean(struct page *);

void nilfs_page_bug(struct page *);

struct page *nilfs_alloc_private_page(struct block_device *, int,

				      unsigned long);

void nilfs_free_private_page(struct page *);

int nilfs_copy_dirty_pages(struct address_space *, struct address_space *);

void nilfs_copy_back_pages(struct address_space *, struct address_space *);

void nilfs_clear_dirty_pages(struct address_space *);

unsigned nilfs_page_count_clean_buffers(struct page *, unsigned, unsigned);

#define NILFS_PAGE_BUG(page, m, a...) \

	do { nilfs_page_bug(page); BUG(); } while (0)

static inline struct buffer_head *

nilfs_page_get_nth_block(struct page *page, unsigned int count)

{

	struct buffer_head *bh = page_buffers(page);

	while (count-- > 0)

		bh = bh->b_this_page;

	get_bh(bh);

	return bh;

}

#endif /* _NILFS_PAGE_H */