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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-04-06 19:01:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-07 08:31:13 -0700
commit0bd49f9446130a6a3914eb07b54db489e3222b34 (patch)
tree5122a227c9cb1cfe92a74c53baf1bb7ca7053435 /fs/nilfs2/page.h
parenta60be987d45dd510aeb54389526f9957cfab106c (diff)
downloadlinux-0bd49f9446130a6a3914eb07b54db489e3222b34.tar.bz2
nilfs2: buffer and page operations
This adds common routines for buffer/page operations used in B-tree node caches, meta data files, or segment constructor (log writer). NILFS uses copy functions for buffers and pages due to the following reasons: 1) Relocation required for COW Since NILFS changes address of on-disk blocks, moving buffers in page cache is needed for the buffers which are not addressed by a file offset. If buffer size is smaller than page size, this involves partial copy of pages. 2) Freezing mmapped pages NILFS calculates checksums for each log to ensure its validity. If page data changes after the checksum calculation, this validity check will not work correctly. To avoid this failure for mmaped pages, NILFS freezes their data by copying. 3) Copy-on-write for DAT pages NILFS makes clones of DAT page caches in a copy-on-write manner during GC processes, and this ensures atomicity and consistency of the DAT in the transient state. In addition, NILFS uses two obsolete functions, nilfs_mark_buffer_dirty() and nilfs_clear_page_dirty() respectively. * nilfs_mark_buffer_dirty() was required to avoid NULL pointer dereference faults: Since the page cache of B-tree node pages or data page cache of pseudo inodes does not have a valid mapping->host, calling mark_buffer_dirty() for their buffers causes the fault; it calls __mark_inode_dirty(NULL) through __set_page_dirty(). * nilfs_clear_page_dirty() was needed in the 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 cloned 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. clear_page_dirty_for_io() caused faults because it does not clear the dirty tag on the page cache. Signed-off-by: Seiji Kihara <kihara.seiji@lab.ntt.co.jp> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2/page.h')
-rw-r--r--fs/nilfs2/page.h76
1 files changed, 76 insertions, 0 deletions
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
new file mode 100644
index 000000000000..8abca4d1c1f8
--- /dev/null
+++ b/fs/nilfs2/page.h
@@ -0,0 +1,76 @@
+/*
+ * 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 */